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130 Evaluation of Opportunities for Converting Indigenous UK Wastes to Wastes and Energy AEA/ED45551/Issue 1 Some water companies are beginning to suggest the co-digestion of waste water and food waste alongside the digestion of bio-solids, such as the proposed site at Cumbernauld in Glasgow by Scottish Water. This arrangement could yield a higher biogas output as well as enabling a higher proportion of ROCs to be earned. Table 69 Risks Associated with Anaerobic Digestion Level of Risk Comment Technical Low to medium Established mature technology with operating commercial plant in existence. Limited experience in UK. Recent incentives may stretch UK suppliers. Poor reputation from early Holsworthy experience. Sensitive to feedstock composition, can be poisoned by Social & Planning trace elements. Medium Not as divisive as an incinerator but transport of slurries in rural areas is a major issue and focus for opposition, as may be large scale transport of food wastes. Financial Low Installations are being financed in the UK at present and further experience should make this easier. Regulatory Medium Receives subsidy via the Renewables Obligation at an enhanced rate of 2 ROCs under the banding arrangements. Policy may change under installations lifetime although current practice is to maintain the financial position of existing plant. The installation is classed as a waste management operation and subject to regulation as such which brings additional costs and responsibility. Digestate disposal is an important consideration and a change of rules could materially affect the operating costs of the installation or even prevent operation. 9.1.1 Anaerobic Digestion of food waste from MSW The AD capacity for solid waste in the UK is growing. From a capacity of 135,000 tonnes in 2004, it increased to 277,000 tonnes through the addition of 6 new plants in 2005 and 2006. 234 This utilisation level is still very small compared to the waste potentially available to it. BERR estimates that the UK generates over 100 million tonnes of wastes that would be suitable for AD (90 million tonnes of agricultural wastes and 9 million tonnes of food waste). It is likely that utilisation levels will continue to grow, assisted by the reclassification of anaerobic digestate to no longer a waste product, so long as it is used as fertiliser on farmland. Defra intend for AD technology to be used throughout the UK by 2020, that it will be “making a significant and measurable contribution to our climate change and wider environmental objectives“ in part through the production of around 10-20TWh of energy. 235 For comparison, Drax power station in North Yorkshire, produces 25TWh annually, approximately 7% of the UK’s electricity mix. 236 234 Anaerobic Digestion and its role in Transport Fuels, Renewable Energy Association, 2007. 235 Anaerobic Digestion – Shared Goals, Defra, 2009, http://www.defra.gov.uk/environment/waste/ad/pdf/ad-sharedgoals-090217.pdf 236 http://www.draxpower.com
Evaluation of Opportunities for Converting Indigenous UK Wastes to Wastes and Energy AEA/ED45551/Issue 1 Almost all UK solid waste AD sites only utilise the biogas collected for the generation of electricity, and some heat required for the process. Little of the remaining heat is utilised, in external heating systems for example. In addition the biogas has the potential to be used in other ways, for example as a transport fuel. Current policy favours the production of electricity. 249 However, the Renewable Energy Strategy and increased targets for renewable heat in the UK may make it more feasible to inject gas into the grid in the future. 237, 238 Current operational AD plants in the UK for solid waste are: • The BioCycle Plant in South Shropshire, run by Greenfinch, has been in operation since 2006 and was built as a Defra Waste Technology Demonstrator Project. The system now takes 4,100 tonnes of kitchen only waste (originally it took kitchen and garden waste but the feedstock was too contaminated) from households and commercial premises, converting it into biogas and ultimately electricity with a 0.2kW output annually. 239 • The Wanlip Composting and AD Plant in Leicester started operation in 2004 at the Severn Trent Sewage Works, using the organic component of MRF from MSW. 240 The waste goes through five processes: homogenisation, sand separation, hydrolysis, digestion, and decantation. The 5mm and smaller component is mixed to a slurry and pumped with air for 24 hours as an aerobic hydrolysis process then the material undergoes an 18 day thermophilic wet AD process, before being composted to produce CLO (compost like output) for further use. The site accepts up to 50,000 tonnes per annum and has a 1.5MW potential output. 166 • Summerleaze Ltd, at Holsworthy, Devon was the UK’s first centralised AD site, and opened in 2005 for the digestion of agricultural slurries. It now handles organic wastes from bakeries and food processors, abattoirs, fish processors, cheese producers, biodiesel manufacturers and local councils in a system capable of processing 80,000 tonnes per annum currently. 241 The methane produced is used to generate 2.7MW, with approximately 10% of this used to run the plant and the remaining 90% exported to the National Grid. 242 One advantage of accepting food waste, is that it attracts higher gate fees than agricultural waste, encouraging the feasibility of the site. • As part of the Western Isles Integrated Waste Management Facility in Scotland a waste treatment centre incorporating recycling and MBT, the EarthTech AD plant, takes up to 12,000 tones of biodegradable municipal waste and generates 0.24MW of electricity annually. This plant also has a CHP system incorporated into it, which is used to heat the AD system itself. • At the Premier Waste AD site in Thornley, Durham, capable of processing 20,000 tonnes/yr of MSW, three concrete towers are used as the AD vessels. This project is part of Defra’s Demonstrator Project, and after some initial problems the project recommenced demonstrator phase in mid 2008. 243 Identifying a comprehensive list of currently functioning AD sites, and sites that will become operational in the future is difficult due to the level of interest in this area. Many potential sites are reported as certainties, when in fact they do not get as far as the planning stage, or markets change and a company decide not to go ahead with a site development. Also, many early AD sites have ceased operation for technical or financial reasons. A planned AD site is at Cumbernauld in Glasgow, for the treatment of 30,000 tonnes per annum of local food waste, by Scottish Water. The site is expected to be operating in 2010, to generate 1MW of 237 EU Requirement Approved Plants Report – Section VI Biogas Plants, 18 Feb 2009, http://www.defra.gov.uk/animalh/byprods/approvals/section6.pdf 238 ENDS Report 404, September 2008, p. 30-33, Biogas scents the sweet smell of success, 239 South Shropshire Biodigester, Ludlow Biocycle South Shropshire/Greenfinch Ltd, Information Sheet, 2008. 240 Anaerobic Digester at Wanlip, BiffaLeicester, http://biffaleicester.co.uk/about/composting.php?&printpage=true 241 Holsworthy Biogas Plant, Case Study 2, http://www.devon.gov.uk/renewable_energy_guide_case_study_2.pdf and “UK’s largest" AD plant permitted to take more food waste, 2008, http://www.letsrecycle.com/do/ecco.py/view_item?listid=37&listcatid=333&listitemid=10429 242 Andigestion, Holsworthy, http://www.andigestion.co.uk/content/holsworthy 243 Defra Factsheet, Premier, http://www.defra.gov.uk/environment/waste/wip/newtech/dem-programme/pdf/Premier.pdf 131
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South East 327 - - 55% of MSW by 20
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Appendix 3 MBT Methods Specific in
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Figure 27 Orchid Environmental proc
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