Defra - Department for Environment, Food and Rural Affairs.

Science Search

Science and Research Projects

Return to Science Search homepage   Return to Project List

Implementation of anaerobic digestion in England and Wales balancing optimal outputs with minimal environmental impacts - AC0409

The potential of AD for renewable energy generation, waste treatment and nutrient management has long been recognised. To date there has been limited uptake of AD in the UK but the steady maturation of the technology, and recent and forthcoming changes in government policy, have greatly increased the market and the level of interest in the technology. The overall objective of this proposal is to develop a tool that will enable Defra to identify optimal type and location of AD plants by:
• Quantifying the amounts different wastes (livestock, household food waste, food waste from commerce and industry, energy crops) throughout England and Wales.
• Applying relevant weightings to the priorities between economic and environmental factors.
AEA and ADAS have formed a strong team to deliver this project. The proposed deliverers are familiar with the various types of AD technology and the related economic and environmental issues and challenges. The team members have undertaken extensive work for Defra on the science, policy, strategy and business opportunities around AD technology and organic manure utilization. The work will be carried out under the following tasks.

Task 1: Review and Compilation of Evidence: All waste streams will be reviewed and disaggregated using GIS, to present them for model optimisation (Task 2). The scope for the use of energy crops to supplement waste streams will also be considered, together with land availability to produce such crops. The ADAS ‘Allowance’ tool will be used to calculate the available land bank within each GIS grid, taking account of relevant legislation and codes of practice.

Task 2: Development of Tool/Model Framework: We will develop a suitable spatially-explicit multi-criteria decision making/multi-objective decision making (MCDM/MODM) model to identify a Pareto-optimal set of solutions to the resource allocation to identify and locate prime areas. The spatial distribution of AD uptake will be assessed against the following criteria:
• Economic performance of the AD plant.
• GHG emission reduction.
• Emissions following application to land: nitrous oxide; nitrate; ammonia.
• Indirect impacts on water quality.
• Displacement of food crops.
• Biodiversity.

Task 3: Multi-criteria Analysis: The tool will be run for E&W, making use of spatial datasets derived in Task 1. The output will be a spatially explicit MCDM/MODM framework to identify Pareto-optimal AD plant types and locations.

Task 4: Outcome by scenarios: A range of scenarios relating to feedstock mix, digestate management, proportion of sites upgrading to grid/transport, quality and digestate application will be explored. Best practice guidelines will be produced to ensure AD projects deliver the best possible outcomes.

Task 5: Identification of AD project locations: The performance of potential AD plants in different areas of the country will be assessed to identify the locations of AD plants based on proximity to substrates and minimal emissions of GHGs from transport of substrates to the plant and of digestate to land application.

Task 6: Development of cost curves for AD projects: The AD plants identified in Task 5 will be presented using cost curves to show priorities for implementation.

Task 7: Environmental economics and examination of trade offs: This task will examine the interactions between the economic, GHG mitigation and overall environmental outcomes. The model and the output will allow Defra to:
1. Set out specific objectives and milestones against the vision set out in January 2009 and the Implementation Plan.
2. Prioritise and adopt relevant demonstration and communication strategies.
3. Highlight any gaps in infrastructure in areas with significant AD potential; e.g., it will indicate if a specific collection strategy for food waste is needed.
4. Measure progress against its vision by tracking specific objectives and milestones, including number of AD plants, energy recovery, GHG saving and
5. Be confident to lead industry and other stakeholders to deliver AD capacity in England and Wales that provides value for money counterbalanced by the relevant environmental considerations.
7. (b) Objectives
General Aims
This project is aimed at providing Defra with:
1. A multi-criteria decision-making tool which can be used to select the optimal type, scale and locations of AD (Anaerobic Digestion) plants by examining feedstock mix combinations, technologies and use of the digestate based on scenarios related to economic and environmental issues, including GHG saving, air quality and water quality.
2. Assessments, made using the tool, which identify a Pareto-optimal set of solutions to the problem of optimal location for AD plants based on system inputs and outputs.
The outputs of the research will inform Defra in its drive to encourage wide scale application of AD in England and Wales.
Specific Objectives
The specific objectives for delivery of this project are as follows.
1. To assess the economic and environmental performance of different AD co-digestion mixes, according to location, feedstock availability and use of digestate.
2. To quantify the net GHG impacts of these AD mixes to include products generated, feedstock production and application to land.
3. To quantify the implications of the range of AD systems identified on water/air quality, biodiversity and impacts through land use change.
4. To identify the best practice use for the digestates generated by the co-digestions mixes identified above and resulting infrastructure requirements.
Project Documents
• FRP - Final Report : AC0409 Phase1 Final   (2088k)
• FRP - Final Report : AC0409 Phase2 Final   (2015k)
Time-Scale and Cost
From: 2010

To: 2011

Cost: £173,313
Contractor / Funded Organisations
AEA Technology
Agriculture and Climate Change              
Biomass technologies              
Climate Change              
Sustainable Farming and Food Science