Select Committee on Environment, Food and Rural Affairs Written Evidence


Memorandum submitted by Natural Systems Limited (Bio 04)

  1.  Re item 9: "What more can be done to make more efficient use, as an energy source, of the by-products of agriculture and forestry (eg wood waste and other organic waste)?".

  2.  Agricultural and forestry organic waste is a low-density energy resource and is often widely distributed and of variable composition. These factors militate against transporting these wastes to a central waste-to-energy station. (An exception to this is found with municipal solid waste collected from large conurbations with a large organic content.)

  3.  Organic waste is, excluding woody waste from forestry, ideally suited to anaerobic conversion into biogas and a solid digestate, which is a valuable soil conditioner able to return valuable nutrients back to the land.

  4.  An entry in the New Spirit Challenge competition run by the IEE in 2003 was won by an entry from New Zealand for a fully integrated energy system for dairy farms. This described how cowshed effluent could be used to generate biogas with a high methane content, and for this gas to be used on-site (not stored or compressed). The biogas is used continuously as the fuel in a combined heat and power (CHP) system. The energy of the biogas is converted and stored both as hot water, for hygiene purposes in the dairy milking plant, and as ice, for cooling a dairy herd's milk output. The idea is the subject of a patent filing by Natural Systems Limited.

  5.  UK dairy farming can use this system to reduce its energy costs and deal with manure and bedding material in an environmentally sound manner. Its practice will return valuable organic fertilizer to the land without broadcasting obnoxious odours, or the danger of effluent runoff polluting waterways from raw effluent (muck spreading).

  6.  A dairy farm can take in additional agricultural waste from neighbouring farms where the transport distance is not too great. On farms where there is no requirement for heat or cooling the CHP system can deliver electrical energy into the local distribution network. The surplus low-grade heat, after meeting the requirement to maintain the anaerobic digester at its operating temperature, can be dumped if it cannot be put to a useful purpose.

  7.  This system provides a low cost system that could be replicated in high volumes helping farmers realize value form their slurry and other wastes. Support for early deployments of this technology will help make the systems financially viable, this support will not be required when the number of installations increases; as the industry will benefit from reduced costs due to the volumes.

  8.  Today slurry disposal is an overhead on the farming business and can cause considerable environmental damage if it is not handled correctly. It also helps reduce the emissions of methane gas by farms, methane is a green house gas 23 times more damaging than CO2.

Natural Systems Limited

January 2006





 
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