Science in Society Archive

Towards 100% Renewables

Funding for Small Scale Anaerobic Digesters in England

UK government starts mining agricultural wastes for renewable energy as municipal and household wastes are becoming scarce Dr Mae Wan Ho

On Farm Anaerobic Digestion Fund

The UK government has set up the On Farm Anaerobic Digestion Fund to help farmers in England install small scale anaerobic digesters on site [1, 2].

The scheme, formally launched 12 October 2013 by DEFRA (Department for Environment, Food and Rural Affairs) Secretary Owen Paterson, allocates £3 million for farmers to apply for loans up to £400 000 to help finance anaerobic digestion (AD) plants on farm, or for a grant of up to £10 000 initially to investigate the environmental and economic potential of AD to deal with the farm wastes.

The fund will be administered by WRAP, an organisation promoting recycling. WRAP has also developed a programme to help in accessing finance, provide case studies and demonstration information, and other support for farmers wanting to use AD on their farms [2]. The fund will be available to build AD plants producing up to 250 kW.

Anaerobic digestion and the circular economy

Liz Goodman, CEO of WRAP told Farmers Guardian [1]: “The use of small-scale anaerobic digestion on farms to treat manures and slurries has a number of economic and environmental benefits and is an excellent example of the circular economy in action.”

This is good news, as I-SIS has been advocating small scale on farm anaerobic digestion since 2005 [3- 5]( Dream Farms, SiS 27; How to Beat Climate Change & Be Food and Energy Rich - Dream Farm 2, SiS 29; Surviving Global Warming, SiS 60), precisely in the context of the circular economy, for recycling farm wastes into food and energy resources  (see Box 1 from [6] Sustainable Agriculture, Green Energies and the Circular Economy, SiS 46, for a list of full advantages).

Advantages of anaerobic digestion of organic wastes

  • Produces an abundant, readily available source of bioenergy that does not take land away from growing food
  • Takes a wide range of feedstock, including livestock and human manure, crop and food residues,  paper, bakery and brewery wastes, slaughterhouse wastes, garden trimmings, etc, and the yields of methane generally better in mixed waste streams
  • Biogas methane is a clean cooking fuel, especially compared to firewood (and dung)
  • Methane can be used as fuel for mobile vehicles or for combined heat and power generation
  • Methane-driven cars are currently the cleanest vehicles on the road by far
  • Biogas methane is a renewable and carbon mitigating fuel (more than carbon neutral); it saves on carbon emission twice over, by preventing the escape of methane and nitrous oxide into the atmosphere and by substituting for fossil fuel
  • Conserves plant nutrients such as nitrogen and phosphorous for soil productivity
  • Produces a superb fertilizer for crops as by-product
  • Prevents pollution of ground water, soil, and air
  • Improves food and farm hygiene, removing 90% or more of harmful chemicals and bacteria
  • Recycles wastes efficiently into food and energy resources for the circular economy

UK biogas boom coming?

Currently, anaerobic digestion of municipal, food and farm wastes is already playing a substantial role in the renewable energy portfolio of European countries such as Sweden, Germany, the Netherlands, France, and China [7] (Renewable Ousting Fossil Energy, SiS 60). The UK is catching up.

Official figures gathered by NNFCC Bioeconomy Consultant and WRAP reveal that the number of AD plants nearly doubled since September 2011 [8]. The UK now has 106 anaerobic digesters outside the water industry processing up to 5.1 million tonnes of food and farm waste every year, with an installed electrical capacity of more than 88 MW. In comparison, Germany has more than 7 000 digesters.

Nearly half (46) of the AD plants currently operating in the UK are community digesters for food waste collected from multiple sources such as supermarkets, hospitality providers and households. These community digesters have a capacity to treat ~1.8 million tonnes of food waste a year and a potential electricity generating capacity of about 56 MW. There are around 200 food waste AD plants currently going through the planning process, of which 20 to 30 will end up being built. The question is whether the demand for municipal waste will lead to a new gold rush. Development has been largely focussed on clusters of anaerobic digesters around major towns and cities. There are approximately 8 million tonnes of business waste and a further 8 million tonnes of household waste suitable for anaerobic digestion, enough to feed no more than 400 new digesters (less if their average size increases, as is likely).

The agricultural sector waste, meanwhile, has remained relatively untapped. There are more than 10 000 dairy farms and 4 000 pig farms in the UK generating 90 to 100 million tonnes of manure and slurry every year. The On Farm Anaerobic Digestion Fund is a small start at exploiting this abundant resource in the coming green and circular economy.

Another good reason for on farm anaerobic digestion is to eliminate farm wastes as major pollutants of water, in compliance with the European Union Water Framework Directive to protect and improve Europe’s water resources (see [9] Using Water Sustainably, SiS 57).

Article first published 23/10/13


  1. “Patterson launches £3m anaerobic digestion loan scheme”, Alistair Driver, Farmers Guardian, 12 October 2013,£3m-anaerobic-digestion-loan-scheme/59370.article
  2. ON Farm AD Fund, accessed 12 October 2013,
  3. Ho MW. Dream Farm. Science in Society 27, 26-28, 2005.
  4. Ho MW. How to beat climate change & be food and energy rich – Dream Farm 2. Science in Society 29, 10-14, 2006.
  5. Ho MW. Surviving global warming. Science in Society 60.
  6. Ho MW.  Sustainable agriculture, green energies and the circular economy. Science in Society 46, 8-13, 2010.
  7. Ho MW. Renewable ousting fossil energy. Science in Society 60.
  8. “Analysis: are we reaching biogas overcapacity in the UK?”, Dr Matthew Aylott, NNFCC The Bioeconomy Consultants,
  9. Ho MW. Using water sustainably. Science in Society 57, 10-11, 2013.

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There are 2 comments on this article so far. Add your comment above.

James Cooley Comment left 24th October 2013 06:06:05
Following the first oil price shock in 1973, I attended a workshop and was inspired to experiment with AD by a farmer who built one on his mixed farm in the Ozarks. My main source of information was a small pamphlet published by a South African pig farmer who supplied most of his own electricity using a self-constructed AD plant and converted diesel generator. This would have been nearly 40 years ago.

Linus Hollis, ScD Comment left 24th October 2013 06:06:49
The biogas from these digesters is full of sulfur & nitrogen compounds, they make NOx & SOx when burnt or in an internal combustion engine. The dairy farmers in California's Central Valley are forced to install EXPENSIVE pollution control devices. The alternative is to pipe the exhaust through a 3-400 litre water column. This filters the NOx & SOx-the water becomes fertiliser quickly & saves funds. Save money while cleaning up the air!