Optimising inputs and outputs from anaerobic digestion processes

Completed

Not Energy Related
Renewable Energy Sources(Bio-Energy, Production of transport biofuels (incl. Production from wastes))
Renewable Energy Sources(Bio-Energy, Production of other biomass-derived fuels (incl. Production from wastes))

Basic and strategic applied research

BIOLOGICAL AND AGRICULTURAL SCIENCES (Biological Sciences)

Not Cross-cutting
Sociological economical and environmental impact of energy (Environmental dimensions)

Project Contact
University of Southampton

Standard

DEFRA

01 January 2007

31 March 2009

23 months

£259,190

No relevance to Underpinning Sectors

South East

DEFRA Waste Management

Project Contact, University of Southampton

The general aim of the work is to better understand the factors influencing the stabilisation of the organic fraction of municipal solid waste (MSW) in the anaerobic digestion process. In particular, the research will address whether stabilisation, as judged by volumetric gas production, solids destruction and bio-stability of the residues, could be improved by co-digestion with other organic wastes from industry, commerce and agriculture. The scientific aim is to gather and analyse data from laboratory and technical scale trials to assess the factors that control the rates of anaerobic digestion, such as nutrient ratios, fibre composition, and build-up of recalcitrant materials. By understanding these factors, it will be possible to establish standard operating conditions to provide a higher degree of quality assurance for the gaseous, fibre and liquor products recovered. A further environmental aim will be to assess the impact on the `value` of the final residues by the inclusion of organics derived from post-collection segregation. Specific technical and scientific objectives: 1. Characterisation of two municipal waste streams used in a baseline study: one from source segregated material and one after post collection segregation. 2. Use of audit data to identify and select potential co-substrate feedstocks from the commercial, industrial and agricultural sectors, as judged by their potential for both maximising biogas production and the resource recovery potential of the digestate. 3. Physical and chemical characterisation of identified co-substrates for digestion. 4. Determination of biochemical methane potential from the two MSW substrates both in isolation and combination with co-substrates from commercial, industrial and agricultural sources. 5. Continuous feed laboratory-scale trials using both types of MSW and co-substrates to establish their influence on the kinetics of the process and the biogas production compared to those established for the baseline waste types. These studies will also determine process loading rates and reactor conditions for optimisation of biogas production. 6. Digestion trials at a technical scale in a pair of 1.5 m3 digesters to validate laboratory data and establish standard operating conditions for digestion. 7. Assessment of the characteristics of digestates (including separation of the solid and liquid fractions) from different mixtures of substrate for their potential value as agricultural products. This will involve characterisation of the digestates to establish their physical and chemical properties and, in particular, positive benefits that could be achieved by enhancing the nutrient balance for their use as artificial fertilizer substitutes. 8. Measurement of the biostability of the solids separated fraction of digestates from different mixtures of substrates in relation to landfill acceptance criteria.

This project seeks ways to maximise the recovery of biowaste both for renewable energy production and to minimise the disposal of biologically unstable organic materials to landfill. The overall aim of the work is to better understand the factors influencing the stabilisation of organic material from both source segregated and post collection mechanical recovered municipal solid waste (MSW). The work further explores the possibility of enhancing biogas production and increasing the value of the final residue from the anaerobic digestion process by co-digestion with a range of wastes from industry, commerce and agriculture. The research will lead to a better managed use of organic resources by raising awareness of anaerobic biowaste treatment and resource recovery options with stakeholders from a variety of different biowaste-producing industries, the agricultural sector, key government departments, the Environment Agency, and communities that could benefit from renewable energy resources at a local level. The recovery of value from biowastes is an essential element in developing a greater national resource productivity and sustainable use of resources whilst at the same time protecting both human health and the environment. The results of the research will contribute to the evidence base for better-informed policy development for the implementation, monitoring and evaluation for sustainable waste management at both a national and local level.

19/12/11