Anaerobic Digestion
This is an executive summary of the final report of our study of the economic and environmental viability of a local anaerobic digestion (AD) facility, using domestic food waste collected by Derbyshire Dales District Council.
In 2010 Sustainable Youlgrave (SY) was jointly funded by East Midlands Development Association and Peak District National Park Authority to carry out a full feasibility study for a farm AD project. This study produced a positive business case for a centralised AD facility processing farm waste at Newhaven. But sadly, despite funding the study to start with, and despite it being a commercially-viable renewable energy project PDNPA would not give it planning permission for a centralised digester which would require waste to be transported around the Park.
Youlgrave Community Land Trust, as successor body to SY, took over this project in 2013 and set out to study the feasibility of a micro-AD plant to process domestic and commercial food waste generated in Youlgrave and three adjacent villages. We were awarded a grant of £10,000 by the AD Network at Southampton University to carry out a business planning exercise for a village-scale digester, sited in or near Youlgrave, using local domestic and trade food waste. The study was carried out for us by Professor David Styles at Bangor University, using a proven life cycle analysis model (LCAD) and the contract was managed by Brian Mallalieu of YCLT.
The early results of this study showed that such a village-level mini-scheme would not be economically viable. We therefore decided to investigate a significantly larger scheme, which would process all DDDC food waste and other appropriate organic waste generated within a wider area. Useful sources of waste identified included a brewery, a bakery, a planned hotel and supermarket and the Agricultural Business Centre in Bakewell. An alternative location, a cattle farm where the use of AD had already been previously studied, was also included. On both sites it was assumed that all of DDDC domestic food waste would be utilised, together with any available commercial food waste, rather than just the waste from the four villages.
The study also included:
(a) the logistics of collection, handling, transport and storage,
(b) the technicalities of waste processing,
(c) the capital cost of the AD/CHP plant as quoted by six suppliers,
(d) household caddie collection,
(e) commercial food waste,
(f) plastic problems,
(g) diesel to bio-fuel switching.
(h) the environmental impact
On the utilisation side the study looked at the potential use and value of the products of AD:
(a) using the biogas generated by the plant to produce heating, and electricity,
(b) upgraded biogas for fleet vehicle fuel,
(b) liquid and solid fertiliser,
(c) income/savings for the Council from waste collection fees.
In brief, our study shows that a scheme that includes DDDC domestic and commercial food waste can be an economically and environmentally viable alternative to the current composting regime. It would also bring the council into compliance with the latest government guidelines, which have promoted anaerobic digestion, which produces biogas, above mere composting which does not. On either the farm or the town site there would be a positive rate of return which would save the Council money on its waste collection contract. On the town site this could be as high as 6% over 10 years or 10% over 20 years.
The total capital cost including civil work would be £1.2m to £1.7m and nett income generation of about £0.25 million per year, after all operating and capital costs, would be a gain for the investor (DDDC). Moreover, there are other opportunities to increase the return, such as inclusion of commercial food waste. The environmental benefits are considerable, saving 500 tonnes of carbon dioxide which do not end up in the atmosphere. Sadly these benefits, though important, do not yield any hard financial returns under current government rules.
We have had useful discussions with Derbyshire Dales District Council officers about our findings. We asked them to consider adding a clause to the new waste contract which would require tenderers to favour AD as the preferred method of disposal for food waste. Sadly, the Council's financial position under austerity means that this will be difficult and indeed there is no local AD facility.
We need a site and a developer.
