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Solid Waste Management in Solid Waste Management in Canada: Current Practice, Canada: Current Practice, Priorities and ResearchPriorities and Research
J. Patrick A. Hettiaratchi, PhD, J. Patrick A. Hettiaratchi, PhD, PEngPEng..Environmental Engineering ProgramEnvironmental Engineering ProgramFaculty of EngineeringFaculty of EngineeringUniversity of CalgaryUniversity of CalgaryCANADACANADA
Solid Waste ManagementSolid Waste Management• Waste composition• Final disposal in Sanitary Landfills • Waste Minimization efforts
• Reduce and Reuse (at source)• Recycle: recyclables collection (on-site) and processing (off-site) • Recovery of Energy (waste to energy) or Resources (composting
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Waste Characteristics: QuantitiesWaste Characteristics: QuantitiesCanada: Overall
Waste Characteristics: compositionWaste Characteristics: composition
100.00Total
15.88.00Others2.63.00Metal8.62.00Plastic2.02.00Glass2.035.00Animal Waste3.020.00Wood18.060.00Yard Waste20.070.00Food Waste28.06.00Paper
Total wt (%)Moisture ContentComponents
City of Calgary
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Waste Characteristics: compositionWaste Characteristics: composition
Toronto Edmonton
Land Disposal of WasteLand Disposal of Waste• Disposal (land based) is central to any solid waste management strategy
• once produced, we cannot eliminate waste, but it is possible to reduce the amounts directed to landfills by adopting reuse, recycle, recovery
Almost always, a solid waste management plan is developed around a landfill
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Problems with LandfillsProblems with Landfills• Groundwater contamination by leachate
• can be controlled with bottom liner systems, cover systems etc. (expensive)• new ways of landfilling (bioreactors)
• Landfill gas escape into the atmosphere• gas extraction and use of passive systems for emission control• new ways of landfilling (bioreactors)
Another common approach: keep the landfill small! Divert, Divert, Divert…..
Waste Diversion in CanadaWaste Diversion in Canada
http://www.geog.utoronto.ca/info/faculty/Maclaren/Lecture%20slides1.pdf
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Waste Diversion: Reduce..Waste Diversion: Reduce..
• Backyard composting
Waste Diversion: Recycle..Waste Diversion: Recycle..
• Recyclables collection from homes • Curbside collection or Blue Box programs ( expensive, but collection efficiency is high)
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Waste Diversion: Recycle..Waste Diversion: Recycle..• Recyclables collection
• Green Box programs (less expensive, but efficiency is low)
Waste Diversion: Recycle..Waste Diversion: Recycle..Green Box operation
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Waste Diversion: Recycle..Waste Diversion: Recycle..• Recyclables processing
• Some are easily processed (metal, glass, paper – if a de-inking plant is available)
• But, others are difficult to process (plastics – since there are several varieties)
Waste Diversion: Recovery of Waste Diversion: Recovery of CompostCompost
• Large scale composting is popular in Canada
• Single feedstock: yard waste, sludge, MSW
• Mixed feedstock: mix solid waste with sludge from wastewater treatment plants
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Yard Waste CompostingYard Waste Composting
Windrow Composting Windrow Composting --EquipmentEquipment
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Edmonton CoEdmonton Co--composting composting FacilityFacility
• In operation since 1999
•The ‘largest’ in North America
The Edmonton Composting Facility composts MSW and de-watered sewage bio-solids.
Capacity: 200,000 tpa of MSW & 25,000 dry tpaof biosolids.
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** Main feature of Edmonton Co-composting Facility: 5 rotating steel drums, each drum 74 m long/4.9 m dia.
Biosolids injected into the drums together with MSW. Composting begins as the material tumble together while travelling for 1-2 days in the drum.
This stage is followed by a 14-day Aerated Windrow operation and curing
Edmonton CoEdmonton Co-- Composting Composting FacilityFacility
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Edmonton CoEdmonton Co-- Composting FacilityComposting Facility
• Aeration Building: size of 14 Ice-hockey rinks
CoCo--composting in Edmontoncomposting in Edmonton
• Capital cost: approximately $100 million
• Overall plant size: 416,500 ft2 (38,690 m2)
• Compost produced: approximately 80,000 tonnes/year
• Compost quality: Class B (??),
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Waste to Energy: Not popular now!!Waste to Energy: Not popular now!!
--Causes air pollution; need expensive air pollution Causes air pollution; need expensive air pollution control equipment to meet air quality standardscontrol equipment to meet air quality standards-- Produces a Produces a ““hazardous wastehazardous waste”” that requires a that requires a ““containment landfillcontainment landfill”” not a sanitary landfillnot a sanitary landfill
100 ton/day waste-to-energy facility in Harrisonburg, VA
Current Conventional “dry-tomb type” Sanitary Landfills are designed and constructed to eliminate problems associated with “Open Dumps”
Sanitary Landfills: accepts the majority of waste
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Conventional Landfill: A Designed Structure!!
Prevention of GW contamination with bottom liner systemsPrevention of GW contamination with bottom liner systems
Leachate is “garbage juice” or an aqueous liquid produced within the landfill
X-section along the length of the landfill
Stream
Area A
Area C
Area BWorking Face (Area D)
Leachate can contaminate Groundwater (unseen) or Surface Water (obvious)
““Dry TombDry Tomb”” landfilllandfill
Current landfills are designed to control Current landfills are designed to control leachateleachate…………....
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Landfill ConstructionLandfill Construction
Final cover
Daily cover
Intermediate cover
Leave it Alone !!!!!Leave it Alone !!!!!
R I PR I P
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CH4 Emissions from Landfills
Other Problems with the DryOther Problems with the Dry--tomb tomb Sanitary Sanitary LandfilllingLandfillling ApproachApproach
Un-sustainable??? Loss of Space…. Need to find new space every few years (Toronto, Edmonton)
Long-term liability: Need to monitor potential impact for a long- time (until waste stability is achieved)
Landfill gas
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Sustainable Landfill: The Future??
The Concept:The Concept:Holistic approach (not “piece-meal” as in conventionallandfills)
Stabilize the waste quickly (Anaerobic and Aerobic)
“Mine” the cell, and extract recyclables & compost
Reuse space
Increase biological activity in landfill cell; possible to extract large quantities of gas in a short period of time
Sustainable Landfill: Stage ISustainable Landfill: Stage I
Anaerobic ReactorAnaerobic Reactor
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Sustainable Landfill: Stage IISustainable Landfill: Stage II
Aerobic ReactorAerobic Reactor
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Calgary Sustainable BiocellCalgary Sustainable Biocell
Pilot Project (1 hectare: 50,000 tonnes of waste)
Partners/Participants: City of Calgary, University of Calgary and Stantech Consultants
Operation:
One-cell operated for six years before mining for resource and space recovery
AerobicYear 5
AerobicYear 4
AnaerobicYear 3
AnaerobicYear 2
AnaerobicYear 1
Mining/Space Recovery
Year 6
Sustainable Landfill OperationSustainable Landfill Operation(Calgary Biocell Concept)(Calgary Biocell Concept)
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Calgary Sustainable BiocellCalgary Sustainable Biocell
Pilot Project (1 hectare: 50,000 tonnes of organic waste)Conventional design for leachate collection
(composite liner etc.), leachate delivery and gas recovery
Innovative Mitigation Measures:
Biocap, or Methane Oxidation Layer (MOL), to control methane gas emissions during construction (intermediate cover) and
operation (final cover)
Gas Production & MigrationGas Production & Migration
Oxidation in Landfill Cover(Methanotrophs)
CH4 & CO2Generation
CO2Emissions CH4 & CO2
EmissionsCommercial
Recovery
CH4 & CO2 LateralMigration
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CHCH44 Oxidation in Landfill CapsOxidation in Landfill Caps
0
20
40
60
80
100
0 50 100 150 200 250 300
Time (days)
% M
etha
ne O
xidi
zed
Landfill Research in Canada: Landfill Research in Canada: Current EmphasisCurrent Emphasis
• Over the last ten years, there has been a change in emphasis;
• Consider the landfill as a single entity requiring a holistic approach for management, rather than a “collection of problems requiring solutions”. • Consider the landfill as a facility for resource recovery (i.e., energy, material and space)
• Research on Bioreactor Landfills:• leachate recirculation and high rate anaerobic degradation• aerobic bioreactors with leachate and oxygen input
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Landfill Research in Developing Landfill Research in Developing CountriesCountries
• What is different?• waste characteristics (i.e., composition, engineeringproperties, biochemical properties)• socio-political considerations (e.g. a role for scavengers in recycling?)
• Pitfalls in “copying” (from developed nations): • some of the regulations, design philosophies anddesign guidelines in North America and Europeare “politically motivated” without clear design bases• only technical considerations are transferable!!
• Research Emphasis?
Landfill Research in Developing Landfill Research in Developing Countries: EmphasisCountries: Emphasis
• waste characterization (fundamental research)• composition, • engineering and biochemical properties
• design guidelines (applied research)• technology/technique transfer (with appropriate modifications)
• socio-political considerations (applied research) • public acceptability and community involvement• (e.g. the role of scavenging in modern solid waste management
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ConclusionsConclusions
• Landfills are central to solid waste management inCanadian communities
• The Canadian landfill design, construction and operation practices are changing
• Consequently research emphasis is also changing
•Researchers and practitioners in developing countries are well advised to consider differences in philosophy, waste character before adopting Canadian landfill techniques
Thank you!!Thank you!!
Questions ??Questions ??…………
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Conventional Landfills in CanadaConventional Landfills in Canada: : GW Contamination ControlGW Contamination Control
• Techniques have been developed to• minimize leachate production
• new designs and material are used in landfill cover systems
• minimize leachate escape from the bottom of landfills• use of low permeable bottom liners• leachate collection systems• leachate treatment (in-situ by re-circulation,
ex-situ treatment methods)
Leachate Collection System
Geotextile4" Perforated Pipe
Geotextile
60 Mil Textured HDPE
Liner System Design
Drainage Layer
Protective Soil Cover
Compacted Clay Liner
Prepared Sungrade
Gravity Drainage
ManholesPumping Station
Storage Ponds
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Conventional Landfills in CanadaConventional Landfills in Canada: : Landfill Gas ControlLandfill Gas Control
• Landfill gas (methane) escape is the primary concern.
• Gas extraction systems are becoming popular•New innovation: Use of Micro-turbines for powerGeneration (operate at low volumes; 150-250 kW)
• Not very economical (even with micro turbines) for smalland medium-scale landfills
• For small/medium landfills, use of methanobiocaps is being tested.
““The ProblemThe Problem”” with Conventional with Conventional LandfillsLandfills
• Conventional landfills are not sustainable.
• Landfill space decreases with time.
•Need to find a new landfill every few years.