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50 Evaluation of Opportunities for Converting Indigenous UK Wastes to Wastes and Energy AEA/ED45551/Issue 1 4.4.6 Conclusions Bio-solids are the product of the waste-water treatment works. Even after several stages of treatment it is still largely comprised of water. Increasing waste-water legislation, and increasing population in the UK, results in increased volumes of bio-solids: up to 1,368,000 dry tonnes in 2004. Much of this waste is ultimately recycled to land as a fertiliser but this use will be restricted in the future due to tighter regulation of nitrogen application to agricultural land in some sensitive areas. 4.5 Agricultural Residues and Waste 4.5.1 Definition Agriculture produces a variety of residues, but only limited waste. The distinction is made between controlled wastes and uncontrolled resides. Wastes are items such as chemicals, plastic, containers and other packaging, and controls on this waste stream were introduced in May 2006. Agricultural waste is too heterogeneous and widely dispersed to provide an easy feedstock. Agricultural residues include animal manures and slurry, and crop straws and husks, which rarely leave the confines of a farm, and therefore are not recorded. Such residues are generally homogeneous which makes them a more realistic potential feedstock. Manure and slurry spread at the place of production, for the benefit of agriculture, is not considered to be waste under the current regulations. In 2005 the European Commission judged that livestock effluent would fall outside the classification of waste if it were subsequently used as a soil fertiliser. 73 The application of these residues to land is a traditional practice that helps to replenish nutrients, and reduces the amount of artificial fertiliser that would otherwise be applied. However, agricultural residues can lead to air, land and water pollution if not managed properly. Farm slurries are many times more polluting than human sewage and when not correctly managed can cause serious environmental damage, particularly by adulterating watercourses and producing odours. Heavy fines can be imposed on farmers for pollution of watercourses with animal slurries. In addition traditional disposal methods are increasingly leading to problems. Defra now advise against general spreading of slurry for example, due to concerns about the loss of ammonia to the air. Such concerns are a major driver to re-evaluate the methods for treating and disposing of farm wastes and residues. 4.5.2 Composition Agricultural residues can be subdivided into two categories: • Wet residues are animal slurries and farmyard manures that have a solid content of under 15%. • Dry residues include straw, husks and processing waste, as well as poultry litter from poultry reared for meat. 73 European Court judgment, Case C-416/02 European Commission v Kingdom of Spain, http://europa.eu.int/smartapi/cgi/sga_doc?smartapi!celexplus!prod!CELEXnumdoc&lg=en&numdoc=62002J0416.
Evaluation of Opportunities for Converting Indigenous UK Wastes to Wastes and Energy AEA/ED45551/Issue 1 Wet Agricultural Residues Wet farm residues are characterised by the livestock and waste reception and collection methods, which are largely consistent throughout the UK. Farm slurries are derived from three major sources: cattle, pigs and egg-laying poultry. In addition to animal effluent, other sources of wet farm residues include parlour/dairy/vegetable washings, waste milk, bio-solids and silage effluent. Currently the majority of these residues are recycled to land. Slurry accumulates and must be managed wherever animals are housed, a particular issue during the over wintering of animals indoors, or in milking parlours and egg production facilities. Slurry handling systems usually consist of floor scrapers to move the slurry into channels from which it is pumped into a storage tank or lagoon. Sophisticated systems also use a separator to remove the fibrous portion of the slurry for sale as a compost base, while the more basic systems allow natural settlement. The type of system used is relevant because it can dramatically affect the level of solids collected. Livestock Numbers and Residue Arisings The key aspect to utilising livestock slurry and manures is that they must be collectable, and in practice this limits the utilisation of the residue to when the animals are housed. When the animals are on pasture fields, especially during the summer months, the manure is dropped onto the field and is unavailable for collection. In addition the type of bedding material used will affect the characteristics of the manure or slurry produced. Common bedding materials include straw, wood chips, sand, or compost. 74 Further, the collectable proportion of wet residues is already widely used as a fertiliser, as discussed above, and so availability is also an issue. The UK estimates of livestock residues vary considerably, as these residues are rarely collected or regulated for disposal by third parties. They are estimated from the number and distribution of livestock, and these will change as livestock farming changes each year. The most recent Environment Agency figure for agricultural wet waste was 45 million tonnes, while work performed by AEA generated the considerably higher figure of 67-88 million tonnes produced annually. The diagram below illustrates the quantity and type of residues from typical UK livestock, and the proportion each produces of slurry and farmyard manure (FYM). Quantity ('000 te) 40000 35000 30000 25000 20000 15000 10000 5000 0 15,124 18,142 34,423 4,481 4,901 2,467 FYM Slurry 4,276 4,036 Dairy Beef Pigs Poultry Sheep Figure 10 Slurry and FYM in UK, by main livestock categories 74 Dairy Waste Anaerobic Digestion Handbook, by Dennis A. Burke P.E., June 2001 http://www.mrec.org/pubs/Dairy%20Waste%20Handbook.pdf UK 51
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South East 327 - - 55% of MSW by 20
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Appendix 3 MBT Methods Specific in
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Figure 27 Orchid Environmental proc
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