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The characterisation and utilisation of grease trap waste

Moyce, A., & Murray, S. (2010). The characterisation and utilisation of grease trap waste: Report on behalf ofAbbey Recycling. Invest Northern Ireland.

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The QUESTOR Centre

Applied Technology Unit

Report on behalf of Abbey Recycling

The characterisation and utilisation of grease trap waste

Prepared by ______________________

Dr Asa Moyce

______________________

Simon Murray

Approved by ______________________

Dr Wilson McGarel

Date: 29th January 2010

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Table of Contents

Executive Summary ................................................................................................................ 3

Original Quote ......................................................................................................................... 4

Changes to original quote ....................................................................................................... 5

1 Composting Overview ...................................................................................................... 6

1.1 Aerobic compost lifecycle .............................................................................................. 6

1.2 Anaerobic composting ................................................................................................... 7

1.3 Composting requirements of waste fats, oils and greases ............................................ 7

1.4 pH neutralisation in composting .................................................................................... 8

1.5 Compost aeration and moisture .................................................................................... 9

1.6 Viable methods to improve the efficiency of composting .............................................. 9

1.7 Overview of the PAS 100 (2005) summary ................................................................. 10

2 The characterisation of the grease trap waste ............................................................... 11

2.1 Analysis and utilisation options for the top fat layer .................................................... 12

2.2 Analysis and utilisation options of the middle layer (grease trap water) ...................... 14

2.3 Problems in using grease trap water in compost ........................................................ 14

2.4 Spreading to land of collected grease trap water ........................................................ 16

2.5 Suitability of the grease trap water to meet the requirements of “dirty water” ............. 16

2.6 Analysis and utilisation options of the bottom food waste layer .................................. 17

3 Compost analysis .......................................................................................................... 18

4 The compost leachate ................................................................................................... 19

5 Alternative uses for waste .............................................................................................. 20

5.1 Description of biodiesel formation ............................................................................... 20

5.2 Blending with woodchips for fuel ................................................................................. 22

6 Conclusion ..................................................................................................................... 23

References ............................................................................................................................ 25

Appendices ........................................................................................................................... 26

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Executive Summary

The clients Pat Quinn and Diarmuid Quinn (Abbey Recycling) directed QUESTOR ATU to carry out an in depth investigation on the grease trap waste they primarily receive from a waste transportation company. The composting of the grease trap waste was proving to be problematic for the company to effectively treat by composting. After an on-site inspection of the grease trap waste in the Abbey Recycling storage facility, the waste was found to separate into three distinct layers. The top layer was a solid fat layer approximately 30cm in depth; the middle layer consisted of grease trap water which made up the bulk of the grease trap waste and the bottom layer consisted predominantly of food waste. Once this analysis was completed a report was compiled, comprising of general composting good practice guidelines including the composting of fats, a summary of the PAS 100 documentation, the Nitrates Directive and Waste Management Licensing, utilisation options of each layer of the grease trap waste as well as exploring the viability of biodiesel production and woodchip combination as a fuel for burners.

The extensive laboratory analysis performed by QUESTOR ATU has revealed the composition of each of the three layers of the grease trap waste. The top fat layer possessed 71.44% dry matter, a carbon: nitrogen ratio of greater than 250:1 and possessed the highest concentration of oils, fats and greases of the three layers. The middle layer at the first sampling consisted of low dry matter (0.95%), total nitrogen (466mg/L) and BOD (480mg/L) but gradually increased to a higher dry matter (2.54%), total nitrogen (600mg/L) and BOD (4622mg/L) by the final sampling. The bottom food waste layer had an average dry matter of 11.16%, an average total nitrogen content of 2870mg/L and an oils, fats and greases content of 49.57g/L. At the time of sampling, the compost contained relatively high oils, fats and greases content of 80g/kg (or 8%) indicating the level of fat in compost is well within the recommended range of 5-15%. The compost leachate still possessed a high level of oils, fats and greases (60g/kg) so it should be collected and re-applied to the compost pile.

At this time, due to the unclassified nature of the grease trap waste, QUESTOR ATU cannot confirm whether the grease trap water may qualify for an exemption or whether a waste management licence for disposal by spreading to land is required. If the grease trap water qualifies for an exemption it may be permitted to be spread as “dirty water” as stated in the Nitrate Directive. Otherwise a more costly method of disposal may be required.

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Original Quote

FAO: Pat Quinn/ Diarmuid Quinn QUESTOR Quote Number: 09Q098

Date: 16/12/09

Stage Description Signature Price

09Q098.1 Characterisation of the liquid wastes which are to be treated.(This doesn’t include collection) assuming three samples

pH @ £1.15 per sample

Conductivity @ £5.45per sample

Chloride (mg/l) @ £5.34 per sample

% Dry matter@ £6.22 per sample

Ammoniacal Nitrogen (NH3-N) (mg/l) @ £5.28 per sample

Total Nitrogen (mg/l) @ £6.55 per sample

Total Phosphate as P (mg/l) @ £7.54 per sample

Alkalinity (mg CaCO3/L) @ £6.21 per sample

Oil, Fats and Greases (mg/l) @ £41.95 per sample

Full metal scan plus digestion @ £45.50 per sample

Nitrate (mg/l) @ £5.67 per sample

Nitrite (mg/l) @ £5.67 per sample

BOD (mg/l) @ £12.35 per sample

£3.45

£16.35

£16.02

£18.66

£15.84

£19.65

£22.62

£18.63

£125.85

£136.50

£17.01

£17.01

£37.05

09Q098.2 Review of the chemical and physical parameters which the treatment must meet to allow spreading on land and suitability to meet the dirty water. 1 person 1 day @ £515.00 per person per day.

£515.00

09Q098.3 Review of the technologies which are available with respect to capital cost, operational cost, environmental factors, etc. using a matrix score sheet. 1 person 2 day @ £515.00 per person per day.

£1030.00

09Q098.4 The three technologies which score best from the matrix will be tested in lab scale 1 person 2 day @ £515.00 per person per day.

£1030.00

09Q098.5 Follow up meeting 2 people ½ day @ £515.00 per person per day

£515.00

09Q098 Grand total £3554.64 + VAT

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Changes to original quote

Since the quote was issued a further site visit to the Abbey recycling facilities in December 2009 was carried out to obtain meaningful and representative samples of each of the layers in the grease trap waste. After consultation with Pat Quinn it was clear that there were a number of questions and issues that needed further information and advice. To fully answer these questions much more detailed analysis of the grease trap waste, compost and compost leachate was required. At the request of the client the investigation also focused on the following points listed below:

1. Composting overview including composting requirements of waste fats, oils and greases, pH neutralisation and compost aeration and moisture.

2. The characterisation of the grease trap waste (the top, middle and bottom layers) and what to with each layer?

3. Compost analysis 4. What to do with the compost leachate? 5. Alternative uses for the grease trap waste including biodiesel and blending with

woodchips for fuel

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1 Composting Overview

Composting can occur under aerobic conditions or anaerobic conditions. This section provides details on both sets of conditions and compares the differences between the two methods (Table 1).

Table 1- Comparison of aerobic and anaerobic composting methods.

Aerobic composting Anaerobic composting

higher maintenance low maintenance

requires regular turning no turning required

reliant on high nitrogen levels less reliant on high nitrogen levels

much less undesirable gases produced noxious gases produced

short timeframe (as little as 1 month) much longer timeframe required greater overall extent of degradation (smaller compost pile) less overall reduction of compost pile

nitrogen converted to nitrates & ammonia nitrogen converted to ammonia (dark and slimy)

compost pile gets hot-killing pathogens compost pile does not heat up

controlled moisture content covered and water saturated gases: carbon dioxide, less odours & less ammonia produced gases: methane, ammonia, hydrogen sulphide

wood waste degraded wood waste not well degraded

1.1 Aerobic compost lifecycle

Decomposition of organic matter under aerobic conditions occurs in defined stages:

1. Psychrophilic (cold temperature loving) bacteria dominate between the temperatures of 0-15oC, slowly releasing heat raising the temperature of the compost by their metabolic activity.

2. As the temperature rises, mesophilic (moderate temperature loving) bacteria establish themselves by growing and reproducing much more rapidly than the psychrophiles, which diminish within the temperature range of 15-40oC. The mesophiles collectively degrade much of the complex organic matter producing enough heat to allow the growth of thermophilic bacteria.

3. At high temperatures between 40-70oC thermophilic (high temperature loving) bacteria continue degradation producing enough heat to kill many pathogens, fly larvae and weed seeds. The heat continues to rise until the thermophiles can no longer tolerate the heat (~68oC). The high temperatures also generate humic acid, which enables plants to assimilate the nutrients in the compost. Turning the compost during this “hot” stage will cool the compost slightly allowing the themophilic bacteria to grow for longer improving the overall quality of the compost.

4. The compost then slowly cools down with first mesophilic bacteria and then psychrophilic bacteria growing on some of the degraded material. Actinomycetes (filamentous bacteria), fungi, worms, and insects may then colonise the compost.

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Resistant compounds such as cellulose and lignin are extensively decomposed by actinomycetes and fungi at this stage. The compost is then ready for use.

Decomposition rates within aerobic composting piles are affected by all factors that commonly affect microbial growth, such as carbon, nitrogen, oxygen, moisture, pH, temperature, and nutrient levels. The composting process continues until all the available biological organic matter is stabilized and it is odour and pathogen free, and the mature compost is a poor breeding substrate for flies and other insects.

1.2 Anaerobic composting

Anaerobic degradation occurs at a much slower rate and results in noxious gases. Methane will also be produced which is approximately twenty times more powerful as a greenhouse gas than carbon dioxide. However, anaerobic composting is less labour intensive as there is no need to turn the pile but this method results in a smaller reduction in the volume of the compost pile. The compost pile will initially support the growth of aerobic bacteria but once the oxygen supply is exhausted, these bacteria die and are replaced by anaerobic bacteria. The available nitrogen is usually reduced to ammonia and the sulphur is reduced to hydrogen sulphide creating an unpleasant smell. (http://tomato-tips.com/aerobic-vs-anaerobic-composting-whats-the-difference.html, December 2009). Anaerobic composting requires excessive levels of water to maintain the anaerobic environment. Materials that should not be composted by anaerobic means are human and pet wastes, meat and bones, dairy products, large quantities of dry leaves, animal fat and oil and wood compounds.

1.3 Composting requirements of waste fats, oils and greases

Successful composting of fat-enriched wastes generally occurs at around 5-15% total fat concentration in the initial mixture (Ruggieri et al. 2008). The effectiveness of composting fats is reduced by a deficiency of nutrients, such as nitrogen and phosphorus compared to the high carbon content of fats. The usual method to improve degradation of the fats is to add a co-substrate to increase the carbon: nitrogen ratio. Various sludges with a low carbon: nitrogen ratio may be incorporated to provide the ideal carbon/nitrogen balance. Table 2 shows the carbon: nitrogen ratios of a number of materials that may be added to compost. Sufficient levels of oxygen and water are required for adequate microbial degradation activity. The ratio of the volume of air to the volume of soil (air-filled porosity) should be within a range of 30-60% (Annan and White 1998). Suitable bulking agents such as wood chips or sawdust are often added to raise the air-filled porosity of compost to within this range. The moisture content of the compost should be around ~50% producing several drops of water when a handful of compost is tightly squeezed.

To increase the carbon content of a compost pile, materials such as dry leaves, dried grass, wood, saw dust and straw may be added. To increase the nitrogen content of the compost, it may be supplemented with green plant material such as grass, weeds, manure, fruit and vegetable waste.

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Table 2- The Carbon/Nitrogen Ratios of Some Common Organic Materials. The C:N ratios are a guideline only (http://www.ecochem.com/t_compost_faq2.html)

Material C:N Ratio Vegetable wastes 10-20:1

Alfalfa hay 13:1 Cow manure 20:1

Apple pomace 21:1

Leaves 40-80:1

Corn stalks 60:1

Oat straw 74:1

Wheat straw 80:1

Paper 150-200:1

Sawdust 100-500:1 Grass clippings 12-25:1

Coffee grounds 20:1

Bark 100-130:1 Fruit wastes 35:01:00

Poultry manure (fresh) 10:1 Horse manure 25:1 Newspaper 50-200:1

Pine needles 60-110:1 Rotted manure 20:1

1.4 pH neutralisation in composting

The pH range is a logarithmic range of the quantity of H+ and OH- ions in solution. The pH scale has a range from 0 to 14. Any pH lower than a neutral pH of 7 is considered to be acidic while any pH above is basic. Extremes of pH are generally very toxic to microorganisms. Most bacteria will be killed in an acidic pH 3 solution, likewise the same effect will occur at a basic pH of 11.5 or more. The extremes in the pH range may cause structural changes (caused by ionisation) in protein functional groups (amino and carboxyl groups) which may lead to a loss in enzyme activity eventually killing the microorganisms.

Composting is known to possess the ability to buffer both acidic and basic pH conditions back to a neutral pH (6-8). As microbial degradation of composted material occurs, the oxidation of organic compounds leads to the formation of both a weak acid (carbon dioxide or CO2) and a weak base (ammonia or NH3 from protein decomposition). Generally the pH of an untreated compost pile decreases in the early stages of decomposition from CO2 production and the formation of organic acids. The pH is then raised as the organic acids are degraded and the temperature rises. Protein decomposition leads to the release of NH3 which also neutralises the acids present. By turning the compost more frequently the rate of aeration is increased which decreases the amount of CO2 in the compost pile, increasing the pH. The pH then tends to stabilise in the near neutral range of 6-8.

If the compost pile contains compounds that are both very low in nitrogen and very low in pH such as the fatty grease trap waste currently received, then the compost may not neutralise at

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all due to such small quantities of NH3 being released as the only proteins present are from the residing microorganisms. The microorganisms numbers able to grow in these conditions will be greatly reduced due to the very acidic conditions present. In this instance a basic additive is likely to be required to neutralise the pH. Additives such as lime, sodium hydroxide, ammonia, calcium carbonate and sodium bicarbonate may be used in this particular application.

To monitor the pH of the various compost piles we suggest the purchase of universal indicator paper. It is very easy to use and requires no calibration so is very suitable for use on location. The operator just needs to dip the paper into an area of moisture or drop a drop of compost liquid onto the paper. The paper will change colour depending on the acidic/basic nature of the compost which is compared to a coloured scale providing instant determination of the pH.

1.5 Compost aeration and moisture

Sufficient aeration in compost is required to allow decomposition to proceed at high rate, but it also removes water from the wet materials within the compost by the air being heated by the activity in the compost as well as the circulating air removing a proportion of the heat generated by exothermic processes involved in aerobic composting. Aeration is a critical control point mentioned in the PAS 100 summary.

The moisture content within the compost should be kept fairly constant at approximately 50% moisture and the material should feel "like a squeezed out sponge". Too much moisture in the compost pile causes nutrients to leach out slowing the process (Hirrel and Riley, undated). The compost temperature within a few days should rise to 60-70 °C. When the temperature begins to fall, more air is required which is added by turning the pile. The moisture content may be adjusted at the same time as some drying out is likely to have occurred. Turning the compost pile is usually required around every 6 to 10 days to maintain the high temperature until the material is uniformly broken down to a homogenous unrecognisable content. A compost pile that has been maintained at peak temperatures for an extended period of time may be ready for maturing within ≥30 days. A time period of around 30–60 days maturing should be adequate to pass the germination test.

1.6 Viable methods to improve the efficiency of composting

At the time of the site visit (December 2009) there was just one composting site currently active at the Abbey recycling facility. To increase the rate of removal/utilisation of the grease trap waste QUESTOR ATU advise the client to set up a number of batches (up to 10) of compost in the area surrounding the grease trap waste storage facility (slurry pits). Although the initial preparation of the correct mixtures of materials in multiple times will initially be time consuming it will save a lot of time in the long term and could reduce the required laboratory analysis costs significantly. If the compost piles are all set up at the same time with same proportion of materials then the carbon: nitrogen ratios of each pile will be very similar. If analytical information is required on the compost piles then just one pile needs to be tested and the obtained results will be representative of all the piles in that batch.

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Faster degradation of compost material is aided by mechanically reducing the size of added material to several millimetres before introducing the material to the compost. The compost should be homogenized as much as possible during the initial preparation of the compost pile. Smaller material particle sizes allow microorganisms to biodegrade more material, multiply faster and generate more heat speeding up the composting process (Hirrel and Riley, undated).

1.7 Overview of the PAS 100 (2005) summary

The PAS 100 aerobic composting guide is concerned primarily with HACCP (Hazard analysis critical control point) and quality control. HACCP planning is considered to be a system of product safety assurance which identifies potential hazards and vital procedures that must be carried out correctly to enable smooth operation without incidents or errors. Development of detailed standard operating procedures (SOP’s) greatly reduce the rate of errors in compost formulation and allow refined recipes to be developed, improving performance.

The catering wastes delivered to Abbey Recycling contain animal by-products and would usually be bound by the strict regulations regarding their disposal. However, catering waste is considered a non-animal by-product if it is subsequently composted (PAS 100).

Batch formation records- including the composition, formation and finish dates, a batch code and a recording of activities carried out on the compost or on each component material (such as mixing, shredding drying, wetting and the use of additives. With a fairly rigorous records system in place the client will be able to discover how the addition of different proportions of materials affect the quality and the time required for compost maturation.

In the HACCP plan the sanitization step is the critical control point for pathogen risk control which is especially important when dealing with catering waste (from animal origin). The critical limits include time, temperature, moisture, turning/mixing or aeration. A composting batch can only be considered sanitized if the composting conditions and batch management were maintained within the critical limits or by analysing a sample of the compost to show it conforms to the pathogen quality requirements.

The compost stabilization and maturation parameters are other examples of critical control points. Maturation may be considered complete after a particular duration of time has passed or the compost has fallen below a certain temperature. A compost pile is considered unstable after a period of time has elapsed if it still contains a high proportion of biodegradable matter that may sustain high microbial activity.

Laboratory analysis can also indicate whether a compost pile has matured and is stable. A carbon: nitrogen ratio of below 20:1 is an indication of compost maturity. A BOD/COD value of less than 0.1 is also likely to correspond to compost stability. A low BOD/COD value may indicate the presence of resistant or recalcitrant compounds or the presence of inhibiting substances preventing microbial biodegradation. The use of several different analytical tools will improve the testing accuracy in compost analysis. Once the compost predominantly consists of recalcitrant compounds and humus-like matter the microbial populations present have no longer have access to utilisable carbon sources and die off leading to further decomposition by Actinomycetes and fungi.

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Product preparation may involve screening to create a particular grade of particle size, blending with other wastes, materials, composts, products or additives, or addition or reduction of the moisture content. Any batches of compost that do not conform to the PAS requirements should be re-composted, dispatched from the site for use or disposed of with notification of the nature of the unconformity. The maximum tolerated limits for the required parameters in compost for general use are listed in Appendix 1.

2 The characterisation of the grease trap waste

The waste is stored in two large slurry pits on the Abbey Recycling premises which were filled to capacity at the time of the site visit (December 2009) (Figure 1). The grease trap waste has separated over time into three distinct layers (Figure 2). As the properties of each layer differs considerably each fraction must be considered separately in regard to the method of utilisation/disposal.

Figure 1- The slurry pit 1 containing the undisturbed fat, grease trap water and food waste layers.

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Figure 2- A diagrammatic profile of the grease trap waste showing the three distinctive separate layers present within the storage facility at Abbey Recycling.

2.1 Analysis and utilisation options for the top fat layer

The top fat layer possesses a high dry matter content (an average of 71.44% total solids), which also indicates the layer possesses a low water content, which would be considered beneficial for composting (Table 3). As a high water content can restrict the passage of oxygen to the microorganisms possibly leading to anaerobic conditions. However, as the top fat layer samples have a carbon: nitrogen ratio of between 254:1 and 593:1 a large quantity of nitrogen-rich material should be added to produce the optimum carbon: nitrogen ratio of 30:1 or the microbial degradation will progress at a much slower rate requiring greater time to mature. The top fat layer is shown in Figure 3.

Table 3- Analysis of the top fat layer

SAMPLE ID Top Fat layer 1 Top Fat layer 2

QUESTOR ID 09-Dec-18 09-Dec-19

pH 3.36 3.28

Total Nitrogen (mg/l as N) 1290 910 Oils,Fats and Greases

(g/kg) 128 301

Dry matter (%) 69.86 73.02

C (%) 71.14 58.40

H (%) 10.21 11.21

N (%) 0.12 0.23

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Figure 3- The top solid fats and grease layer was approximately 30cm deep making sampling of the liquid layer underneath very difficult.

The almost completely solid top fat layer should be broken into smaller less coarse fragments, to aid faster microbial biodegradation of the fatty material. The average amount of oils, fats and greases in the two samples was 214.5g/kg (21.45%). This layer contains the majority of the fat in the grease trap waste and this should either be scrapped off the top of the middle layer to stop further contamination of the grease trap water (middle layer) or remove the middle layer (grease trap water) leaving behind the top and bottom layers.

A solid portion of the top fat was tested for oils, fats and greases as well as the mixed semi-liquid top fat layer and to our surprise found the solid fat contained less collectively entitled “fat” than the mixed top layer (80g/kg compared to an average of 214.5g/L). This could indicate a higher presence of unsaturated fats existing in a liquid state in the top fat layer while the solid lumps may have consisted of a higher proportion of saturated fats in the solid state as well as a large quantity of unidentified solids.

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2.2 Analysis and utilisation options of the middle layer (grease trap water)

The middle layer (grease trap water) makes up the vast majority of the delivered grease trap waste (~70% by volume). This aqueous layer was light brown in colour and homogenous in consistency. The middle layer was analysed on three separate occasions over the course of three months to observe whether there were any changes in the properties of the grease trap water over time (Table 4).

Table 4- Analysis of Abbey Recycling grease trap water samples. The parameters required for the classification of “dirty water” are highlighted in red.

SAMPLE ID Grease Trap Water 11/09/09

Grease Trap Water 03/11/09

Grease Trap Water 10/12/09

sample 1 sample 2 sample 3

pH 3.5 3.45 4.92 Conductivity (mS @ 25°C) 4.17 - -

Chloride (mg/l) 715 - -

Dry Matter (%) 0.95 1.07 2.54 Total Ammonia (mg/l as N) 84.9 - -

Total Nitrogen (mg/l as N) 466 524 600 Total Phosphate (mg/l as P) 39 - 61

Alkalinity (mgCaCO3/l) 0 - - Oils,Fats and Greases (mg/l) 88 169 372

Nitrate (mg/l as N) 3 - -

Nitrite (mg/l as N) <0.003 - -

BOD (mg/l) 480 381 4622 COD (mg/l) - - 18070

The biochemical oxygen demand (BOD) test measures the rate of oxygen uptake by micro-organisms in a sample of water at a temperature of 20°C and over a period of five days in the dark. The test gives an indication of the quality of water or various effluents. The low pH of the grease trap water samples indicates the partial degradation of the long chain fats and oils producing fatty acids. Dilution of the grease trap waste will have very little effect on the pH. It would be down to the clients discretion whether the pH may require neutralisation before use as either a fertiliser or an additive to compost.

2.3 Problems in using grease trap water in compost

The grease trap water samples (1, 2 and 3) consisted of too much water to be effectively used in aerobic composting. The levels of fat present within the samples was much lower than expected (less than 400mg/L in each sample), the quantity of grease trap water added to compost should be restricted as too high a water content will prevent oxygen circulation within the compost resulting in anaerobic conditions. The pH of the compost is not usually a

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concern when kept aerobic, but high quantities of the acidic grease trap water could cause problems if the overall pH drops below 5. If this is the case a strongly alkaline compound such as lime may be added to raise the pH to a more neutral level, increasing the microbial activity within the compost. A more concentrated fatty waste with a lower water content would be more appropriate for use in aerobic composting. In both aerobic and anaerobic composting, increasing the surface area on which microorganisms can act will promote faster decomposition. Chopping the compostable materials into smaller pieces will increase the available surface area for microorganisms.

The grease trap waste water (the middle layer) has been analysed on three separate occasions over a three month period. The results obtained are shown in Table 4. If permitted by the Northern Ireland Environmental Agency legislation the preferred method of utilisation for the grease trap water would be to spread it on land as “dirty water”. The tabulated results show an increase in the required parameters over time (dry matter, total nitrogen and BOD). It is likely that additional organic compounds from the bottom food waste layer and the fat layer are becoming increasingly incorporated into the middle grease trap water layer over time. The rise in these parameters may also be caused by the microbial biodegradation of the fats and other organic compounds present at the grease trap water/ food waste and grease trap water/top fat layer interfaces and the subsequent microbial growth and reproduction on the obtained sources of carbon and energy.

The problem is that the longer the grease trap water is stored in the slurry pits the worse its condition becomes in regard to the BOD and other related parameters. For the grease trap water to be utilised as “dirty water” it should be separated from the thick (high BOD) top and bottom layers on arrival, by the use of a settling tank. The grease trap water can then be tested as soon as possible to see whether it conforms to the maximum tolerated limit on each of the required parameters. Once it has been separated it can be spread relatively quickly on the surrounding agricultural land leaving the top and the bottom layers. The top and bottom layers may be processed by dewatering (if required) to further reduce the water content of the fatty waste to make it more suitable for use in composting. The removal followed by the subsequent dispensing of grease trap water will free up much more storage space for further deliveries of grease trap waste.

If the undivided grease trap waste was stored for an extended period of time in the slurry pits the middle layer would not be suitable for spreading leaving very few options for its disposal. If the grease trap water was found to be just above the maximum tolerated values then it could be diluted appropriately with water such as collected rain water in open drums or barrels. If the testing of the grease trap water for the three required parameters is considered too expensive for batch testing an alternative plan may be considered. QUESTOR ATU can demonstrate how to measure the dry matter of the grease trap layer to the client allowing this analysis to be performed by Abbey Recycling. The equipment required is a balance and an oven capable of reaching 160oC. If the dry matter is well below the threshold of 1% it could be surmised that the other values were also below the required threshold. If the dry matter was close to or above the threshold then a sample may be sent for analysis to find out to what extent the grease trap waste requires dilution to meet the required parameter thresholds.

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2.4 Spreading to land of collected grease trap water

After several telephone conversations with Bryan Irvine from DARD it has become clear the rules and regulations set by DARD are superseded by those set by the Northern Ireland Environmental Agency (NIEA) in regard to the type of Waste Management licence (or exemption) held by Abbey Recycling.

After consultation with Jim Wright (N.I. Environmental Agency, phone no. 02890569435) the exemption currently held by Abbey Recycling ("Biodegradable kitchen and canteen waste", EWC code 20 01 08) only permits the grease trap waste to be treated via composting. This code does not qualify for the necessary exemption allowing the spreading to land of the grease trap water (middle layer). A waste management licence could be applied for in this circumstance, but this is not recommended as it is a drawn out and costly process requiring a planning procedure and discharge consent. The exemptions generally cover smaller scale activities that are unlikely to cause any negative impact on the surrounding agricultural area. The application for an exemption incurs a much lower cost as well.

There are two EWC codes that the grease trap waste may qualify for in Table 3 of the Environmental Protection Waste Management Licensing Regulations (see Appendix 2). The first code is 19 05 03 “off-specification compost consisting only of biodegradable waste” and the second code is 20 02 01 “biodegradable waste”. If the grease trap water (middle layer) can be classed as one of these wastes either after a treatment process or “as is” then an exemption may then be applied for, which may then allow the spreading of grease trap water provided it passes the accepted limits for “Dirty Water” onto the surrounding agricultural land. If the clients decide to follow this route they will need to contact the N.I. Environmental Agency for further instructions. QUESTOR ATU has supplied an electronic copy of the application form and guidance notes along with the Waste Management Licensing Regulations (Northern Ireland) 2003 document on a compact disk.

2.5 Suitability of the grease trap water to meet the requirements of “dirty water”

Provided the grease trap water qualifies for an exemption to allow the spreading to land and it passes the required limits stated in the Nitrate Directive the middle layer may be disposed of as “dirty water”. Dirty water is classified in the Nitrate Directive to be a low dry matter waste consisting of water contaminated by manure, urine, effluent, milk, and/or cleaning materials and it must possess a biochemical oxygen demand of no greater than 2000mg/L and must also have a dry matter of less than 1%. The total nitrogen in a sample is limited to 0.3g/L or 300mg/L to be classed as “dirty water”. Dirty water has no restrictions regarding when it can be spread on land and so may be distributed regularly all year round, reducing the total volume of liquid waste contained within the storage facility. For further information on the Nitrate Directive see Appendix 3.

The grease trap water of samples 1 and 2 averages out at 1.01%, just above the 1% limit of dry matter. The biological oxygen demand of the grease trap water waste is well below the BOD limit of 2000mg/L. The parameter that is well over limit is the total nitrogen value of the grease trap water. The average total nitrogen value was 495mg/L which is 195mg/L above the maximum accepted limit. The grease trap water samples as they stand do not pass for dirty water but by simply diluting the grease trap water with tap water in a ratio of 1:1 the parameters would fall below the required limits and allow spreading of the waste throughout the year.

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2.6 Analysis and utilisation options of the bottom food waste layer

The bottom layer of the grease trap waste was obviously above the specifications required to pass as “dirty water” so this method of utilisation could not be considered in its present form. The collected samples were centrifuged to produce a pellet of the suspended solids and a supernatant liquid which was then tested to see if it met the maximum tolerated levels of the required parameters of “dirty water”. Unfortunately the BOD, total nitrogen and suspended solids (Table 5) were well above these levels indicating this processed liquid is unsuitable for spreading to land in this instance.

Table 5- Analysis of the processed and unprocessed bottom food waste layer

Sample description

Bottom layer food waste sample 1

Bottom layer food waste sample 2

Centrifuged supernatant

sample 1

Centrifuged supernatant

sample 2

QUESTOR ID 09-Dec-20 09-Dec-21 09-Dec-20 09-Dec-21

pH 3.39 3.39 3.38 3.36

Total Nitrogen (mg/l as N) 2360 3380 660 790 Total Phosphate (mg/l as

P) ‐ ‐ 147 159 Oils,Fats and Greases

(g/L) 31.112 68.020 2.104 1.202

Suspended Solids (mg/l) ‐ ‐ 3308 4932

COD (mg/l) ‐ ‐ 36500 42100

BOD (mg/l) ‐ ‐ 6062 6742

Total Solids (%) 6.76 15.56 ‐ ‐

The food waste layer is also suitable for use in composting and this would be the intended method of utilisation. Extra dry materials should be added to the compost pile to balance out the water content of the food waste layer so that the compost contains the optimum quantity of water.

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3 Compost analysis

In an attempt to optimise the conditions for successful composting of the grease trap waste the carbon: nitrogen ratio of the compost, the compost leachate and the solid top fat layer were determined by means of the CHN test. The oil, fat and grease content of the compost, the compost leachate and the individual grease trap waste components was also determined to allow the total concentration of fat to be estimated by the client in the current and future compost piles (Table 6).

Table 6- Oils, fats and greases testing and CHN analysis of grease trap waste layers and compost materials.

SAMPLE ID

Top layer

1 Top

layer 2 Middle layer 1

Middle layer 2

Middle layer 3

Bottom layer 1

Bottom layer 2 Fats Compost

Compost leachate

QUESTOR ID

09-Dec-18

09-Dec-19

09-Dec-20

09-Dec-21

09-Dec-22 09-Dec-20 09-Dec-21 09-Dec-23 09-Dec-24 09-Dec-25

Oils,Fats and Greases (g/L unless

solid) 128 301 g 0.088 0.169 0.372 31.112 68.02 80 g/kg 72 g/kg 60 g/kg

C (%) 71.14 58.40 - - - - - 55.84 18.11 75.01

H (%) 10.21 11.21 - - - - 12.45 10.03 12.01

N (%) 0.12 0.23 - - - - - 0.00 0.60 0.01

Analysis of the compost revealed it contained 72g/kg of oils, fat and greases. The CHN test (carbon, hydrogen and nitrogen) revealed that the compost had 18.11% of carbon and 0.60% of nitrogen which equates to a ratio of 30.18 to 1. This ratio is very suitable to produce good compost in the fullness of time (Figure 4). If insufficient quantities of nitrogen are added to the compost the degradation will proceed at a much slower rate. However, nitrogen deficient compost may be increased by the action of nitrogen-fixing bacteria followed by the subsequent microbial growth on the fats present. At the time of sampling, the compost contained a relatively high oil, fat and grease content of 80g/kg (or 8%) indicating the level of fat in compost is well within the recommended range of 5-15% (Ruggieri et al. 2008). This figure also suggests that the composting process needs to continue for a longer time period before all the fat is biodegraded and the pile stabilises (also indicated by temperature).

The sample of solid top fat analysed by the same means as the compost was found to possess 55.84% carbon and 0% nitrogen. Due to this material containing absolutely no nitrogen at all it should be added carefully with nitrogen rich material to keep the most efficient carbon: nitrogen ratio for faster degradation (for more carbon: nitrogen ratio information refer back to Table 2).

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Figure 4- The compost heap, with steam, odours and volatile organic compounds escaping the compost pile and entering the surrounding atmosphere.

4 The compost leachate

The client queried what to do with the greasy dark brown/black liquid residue leaving the compost pile (shown in Figure 5). The liquid run-off could be collected in the next batch within drainage channels surrounding the compost, then the residue may be collected and reapplied to the compost when it is next being tossed or mixed. Analysis of the liquid run-off indicated that the carbon: hydrogen ratio of the organic material had increased relative to both the compost material and the solid fat sampled. This information may indicate either the compounds in the leachate have been partially degraded or the run-off contains a higher ratio of unsaturated fat. As there is almost no nitrogen in the run-off (0.01%), the reapplication of large quantities of liquid run-off may require additional nitrogen-rich containing materials to be added (refer to back to Table 2 for examples).

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Figure 5- A fat oily leachate that pours out of the compost at thermophilic temperatures

5 Alternative uses for waste

There are a number of options to consider when deciding how to use or dispose of the various layers in the grease trap waste. These include the production of biodiesel or the formation of solid fuels for wood chip burners. The use of waste fat in animal feed is no longer permitted.

5.1 Description of biodiesel formation

The production of fatty acid methyl esters (biodiesel) is a well-known chemical process. Currently three common types of biodiesel production technologies are available and their selection will depend on feedstock quality and the state-of-art of a facility. Methyl esters can be produced from fats and oils which are composed of molecules called triglycerides. Each triglyceride is composed of three long-chain fatty acids of 8 to 22 carbons attached to a glycerol backbone. The glycerol molecules are almost completely removed from the final biodiesel products. Biodiesel is composed of fatty acid chains that are chemically bonded to one methanol molecule. When the fatty acid chains break off the triglyceride, they are known as free fatty acids. Feedstocks that contain free fatty acids can be used as biodiesel feedstocks, but require different conversion processes. Commercially used processes for biodiesel production are as follows:

Base catalysed transesterification with refined oils Base catalysed transesterification with low free fatty acid greases and fats Acid esterification followed by transesterification of low or high free fatty acid

greases and fats.

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Each of these processes typically utilises methanol (ethanol has been considered as well) in the presence of a base catalyst such as sodium or potassium hydroxide to produce mono-alkyl ester based oxygenated fuel (methyl or ethyl esters) commonly known as biodiesel and glycerine as a by-product.

Natural vegetable oils and animal fats are extracted or pressed to obtain crude oil or fat. These usually contain free fatty acids, phospholipids, sterols, water, odorants and other impurities. Even refined oils and fats contain small amounts of free fatty acids and water. The free fatty acid and water contents have significant effects on the transesterification of glycerides with alcohols using alkaline or acid catalysts; they also interfere with the separation of fatty acid esters and glycerol. Considerable research has been done on vegetable oils as diesel fuel. That research included palm oil, soybean oil, sunflower oil, coconut oil, rapeseed oil and tung oil.

Animal fats, although mentioned frequently, have not been studied to the same extent as vegetable oils. Some methods applicable to vegetable oils are not applicable to animal fats because of natural property differences. Some natural glycerides contain higher levels of unsaturated fatty acids; they are liquids at room temperature. Their direct use as biodiesel fuel is precluded by high viscosities. Fats, however, contain more saturated fatty acids. They are solid at room temperature and cannot be used as fuel in a diesel engine in their original form. Because of the problems such as carbon deposits in the engine, engine durability and lubricating oil contamination associated with the use of oils and fats as diesel fuels, they must be derived to be compatible with existing engines. Figure 6 illustrates the general process for the manufacture of biodiesel. The equipment required would be costly and with such a small margin in the production it is unlikely to be financially viable.

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Figure 6- The process illustrated above is the general process for the production of biodiesel from vegetable oils.

Abbey Recycling were contemplating using the small portion of top fats (approximately 5% of the total volume) to manufacture biodiesel. Due to the low quality of the fat layers and the increasing costs of the additional chemicals required to manufacture the bio-fuel, it would not be a cost effective use of the material. The fats would also be difficult to process due to the inconsistent nature of their collection, which would require the transesterification process recipe to be varied on a batch by batch basis. It is the view of QUESTOR ATU that to consider using this process would be to over-engineer the solution as the fat layers can be used in the composting process as long as they are added in a controlled manner to stabilise the carbon to nitrogen ratio.

5.2 Blending with woodchips for fuel

Wood chips have become an important fuel source as environmental consciousness increases amongst the general public and alternatives to fossils fuels are sought for domestic heating. Due to the inherent lower calorific value of wood chips (compared to fossil fuels e.g. coal) there are several key disadvantages associated with their use; larger appliances are required to generate the same heat output, more space is required for fuel storage and more frequent fuel deliveries are required.

The impact of these disadvantages can be lessened by blending wood chips with another fuel of higher energy content. This has been successfully carried out by co-combustion with coal

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(Energy for Industry (NZ) 2008) and with fuel derived from municipal solid waste (Patino et al. 2008), but no examples have been found of wood pellets being upgraded by combination with grease trap or other oily wastes.

It can be shown by calculation (see supplementary CD) that the grease layer can be used to increase the calorific value of wood chips for use in boilers, but that the removal of at least 50% of the water from the grease layer (in addition to that removed by settling) is required to do this. It is likely that much greater dewatering will be required in order to justify the capital and operating costs involved in the dewatering and blending steps and therefore this option can be considered cost prohibitive.

Additionally, given the source of the waste, it is likely to that the burning of this material is prohibited under the Animal By-Products Regulations (Northern Ireland) (UK Government 2003).

6 Conclusion

To summarise the findings in this report, we recommend the grease trap waste should be separated on arrival to the Abbey Recycling facilities. This is carried out by placing the grease trap waste into a settling tank and once the three characterised layers have formed the middle layer is removed leaving the top fat layer and the bottom food waste layer. The top and bottom layers are suitable for blending into compost provided additional nitrogen-rich materials are added to compensate for nitrogen deficient grease trap waste.

The middle layer is not suitable for use in composting due to it being almost entirely comprised of water. Adding too much water to the compost will prevent adequate aeration, cause foul-smelling odours and lead to anaerobic conditions if not turned regularly. Anaerobic conditions are not desired as the compost will not heat up in the same way as aerobic composting meaning many pathogenic species of bacteria would still be present in the stabilised compost end-product.

The most cost-effective method of disposal for the grease trap water (middle layer) is to be spread as “dirty water” under the legislation stated in the Nitrate Directive. However, Abbey recycling do not currently possess the required exemption code to legally do so. An application to the N. I. Environmental Agency is required to attain this exemption, but if it is successful it would alleviate the current problems associated with composting the grease trap water. If the exemption was granted then the grease trap water would have to possess a dry matter, BOD and a total nitrogen value below the maximum accepted limits. The analysis performed on the grease trap water on three separate occasions has revealed the middle layer becomes progressively less compliant in respect to these three parameters over time. For the grease trap water to pass as “dirty water” it must be separated immediately from the top and bottom layers possessing much higher dry matter and BOD values preventing the contamination of the middle layer over time observed during this investigation.

Should the exemption for spreading onto land not be granted, other less financially viable options must be considered. An application for a waste management licence could be lodged, but this process is expensive, time consuming and has no guarantee of success. Alternatively, a waste water treatment plant could be contacted to establish whether they are willing to accept the grease trap water. This may incur significant costs and given this layer is not

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suitable for biodiesel formation or wood chip recombination the costs of disposing this grease trap water may outweigh the revenue obtained from accepting the grease trap waste.

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References

Annan, J.S., White, R.K., (1998). Evaluation of techniques for measuring air filled porosity in composts of municipal biosolids and wood chips. In: Das, K.C., Graves, E.F. (Eds.), Composting in the Southeast-Proceedings of the 1998 Conference, SC, USA, pp. 88–96.

Green, D.W. & Perry, R.H. (2008). Section 2: Physical and Chemical Data. Perry's Chemical Engineers' Handbook, 8th Edition edn, McGraw-Hill, pp. 2-1-2-202.

Patino, D., Moran, J., Porteiro, J., Collazo, J., Granada, E. & Miguez, J.L. (2008) Improving the cofiring process of wood pellet and refuse derived fuel in a small-scale boiler plant. Energy and Fuels, 22, 3, p. 2121-2128.

Rogers, G.F.C. & Mayhew, Y.R. 1994, Thermodynamic and Transport Properties of Fluids (S.I. Units).

Ruggieri L., Artola A., Gea T., Sanchez A. (2008) Biodegradation of animal fats in a co-composting process with wastewater sludge. International Biodeterioration & Biodegradation 62 (2008) 297-303

Energy for Industry (NZ) 2008, Co-firing of biomass with coal at the Dunedin Energy Centre.

HMG (2003), Animal By-Product Regulations (Northern Ireland).

http://tomato-tips.com/aerobic-vs-anaerobic-composting-whats-the-difference.html

http://www.ecochem.com/t_compost_faq2.html

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Appendices

Appendix 1

Minimum compost quality for general use (PAS 100 Summary)

parameter test method unit upper limit

Salmonella BS EN ISO 6579 25g fresh mass absent

E. Coli BS ISO 11866-3 CFU/g fresh mass 1000

Cadmium BS EN 13650 mg/kg dry matter 1.5

Chromium BS EN 13650 mg/kg dry matter 100

Copper BS EN 13650 mg/kg dry matter 200

Lead BS EN 13650 mg/kg dry matter 200

Mercury BS ISO 16772 mg/kg dry matter 1

Nickel BS EN 13650 mg/kg dry matter 50

Zinc BS EN 13650 mg/kg dry matter 400

Microbial respiration rate ORG 0020 mg CO2/g organic matter/day 16

Germination and growth test BSI PAS 100:2005 Annex D

reduction in plant germination in compost as % of germinated plants in peat control 20

reduction in plant mass in compost as % of plant mass in peat control 20

any visible abnormalities 0

germinating weed seeds BSI PAS 100:2005 Annex D mean no. /L of compost 0

total glass, metal, plastic and other non-stone fragments >2mm

BSI PAS 100:2005 Annex D % mass/mass of air dried sample

0.5 (of which 0.25 is plastic)

stones >4mm (other than mulch)

BSI PAS 100:2005 Annex D % mass/mass of air dried sample 8

stones >4mm in mulch 16

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Appendix 2

Wastes identified by European Waste Catalogue (EWC) codes, Table 3 (Waste Management Licensing Regulations (Northern Ireland) 2003).

EWC Code Types of waste Limitation

PART I

Wastes from agriculture, horticulture, aquaculture, forestry,hunting and fishing (02 01)

02 01 03 plant-tissue waste

Wastes from sugar processing (02 04)

02 04 01 soil from cleaning and washing beet

Wastes from wood processing and the production of panels and furniture (03 01)

03 01 01 waste bark and cork

03 01 05 Sawdust, shavings, cuttings, wood, particle board or veneer other than those mentioned in 03 01 04

Except whole wood, particle board and plastic veneer

Wastes from pulp, paper and cardboard production and

processing (03 03)

03 03 01 waste bark and wood

Soil (including excavated soil from contaminated sites),

stones and dredging spoil (17 05)

17 05 04 soil and stones other than those mentioned in 17 05 03

Wastes from aerobic treatment of solid wastes (19 05)

19 05 03 off-specification compost consisting only of

biodegradable waste

Garden and park wastes (including cemetery waste) (20 02)

20 02 01 biodegradable waste

20 02 02 soil and stones

PART II

Wastes from agriculture, horticulture, aquaculture, forestry,

hunting and fishing (02 01)

02 01 99 Waste not otherwise specified Straw, wood or paper–based bedding waste, slurry or dirty water

from stables, zoos, animal parks or

livestock markets only

Wastes from the preparation and processing of meat, fish

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and other foods of animal origin (02 02)

02 02 03 Materials unsuitable for consumption or processing Blood and gut contents from

abattoirs or poultry preparation plants only

Wastes from fruit, vegetables, cereals, edible oils, cocoa,

coffee, tea and tobacco preparation and processing;

conserve production; yeast and yeast extract production;

molasses preparation and fermentation (02 03)

02 03 01 to

02 03 05

All types within 02 03 01 to 02 03 05

Wastes from sugar processing (02 04)

02 04 01 to 02 04 03


Wastes from the dairy products industry (02 05)

02 05 01 to

02 05 02


Wastes from the baking and confectionery industry (02 06)

02 06 01 to 02 06 03


Wastes from the production of alcoholic and non-alcoholic

beverages (except coffee, tea and cocoa) (02 07)

02 07 01 to

02 07 05


Wastes from pulp, paper and cardboard production and

processing (03 03)

03 03 05 De-inking sludges from paper recycling

03 03 09 lime mud waste

03 03 99 Waste not elsewhere specified De-inked paper pulp

from paper recycling

Wastes from the leather and fur industry (04 01)

04 01 07 sludges, in particular from on-site effluent treatment

free of chromium

Wastes from the textile industry (04 02)

04 02 10 organic matter from natural products (for example

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grease, wax)

04 02 15 Wastes from finishing other than those mentioned in 04 02 14

04 02 20 sludges from on-site effluent treatment other than those

mentioned in 04 02 19

04 02 21 Wastes from unprocessed textile fibres

04 02 22 Wastes from processed textile fibres

Wastes from manufacture of cement, lime and plaster and

articles and products made from them (10 13)

10 13 04 Wastes from calcination and hydration of lime

Soil (including excavated soil from contaminated sites),

stones and dredging spoil (17 05)

17 05 06 dredging spoil other than those mentioned in 17 05 05

Wastes from anaerobic treatment of waste (19 06)

19 06 03 liquor from anaerobic treatment of municipal waste

19 06 04 digestate from anaerobic treatment of municipal waste

19 06 05 liquor from anaerobic treatment of animal and vegetable waste

19 06 06 digestate from anaerobic treatment of animal and

vegetable waste

Wastes from the preparation of water intended for human

consumption or for industrial use (19 09)

19 09 02 Sludges from water clarification

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Appendix 3

Implementation of the Nitrate Directive

Northern Ireland suffers from a number of water quality problems affecting a large number of rivers and lakes which in some cases extending to marine waters. The nitrates Directive aim to reduce the pollution of water caused by the application of inorganic fertiliser and manure on farmland. The mandatory standard set by the Surface Water Directive is that 95% of (surface and groundwater) samples should be less than 50mg/L nitrate. A guide standard was also set that 90% of samples should be less than 25mg/L nitrate.

The Nitrates directive also applies to eutrophic (enriched nutrient) water sources or water sources under threat of becoming eutrophic where a significant amount of the nitrates present are from agricultural practices. Eutrophication is caused by excessive quantities of nitrogen and particularly phosphorus in fresh water sources and nitrogen in seawater. The dissolved nutrients lead to an accelerated growth of algal blooms reducing the levels of dissolved oxygen which leads to the extinction of higher organisms.

Eutrophication leads to health risks from contamination of drinking water supplies and recreational waters by toxic algae and algal scums, extra costs in removing algae from water treatment facilities, loss of biodiversity, loss of fisheries, results in limits or added costs for industry and agriculture and undesirable odours and loss of transparency of the water source.

Grease trap water waste may contain sufficient levels of nitrogen and phosphorus that may cause environmental problems if not disposed of properly. This is more likely to occur if the grease trap water has been stored for extended periods of time as nitrogen-fixing bacteria will increase the total nitrogen content. Inadequate spreading of grease trap waste water onto farmland may result in high levels of phosphorus and nitrate entering surface waters leading to a proliferation of algal blooms consuming the available oxygen and killing any fish present. Spreading of grease trap waste may cause undesirable odours emanating from the surrounding area and may attract rodents to the location.

Requirements of the Nitrates directive

A closed period exists when organic and inorganic fertilisers may not be applied (between the 15th of September to 31st January). Organic manure, excluding farmyard manure, may not be applied to any land between 15 October in any year and 31 January of the following year. A minimum storage capacity is required that must exceed the storage requirement for manure produced over the closed period. The application of fertilisers on land is limited so the quantities applied do not exceed the nitrogen requirements of the crops. The calculation should also take into a count the nitrogen present in the soil.

Nitrogen fertiliser land application requirements

The current legislation as stated in the nitrates action programme regulations (Northern Ireland) 2006 that should be followed when spreading the grease trap waste water (nitrogen fertiliser) on land are listed below:

1. The land application of nitrogen fertiliser shall be done in an accurate and uniform manner and, other than for dirty water, in accordance with paragraphs (2) to (8).

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2. The land application of nitrogen fertiliser shall not be permitted when: - (a) soil is waterlogged; or (b) land is flooded or likely to flood; or (c) the soil has been frozen for 12 hours or longer in the preceding 24 hours; or (d) land is snow-covered; or (e) heavy rain is forecast within 48 hours; or (f) the land is steeply sloping land where, taking into account factors such as proximity to waterways, soil condition, ground cover and rainfall there is a significant risk of causing water pollution. 3. The land application of nitrogen fertiliser shall not be permitted on any land in a location or manner which would make it likely that the nitrogen fertiliser will directly enter a waterway or water contained in any underground strata. 4. The land application of chemical fertiliser shall not be permitted within 1.5 m of any waterway. 5. The land application of organic manures shall not be permitted within: – (a) 20m of lakes; or (b) 50m of a borehole, spring or well; or (c) 250m of a borehole used for a public water supply; or (d) 15m of exposed cavernous or eroded limestone features (such as swallow–holes and collapse features); or (e) 10m of any waterway, other than lakes, including open areas of water, open field drains or any drain which has been backfilled to the surface with permeable material such as stone/aggregate; except that (f) the distance for (e) may be reduced to 3m of any waterway where the land has an average incline less than 10% towards the waterway and where: (i) organic manures are spread by band-spreaders, trailing hose or trailing shoe or soil injection; or (ii) the adjoining area is less than 1 hectare in size or not more than 50m in width. 6. The maximum land application of solid organic manure shall be 50 tonnes per hectare at any one time provided this does not exceed the limits set out in regulation 9(1) and 10(3) and a period of at least 3 weeks shall be left between such land applications. 7. The maximum land application of slurry shall be 50 m3/ha at any one time provided this does not exceed the limits set out in regulation 9(1) and 10(3) and a period of at least 3 weeks shall be left between such land applications. 8. The land application of slurry shall only be permitted by spreading close to the ground using inverted splash plate spreading, band-spreading, trailing hose, trailing shoe, soil injection or soil incorporation method.

Documents

The characterisation and utilisation of grease trap waste€¦ · Directive and Waste Management Licensing, utilisation options of each layer of the grease trap waste as well as exploring