Draft PPS18: Renewable Energy
Annex 1 Energy from Waste (Biological Processes) Technology: Other Prouducts
C20. As well as biogas, two other important by-products of AD are liquors and solid organic materials. The digestate liquor is a nitrogen rich fertiliser and is generally used on the farms on which it was produced. A potentially wider market has yet to be fully developed, although some AD schemes have successfully bottled and sold the liquor as a liquid fertiliser. Solid organic materials that have undergone incomplete digestion can either be used without further pre-treatment as a soil conditioner or further processed to yield agricultural compost which can be an effective substitute for peat.
C21. When heavy metals and other potentially toxic materials have been removed from MSW it is possible to complete the stabilisation of the digestate solids by composting. The treated product can then be used as a soil conditioner, an organic mulch or for use in land reclamation. If, however, the digestate solid contains significant amounts of heavy metals and toxins, disposal to landfill will be necessary. In such cases reference should be made to the appropriate waste management licensing controls and legislation.