Solid Waste Mechanical Heat Treatment of Municipal Mechanical

www.defra.gov.uk

Mechanical Biological Treatment &Mechanical Heat Treatment of MunicipalSolid Waste

www.defra.gov.uk

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This Waste Management Technology Brief is one of a series of documents prepared under the NewTechnologies work stream of the Defra Waste Implementation Programme. The Briefs areaddressing potentially important new technologies which may have an increasing role in divertingMunicipal Solid Waste (MSW) from landfill into a more sustainable and integrated wastemanagement alternative, extracting materials and energy from MSW for recovery and reducingquantities remaining for disposal. Other titles in this series include: An Introductory Guide to WasteManagement Options; Advanced Biological Treatment; and Advanced Thermal Treatment.

It should be noted that these documents are intended as guides to each generic technology areaand for more detailed or specific information on any particular technology, it is recommended thatthe Defra Waste Technology Data Centre is used as a resource. These Briefs deal primarily with thetreatment and processing of unsorted MSW and not source segregated wastes which are addressedby the activities of the Waste & Resources Action Programme (WRAP). Relevant references andsources of further information are cited throughout each document in this series.

The prime audience for these Briefs are local authorities, in particular waste management officers,members and other key decision makers for MSW management in England. For further informationon new technologies contact the New Technologies Supporter Helpline on 0870 2409894, email:[email protected]

Prepared by Enviros Consulting Limited on behalf of Defra as part of the New TechnologiesSupporter Programme.

We acknowledge support from the Department for Environment, Food & Rural Affairs, theEnvironment Agency, the Waste and Resources Action Programme, Be Environmental Ltd, RPS and Stuart McLanaghan of Associates in Industrial Ecology.

Disclaimer: Please read the note below before using this Document

This Document has been produced by Enviros Consulting Limited (Technical Advisors) on behalf ofDefra to provide assistance to Local Authorities and the waste management market generallythrough awareness raising of the key municipal waste management options for the diversion of BMWfrom landfill. The Document has been developed in good faith by the Advisors on behalf of Defra,and neither Defra nor its Advisers shall incur any liability for any action or omission arising out of anyreliance being placed on the Document by any Local Authority or organisation or other person. AnyLocal Authority or organisation or other person in receipt of this Document should take their ownlegal, financial and other relevant professional advice when considering what action (if any) to takein respect of any waste strategy, initiative, proposal, or other involvement with any wastemanagement option or technology, or before placing any reliance on anything contained therein.

Crown Copyright, 2005V.1.0

Glossary Preamble

Aerobic In the presence of oxygen.

Aerobic Digestion/Composting Biological decomposition of organic materials by micro-organismsunder controlled, aerobic, conditions to a relatively stable humus-like material called compost.

Anaerobic In the absence of oxygen.

Anaerobic Digestion A process where biodegradable material is encouraged to breakdown in the absence of oxygen. Material is placed in to anenclosed vessel and in controlled conditions the waste breaks downtypically into a digestate, liquor and biogas

Animal By-Products Regulation Legislation governing the processing of wastes derived from animalsources.

Biodegradable Capable of being degraded by plants and animals. Biodegradablemunicipal waste includes paper and card, food and garden waste,and a proportion of other wastes, such as textiles.

Biogas Gas resulting from the fermentation of waste in the absence of air(methane/carbon dioxide).

Biodegradable Municipal Waste(BMW)

The component of Municipal Solid Waste capable of beingdegraded by plants and animals. Biodegradable Municipal Wasteincludes paper and card, food and garden waste, and a proportionof other wastes, such as textiles.

Co-combustion Combustion of wastes as a fuel in an industrial or other (non wastemanagement) process.

Digestate Solid and/or liquid product resulting from Anaerobic Digestion.

Feedstock Raw material required for a process.

Floc A small loosely aggregated mass of flocculent material. In thisinstance referring to Refuse Derived Fuel or similar.

Greenhouse Gas A term given to those gas compounds in the atmosphere thatreflect heat back toward earth rather than letting it escape freelyinto space. Several gases are involved, including carbon dioxide(CO2), methane (CH4), nitrous oxide (N2O), ozone, water vapourand some of the chlorofluorocarbons.

Green Waste Waste vegetation and plant matter from household gardens, localauthority parks and gardens and commercial landscaped gardens.

Global Warming The progressive gradual rise of the earth's surface temperaturethought to be caused by the greenhouse effect and responsible forchanges in global climate patterns. An increase in the near surfacetemperature of the Earth. Global warming has occurred in thedistant past as the result of natural influences, but the term is mostoften used to refer to the warming predicted to occur as a result ofincreased emissions of greenhouse gases form man - made sources.

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Page number

Preamble 1

Introduction 2

How it Works 3

Mechanical Biological Treatment 3Mechanical Heat Treatment 6Summary 8

Markets for the Outputs 9

Recovery from MBT 9Recovery from MHT 11

Track Record 13

Contractual and Financing Issues 14

Grants and Funding 14Contractual Arrangements 14

Planning and Permitting Issues 16

Planning 16Plant Siting 16Traffic 16Air Emissions/Health Effects 16Dust/Odour 16Flies, Vermin and Birds 17Noise 17Litter 17Water Resources 17Visual Intrusion 17Size and Landtake 18Public Concern 18Environmental Impact Assessment 18Licensing/Permitting 18

Social and Perception Issues 19

Social Considerations 19Public Perception 19

Costs of MBT/MHT Systems 20

Contribution to National Targets 21

Recycling 21Composting 21Landfill Allowance Trading Scheme (LATS) 21Recovery 22Renewables 22

Further Reading and Sources of Information 23

Glossary 24

Contents Glossary

Incineration The controlled thermal treatment of waste by burning, either toreduce its volume or toxicity. Energy recovery from incineration canbe made by utilising the calorific value of the waste to produceheat and/or power.

In-vessel Composting The aerobic decomposition of shredded and mixed organic wastewithin and enclosed container, where the control systems formaterial degradation are fully automated. Moisture, temperature,and odour can be regulated, and stable compost can be producedmuch more quickly than outdoor windrow composting.

Materials Recycling Facility/Material Recovery Facility (MRF)

Dedicated facility for the sorting/separation of recyclable materials.

Mechanical Biological Treatment(MBT)

A generic term for mechanical sorting/separation technologies usedin conjunction with biological treatment processes, such ascomposting.

Municipal Solid Waste (MSW) Household waste and any other wastes collected by the WasteCollection Authority, or its agents, such as municipal parks andgardens waste, beach cleansing waste, commercial or industrialwaste, and waste resulting from the clearance of fly-tippedmaterials.

Recyclate/Recyclable materials Post-use materials that can be recycled for the original purpose, orfor different purposes.

Recycling Involves the processing of wastes, into either the same product or adifferent one. Many non-hazardous wastes such as paper, glass,cardboard, plastics and scrap metals can be recycled. Hazardouswastes such as solvents can also be recycled by specialist companies.

Refuse Derived Fuel (RDF) A fuel produced from combustible waste that can be stored andtransported, or used directly on site to produce heat and/or power.

Renewables Obligation Introduced in 2002 by the Department of Trade and Industry, thissystem creates a market in tradable renewable energy certificates,for which each supplier of electricity must demonstrate compliancewith increasing Government targets for renewable energygeneration.

Solid Recovered Fuel Refuse Derived Fuel meeting a standard specification, currentlyunder development by a CEN standards committee.

Source-segregated/Source-separated

Usually applies to household waste collection systems whererecyclable and/or organic fractions of the waste stream areseparated by the householder and are often collected separately.

Statutory Best Value PerformanceIndicators

Local Authorities submit performance data to Government in theform of annual performance indicators (PIs). The Recycling andComposting PIs have statutory targets attached to them whichAuthorities are required to meet.

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Municipal Solid Waste (MSW) is waste collected by oron behalf of a local authority. It comprises mostlyhousehold waste and it may include somecommercial and industrial wastes. Nationally, thequantity of MSW is currently increasing year on year,presenting a growing problem for local authoritiesparticularly as new legislation, which limits (byimplication1) the amount of mixed MSW that can besent to landfill, comes into effect.

One of the guiding principles for European and UKwaste management has been the concept of ahierarchy of waste management options, where themost desirable option is not to produce the waste inthe first place (waste prevention) and the leastdesirable option is to dispose of the waste with norecovery of either materials and/or energy. Betweenthese two extremes there are a wide variety of wastetreatment options that may be used as part of awaste management strategy to recover materials (forexample furniture reuse, glass recycling or organicwaste composting) or generate energy from thewastes (for example through incineration, ordigesting biodegradable wastes to produce usablegases).

At present more than 75% of all MSW generated inEngland is disposed of in landfills. However,European and UK legislation has been put in placeto limit the amount of biodegradable municipalwaste (BMW) sent for disposal in landfill. Thediversion of this material is currently the mostsignificant challenge facing the management ofMunicipal Solid Waste in the UK.

There are a wide variety of alternative wastemanagement options and strategies available fordealing with Municipal Solid Waste to limit theresidual amount left for disposal to landfill. The aimof this guide is to provide impartial informationabout the range of technologies referred to asMechanical Biological Treatment (MBT) andMechanical Heat Treatment (MHT). Thesetechnologies are pre-treatment technologies whichcontribute to the diversion of MSW from landfillwhen operated as part of a wider integratedapproach involving additional treatment stages.They are part of a range of new alternativescurrently being assessed and investigated throughthe New Technologies work stream of Defra.

Further details about the new technologies featuredin this report are available from Defra's WasteTechnology Data Centre:

http://www.environment-agency.gov.uk/wtd

The technologies described in this Brief - MechanicalBiological Treatment and Mechanical Heat Treatment- have a varying, track record in England (and theUK). MBT plant, have a chequered history in the UK,early examples of similar processes including 'RefuseDerived Fuel' (RDF) processing plant and residualwaste Materials Recovery Facilities ('Dirty MRFs'). Thenew MBT technologies are now second or thirdgeneration plant including many well provenexamples. On the continent many of these processesare established viable and bankable. The aim of thisdocument is to raise awareness and help bring theUK up to that standard.

This guide is designed to be read in conjunction withthe other Waste Management Technology Briefs inthis series and with the case studies provided onDefra's Waste Technology Data Centre. Otherrelevant sources of information are identifiedthroughout the document.

The Waste Technology Data Centrewww.environment-agency.gov.uk/wtd

New Technologies Supporter Helpline Tel. 0870 240 9894 E: [email protected]

Defra New Technologies website,http://www.defra.gov.uk/environment/waste/wip/newtech/index.htm

Integrated Pollution Prevention and Control, DraftReference Document on Best Available Techniquesfor the Waste Treatments Industries, EuropeanCommission - Directorate General Joint ResearchCentre, January 2004

Refuse Derived Fuel, Current Practice andPerspectives (B4-3040/2000/306517/Mar/E3), EuropeanCommission - Directorate General Environment, July 2003

Procurement Toolkithttp://lasupport.defra.gov.uk/Default.aspx?Menu=Menu&Module=Article&ArticleID=102

For Works Contracts: the Institution of CivilEngineers 'New Engineering Contract'www.ice.org.uk

For large scale Waste Services Contracts through PFIAND following the Negotiated Procedures the 4ps'Waste Procurement Pack' www.4ps.gov.uk

Planning for Waste Management Facilities - AResearch Study. ODPM, 2004.http://www.odpm.gov.uk/stellent/groups/odpm_planning/documents/page/odpm_plan_030747.pdf

AiIE Ltd, 2003, Review of residual waste treatmenttechnologies, Report prepared on behalf of Kingstonupon Hull City Council and East Riding of YorkshireCouncilhttp/www.eastriding.gov.uk/environment/pdf/waste_treatment_technologies.pdf

The Additional Paper to the Strategy Unit, WasteNot Want Not study, 'Delivering the LandfillDirective: The Role of New & EmergingTechnologies', Dr Stuart McLanaghanhttp://www.number10.gov.uk/files/pdf/technologies-landfill.pdf

WRAP Organics websitehttp://www.wrap.org.uk/materials/organics/

The Composting Association, including reports onAnaerobic Digestion and Directory of In-VesselComposting.http://www.compost.org.uk/dsp_home.cfm

Chartered Institution of Wastes Management.http://www.ciwm.co.uk

Mechanical Biological Treatment: A Guide forDecision Makers, Processes, Policies and Markets(2005), by Juniper consultancy Ltd for SitaEnvironmental Trust.http://www.sitaenvtrust.org.uk/research/overview

Introduction Further Reading and Sources of Information

1Targets pertain to the biodegradable fraction

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As any MBT plants developed in the UK are likely tovary in their method of operation, the stability test islikely to be applied to each MBT plant on a regularbasis. Figure 3 shows a hypothetical mass balancecalculation showing the contribution of an MBTplant to BMW diversion. Up to date informationrelating to LATS can be obtained from the NewTechnologies Supporter Helpline and Defra's LATSinformation webpage15.

As the requirements of the Landfill Directive relateto the amount of biodegradable material landfilled,the stability of materials diverted from landfill viaMBT will not need to be measured.

Recovery

MBT and MHT technologies will only contributetowards recovery targets through the waste streamsthat are sent to an energy recovery process. This maybe either RDF combusted or degraded in a thermalplant (e.g. Energy from Waste, Advanced ThermalTreatment or co-combusted in a Cement Kiln), or thebiological stream that is processed in an AnaerobicDigestion plant (see the specific guidance for BVPI82c and also 82b for AD). For more details see theDefra website16.

Renewables

If energy is recovered from the sorted materials(RDF) arising from an MBT or MHT plant, this wouldcount as renewable under the Renewable Energytargets.

The Government has also introduced an incentivisedmarket for Renewable Energy through the'Renewables Obligation'. The combustion of RefuseDerived Fuel from an MBT or MHT process in anEnergy from Waste plant at present would notqualify for this incentive and a co-combustionapplication is also unlikely to qualify. But the otherrecovery techniques of Anaerobic Digestion andAdvanced Thermal Treatment (see the other Briefs inthis series) do qualify for Renewables ObligationCertificates (ROCs) under this scheme (for moreinformation see page 11).

The ROCs scheme is currently out to consultation, forup-to-date information regarding RDF and ROCs seethe DTI website17 or the New Technologies SupporterHelpline tel. 0870 2409894 [email protected]

This section comprises an overview of the principlesof Mechanical Biological Treatment (MBT) andMechanical Heat Treatment (MHT) processes. Itshould be noted that there are a myriad of acronymsand titles ascribed to different treatmenttechnologies falling within this Brief, however forthe purpose of clarity this document differentiatesonly two principle technology categories. Thoseinvolving biological treatment in conjunction withmechanical processing (MBT) and those usingthermal treatment in conjunction with mechanicalprocessing (MHT).

The generic purpose of all these processes is toseparate a mixed waste stream into severalcomponent parts, to give further options forrecycling and recovery.

Mechanical Biological Treatment Facility, Cologne

Mechanical Biological Treatment

Mechanical Biological Treatment is a generic term foran integration of several processes commonly foundin other waste management technologies such asMaterials Recovery Facilities (MRFs), sorting andcomposting plant. MBT plant can incorporate anumber of different processes in a variety ofcombinations. Additionally, MBT plant can be builtfor a range of purposes.

A common aspect of all MBT plant used for MSWmanagement is to sort mixed waste into differentfractions using mechanical means; and to extractmaterials for recycling. The exact mix oftechnologies employed in an MBT facility will

depend on the additional objectives of the plant.These objectives would typically be one or more ofthe following:

• part stabilise the waste prior to landfilling;

• biologically process a segregated 'organic rich'component of the waste [for example, to form alow grade soil conditioner]; and

• produce a segregated high calorific value wasteto feed an appropriate thermal process to utiliseits energy potential.

The biological element of an MBT process may eithertake place prior to or after mechanical sorting of thewaste, as illustrated in Figure 1. Each approach hasits own particular application and examples of bothmethodologies are described in the case studiesbelow and in more detail on the Waste TechnologyData Centre.

Contribution to National Targets How it Works

Box 1 Fuel from mixed waste processingoperations

The current prevalent term used for a fuelproduced from combustible waste is Refuse DerivedFuel (RDF). The types of technologies used toprepare/segregate a fuel fraction from MSWinclude many of the MBT/BMT and MHT processesdescribed within this Brief. A CEN TechnicalCommittee (TC 343) is currently progressingstandardisation work on fuels prepared fromwastes, classifying a Solid Recovered Fuel (SRF). It isanticipated that once standards are developed andbecome accepted by users that SRF will become theterminology used by the waste managementindustry. Other terminology has also beenintroduced to the industry as various fuelcompositions may be prepared from waste bydifferent processes. Examples include'Biodegradable Fuel Product' (BFP) and 'RefinedRenewable Biomass Fuel' (RRBF).

Within this Brief, Refuse Derived Fuel will be usedas a term to cover the various fuel productsprocessed from MSW.

15 http://www.defra.gov.uk/environment/waste/localauth/lats/index.htm16 http://www.defra.gov.uk/environment/waste/localauth/index.htm17 http://www.dti.gov.uk/energy/renewables/

Figure 3 : Hypothetical MBT Mass Balance

This hypothetical example is based on information available from the Environment Agency at the time of writing. It can be seen that although the proportion ofBMW in the rejects from the MBT plant is higher in the residual output than in the input (78% vs 69%), this is off-set by a decrease in overall tonnage and by thedecreased biodegrabability (increased stability) of the material. In this hypothetical example, 62 tonnes of BMW enters the plant (with a biodegradabilitymeasure of 10) and the residual material contains 42 tonnes of BMW (with a biodegrabability measure of 5). The Environment Agency have indicated that thetonnes of BMW counted as being landfilled from an MBT plant will take into account the material's increased stability (based on testing the material) and thattherefore in this example the BMW tonnage being landfilled from the MBT plant would be equivalent to 21 tonnes (as the biodegradability measure has halved).

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Figure 1 : An illustration of the potential Mechanical Biological Treatment options

The combination of mechanical waste preparation and separation techniques used and their configurations aremany and varied. Box 2 illustrates the typical options used in MBT systems.

Recycling

Recyclate derived from a mixed waste processingplant (either MBT or MHT) of household wastequalifies for BVPI 82a (Recycling) at the point atwhich it leaves the plant to be sent to thereprocessor. The material must pass to thereprocessor (and not be rejected for quality reasons)to count as recycling. The same would also apply toglass used as an aggregate. It should be noted thatsome materials may have market limitations due tobeing derived from a mixed MSW source. Forexample British Standard BS EN 643 states that'Recovered paper from refuse sorting stations is notsuitable for use in the paper industry.' Although thisstandard is not legally binding, it is supported by themain trade associations for the paper recyclingsector.

Further information about BVPIs can be obtainedfrom the Defra website14.

Composting

Where MBT or MHT processes are configured toproduce an organic rich stream to be utilised as alow grade soil conditioner for example, this materialmay (but is 'unlikely to' see below) qualify ascomposting under BVPI 82b. These types of mixedwaste processing technologies are expected toproduce a low grade soil conditioner which could beutilised in applications such as landfill restoration orsome bulk fill uses (provided that the appropriateengineering and quality standards are met).

These materials will only qualify as 'composted'under the Best Value Performance Indicator (BVPI82b) if the output meets the appropriate criteria foruse in the intended application. Some wastemanagement contractors have demonstrated thatthere is a market for these materials, however thecurrent Best Value Performance Indicator Guidance(as of November 2004) states the criteria forcomposting should be 'a product that has beensanitised and stabilised, is high in humic substances,and can be used as a soil improver, as an ingredientin growing media or blended to produce a top soilthat will meet British Standard BS2882 incorporating

amendment no.1…' It also states that it is 'unlikelythat products of a Mechanical Biological Treatmentprocess will meet this definition.' However if thedefinition could be achieved then the product wouldqualify as BVPI 82b.

The definition of BVPI 82b has been amended toinclude waste which has been treated through aprocess of anaerobic digestion.

For more information on the processes for the organicfraction from mixed waste processing, see theAdvanced Biological Treatment Brief, in this series.

For the latest position with regard to Best ValuePerformance Indicators for MBT and MHT see theDefra website or contact the Supporter Helpline tel. 0870 2409894 [email protected]

Landfill Allowance Trading Scheme (LATS)

The European Landfill Directive and the UK'senabling act, the Waste & Emissions Trading Act2003, require the diversion of biodegradablemunicipal waste (BMW) from landfill. Both MBT andMHT systems have the potential to divert BMW fromlandfill. Any outputs that are recycled, used as soilconditioner (under an exemption) or burnt as RDFand which are not landfilled will count directlytowards diversion targets. The ability of MBT & MHTto meet a high level of landfill diversion willtherefore depend upon the availability of marketsfor, and the quality of, the process outputs.

However, MBT plant can also be used to bio-stabilisewaste prior to landfilling. In this case biologicaltreatment is used to reduce the waste's potential todegrade and produce methane once landfilled. TheEnvironment Agency (EA) are currently developing amethodology to determine the 'stability' or'biodegradablity' of any outputs from an MBT plantwhich are sent to landfill. This test will be used todetermine the amount of biodegradable materialbeing landfilled in accordance with the LandfillAllowance Trading Scheme (LATS).

How it Works Contribution to National Targets

14 http://www.defra.gov.uk/environment/waste/localauth/index.htm

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The cost of constructing, operating and maintainingMBT and MHT facilities are addressed using acommon cost model on Defra's Waste TechnologyData Centre. Both capital and operating costs areincluded on specific technologies which may be usedfor the purposes of indicative comparisons ratherthan accurate reflections of actual costs.

It should also be noted that MBT and MHT systemsare sensitive to the markets and outlets for recycledmaterials, RDF and soil conditioners that areproduced by different processes. Partnershipsbetween MBT operators and potential users ofoutputs should be established at the earliestopportunity and indeed care should be taken toensure plant can deliver materials of sufficientquality.

Typically around 50% of the capital costs foroperating an MBT plant will be to cover capitaldepreciation. As a result these need to be viewed aslarge capital investments with a lifespan of not lessthan 10 or more usually 20 years.

It is vital in any negotiation, that a true appreciationof the cost of essential repairs and refurbishment betaken into account. Additionally the undevelopedmarkets (and risks associated with loss of markets)for products/outputs of these processes needs to bereflected in cost models. Any building should havesufficient capacity to house new separationequipment. Typically plants less than 40ktpa capacityare unlikely to be viable.

For cost information on examples of differentprocesses see Defra's Waste Technology Data Centrewww.environment-agency.gov.uk/wtd

Box 2

Mechanical Waste Preparation Technologies

Mechanical Waste Separation Technologies

Costs of MBT/MHT Systems How it Works

Technology Principle Key Concerns

Hammer Mill Material significantly reduced in size by swingingsteel hammers

Wear on Hammers, pulverising and'loss' of glass/aggregates, exclusionof pressurised containers

Shredder Rotating knives or hooks rotate at a slow speed withhigh torque. The shearing action tears or cuts mostmaterials

Large, strong objects can physicallydamage, exclusion of pressurisedcontainers

Rotating Drum Material is lifted up the sides of a rotating drum andthen dropped back into the centre. Uses gravity totumble, mix, and homogenize the wastes. Dense,abrasive items such as glass or metal will help breakdown the softer materials, resulting in considerablesize reduction of paper and other biodegradablematerials

Gentle action - high moisture offeedstock can be a problem

Ball Mill Rotating drum using heavy balls to break up orpulverise the waste

Wear on balls, pulverising and'loss' of glass/aggregates

Wet RotatingDrum with Knives

Waste is wetted, forming heavy lumps which breakagainst the knives when tumbled in the drum

Relatively low size reduction.Potential for damage from largecontraries

Bag Splitter A more gentle shredder used to split plastic bagswhilst leaving the majority of the waste intact

Not size reduction, may bedamaged by large strong objects

Technology Separation Property Materials Targeted Key Concerns

Trommels and Screens Size and density Oversize - paper, plasticSmall - organics, glass, fines

Air containment andcleaning

Manual Separation Visual examination Plastics, contaminants,oversize, not usually for MSW

Ethics of role, Health &Safety issues

Magnetic Separation Magnetic Properties Ferrous metals

Eddy Current Separation Electrical Conductivity Non ferrous metals

Wet SeparationTechnology

Differential Densities Floats - Plastics, organicsSinks - stones, glass

Produces wet waste streams

Air Classification Weight Light - plastics, paperHeavy - stones, glass

Air cleaning

Ballistic Separation Density and Elasticity Light - plastics, paperHeavy - stones, glass

Optical Separation Optical properties Specific plastic polymers Rates of throughput

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In addition to the various mechanical technologiesthere are also a variety of different biologicaltreatment techniques which are used in MBT plant.These are described in greater detail in theAdvanced Biological Treatment Brief, in this series.Box 3 below outlines the key categories of biologicaltreatment.

Whilst a variety of treatment and mechanicalseparation options are offered, these need to beoptimised in terms of the outputs in order to findoutlets for the various materials/fuels derived fromthe process (see Markets for the Outputs section). Itis important to retain the flexibility (for example byallowing sufficient space within buildings) to adaptthe process to produce different outputs to meet theneeds of the market.

Case Studies

The following case studies illustrate examples ofMBT systems and relate these to the differentmechanical preparation, separation and biologicaltreatment techniques, described in Boxes 2 & 3.

The Arrow Bio Process The key process stages of the Arrow Bio processinclude: MSW reception, bag splitting, a wetseparator (where the biodegradable material isseparated from the ferrous and non ferrous metalsand other heavy material), the “Hydrocrusher”(which separates the fibres in the biodegradable

material), followed by a two stage anaerobicdigestion. The gas from the digesters is burnt in anengine-powered generator.

It is accepted that the rate-controlling step in theanaerobic digestion of MSW is the hydrolysis ofcomplex materials, such as cellulose and lignin, intosmall soluble molecules such as glucose, which canbe easily digested. In the Arrow Bio process themechanical shredding of the material in the"Hydrocrusher" accelerates the process. This resultsin substantially more of the biodegradable materialbeing made available for conversion into gas.

Arrow Bio uses two digesters in series. The two-vessel design provides better control of the digestionprocess with a consequential increase in efficiency.The biogas is burnt in a spark ignition engine drivinga generator. Steam could be raised in a waste heatboiler using the hot exhaust gas from the engine.

Ecodeco ProcessThe main process steps proposed for a UK facilityare: waste reception; shredding to around 200mm;forced aeration composting to give bio-drying; andfinally material separation in a MRF.

In the composting stage air is drawn through thewaste which has been heaped in a hall. The bio-decomposition generates heat, that, in turn, driesthe material to the stage where further compostingcannot proceed. Air from the hall is cleaned via abio-filter prior to release.

In the MRF facility, metals are removed and recycled,and the dense and light fractions separated. Thedense fraction normally goes to landfill. The lighterorganic and plastics fraction needs a market. It canbe further separated or processed to a specificationneeded for a particular application. Variousapplications including land remediation and use as afuel are currently under development.

Mechanical Heat Treatment

Mechanical Heat Treatment (MHT) is a relatively newterm. It is used to describe configurations ofmechanical and thermal, including steam, basedtechnologies. New waste management technologieswhich use other (higher temperature) thermaltreatment processes are dealt with in a separateBrief in this series 'Advanced Thermal Treatment'.

This section contains a discussion of the social andpublic perception considerations of MBT and MHTfacilities.

Social Considerations

Any new facility is likely to impact on the localresidents and may provide both positive andnegative impacts. Potential impacts on local amenity(odour, noise, dust, landscape) are importantconsiderations when siting any waste managementfacility. These issues are examined in more detail inthe Planning Section of this brief. Transport impactsassociated with the delivery of waste and onwardtransport of process outputs may lead to impacts onthe local road network. The Planning andPermitting section of this document provides anestimate of potential vehicle movements.

An MBT or MHT facility may also provide positivesocial impacts in the form of employmentopportunities and educational opportunities. Typicalemployment for a MBT / MHT plant of 50,000tpacapacity would be 2 - 8 persons at any one time(more if manual picking operations are used). Theplant may be operated on a shift system, forexample to allow for 24 hour operations. Thesefacilities are also likely to provide vocational trainingfor staff. Many new facilities are built with a visitorscentre to enable local groups to view the facility andlearn more about how it operates.

Public Perception

Public opinion on waste management issues is wideranging, and can often be at extreme ends of thescale. Typically, the most positively viewed wastemanagement options for MSW are recycling andcomposting. However, this is not necessarily reflectedin local attitudes towards the infrastructurecommonly required to process waste to compost, orsort mixed recyclables. It should be recognised thatthere is always likely to be some resistance to anywaste management facility within a locality.

At present there is a relatively low level ofunderstanding of the concept of MBT by the public.In public consultations these technologies scoresinconsistently when explained in detail as a residualwaste treatment technology.

Two examples of public consultations highlightingthe diversity of opinion with regard to MBT arehighlighted in Box 5.

Mechanical Heat Treatment is a more recent conceptand it is unclear as to the public perception of thisoption at present. Indeed, there is limitedinternational experience with MHT and so publicperception has yet to be fully tested. It may be that,as a mixed waste processing facility, MHT will have asimilar perception as that for MBT. Alternatively,there may be a more negative perception due to adistrust of 'thermal' based techniques.

Overall, experience in developing wastemanagement strategies has highlighted theimportance of proactive communication with thepublic over waste management options. The use ofrealistic and appropriate models, virtual 'walk -throughs' / artists impressions should be used toaccurately inform the public. Good practice in termsof public consultation and engagement is animportant aspect in gaining acceptance for planningand developing waste management infrastructure.

How it Works Social and Perception Issues

Box 3 Biological Treatment Options

Biological Treatment Key Concerns

Aerobic - Bio-drying/Biostabilisation: partialcomposting of the (usually)whole waste

See AdvancedBiological TreatmentBrief

Aerobic - In-VesselComposting: may be used toeither biostabilise the wasteor process a segregatedorganic rich fraction


Anaerobic Digestion: used toprocess an segregated organicrich fraction


Box 5 Public consultation on MBT

A public consultation in an area of Wales resultedin a clear preference that any waste that could notbe recycled or composted should be dealt withthrough MBT. Respondents felt that an MBT-ledstrategy was a positive approach for residualwaste whether it aims to achieve or exceeddiversion targets.

Conversely, a large scale public consultation in anarea of England revealed the opposite reactionwith MBT being the least favoured approach ofthe residual waste treatment options.

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Size and Landtake

Table 3 shows the land area required for thebuilding footprint and also for the entire site(including supporting site infrastructure) forMechanical Biological and Mechanical HeatTreatment facilities.

Table 3 : Landtake

a Source: Review of Residual Waste Treatment Options, 2003, AiIE

b Source: Planning for Waste Management facilities, ODPM, 2004

c Source: Waste Technology Data Centre, 2004

An average MBT plant may have a height of 10 -20m. Some facilities may also have a stack if usingparticular air clean-up systems, potentially increasingoverall height. For more information on Landtakefor specific waste management operations, seeDefra's Waste Technology Data Centre11.

Public Concern

The Social and Perception Issues section, relates topublic concern. In general public concerns aboutwaste facilities in general relate to amenity issues(odour, dust, noise, traffic, litter etc).

Environmental Impact Assessment

It is likely that an Environmental Impact Assessment(EIA) will be required for an MBT or MHT facility aspart of the planning process.

Whether a development requires a statutory EIA isdefined under the Environmental Impact Assessment(England and Wales) Regulations 1999. Furtherguidance is available in the DETR circular 02/99 onEnvironmental Impact Assessment.

For more information on Planning issues associatedwith waste management options see Planning forWaste Management Facilities - A Research Study.Office of the Deputy Prime Minister, 200412.

Licensing/Permitting

If a MBT/MHT plant processes over 50tonnes per dayit may be assumed that they will require a PollutionPrevention & Control (PPC) permit to operate, ifprocessing less than this quantity a wastemanagement license would be required. If theprocess is shown to produce a fuel (e.g. RDF) ratherthan a waste, then it would be subject to PPCirrespective of the tonnage threshold. For moreinformation on licensing & permitting see theEnviroment Agency website13.

Figure 2 below illustrates the variety of options withthe concept of MHT, which are likely to use similarmechanical preparation and separation technologiesto those described in Box 2, page 5. This is alsoillustrated by the case studies which follow.

Figure 2 : Mechanical Heat Treatment

The most common system being promoted for thetreatment of MSW using MHT is autoclaving (see Box4). This technology is in common use for thetreatment of some clinical wastes and also forcertain rendering processes for animal wastes.However its application to MSW is a recentinnovation, and there is limited commercialexperience on this feedstock material.

Different MHT systems may be configured to meetvarious objectives with regard to the waste outputsfrom the process (Figure 2). The alternatives(depending on the system employed) may be one ormore of the following:

• Separate an 'organic rich' component of thewaste for subsequent biological processing [forexample to form a low grade soil conditioner];

• produce a segregated high calorific value waste(RDF/SRF see box 1, p.3) to be applied in anappropriate process to utilise its energy potential;and

• extract materials for recycling (typically glass andmetals, potentially plastics and the 'fibrous'organic and paper fraction).


Case Studies

The following case studies illustrate examples ofMHT system and relate these to the differentmechanical preparation, separation and heattreatment techniques, previously described in Boxes2 & 4.

Fairport ProcessThis process uses conventional mechanical handlingand processing plant.

The Fairport process dries the waste to enable it tobe more efficiently separated and hence produceseveral recyclate streams. The final stage of theseparation uses the "Fairport separator". This highefficiency device results in several separations on thebasis of size and density. Fairport then blend thesefractions together with other materials to produce afuel meeting a predefined specification.

Planning and Permitting Issues How it Works

Mechanical Preparation& Heat Treatment

Reject to Landfill

Fuel Fraction(RDF)

SoilContainers

Recyclables

MSW

Box 4 Heat Treatment Options

Heat Treatment Process Key Concerns

Autoclaving - batch, steamprocessing in a vessel underthe action of pressure

Batch nature ofprocess

Continuous heat treatment ina vessel, not under the actionof pressure

Limited track record

SizeBuilding

AreaTotal

Landtake

MBT Plant Ab

MBT Plant Bc

MBT Plant Cc

MBT Plant Da

MBT Plant Ea

MHT Plant Ac

MHT Plant Ba

50,000tpa

75,000tpa

140,000tpa

180,000tpa

100,000tpa

150,000tpa

3,000m2

5,500m2

9,000m2

4,300m2

15,000m2

0.36m2/t

35,000m2

18,000m2

11www.environment-agency,gov.uk/wtd

12http://www.odpm.gov.uk/stellent/groups/odpm_planning/documents/page/odpm_plan_030747.pdf

13http://www.environment-agency.gov.uk/subjects/waste/?lang=_e

MechanicalSeparation

8 17

The energy for the drying stage is from a gas burner,this ensures that the more valuable renewableenergy in the feed is not lost from the products.

A demonstration plant has already been built andtested in Lancashire. The technology will likely bemost appropriate at the +70,000 T/yr. scale andhence serve a large town or city.

Estech ProcessThis process uses wet steam under pressure(autoclave) to clean materials, soften plastics andreduce biodegradable material into a fibre.Following the autoclaving or "cooking" process thematerials can be more easily and effectivelyseparated in a MRF.

The key process stages include waste reception andstorage, waste feeding, autoclaving, materialsseparation with recyclates recovery.

The autoclave stage is central to the process andoperates as a batch operation. After charging withwaste the autoclave drum is sealed and rotationstarted. Saturated steam at c. 160°C is injected intothe vessel and the pressure maintained at 5 bargauge for a period of up to 45 minutes to allow theprocess to fully "cook" the waste. After "cooking",the steam flow is stopped and the pressure ventedvia a condenser. The "cooked" material is dischargedand separated by a series of screens and recoverysystems. The primary product is a fibre. It isunderstood that a number of development projectsand joint ventures have been created by Estech togenerate useful markets for the fibre. Alternativelythe fibre could constitute a Refuse Derived Fuel.

The secondary streams comprise of mixed plastics, aglass and aggregate stream and separate ferrous andnon-ferrous metals. All these streams areexceptionally clean having been steam cleaned.

The full cycle of loading, treatment and sorting isnormally completed within 90 minutes.

Summary

This section illustrates that Mechanical HeatTreatment and Mechanical Biological Treatmentsystems can be described as two simple concepts:either to separate the waste and then treat; or totreat the waste and then separate. The treatmentphase may be either thermal or biological and thereare a wide variety of separation techniques.

MBT and MHT, as illustrated by the case studies,represent significant facilities, which are capitalintensive (see Costs of MBT/MHT Systems section)and are anticipated to be in operation for 15 - 20years. In this instance of emergent markets foroutputs from such processes it is prudent to ensuresufficient installed capacity for flexibility within anyplant (which may require new equipment, etc) toadapt to the needs of the market.

Flies, Vermin and Birds

MBT and MHT processing is unlikely to attractvermin and birds due to majority of wastethroughput and operations being completelyenclosed in buildings. However, during hot weatherit is possible that flies could accumulate, especially ifthey have been brought in during delivery of thewaste. Effective housekeeping and on sitemanagement of tipping and storage areas isessential to minimise the risk from vermin and otherpests. In some operations waste heat from theprocess may be used in fresh input waste to bringtemperatures to levels above which flies can live.Similarly, waste storage in some MBT plant isdesigned to be less that the breeding cycle of verminsuch as rats.

Noise

Noise is an issue that will be controlled under thewaste licensing regulations. The main contributors tonoise associated with MBT/MHT are likely to be:

• vehicle movements/manoeuvring;

• traffic noise on the local road networks;

• mechanical processing such as shredders, screens,trommels and ball mills; and

• air extraction fans and ventilation systems.

Litter

Any waste which contains plastics and paper aremore likely to lead to litter problems. With MBT /MHT as long as good working practices are adheredto and vehicles use covers and reception andprocessing are undertaken indoors, litter problemscan be minimised.

Water Resources

Pollution to water is unlikely due to MBT facilitiesbeing under cover and rainfall is unlikely to comeinto contact with the process. Even so, any washdown waters or liquid within the waste will need tobe managed using a drainage system on site. Somewater is likely to be used in MHT processes. This isoften cited as being reused within the process, butagain such process water will need to be managed.

The case studies on the Waste Technology DataCentre include an assessment of water usage.

Visual Intrusion

Construction of any building will have an effect onthe visual landscape of an area. Visual intrusionissues should be dealt with on a site specific basisand the following items should be considered:

• Direct effect on landscape by removal of itemssuch as trees or undertaking major earthworks;

• Site setting; is the site close to listed buildings,conservation areas or sensitive viewpoints;

• Existing large buildings and structures in the area;

• The potential of a stack associated with some airclean up systems for mixed waste processingoperations may impact on visual intrusion;

• Use of screening features (trees, hedges, banksetc); and

• The number of vehicles accessing the site andtheir frequency.

Most of these facilities are housed in 'warehouse'type clad steel buildings.

External view of MBT facility

How it Works Planning and Permitting Issues

16 9

This section contains information on the planningand regulatory issues associated with MBT/MHTfacilities based on case studies of existing facilitiesand information on planning from the Office of theDeputy Prime Minister research report.

Planning

When considering the planning implications for anMBT/MHT facility the following issues have beenconsidered:

• Plant/Facility Siting;

• Traffic;

• Air Emissions/Health Effects;

• Dust/Odour;

• Flies, Vermin and Birds;

• Noise;

• Litter;

• Water Resources;

• Visual Intrusion; and

• Public Concern.

Some of these criteria are discussed elsewhere in thisguide but a brief overview of each is provided here.

Plant Siting

Mixed waste processing (such as MBT and MHT) cantake place in many different buildings at a variety oflocations but the following considerations should bemade:

• Preference should be given to industrial ordegraded sites or sited close to or with existingwaste management facilities;

• General concerns about bio-aerosols frombiological processing may require an MBT site tobe located at least 250m from any sensitivereceptors; and

• The site chosen should be close to the PrimaryRoad Network, especially if it is to be a largescale/centralised facility where the site should beappropriate for the movement of HGV trafficwithout major restriction.

Traffic

Centralised waste facilities will most likely be servedby large numbers of HGVs with a potential impacton local roads and the amenity of local residents. Itis likely that the site layout/road configuration willneed to be suitable to accept a range of light andheavy vehicles. Mixed waste processing operationsare designed to split a mixed waste stream into anumber of individual streams some of which are lowtonnage or low bulk density. As a result trafficimplications may be greater than initially considered.

The traffic movements anticipated from a 50,000tpaplant would be 20 - 30 refuse collection vehicles perday. This would be reduced if bulk transport systemsare used.

Air Emissions/Health Effects

Air emissions and health impacts for this type offacility are most likely to be linked to trafficmovements and potentially bio-aerosols frombiological processing. Although there is not muchexperience of this type of technology in the UKthere is extensive work which can be drawn uponabout biological processing which could be used inplanning applications.

Progress has been made in Europe towards thermalemissions clean-up using 850°C for two seconds.Other systems use biofilters to clean up emissions.For more details see the case studies and the WasteTechnology Data Centre (www.environment-agency.gov.uk/wtd).

Dust/Odour

Any waste management operations can give rise todust and odours. These can be minimised by goodbuilding design, performing all operations undercontrolled conditions indoors and good workingpractices and effective management undertaken fordust suppression from vehicle movements. Manymixed waste processing operations such as MBT andMHT operate under negative pressure withinbuildings with air passed through an emissions cleanup process.

In the UK, at present, the market for many of theoutputs from MBT and MHT does not exist.Considerable effort is being undertaken by a numberof organisations and individuals to change thissituation. Plants being specified today will need toprovide materials into an as yet undevelopedmarket. Clearly it is prudent to design for, or at leastmaintain the option of creating, flexibility in thedegree and type of materials separation that anyproposed plant can achieve.

The following section summarises some key issueswith regard to the outlets for outputs derived fromMBT and MHT processing of MSW.

Recovery from MBT

Attention needs to be paid to the quality ofrecovered materials arising from MBT processes.Certain technologies have the ability to achieveexceedingly clean materials, others do not (see casestudies and the Waste Technology Data Centre).

When considering quantities and quality ofrecovered materials it is important that any massbalance accurately reflects the nature of materialsfed into the plant.

Materials Recycling Recyclables derived from the various MBT processesare typically of a lower quality than those derivedfrom a separate household recyclate collectionsystem and therefore have a lower potential for highvalue markets. The types of materials recovered fromMBT processes almost always include metals (ferrousand non-ferrous) and for many systems this is theonly recyclate extracted. However these plant canhelp enhance overall recycling levels and enablerecovery of certain constituent items that would nototherwise be collected in household systems (e.g.steel coat hangers, paper clips etc.).

Other materials which may be extracted from MBTprocesses include glass, textiles, paper/card, andplastics.

The most common of these is glass, which may besegregated with other inert materials such as stones,for use as a low grade aggregate. The extent of glassrecovery is enhanced by the nature of any wastepreparation process (see Box 2, page 5).

Textiles, paper and plastics, if extracted, are unlikelyto receive a significant income as a recyclate and insome instances may not yield a positive value. Mostof these plant can experience problems with theheavier textiles such as carpets. Clearly none are likelyto separate textiles into different types of fibre.

Paper is unlikely to be segregated in isolation ofsome textiles, plastic film, etc. unless hand-picked.

The plastics separated from these processes willalmost always be mixed plastics, whilst thetechnology is available to separate individual plastictypes it is expensive and unlikely to be applied tomost MBT processes. Whilst markets are beingdeveloped for mixed plastics, these applications arelimited at present.

For more information on the contribution of MBT toBest Value Performance Indicators and recycling seepage 21 and for the latest developments, see theBVPI website http://www.defra.gov.uk/environment/waste/localauth/index.htm or contact the SupporterHelpline tel. 0870 2409894 [email protected]

Soil ConditionersThe mechanically separated organic fraction frommixed waste streams will typically represent a lowervalue output than that from source segregatedorganic materials. This is largely due to the highinclusion of non-biodegradable material likely to bepresent in compostable materials from mixed wastestreams. This will also limit the potential applicationsof the material.

It should be noted that many of the aerobic MBTprocesses are designed for bio-drying and not bio-stabilisation as required by compost/soil conditioner,therefore further biological processing of thesewastes would be required prior to any use on land.

Planning and Permitting Issues Markets for the Outputs

10 15

The output from this type of process is expected tobe a low grade soil conditioner which may beutilised in applications such as landfill restoration orsome engineering end uses (provided that theappropriate biological, quality and aestheticstandards are achieved).

These markets are traditionally low value andmaterials may be in competition with other moretraditional soil improvers such as sewage sludge,poultry waste or source segregated green wastederived compost. There is also the issue of gainingthe confidence of the market in terms of the qualityof the product.

Additionally, the process used to develop these soilconditioners will need to comply with the Animal By-Products Regulations in order for the materials to beused on land. Furthermore, at present, low grade soilconditioners generated by MBT plants require awaste management license, or an exemption fromlicensing, if they are to be spread on land. Thecurrent status for these materials (EA Feb. 2005) isthat unless an exemption is granted, the materialwill not be classified as having been diverted fromlandfill, and therefore may count (if not bio-stabilised) against Landfill Allowances.

For more information on Animal By Products andoutlets for the organic outputs from MBT, see theAdvanced Biological Treatment Waste ManagementTechnology Brief, as part of this series and the StateVeterinary Service2.

For more information on the contribution of MBT toBest Value Performance Indicators and compostingsee page 21 and for the latest developments, see theBVPI website3 or contact the Supporter Helpline tel.0870 2409894 [email protected]

Materials Recovered for Energy Where the MSW is sorted/treated to produce a highcalorific value waste stream comprising significantproportions of the available combustible materials suchas mixed paper, plastics and card, this stream may beknown as Refuse Derived Fuel (RDF - see Box 1, p.3).

There are a number of dedicated conventionalcombustion plant that use RDF as a fuel to generateelectricity (see Table 1). This type of fuel that wouldalso be appropriate for a Fluidised-Bed energy fromwaste plant (which requires a prepared wastefeedstock for the combustion process).

Table 1 : Conventional technology plant generatingelectricity from RDF

RDF may also be utilised within some AdvancedThermal Treatment (ATT) processes. An appropriatelyscaled, dedicated ATT plant could represent a part ofan integrated strategy in combination with MBT. Aseparate Waste Management Technology Brief, inthis series, is available on the subject of ATTprocesses. Please also see page 22, Renewables, forextra information.

The energy use incurred in the separation of wastetypically involves around 15 - 20% of the energy valueof the waste. If the RDF is to be used as an energysource, to establish any environmental benefit asopposed to combusting the waste in a mass burnEnergy from Waste plant, then either: a highefficiency Advanced Thermal Treatment process needsto be used, or; the RDF needs to be used as areplacement fuel, for example for fossil fuels. Not allATT processes will offer the efficiencies appropriate.

Before initiating any procurement or funding processfor a new waste management treatment facility, thefollowing issues should be considered: performancerequirements; waste inputs; project duration; projectcost; available budgets; availability of sites; planningstatus; interface with existing contracts; timescales;governance and decision making arrangements;market appetite and risk allocation.

Further guidance on these issues can be obtainedfrom:

Procurement Toolkit7

For Works Contracts: the Institution of CivilEngineers 'New Engineering Contract'8

For large scale Waste Services Contracts throughPFI AND following the Negotiated Procedures the4ps 'Waste Procurement Pack'9

The Local Government PFI project support guide10

Markets for the Outputs Contractual and Financing Issues

RDFCombustion

plantOperator

Ktonnes/

year

NetCapacity

(MW)

Pebsham

Neath PortTalbot (currentlynot operational)

Utilised bySlough Heat& Power

HLC

75

135

2.5

8.2

7 http://lasupport.defra.gov.uk/Default.aspx?Menu=Menu&Module=Article&ArticleID=102

8 available at www.ice.org.uk

9 available at www.4ps.gov.uk

10 www.local.odpm.gov.uk/pfi/grantcond.pdf2 www.defra.gov.uk/animalh/by-prods/default.htm

3 http://www.defra.gov.uk/ environment/waste/localauth/index.htm

1411

Grants & Funding

Development of MBT and MHT plant will involvecapital expenditure of several million pounds. Thereare a number of potential funding sources for LocalAuthorities planning to develop such facilities,including:

Capital Grants: general grants may be availablefrom national economic initiatives and EUstructural funds;

Prudential Borrowing: the Local GovernmentAct 2003 provides for a new 'prudential' systemof capital finance controls;

PFI Credits and Private Sector Financing:under the Private Finance Initiative a wasteauthority can obtain an annual subsidy fromcentral government through a Special Grant;

Other Private-Sector Financing: A contractormay be willing to enter a contract to provide anew facility and operate it. The contractor'scharges for this may be expressed as gate fees; and

Existing sources of local authority funding:for example National Non-Domestic Ratepayments (distributed by central government),credit (borrowing) approvals, local tax raisingpowers (council tax), income from rents, fees,charges and asset sales (capital receipts). Inpractice capacity for this will be limited.

Contractual Arrangements

Medium and large scale municipal wastemanagement contracts are usually procured throughthe negotiated procedure of the OJEU process.

The available contractual arrangement between theprivate sector provider (PSP) and the waste disposalauthority (or partnership) may be one of thefollowing:

Separate Design; Build; Operate; andFinance:The waste authority contracts separatelyfor the works and services needed, and providesfunding by raising capital for each of the maincontracts. The contract to build the facility wouldbe based on the council's design and specificationand the council would own the facility onceconstructed;

Design & Build; Operate; Finance: A contract islet for the private sector to provide both thedesign and construction of a facility to specifiedperformance requirements. The waste authorityowns the facility that is constructed and makesseparate arrangements to raise capital. Operationwould be arranged through a separate Operationand Maintenance contract;

Design, Build and Operate; Finance: TheDesign and Build and Operation and Maintenancecontracts are combined. The waste authorityowns the facility once constructed and makesseparate arrangements to raise capital;

Design, Build, Finance and Operate (DBFO):This contract is a Design and Build and Operatebut the contractor also provides the financing ofthe project. The contractor designs, constructsand operates the plant to agreed performancerequirements. Regular performance paymentsare made over a fixed term to recover capital andfinancing costs, operating and maintenanceexpenses, plus a reasonable return. At the end ofthe contract, the facility is usually transferredback to the client in a specified condition; and

DBFO with PFI: This is a Design, Build, Financeand Operate contract, but it is procured underthe Private Finance Initiative. In this case thewaste authority obtains funding for futurepayment obligations from Government as asupplement to finance from its own and privatesector sources.

The majority of large scale waste managementcontracts currently being procured in England areDesign, Build, Finance and Operate contracts andmany waste disposal authorities in two tier Englisharrangements (County Councils) are currentlyseeking to partner with their Waste CollectionAuthorities (usually District or Borough Councils).Sometimes partnerships are also formed withneighbouring Unitary Authorities to maximise theefficiency of the waste management service andmake the contract more attractive to the PrivateSector Provider.

Refuse Derived Fuel

The other option for RDF is to co-combust with otherfuels, such as coal, in power generation, cementproduction or other large thermal processes. Theadvantage of this option is that the infrastructuremay already be in place; a disadvantage is that theoutlet for the fuel is subject to obtaining a contractof sufficient duration and tonnage, with acommercial partner.

The co-combustion of RDF is an emerging market. Itis currently anticipated that cement kilns provide themajority of potential capacity for using RDF, giventhe current political, regulatory and commercialenvironment. It is estimated that the British cementindustry will be able to utilise up to 500,000 tonnesper annum of RDF or other packaging waste. Thereis however, competition from other wastes to beprocessed within the cement production processincluding tyres, some hazardous wastes, secondaryliquid fuels etc.

Consequently it is expected that there may becompetition (and competitive gate fees) foracceptance of RDF at cement kilns. Emphasis shouldbe put on developing sustainable markets formaterials.

As an emerging market there are also potential risksin terms of the operations of large thermal facilitiesaccepting RDF from mixed waste processing as a fuelsource. However, waste contractors are developingrelationships with the cement industry to try andmeet their specifications and provide a usefulindustrial fuel and waste recovery operation.

RDF is currently classified as a waste and thereforeany facility using the fuel will be subject to therequirements of the Waste Incineration Directive.None of the RDF material can be processed in any ofthe UK coal fired power stations if the WasteIncineration Directive is deemed to be applicable.

The processing of waste to generate electricity will,in certain circumstances, be eligible for aGovernment incentive for renewable energyproduction. The incentive scheme is known as theRenewables Obligation Order and the sale ofelectricity derived from these processes could qualifyfor Renewables Obligation Certificates (or ROCs)thereby securing a premium price for electricity sales.RDF does not currently qualify for ROCs unless it isused in 'advanced conversion technologies',including pyrolysis or gasification plant (see theAdvanced Thermal Treatment Brief). TheRenewables Obligation Order is due to be consultedupon this year (2005) for possible revisions to thesystem. Up-to-date information regarding RDF andROCs can be obtained from the DTI website4 or theNew Technologies Supporter Helpline tel. 08702409894 [email protected].

For more information on the contribution of MBT toBest Value Performance Indicators see page 21 andfor the latest developments, see the BVPI website5 orcontact the Supporter Helpline tel. 0870 [email protected]

Recovery from MHT

Materials RecyclingGlass and metals derived from some MHT processeshave the potential to be significantly cleaner thanthose from MBT processes due to the action of steamcleaning, which removes glues and labels. Otherrecyclables such as plastics may also be extractedfrom some systems; however certain plastic materialsmay also be deformed by the heat of the process,potentially making them more or less difficult torecycle in some instances.

An emerging area of potential recycling from someMHT systems is the use of the separated cellulosefibrous material which may be a by-product of theprocess.

Contractual and Financing Issues Markets for the Outputs

4 http://www.dti.gov.uk/energy/renewables/


12 13

This fibre may be used as a raw material in recycledproducts, biologically processed for use as a lowgrade soil conditioner, as a bio-stabilised residue fordisposal, or utilised for its combustible properties asa fuel (see below).

Work is being undertaken to evaluate use of thefibre as a raw material for example by mixing thefibre together with crushed shale and a resin tomanufacture products (e.g. composite such as floortiles). The market for recycled products made withfibre from MHT processes is under development atpresent.

For more information on the contribution of MHT toBest Value Performance Indicators and recycling seepage 21 and for the latest developments, see theBVPI website6 or contact the Supporter Helpline tel.0870 2409894 [email protected]

Materials Recovery for Energy Some MHT systems are configured to produce RDF(or alternatives, see Box 1, page 3) for combustion inanother process, as described under MBT. The samemarket issues are anticipated for this output as forthe equivalent MBT output. However some systemsare designed to process RDF to a particular fuelspecification tailored to a specific market demand.For more detail on RDF markets refer to the MBTsection above. The fibre produced by an MHT plantwill have different characteristics to an RDFproduced by an MBT plant and this may affect theoperational requirements for this material.

For more information on the contribution of MHT toBest Value Performance Indicators and recovery seepage 22 and for the latest developments, see theBVPI website6 or contact the Supporter Helpline tel.0870 2409894 [email protected]


The concept of MBT originated in Germany where itis an established waste treatment method.Regulatory restrictions on landfill space, the searchfor alternatives to incineration / Energy from Waste,and increased costs of landfill disposal have been themajor drivers for the development of thesetechnologies. The largest European markets forestablished MBT plant include Germany, Austria,Italy, Switzerland and the Netherlands, with otherssuch as the UK growing fast. Furthermore, othercountries outside Europe are also using thistechnology.

Since the early 1990s, MBT processes have changedsignificantly, so today, numerous configurations ofplant have developed, and these are provided by avariety of companies.

There are over 70 MBT facilities in operation inEurope, with over 40 MBT facilities operating inGermany. However, not all of these facilities arecommercial and some of those included in Table 2include pilot and demonstration plants.


The concept of Mechanical Heat Treatment is newfor MSW and therefore most of the operationalexperience is based on small scale or mobiledemonstration plant. There is due to be a 70,000tpaMHT plant operating on MSW in Minnesota fromCR3 Inc.

Table 2 : Examples of MBT plant operational in Europe

Markets for the Outputs Track Record

Technology Provider Country No of Plants

Hese Umwelt

EcoDeco

Cambridge RecyclingServices Ltd

Civic EnvironmentalSystems

Sutco

Electrowatt-Ekono

Herhof

Dranco

ISKA

Horstmann

Wehrle Werk

BTA

BTA

Dranco

Ionics Itabila

Snamprogetti

Valorga

EcoDeco

Herhof

Valorga

Linde

Dranco

BTA/Roediger

Citec

Citec/Vagron

Valorga

Valorga

Vagron

Dranco

Dranco

VKW

VKW

VKW

UK

UK

UK

UK

Germany

Germany

Germany

Germany

Germany

Germany

Germany

Germany

Italy

Italy

Italy

Italy

Italy

Italy

Italy

Spain

Spain

Spain

Poland

Finland

Holland

Belgium

France

Netherlands

Switzerland

Austria

Austria

Italy

Turkey

1

1

1

1

5

1

3

2

1

4

1

1

1

1

1

1

1

4

1

2

1

1

1

1

1

1

2

1

1

1

1

1

1


12 13

This fibre may be used as a raw material in recycledproducts, biologically processed for use as a lowgrade soil conditioner, as a bio-stabilised residue fordisposal, or utilised for its combustible properties asa fuel (see below).

Work is being undertaken to evaluate use of thefibre as a raw material for example by mixing thefibre together with crushed shale and a resin tomanufacture products (e.g. composite such as floortiles). The market for recycled products made withfibre from MHT processes is under development atpresent.

For more information on the contribution of MHT toBest Value Performance Indicators and recycling seepage 21 and for the latest developments, see theBVPI website6 or contact the Supporter Helpline tel.0870 2409894 [email protected]

Materials Recovery for Energy Some MHT systems are configured to produce RDF(or alternatives, see Box 1, page 3) for combustion inanother process, as described under MBT. The samemarket issues are anticipated for this output as forthe equivalent MBT output. However some systemsare designed to process RDF to a particular fuelspecification tailored to a specific market demand.For more detail on RDF markets refer to the MBTsection above. The fibre produced by an MHT plantwill have different characteristics to an RDFproduced by an MBT plant and this may affect theoperational requirements for this material.

For more information on the contribution of MHT toBest Value Performance Indicators and recovery seepage 22 and for the latest developments, see theBVPI website6 or contact the Supporter Helpline tel.0870 2409894 [email protected]


The concept of MBT originated in Germany where itis an established waste treatment method.Regulatory restrictions on landfill space, the searchfor alternatives to incineration / Energy from Waste,and increased costs of landfill disposal have been themajor drivers for the development of thesetechnologies. The largest European markets forestablished MBT plant include Germany, Austria,Italy, Switzerland and the Netherlands, with otherssuch as the UK growing fast. Furthermore, othercountries outside Europe are also using thistechnology.

Since the early 1990s, MBT processes have changedsignificantly, so today, numerous configurations ofplant have developed, and these are provided by avariety of companies.

There are over 70 MBT facilities in operation inEurope, with over 40 MBT facilities operating inGermany. However, not all of these facilities arecommercial and some of those included in Table 2include pilot and demonstration plants.


The concept of Mechanical Heat Treatment is newfor MSW and therefore most of the operationalexperience is based on small scale or mobiledemonstration plant. There is due to be a 70,000tpaMHT plant operating on MSW in Minnesota fromCR3 Inc.

Table 2 : Examples of MBT plant operational in Europe

Markets for the Outputs Track Record

Technology Provider Country No of Plants

Hese Umwelt

EcoDeco

Cambridge RecyclingServices Ltd

Civic EnvironmentalSystems

Sutco

Electrowatt-Ekono

Herhof

Dranco

ISKA

Horstmann

Wehrle Werk

BTA

BTA

Dranco

Ionics Itabila

Snamprogetti

Valorga

EcoDeco

Herhof

Valorga

Linde

Dranco

BTA/Roediger

Citec

Citec/Vagron

Valorga

Valorga

Vagron

Dranco

Dranco

VKW

VKW

VKW

UK

UK

UK

UK

Germany

Germany

Germany

Germany

Germany

Germany

Germany

Germany

Italy

Italy

Italy

Italy

Italy

Italy

Italy

Spain

Spain

Spain

Poland

Finland

Holland

Belgium

France

Netherlands

Switzerland

Austria

Austria

Italy

Turkey

1

1

1

1

5

1

3

2

1

4

1

1

1

1

1

1

1

4

1

2

1

1

1

1

1

1

2

1

1

1

1

1

1


1411

Grants & Funding

Development of MBT and MHT plant will involvecapital expenditure of several million pounds. Thereare a number of potential funding sources for LocalAuthorities planning to develop such facilities,including:

Capital Grants: general grants may be availablefrom national economic initiatives and EUstructural funds;

Prudential Borrowing: the Local GovernmentAct 2003 provides for a new 'prudential' systemof capital finance controls;

PFI Credits and Private Sector Financing:under the Private Finance Initiative a wasteauthority can obtain an annual subsidy fromcentral government through a Special Grant;

Other Private-Sector Financing: A contractormay be willing to enter a contract to provide anew facility and operate it. The contractor'scharges for this may be expressed as gate fees; and

Existing sources of local authority funding:for example National Non-Domestic Ratepayments (distributed by central government),credit (borrowing) approvals, local tax raisingpowers (council tax), income from rents, fees,charges and asset sales (capital receipts). Inpractice capacity for this will be limited.

Contractual Arrangements

Medium and large scale municipal wastemanagement contracts are usually procured throughthe negotiated procedure of the OJEU process.

The available contractual arrangement between theprivate sector provider (PSP) and the waste disposalauthority (or partnership) may be one of thefollowing:

Separate Design; Build; Operate; andFinance:The waste authority contracts separatelyfor the works and services needed, and providesfunding by raising capital for each of the maincontracts. The contract to build the facility wouldbe based on the council's design and specificationand the council would own the facility onceconstructed;

Design & Build; Operate; Finance: A contract islet for the private sector to provide both thedesign and construction of a facility to specifiedperformance requirements. The waste authorityowns the facility that is constructed and makesseparate arrangements to raise capital. Operationwould be arranged through a separate Operationand Maintenance contract;

Design, Build and Operate; Finance: TheDesign and Build and Operation and Maintenancecontracts are combined. The waste authorityowns the facility once constructed and makesseparate arrangements to raise capital;

Design, Build, Finance and Operate (DBFO):This contract is a Design and Build and Operatebut the contractor also provides the financing ofthe project. The contractor designs, constructsand operates the plant to agreed performancerequirements. Regular performance paymentsare made over a fixed term to recover capital andfinancing costs, operating and maintenanceexpenses, plus a reasonable return. At the end ofthe contract, the facility is usually transferredback to the client in a specified condition; and

DBFO with PFI: This is a Design, Build, Financeand Operate contract, but it is procured underthe Private Finance Initiative. In this case thewaste authority obtains funding for futurepayment obligations from Government as asupplement to finance from its own and privatesector sources.

The majority of large scale waste managementcontracts currently being procured in England areDesign, Build, Finance and Operate contracts andmany waste disposal authorities in two tier Englisharrangements (County Councils) are currentlyseeking to partner with their Waste CollectionAuthorities (usually District or Borough Councils).Sometimes partnerships are also formed withneighbouring Unitary Authorities to maximise theefficiency of the waste management service andmake the contract more attractive to the PrivateSector Provider.

Refuse Derived Fuel

The other option for RDF is to co-combust with otherfuels, such as coal, in power generation, cementproduction or other large thermal processes. Theadvantage of this option is that the infrastructuremay already be in place; a disadvantage is that theoutlet for the fuel is subject to obtaining a contractof sufficient duration and tonnage, with acommercial partner.

The co-combustion of RDF is an emerging market. Itis currently anticipated that cement kilns provide themajority of potential capacity for using RDF, giventhe current political, regulatory and commercialenvironment. It is estimated that the British cementindustry will be able to utilise up to 500,000 tonnesper annum of RDF or other packaging waste. Thereis however, competition from other wastes to beprocessed within the cement production processincluding tyres, some hazardous wastes, secondaryliquid fuels etc.

Consequently it is expected that there may becompetition (and competitive gate fees) foracceptance of RDF at cement kilns. Emphasis shouldbe put on developing sustainable markets formaterials.

As an emerging market there are also potential risksin terms of the operations of large thermal facilitiesaccepting RDF from mixed waste processing as a fuelsource. However, waste contractors are developingrelationships with the cement industry to try andmeet their specifications and provide a usefulindustrial fuel and waste recovery operation.

RDF is currently classified as a waste and thereforeany facility using the fuel will be subject to therequirements of the Waste Incineration Directive.None of the RDF material can be processed in any ofthe UK coal fired power stations if the WasteIncineration Directive is deemed to be applicable.

The processing of waste to generate electricity will,in certain circumstances, be eligible for aGovernment incentive for renewable energyproduction. The incentive scheme is known as theRenewables Obligation Order and the sale ofelectricity derived from these processes could qualifyfor Renewables Obligation Certificates (or ROCs)thereby securing a premium price for electricity sales.RDF does not currently qualify for ROCs unless it isused in 'advanced conversion technologies',including pyrolysis or gasification plant (see theAdvanced Thermal Treatment Brief). TheRenewables Obligation Order is due to be consultedupon this year (2005) for possible revisions to thesystem. Up-to-date information regarding RDF andROCs can be obtained from the DTI website4 or theNew Technologies Supporter Helpline tel. 08702409894 [email protected].

For more information on the contribution of MBT toBest Value Performance Indicators see page 21 andfor the latest developments, see the BVPI website5 orcontact the Supporter Helpline tel. 0870 [email protected]

Recovery from MHT

Materials RecyclingGlass and metals derived from some MHT processeshave the potential to be significantly cleaner thanthose from MBT processes due to the action of steamcleaning, which removes glues and labels. Otherrecyclables such as plastics may also be extractedfrom some systems; however certain plastic materialsmay also be deformed by the heat of the process,potentially making them more or less difficult torecycle in some instances.

An emerging area of potential recycling from someMHT systems is the use of the separated cellulosefibrous material which may be a by-product of theprocess.

Contractual and Financing Issues Markets for the Outputs

4 http://www.dti.gov.uk/energy/renewables/


10 15

The output from this type of process is expected tobe a low grade soil conditioner which may beutilised in applications such as landfill restoration orsome engineering end uses (provided that theappropriate biological, quality and aestheticstandards are achieved).

These markets are traditionally low value andmaterials may be in competition with other moretraditional soil improvers such as sewage sludge,poultry waste or source segregated green wastederived compost. There is also the issue of gainingthe confidence of the market in terms of the qualityof the product.

Additionally, the process used to develop these soilconditioners will need to comply with the Animal By-Products Regulations in order for the materials to beused on land. Furthermore, at present, low grade soilconditioners generated by MBT plants require awaste management license, or an exemption fromlicensing, if they are to be spread on land. Thecurrent status for these materials (EA Feb. 2005) isthat unless an exemption is granted, the materialwill not be classified as having been diverted fromlandfill, and therefore may count (if not bio-stabilised) against Landfill Allowances.

For more information on Animal By Products andoutlets for the organic outputs from MBT, see theAdvanced Biological Treatment Waste ManagementTechnology Brief, as part of this series and the StateVeterinary Service2.

For more information on the contribution of MBT toBest Value Performance Indicators and compostingsee page 21 and for the latest developments, see theBVPI website3 or contact the Supporter Helpline tel.0870 2409894 [email protected]

Materials Recovered for Energy Where the MSW is sorted/treated to produce a highcalorific value waste stream comprising significantproportions of the available combustible materials suchas mixed paper, plastics and card, this stream may beknown as Refuse Derived Fuel (RDF - see Box 1, p.3).

There are a number of dedicated conventionalcombustion plant that use RDF as a fuel to generateelectricity (see Table 1). This type of fuel that wouldalso be appropriate for a Fluidised-Bed energy fromwaste plant (which requires a prepared wastefeedstock for the combustion process).

Table 1 : Conventional technology plant generatingelectricity from RDF

RDF may also be utilised within some AdvancedThermal Treatment (ATT) processes. An appropriatelyscaled, dedicated ATT plant could represent a part ofan integrated strategy in combination with MBT. Aseparate Waste Management Technology Brief, inthis series, is available on the subject of ATTprocesses. Please also see page 22, Renewables, forextra information.

The energy use incurred in the separation of wastetypically involves around 15 - 20% of the energy valueof the waste. If the RDF is to be used as an energysource, to establish any environmental benefit asopposed to combusting the waste in a mass burnEnergy from Waste plant, then either: a highefficiency Advanced Thermal Treatment process needsto be used, or; the RDF needs to be used as areplacement fuel, for example for fossil fuels. Not allATT processes will offer the efficiencies appropriate.

Before initiating any procurement or funding processfor a new waste management treatment facility, thefollowing issues should be considered: performancerequirements; waste inputs; project duration; projectcost; available budgets; availability of sites; planningstatus; interface with existing contracts; timescales;governance and decision making arrangements;market appetite and risk allocation.

Further guidance on these issues can be obtainedfrom:

Procurement Toolkit7

For Works Contracts: the Institution of CivilEngineers 'New Engineering Contract'8

For large scale Waste Services Contracts throughPFI AND following the Negotiated Procedures the4ps 'Waste Procurement Pack'9

The Local Government PFI project support guide10

Markets for the Ouputs Contractual and Financing Issues

RDFCombustion

plantOperator

Ktonnes/

year

NetCapacity

(MW)

Pebsham

Neath PortTalbot (currentlynot operational)

Utilised bySlough Heat& Power

HLC

75

135

2.5

8.2

7 http://lasupport.defra.gov.uk/Default.aspx?Menu=Menu&Module=Article&ArticleID=102

8 available at www.ice.org.uk

9 available at www.4ps.gov.uk

10 www.local.odpm.gov.uk/pfi/grantcond.pdf2 www.defra.gov.uk/animalh/by-prods/default.htm

3 http://www.defra.gov.uk/ environment/waste/localauth/index.htm

16 9

This section contains information on the planningand regulatory issues associated with MBT/MHTfacilities based on case studies of existing facilitiesand information on planning from the Office of theDeputy Prime Minister research report.

Planning

When considering the planning implications for anMBT/MHT facility the following issues have beenconsidered:

• Plant/Facility Siting;

• Traffic;

• Air Emissions/Health Effects;

• Dust/Odour;

• Flies, Vermin and Birds;

• Noise;

• Litter;

• Water Resources;

• Visual Intrusion; and

• Public Concern.

Some of these criteria are discussed elsewhere in thisguide but a brief overview of each is provided here.

Plant Siting

Mixed waste processing (such as MBT and MHT) cantake place in many different buildings at a variety oflocations but the following considerations should bemade:

• Preference should be given to industrial ordegraded sites or sited close to or with existingwaste management facilities;

• General concerns about bio-aerosols frombiological processing may require an MBT site tobe located at least 250m from any sensitivereceptors; and

• The site chosen should be close to the PrimaryRoad Network, especially if it is to be a largescale/centralised facility where the site should beappropriate for the movement of HGV trafficwithout major restriction.

Traffic

Centralised waste facilities will most likely be servedby large numbers of HGVs with a potential impacton local roads and the amenity of local residents. Itis likely that the site layout/road configuration willneed to be suitable to accept a range of light andheavy vehicles. Mixed waste processing operationsare designed to split a mixed waste stream into anumber of individual streams some of which are lowtonnage or low bulk density. As a result trafficimplications may be greater than initially considered.

The traffic movements anticipated from a 50,000tpaplant would be 20 - 30 refuse collection vehicles perday. This would be reduced if bulk transport systemsare used.

Air Emissions/Health Effects

Air emissions and health impacts for this type offacility are most likely to be linked to trafficmovements and potentially bio-aerosols frombiological processing. Although there is not muchexperience of this type of technology in the UKthere is extensive work which can be drawn uponabout biological processing which could be used inplanning applications.

Progress has been made in Europe towards thermalemissions clean-up using 850°C for two seconds.Other systems use biofilters to clean up emissions.For more details see the case studies and the WasteTechnology Data Centre (www.environment-agency.gov.uk/wtd).

Dust/Odour

Any waste management operations can give rise todust and odours. These can be minimised by goodbuilding design, performing all operations undercontrolled conditions indoors and good workingpractices and effective management undertaken fordust suppression from vehicle movements. Manymixed waste processing operations such as MBT andMHT operate under negative pressure withinbuildings with air passed through an emissions cleanup process.

In the UK, at present, the market for many of theoutputs from MBT and MHT does not exist.Considerable effort is being undertaken by a numberof organisations and individuals to change thissituation. Plants being specified today will need toprovide materials into an as yet undevelopedmarket. Clearly it is prudent to design for, or at leastmaintain the option of creating, flexibility in thedegree and type of materials separation that anyproposed plant can achieve.

The following section summarises some key issueswith regard to the outlets for outputs derived fromMBT and MHT processing of MSW.

Recovery from MBT

Attention needs to be paid to the quality ofrecovered materials arising from MBT processes.Certain technologies have the ability to achieveexceedingly clean materials, others do not (see casestudies and the Waste Technology Data Centre).

When considering quantities and quality ofrecovered materials it is important that any massbalance accurately reflects the nature of materialsfed into the plant.

Materials Recycling Recyclables derived from the various MBT processesare typically of a lower quality than those derivedfrom a separate household recyclate collectionsystem and therefore have a lower potential for highvalue markets. The types of materials recovered fromMBT processes almost always include metals (ferrousand non-ferrous) and for many systems this is theonly recyclate extracted. However these plant canhelp enhance overall recycling levels and enablerecovery of certain constituent items that would nototherwise be collected in household systems (e.g.steel coat hangers, paper clips etc.).

Other materials which may be extracted from MBTprocesses include glass, textiles, paper/card, andplastics.

The most common of these is glass, which may besegregated with other inert materials such as stones,for use as a low grade aggregate. The extent of glassrecovery is enhanced by the nature of any wastepreparation process (see Box 2, page 5).

Textiles, paper and plastics, if extracted, are unlikelyto receive a significant income as a recyclate and insome instances may not yield a positive value. Mostof these plant can experience problems with theheavier textiles such as carpets. Clearly none are likelyto separate textiles into different types of fibre.

Paper is unlikely to be segregated in isolation ofsome textiles, plastic film, etc. unless hand-picked.

The plastics separated from these processes willalmost always be mixed plastics, whilst thetechnology is available to separate individual plastictypes it is expensive and unlikely to be applied tomost MBT processes. Whilst markets are beingdeveloped for mixed plastics, these applications arelimited at present.

For more information on the contribution of MBT toBest Value Performance Indicators and recycling seepage 21 and for the latest developments, see theBVPI website http://www.defra.gov.uk/environment/waste/localauth/index.htm or contact the SupporterHelpline tel. 0870 2409894 [email protected]

Soil ConditionersThe mechanically separated organic fraction frommixed waste streams will typically represent a lowervalue output than that from source segregatedorganic materials. This is largely due to the highinclusion of non-biodegradable material likely to bepresent in compostable materials from mixed wastestreams. This will also limit the potential applicationsof the material.

It should be noted that many of the aerobic MBTprocesses are designed for bio-drying and not bio-stabilisation as required by compost/soil conditioner,therefore further biological processing of thesewastes would be required prior to any use on land.

Planning and Permitting Issues Markets for the Ouputs

8 17

The energy for the drying stage is from a gas burner,this ensures that the more valuable renewableenergy in the feed is not lost from the products.

A demonstration plant has already been built andtested in Lancashire. The technology will likely bemost appropriate at the +70,000 T/yr. scale andhence serve a large town or city.

Estech ProcessThis process uses wet steam under pressure(autoclave) to clean materials, soften plastics andreduce biodegradable material into a fibre.Following the autoclaving or "cooking" process thematerials can be more easily and effectivelyseparated in a MRF.

The key process stages include waste reception andstorage, waste feeding, autoclaving, materialsseparation with recyclates recovery.

The autoclave stage is central to the process andoperates as a batch operation. After charging withwaste the autoclave drum is sealed and rotationstarted. Saturated steam at c. 160°C is injected intothe vessel and the pressure maintained at 5 bargauge for a period of up to 45 minutes to allow theprocess to fully "cook" the waste. After "cooking",the steam flow is stopped and the pressure ventedvia a condenser. The "cooked" material is dischargedand separated by a series of screens and recoverysystems. The primary product is a fibre. It isunderstood that a number of development projectsand joint ventures have been created by Estech togenerate useful markets for the fibre. Alternativelythe fibre could constitute a Refuse Derived Fuel.

The secondary streams comprise of mixed plastics, aglass and aggregate stream and separate ferrous andnon-ferrous metals. All these streams areexceptionally clean having been steam cleaned.

The full cycle of loading, treatment and sorting isnormally completed within 90 minutes.

Summary

This section illustrates that Mechanical HeatTreatment and Mechanical Biological Treatmentsystems can be described as two simple concepts:either to separate the waste and then treat; or totreat the waste and then separate. The treatmentphase may be either thermal or biological and thereare a wide variety of separation techniques.

MBT and MHT, as illustrated by the case studies,represent significant facilities, which are capitalintensive (see Costs of MBT/MHT Systems section)and are anticipated to be in operation for 15 - 20years. In this instance of emergent markets foroutputs from such processes it is prudent to ensuresufficient installed capacity for flexibility within anyplant (which may require new equipment, etc) toadapt to the needs of the market.

Flies, Vermin and Birds

MBT and MHT processing is unlikely to attractvermin and birds due to majority of wastethroughput and operations being completelyenclosed in buildings. However, during hot weatherit is possible that flies could accumulate, especially ifthey have been brought in during delivery of thewaste. Effective housekeeping and on sitemanagement of tipping and storage areas isessential to minimise the risk from vermin and otherpests. In some operations waste heat from theprocess may be used in fresh input waste to bringtemperatures to levels above which flies can live.Similarly, waste storage in some MBT plant isdesigned to be less that the breeding cycle of verminsuch as rats.

Noise

Noise is an issue that will be controlled under thewaste licensing regulations. The main contributors tonoise associated with MBT/MHT are likely to be:

• vehicle movements/manoeuvring;

• traffic noise on the local road networks;

• mechanical processing such as shredders, screens,trommels and ball mills; and

• air extraction fans and ventilation systems.

Litter

Any waste which contains plastics and paper aremore likely to lead to litter problems. With MBT /MHT as long as good working practices are adheredto and vehicles use covers and reception andprocessing are undertaken indoors, litter problemscan be minimised.

Water Resources

Pollution to water is unlikely due to MBT facilitiesbeing under cover and rainfall is unlikely to comeinto contact with the process. Even so, any washdown waters or liquid within the waste will need tobe managed using a drainage system on site. Somewater is likely to be used in MHT processes. This isoften cited as being reused within the process, butagain such process water will need to be managed.

The case studies on the Waste Technology DataCentre include an assessment of water usage.

Visual Intrusion

Construction of any building will have an effect onthe visual landscape of an area. Visual intrusionissues should be dealt with on a site specific basisand the following items should be considered:

• Direct effect on landscape by removal of itemssuch as trees or undertaking major earthworks;

• Site setting; is the site close to listed buildings,conservation areas or sensitive viewpoints;

• Existing large buildings and structures in the area;

• The potential of a stack associated with some airclean up systems for mixed waste processingoperations may impact on visual intrusion;

• Use of screening features (trees, hedges, banksetc); and

• The number of vehicles accessing the site andtheir frequency.

Most of these facilities are housed in 'warehouse'type clad steel buildings.

External view of MBT facility

How it Works Planning and Permitting Issues

18 7

Size and Landtake

Table 3 shows the land area required for thebuilding footprint and also for the entire site(including supporting site infrastructure) forMechanical Biological and Mechanical HeatTreatment facilities.

Table 3 : Landtake

a Source: Review of Residual Waste Treatment Options, 2003, AiIE

b Source: Planning for Waste Management facilities, ODPM, 2004

c Source: Waste Technology Data Centre, 2004

An average MBT plant may have a height of 10 -20m. Some facilities may also have a stack if usingparticular air clean-up systems, potentially increasingoverall height. For more information on Landtakefor specific waste management operations, seeDefra's Waste Technology Data Centre11.

Public Concern

The Social and Perception Issues section, relates topublic concern. In general public concerns aboutwaste facilities in general relate to amenity issues(odour, dust, noise, traffic, litter etc).

Environmental Impact Assessment

It is likely that an Environmental Impact Assessment(EIA) will be required for an MBT or MHT facility aspart of the planning process.

Whether a development requires a statutory EIA isdefined under the Environmental Impact Assessment(England and Wales) Regulations 1999. Furtherguidance is available in the DETR circular 02/99 onEnvironmental Impact Assessment.

For more information on Planning issues associatedwith waste management options see Planning forWaste Management Facilities - A Research Study.Office of the Deputy Prime Minister, 200412.

Licensing/Permitting

If a MBT/MHT plant processes over 50tonnes per dayit may be assumed that they will require a PollutionPrevention & Control (PPC) permit to operate, ifprocessing less than this quantity a wastemanagement license would be required. If theprocess is shown to produce a fuel (e.g. RDF) ratherthan a waste, then it would be subject to PPCirrespective of the tonnage threshold. For moreinformation on licensing & permitting see theEnviroment Agency website13.

Figure 2 below illustrates the variety of options withthe concept of MHT, which are likely to use similarmechanical preparation and separation technologiesto those described in Box 2, page 5. This is alsoillustrated by the case studies which follow.

Figure 2 : Mechanical Heat Treatment

The most common system being promoted for thetreatment of MSW using MHT is autoclaving (see Box4). This technology is in common use for thetreatment of some clinical wastes and also forcertain rendering processes for animal wastes.However its application to MSW is a recentinnovation, and there is limited commercialexperience on this feedstock material.

Different MHT systems may be configured to meetvarious objectives with regard to the waste outputsfrom the process (Figure 2). The alternatives(depending on the system employed) may be one ormore of the following:

• Separate an 'organic rich' component of thewaste for subsequent biological processing [forexample to form a low grade soil conditioner];

• produce a segregated high calorific value waste(RDF/SRF see box 1, p.3) to be applied in anappropriate process to utilise its energy potential;and

• extract materials for recycling (typically glass andmetals, potentially plastics and the 'fibrous'organic and paper fraction).


Case Studies

The following case studies illustrate examples ofMHT system and relate these to the differentmechanical preparation, separation and heattreatment techniques, previously described in Boxes2 & 4.

Fairport ProcessThis process uses conventional mechanical handlingand processing plant.

The Fairport process dries the waste to enable it tobe more efficiently separated and hence produceseveral recyclate streams. The final stage of theseparation uses the "Fairport separator". This highefficiency device results in several separations on thebasis of size and density. Fairport then blend thesefractions together with other materials to produce afuel meeting a predefined specification.

Planning and Permitting Issues How it Works

Mechanical Preparation& Heat Treatment

Reject to Landfill

Fuel Fraction(RDF)

SoilContainers

Recyclables

MSW

Box 4 Heat Treatment Options

Heat Treatment Process Key Concerns

Autoclaving - batch, steamprocessing in a vessel underthe action of pressure

Batch nature ofprocess

Continuous heat treatment ina vessel, not under the actionof pressure

Limited track record

SizeBuilding

AreaTotal

Landtake

MBT Plant Ab

MBT Plant Bc

MBT Plant Cc

MBT Plant Da

MBT Plant Ea

MHT Plant Ac

MHT Plant Ba

50,000tpa

75,000tpa

140,000tpa

180,000tpa

100,000tpa

150,000tpa

3,000m2

5,500m2

9,000m2

4,300m2

15,000m2

0.36m2/t

35,000m2

18,000m2

11www.environment-agency,gov.uk/wtd

12http://www.odpm.gov.uk/stellent/groups/odpm_planning/documents/page/odpm_plan_030747.pdf

13http://www.environment-agency.gov.uk/subjects/waste/?lang=_e

MechanicalSeparation

6 19

In addition to the various mechanical technologiesthere are also a variety of different biologicaltreatment techniques which are used in MBT plant.These are described in greater detail in theAdvanced Biological Treatment Brief, in this series.Box 3 below outlines the key categories of biologicaltreatment.


Case Studies

The following case studies illustrate examples ofMBT systems and relate these to the differentmechanical preparation, separation and biologicaltreatment techniques, described in Boxes 2 & 3.

The Arrow Bio Process The key process stages of the Arrow Bio processinclude: MSW reception, bag splitting, a wetseparator (where the biodegradable material isseparated from the ferrous and non ferrous metalsand other heavy material), the “Hydrocrusher”(which separates the fibres in the biodegradable

material), followed by a two stage anaerobicdigestion. The gas from the digesters is burnt in anengine-powered generator.

It is accepted that the rate-controlling step in theanaerobic digestion of MSW is the hydrolysis ofcomplex materials, such as cellulose and lignin, intosmall soluble molecules such as glucose, which canbe easily digested. In the Arrow Bio process themechanical shredding of the material in the"Hydrocrusher" accelerates the process. This resultsin substantially more of the biodegradable materialbeing made available for conversion into gas.

Arrow Bio uses two digesters in series. The two-vessel design provides better control of the digestionprocess with a consequential increase in efficiency.The biogas is burnt in a spark ignition engine drivinga generator. Steam could be raised in a waste heatboiler using the hot exhaust gas from the engine.

Ecodeco ProcessThe main process steps proposed for a UK facilityare: waste reception; shredding to around 200mm;forced aeration composting to give bio-drying; andfinally material separation in a MRF.

In the composting stage air is drawn through thewaste which has been heaped in a hall. The bio-decomposition generates heat, that, in turn, driesthe material to the stage where further compostingcannot proceed. Air from the hall is cleaned via abio-filter prior to release.

In the MRF facility, metals are removed and recycled,and the dense and light fractions separated. Thedense fraction normally goes to landfill. The lighterorganic and plastics fraction needs a market. It canbe further separated or processed to a specificationneeded for a particular application. Variousapplications including land remediation and use as afuel are currently under development.


Mechanical Heat Treatment (MHT) is a relatively newterm. It is used to describe configurations ofmechanical and thermal, including steam, basedtechnologies. New waste management technologieswhich use other (higher temperature) thermaltreatment processes are dealt with in a separateBrief in this series 'Advanced Thermal Treatment'.

This section contains a discussion of the social andpublic perception considerations of MBT and MHTfacilities.

Social Considerations

Any new facility is likely to impact on the localresidents and may provide both positive andnegative impacts. Potential impacts on local amenity(odour, noise, dust, landscape) are importantconsiderations when siting any waste managementfacility. These issues are examined in more detail inthe Planning Section of this brief. Transport impactsassociated with the delivery of waste and onwardtransport of process outputs may lead to impacts onthe local road network. The Planning andPermitting section of this document provides anestimate of potential vehicle movements.

An MBT or MHT facility may also provide positivesocial impacts in the form of employmentopportunities and educational opportunities. Typicalemployment for a MBT / MHT plant of 50,000tpacapacity would be 2 - 8 persons at any one time(more if manual picking operations are used). Theplant may be operated on a shift system, forexample to allow for 24 hour operations. Thesefacilities are also likely to provide vocational trainingfor staff. Many new facilities are built with a visitorscentre to enable local groups to view the facility andlearn more about how it operates.

Public Perception

Public opinion on waste management issues is wideranging, and can often be at extreme ends of thescale. Typically, the most positively viewed wastemanagement options for MSW are recycling andcomposting. However, this is not necessarily reflectedin local attitudes towards the infrastructurecommonly required to process waste to compost, orsort mixed recyclables. It should be recognised thatthere is always likely to be some resistance to anywaste management facility within a locality.

At present there is a relatively low level ofunderstanding of the concept of MBT by the public.In public consultations these technologies scoresinconsistently when explained in detail as a residualwaste treatment technology.

Two examples of public consultations highlightingthe diversity of opinion with regard to MBT arehighlighted in Box 5.

Mechanical Heat Treatment is a more recent conceptand it is unclear as to the public perception of thisoption at present. Indeed, there is limitedinternational experience with MHT and so publicperception has yet to be fully tested. It may be that,as a mixed waste processing facility, MHT will have asimilar perception as that for MBT. Alternatively,there may be a more negative perception due to adistrust of 'thermal' based techniques.

Overall, experience in developing wastemanagement strategies has highlighted theimportance of proactive communication with thepublic over waste management options. The use ofrealistic and appropriate models, virtual 'walk -throughs' / artists impressions should be used toaccurately inform the public. Good practice in termsof public consultation and engagement is animportant aspect in gaining acceptance for planningand developing waste management infrastructure.

How it Works Social and Perception Issues

Box 3 Biological Treatment Options

Biological Treatment Key Concerns

Aerobic - Bio-drying/Biostabilisation: partialcomposting of the (usually)whole waste


Aerobic - In-VesselComposting: may be used toeither biostabilise the wasteor process a segregatedorganic rich fraction


Anaerobic Digestion: used toprocess an segregated organicrich fraction


Box 5 Public consultation on MBT

A public consultation in an area of Wales resultedin a clear preference that any waste that could notbe recycled or composted should be dealt withthrough MBT. Respondents felt that an MBT-ledstrategy was a positive approach for residualwaste whether it aims to achieve or exceeddiversion targets.

Conversely, a large scale public consultation in anarea of England revealed the opposite reactionwith MBT being the least favoured approach ofthe residual waste treatment options.

20 5

The cost of constructing, operating and maintainingMBT and MHT facilities are addressed using acommon cost model on Defra's Waste TechnologyData Centre. Both capital and operating costs areincluded on specific technologies which may be usedfor the purposes of indicative comparisons ratherthan accurate reflections of actual costs.

It should also be noted that MBT and MHT systemsare sensitive to the markets and outlets for recycledmaterials, RDF and soil conditioners that areproduced by different processes. Partnershipsbetween MBT operators and potential users ofoutputs should be established at the earliestopportunity and indeed care should be taken toensure plant can deliver materials of sufficientquality.

Typically around 50% of the capital costs foroperating an MBT plant will be to cover capitaldepreciation. As a result these need to be viewed aslarge capital investments with a lifespan of not lessthan 10 or more usually 20 years.

It is vital in any negotiation, that a true appreciationof the cost of essential repairs and refurbishment betaken into account. Additionally the undevelopedmarkets (and risks associated with loss of markets)for products/outputs of these processes needs to bereflected in cost models. Any building should havesufficient capacity to house new separationequipment. Typically plants less than 40ktpa capacityare unlikely to be viable.

For cost information on examples of differentprocesses see Defra's Waste Technology Data Centrewww.environment-agency.gov.uk/wtd

Box 2

Mechanical Waste Preparation Technologies

Mechanical Waste Separation Technologies

Costs of MBT/MHT Systems How it Works

Technology Principle Key Concerns

Hammer Mill Material significantly reduced in size by swingingsteel hammers

Wear on Hammers, pulverising and'loss' of glass/aggregates, exclusionof pressurised containers

Shredder Rotating knives or hooks rotate at a slow speed withhigh torque. The shearing action tears or cuts mostmaterials

Large, strong objects can physicallydamage, exclusion of pressurisedcontainers

Rotating Drum Material is lifted up the sides of a rotating drum andthen dropped back into the centre. Uses gravity totumble, mix, and homogenize the wastes. Dense,abrasive items such as glass or metal will help breakdown the softer materials, resulting in considerablesize reduction of paper and other biodegradablematerials

Gentle action - high moisture offeedstock can be a problem

Ball Mill Rotating drum using heavy balls to break up orpulverise the waste

Wear on balls, pulverising and'loss' of glass/aggregates

Wet RotatingDrum with Knives

Waste is wetted, forming heavy lumps which breakagainst the knives when tumbled in the drum

Relatively low size reduction.Potential for damage from largecontraries

Bag Splitter A more gentle shredder used to split plastic bagswhilst leaving the majority of the waste intact

Not size reduction, may bedamaged by large strong objects

Technology Separation Property Materials Targeted Key Concerns

Trommels and Screens Size and density Oversize - paper, plasticSmall - organics, glass, fines

Air containment andcleaning

Manual Separation Visual examination Plastics, contaminants,oversize, not usually for MSW

Ethics of role, Health &Safety issues

Magnetic Separation Magnetic Properties Ferrous metals

Eddy Current Separation Electrical Conductivity Non ferrous metals

Wet SeparationTechnology

Differential Densities Floats - Plastics, organicsSinks - stones, glass

Produces wet waste streams

Air Classification Weight Light - plastics, paperHeavy - stones, glass

Air cleaning

Ballistic Separation Density and Elasticity Light - plastics, paperHeavy - stones, glass

Optical Separation Optical properties Specific plastic polymers Rates of throughput

4 21

Figure 1 : An illustration of the potential Mechanical Biological Treatment options

The combination of mechanical waste preparation and separation techniques used and their configurations aremany and varied. Box 2 illustrates the typical options used in MBT systems.

Recycling

Recyclate derived from a mixed waste processingplant (either MBT or MHT) of household wastequalifies for BVPI 82a (Recycling) at the point atwhich it leaves the plant to be sent to thereprocessor. The material must pass to thereprocessor (and not be rejected for quality reasons)to count as recycling. The same would also apply toglass used as an aggregate. It should be noted thatsome materials may have market limitations due tobeing derived from a mixed MSW source. Forexample British Standard BS EN 643 states that'Recovered paper from refuse sorting stations is notsuitable for use in the paper industry.' Although thisstandard is not legally binding, it is supported by themain trade associations for the paper recyclingsector.

Further information about BVPIs can be obtainedfrom the Defra website14.

Composting

Where MBT or MHT processes are configured toproduce an organic rich stream to be utilised as alow grade soil conditioner for example, this materialmay (but is 'unlikely to' see below) qualify ascomposting under BVPI 82b. These types of mixedwaste processing technologies are expected toproduce a low grade soil conditioner which could beutilised in applications such as landfill restoration orsome bulk fill uses (provided that the appropriateengineering and quality standards are met).

These materials will only qualify as 'composted'under the Best Value Performance Indicator (BVPI82b) if the output meets the appropriate criteria foruse in the intended application. Some wastemanagement contractors have demonstrated thatthere is a market for these materials, however thecurrent Best Value Performance Indicator Guidance(as of November 2004) states the criteria forcomposting should be 'a product that has beensanitised and stabilised, is high in humic substances,and can be used as a soil improver, as an ingredientin growing media or blended to produce a top soilthat will meet British Standard BS2882 incorporating

amendment no.1…' It also states that it is 'unlikelythat products of a Mechanical Biological Treatmentprocess will meet this definition.' However if thedefinition could be achieved then the product wouldqualify as BVPI 82b.

The definition of BVPI 82b has been amended toinclude waste which has been treated through aprocess of anaerobic digestion.

For more information on the processes for the organicfraction from mixed waste processing, see theAdvanced Biological Treatment Brief, in this series.

For the latest position with regard to Best ValuePerformance Indicators for MBT and MHT see theDefra website or contact the Supporter Helpline tel. 0870 2409894 [email protected]

Landfill Allowance Trading Scheme (LATS)

The European Landfill Directive and the UK'senabling act, the Waste & Emissions Trading Act2003, require the diversion of biodegradablemunicipal waste (BMW) from landfill. Both MBT andMHT systems have the potential to divert BMW fromlandfill. Any outputs that are recycled, used as soilconditioner (under an exemption) or burnt as RDFand which are not landfilled will count directlytowards diversion targets. The ability of MBT & MHTto meet a high level of landfill diversion willtherefore depend upon the availability of marketsfor, and the quality of, the process outputs.

However, MBT plant can also be used to bio-stabilisewaste prior to landfilling. In this case biologicaltreatment is used to reduce the waste's potential todegrade and produce methane once landfilled. TheEnvironment Agency (EA) are currently developing amethodology to determine the 'stability' or'biodegradablity' of any outputs from an MBT plantwhich are sent to landfill. This test will be used todetermine the amount of biodegradable materialbeing landfilled in accordance with the LandfillAllowance Trading Scheme (LATS).

How it Works Contribution to National Targets


22 3

As any MBT plants developed in the UK are likely tovary in their method of operation, the stability test islikely to be applied to each MBT plant on a regularbasis. Figure 3 shows a hypothetical mass balancecalculation showing the contribution of an MBTplant to BMW diversion. Up to date informationrelating to LATS can be obtained from the NewTechnologies Supporter Helpline and Defra's LATSinformation webpage15.

As the requirements of the Landfill Directive relateto the amount of biodegradable material landfilled,the stability of materials diverted from landfill viaMBT will not need to be measured.

Recovery

MBT and MHT technologies will only contributetowards recovery targets through the waste streamsthat are sent to an energy recovery process. This maybe either RDF combusted or degraded in a thermalplant (e.g. Energy from Waste, Advanced ThermalTreatment or co-combusted in a Cement Kiln), or thebiological stream that is processed in an AnaerobicDigestion plant (see the specific guidance for BVPI82c and also 82b for AD). For more details see theDefra website16.

Renewables

If energy is recovered from the sorted materials(RDF) arising from an MBT or MHT plant, this wouldcount as renewable under the Renewable Energytargets.

The Government has also introduced an incentivisedmarket for Renewable Energy through the'Renewables Obligation'. The combustion of RefuseDerived Fuel from an MBT or MHT process in anEnergy from Waste plant at present would notqualify for this incentive and a co-combustionapplication is also unlikely to qualify. But the otherrecovery techniques of Anaerobic Digestion andAdvanced Thermal Treatment (see the other Briefs inthis series) do qualify for Renewables ObligationCertificates (ROCs) under this scheme (for moreinformation see page 11).

The ROCs scheme is currently out to consultation, forup-to-date information regarding RDF and ROCs seethe DTI website17 or the New Technologies SupporterHelpline tel. 0870 2409894 [email protected]

This section comprises an overview of the principlesof Mechanical Biological Treatment (MBT) andMechanical Heat Treatment (MHT) processes. Itshould be noted that there are a myriad of acronymsand titles ascribed to different treatmenttechnologies falling within this Brief, however forthe purpose of clarity this document differentiatesonly two principle technology categories. Thoseinvolving biological treatment in conjunction withmechanical processing (MBT) and those usingthermal treatment in conjunction with mechanicalprocessing (MHT).

The generic purpose of all these processes is toseparate a mixed waste stream into severalcomponent parts, to give further options forrecycling and recovery.

Mechanical Biological Treatment Facility, Cologne


Mechanical Biological Treatment is a generic term foran integration of several processes commonly foundin other waste management technologies such asMaterials Recovery Facilities (MRFs), sorting andcomposting plant. MBT plant can incorporate anumber of different processes in a variety ofcombinations. Additionally, MBT plant can be builtfor a range of purposes.

A common aspect of all MBT plant used for MSWmanagement is to sort mixed waste into differentfractions using mechanical means; and to extractmaterials for recycling. The exact mix oftechnologies employed in an MBT facility will

depend on the additional objectives of the plant.These objectives would typically be one or more ofthe following:

• part stabilise the waste prior to landfilling;

• biologically process a segregated 'organic rich'component of the waste [for example, to form alow grade soil conditioner]; and

• produce a segregated high calorific value wasteto feed an appropriate thermal process to utiliseits energy potential.

The biological element of an MBT process may eithertake place prior to or after mechanical sorting of thewaste, as illustrated in Figure 1. Each approach hasits own particular application and examples of bothmethodologies are described in the case studiesbelow and in more detail on the Waste TechnologyData Centre.

Contribution to National Targets How it Works

Box 1 Fuel from mixed waste processingoperations

The current prevalent term used for a fuelproduced from combustible waste is Refuse DerivedFuel (RDF). The types of technologies used toprepare/segregate a fuel fraction from MSWinclude many of the MBT/BMT and MHT processesdescribed within this Brief. A CEN TechnicalCommittee (TC 343) is currently progressingstandardisation work on fuels prepared fromwastes, classifying a Solid Recovered Fuel (SRF). It isanticipated that once standards are developed andbecome accepted by users that SRF will become theterminology used by the waste managementindustry. Other terminology has also beenintroduced to the industry as various fuelcompositions may be prepared from waste bydifferent processes. Examples include'Biodegradable Fuel Product' (BFP) and 'RefinedRenewable Biomass Fuel' (RRBF).

Within this Brief, Refuse Derived Fuel will be usedas a term to cover the various fuel productsprocessed from MSW.

15 http://www.defra.gov.uk/environment/waste/localauth/lats/index.htm16 http://www.defra.gov.uk/environment/waste/localauth/index.htm17 http://www.dti.gov.uk/energy/renewables/

Figure 3 : Hypothetical MBT Mass Balance

This hypothetical example is based on information available from the Environment Agency at the time of writing. It can be seen that although the proportion ofBMW in the rejects from the MBT plant is higher in the residual output than in the input (78% vs 69%), this is off-set by a decrease in overall tonnage and by thedecreased biodegrabability (increased stability) of the material. In this hypothetical example, 62 tonnes of BMW enters the plant (with a biodegradabilitymeasure of 10) and the residual material contains 42 tonnes of BMW (with a biodegrabability measure of 5). The Environment Agency have indicated that thetonnes of BMW counted as being landfilled from an MBT plant will take into account the material's increased stability (based on testing the material) and thattherefore in this example the BMW tonnage being landfilled from the MBT plant would be equivalent to 21 tonnes (as the biodegradability measure has halved).

2 23

Municipal Solid Waste (MSW) is waste collected by oron behalf of a local authority. It comprises mostlyhousehold waste and it may include somecommercial and industrial wastes. Nationally, thequantity of MSW is currently increasing year on year,presenting a growing problem for local authoritiesparticularly as new legislation, which limits (byimplication1) the amount of mixed MSW that can besent to landfill, comes into effect.

One of the guiding principles for European and UKwaste management has been the concept of ahierarchy of waste management options, where themost desirable option is not to produce the waste inthe first place (waste prevention) and the leastdesirable option is to dispose of the waste with norecovery of either materials and/or energy. Betweenthese two extremes there are a wide variety of wastetreatment options that may be used as part of awaste management strategy to recover materials (forexample furniture reuse, glass recycling or organicwaste composting) or generate energy from thewastes (for example through incineration, ordigesting biodegradable wastes to produce usablegases).

At present more than 75% of all MSW generated inEngland is disposed of in landfills. However,European and UK legislation has been put in placeto limit the amount of biodegradable municipalwaste (BMW) sent for disposal in landfill. Thediversion of this material is currently the mostsignificant challenge facing the management ofMunicipal Solid Waste in the UK.

There are a wide variety of alternative wastemanagement options and strategies available fordealing with Municipal Solid Waste to limit theresidual amount left for disposal to landfill. The aimof this guide is to provide impartial informationabout the range of technologies referred to asMechanical Biological Treatment (MBT) andMechanical Heat Treatment (MHT). Thesetechnologies are pre-treatment technologies whichcontribute to the diversion of MSW from landfillwhen operated as part of a wider integratedapproach involving additional treatment stages.They are part of a range of new alternativescurrently being assessed and investigated throughthe New Technologies work stream of Defra.

Further details about the new technologies featuredin this report are available from Defra's WasteTechnology Data Centre:

http://www.environment-agency.gov.uk/wtd

The technologies described in this Brief - MechanicalBiological Treatment and Mechanical Heat Treatment- have a varying, track record in England (and theUK). MBT plant, have a chequered history in the UK,early examples of similar processes including 'RefuseDerived Fuel' (RDF) processing plant and residualwaste Materials Recovery Facilities ('Dirty MRFs'). Thenew MBT technologies are now second or thirdgeneration plant including many well provenexamples. On the continent many of these processesare established viable and bankable. The aim of thisdocument is to raise awareness and help bring theUK up to that standard.

This guide is designed to be read in conjunction withthe other Waste Management Technology Briefs inthis series and with the case studies provided onDefra's Waste Technology Data Centre. Otherrelevant sources of information are identifiedthroughout the document.

The Waste Technology Data Centrewww.environment-agency.gov.uk/wtd

New Technologies Supporter Helpline Tel. 0870 240 9894 E: [email protected]

Defra New Technologies website,http://www.defra.gov.uk/environment/waste/wip/newtech/index.htm

Integrated Pollution Prevention and Control, DraftReference Document on Best Available Techniquesfor the Waste Treatments Industries, EuropeanCommission - Directorate General Joint ResearchCentre, January 2004

Refuse Derived Fuel, Current Practice andPerspectives (B4-3040/2000/306517/Mar/E3), EuropeanCommission - Directorate General Environment, July 2003

Procurement Toolkithttp://lasupport.defra.gov.uk/Default.aspx?Menu=Menu&Module=Article&ArticleID=102

For Works Contracts: the Institution of CivilEngineers 'New Engineering Contract'www.ice.org.uk

For large scale Waste Services Contracts through PFIAND following the Negotiated Procedures the 4ps'Waste Procurement Pack' www.4ps.gov.uk

Planning for Waste Management Facilities - AResearch Study. ODPM, 2004.http://www.odpm.gov.uk/stellent/groups/odpm_planning/documents/page/odpm_plan_030747.pdf

AiIE Ltd, 2003, Review of residual waste treatmenttechnologies, Report prepared on behalf of Kingstonupon Hull City Council and East Riding of YorkshireCouncilhttp/www.eastriding.gov.uk/environment/pdf/waste_treatment_technologies.pdf

The Additional Paper to the Strategy Unit, WasteNot Want Not study, 'Delivering the LandfillDirective: The Role of New & EmergingTechnologies', Dr Stuart McLanaghanhttp://www.number10.gov.uk/files/pdf/technologies-landfill.pdf

WRAP Organics websitehttp://www.wrap.org.uk/materials/organics/

The Composting Association, including reports onAnaerobic Digestion and Directory of In-VesselComposting.http://www.compost.org.uk/dsp_home.cfm

Chartered Institution of Wastes Management.http://www.ciwm.co.uk

Mechanical Biological Treatment: A Guide forDecision Makers, Processes, Policies and Markets(2005), by Juniper consultancy Ltd for SitaEnvironmental Trust.http://www.sitaenvtrust.org.uk/research/overview

Introduction Further Reading and Sources of Information

1Targets pertain to the biodegradable fraction

24 1

This Waste Management Technology Brief is one of a series of documents prepared under the NewTechnologies work stream of the Defra Waste Implementation Programme. The Briefs areaddressing potentially important new technologies which may have an increasing role in divertingMunicipal Solid Waste (MSW) from landfill into a more sustainable and integrated wastemanagement alternative, extracting materials and energy from MSW for recovery and reducingquantities remaining for disposal. Other titles in this series include: An Introductory Guide to WasteManagement Options; Advanced Biological Treatment; and Advanced Thermal Treatment.

It should be noted that these documents are intended as guides to each generic technology areaand for more detailed or specific information on any particular technology, it is recommended thatthe Defra Waste Technology Data Centre is used as a resource. These Briefs deal primarily with thetreatment and processing of unsorted MSW and not source segregated wastes which are addressedby the activities of the Waste & Resources Action Programme (WRAP). Relevant references andsources of further information are cited throughout each document in this series.

The prime audience for these Briefs are local authorities, in particular waste management officers,members and other key decision makers for MSW management in England. For further informationon new technologies contact the New Technologies Supporter Helpline on 0870 2409894, email:[email protected]

Prepared by Enviros Consulting Limited on behalf of Defra as part of the New TechnologiesSupporter Programme.

We acknowledge support from the Department for Environment, Food & Rural Affairs, theEnvironment Agency, the Waste and Resources Action Programme, Be Environmental Ltd, RPS and Stuart McLanaghan of Associates in Industrial Ecology.

Disclaimer: Please read the note below before using this Document

This Document has been produced by Enviros Consulting Limited (Technical Advisors) on behalf ofDefra to provide assistance to Local Authorities and the waste management market generallythrough awareness raising of the key municipal waste management options for the diversion of BMWfrom landfill. The Document has been developed in good faith by the Advisors on behalf of Defra,and neither Defra nor its Advisers shall incur any liability for any action or omission arising out of anyreliance being placed on the Document by any Local Authority or organisation or other person. AnyLocal Authority or organisation or other person in receipt of this Document should take their ownlegal, financial and other relevant professional advice when considering what action (if any) to takein respect of any waste strategy, initiative, proposal, or other involvement with any wastemanagement option or technology, or before placing any reliance on anything contained therein.

Crown Copyright, 2005V.1.0

Glossary Preamble

Aerobic In the presence of oxygen.

Aerobic Digestion/Composting Biological decomposition of organic materials by micro-organismsunder controlled, aerobic, conditions to a relatively stable humus-like material called compost.

Anaerobic In the absence of oxygen.

Anaerobic Digestion A process where biodegradable material is encouraged to breakdown in the absence of oxygen. Material is placed in to anenclosed vessel and in controlled conditions the waste breaks downtypically into a digestate, liquor and biogas

Animal By-Products Regulation Legislation governing the processing of wastes derived from animalsources.

Biodegradable Capable of being degraded by plants and animals. Biodegradablemunicipal waste includes paper and card, food and garden waste,and a proportion of other wastes, such as textiles.

Biogas Gas resulting from the fermentation of waste in the absence of air(methane/carbon dioxide).

Biodegradable Municipal Waste(BMW)

The component of Municipal Solid Waste capable of beingdegraded by plants and animals. Biodegradable Municipal Wasteincludes paper and card, food and garden waste, and a proportionof other wastes, such as textiles.

Co-combustion Combustion of wastes as a fuel in an industrial or other (non wastemanagement) process.

Digestate Solid and/or liquid product resulting from Anaerobic Digestion.

Feedstock Raw material required for a process.

Floc A small loosely aggregated mass of flocculent material. In thisinstance referring to Refuse Derived Fuel or similar.

Greenhouse Gas A term given to those gas compounds in the atmosphere thatreflect heat back toward earth rather than letting it escape freelyinto space. Several gases are involved, including carbon dioxide(CO2), methane (CH4), nitrous oxide (N2O), ozone, water vapourand some of the chlorofluorocarbons.

Green Waste Waste vegetation and plant matter from household gardens, localauthority parks and gardens and commercial landscaped gardens.

Global Warming The progressive gradual rise of the earth's surface temperaturethought to be caused by the greenhouse effect and responsible forchanges in global climate patterns. An increase in the near surfacetemperature of the Earth. Global warming has occurred in thedistant past as the result of natural influences, but the term is mostoften used to refer to the warming predicted to occur as a result ofincreased emissions of greenhouse gases form man - made sources.

25

Page number

Preamble 1

Introduction 2

How it Works 3

Mechanical Biological Treatment 3Mechanical Heat Treatment 6Summary 8

Markets for the Outputs 9

Recovery from MBT 9Recovery from MHT 11

Track Record 13

Contractual and Financing Issues 14

Grants and Funding 14Contractual Arrangements 14

Planning and Permitting Issues 16

Planning 16Plant Siting 16Traffic 16Air Emissions/Health Effects 16Dust/Odour 16Flies, Vermin and Birds 17Noise 17Litter 17Water Resources 17Visual Intrusion 17Size and Landtake 18Public Concern 18Environmental Impact Assessment 18Licensing/Permitting 18

Social and Perception Issues 19

Social Considerations 19Public Perception 19

Costs of MBT/MHT Systems 20

Contribution to National Targets 21

Recycling 21Composting 21Landfill Allowance Trading Scheme (LATS) 21Recovery 22Renewables 22

Further Reading and Sources of Information 23

Glossary 24

Contents Glossary

Incineration The controlled thermal treatment of waste by burning, either toreduce its volume or toxicity. Energy recovery from incineration canbe made by utilising the calorific value of the waste to produceheat and/or power.

In-vessel Composting The aerobic decomposition of shredded and mixed organic wastewithin and enclosed container, where the control systems formaterial degradation are fully automated. Moisture, temperature,and odour can be regulated, and stable compost can be producedmuch more quickly than outdoor windrow composting.

Materials Recycling Facility/Material Recovery Facility (MRF)

Dedicated facility for the sorting/separation of recyclable materials.

Mechanical Biological Treatment(MBT)

A generic term for mechanical sorting/separation technologies usedin conjunction with biological treatment processes, such ascomposting.

Municipal Solid Waste (MSW) Household waste and any other wastes collected by the WasteCollection Authority, or its agents, such as municipal parks andgardens waste, beach cleansing waste, commercial or industrialwaste, and waste resulting from the clearance of fly-tippedmaterials.

Recyclate/Recyclable materials Post-use materials that can be recycled for the original purpose, orfor different purposes.

Recycling Involves the processing of wastes, into either the same product or adifferent one. Many non-hazardous wastes such as paper, glass,cardboard, plastics and scrap metals can be recycled. Hazardouswastes such as solvents can also be recycled by specialist companies.

Refuse Derived Fuel (RDF) A fuel produced from combustible waste that can be stored andtransported, or used directly on site to produce heat and/or power.

Renewables Obligation Introduced in 2002 by the Department of Trade and Industry, thissystem creates a market in tradable renewable energy certificates,for which each supplier of electricity must demonstrate compliancewith increasing Government targets for renewable energygeneration.

Solid Recovered Fuel Refuse Derived Fuel meeting a standard specification, currentlyunder development by a CEN standards committee.

Source-segregated/Source-separated

Usually applies to household waste collection systems whererecyclable and/or organic fractions of the waste stream areseparated by the householder and are often collected separately.

Statutory Best Value PerformanceIndicators

Local Authorities submit performance data to Government in theform of annual performance indicators (PIs). The Recycling andComposting PIs have statutory targets attached to them whichAuthorities are required to meet.

www.defra.gov.uk

Mechanical Biological Treatment &Mechanical Heat Treatment of MunicipalSolid Waste

www.defra.gov.uk

Documents

Solid Waste Mechanical Heat Treatment of Municipal Mechanical