Proceedings

Organic materials have been applied to land over many years, for their nutrient content and soil conditioning properties. A great deal of data and research currently exists for some of these materials (e.g. composts and sewage sludge), and their behaviour once applied to land is comparatively well understood. However, a gap in the data exists for materials from more novel processes and established processes using new feedstocks (e.g. anaerobic digestion of food wastes).  The objective of this study was  to compile  disparate data  sets  that exists for  these organic materials  that are currently being applied to land, to give a state of the art assessment of  potential benefits and risks. Data was collated from over 50 research studies, and from data supplied by 2500 operators for regulatory compliance.  The performance and issues associated with particular waste types was then ranked using a risk assessment framework developed for the project. The application of these wastes was determined in terms of benefit and potential impact for a number of specific receptors which include:  Emissions to air (greenhouse gases and ammonia) ; ground and surface water ;  agronomic benefit ;  pathogens and soil.

The assessment methodology focussed on the baseline properties of  the various organic materials  linked to the feedstock and process from which the material was produced. The study establishes where similarities exist between residues from similar types of processes, and highlights the main differences between materials. The work highlights where there are gaps in knowledge to enable Defra to prioritise future research.