West Cumbria is well suited to establishing Energy Farms because of large cattle and dairy herds which produce substantial amounts of slurry, which is an important feedstock for AD plants. They have large herds because the areas are good for growing grass, which is a very high energy feedstock for AD plants.(3)
Apart from farmers, the water industry – which has to deal with 1.73 million tonnes of sewage sludge annually, businesses which produce food waste, and local authorities, could all make use of digesters. If all the organic waste in Britain were recycled in this way, enough energy would be generated to provide two million homes with heat and electricity. Cumbria Councils are encouraging householders to use food waste digesters, rather than organising separate food waste collections as in other parts of the UK with the collected waste dispatched to an anaerobic digester. It is possible that in rural areas this is the best way forward given the carbon implications of organising food waste collections. But individual household food waste digesters can be a lot of work, so may only be taken up by a very small minority. It may be more effective for local borough councils to work with farmers to develop a network of anaerobic digesters, especially if food waste collections can be done in conjunction with other recycling collections.
Anearobic Digestion Plant in Stornoway.
There are three main uses for biogas produced by a digester – onsite Combined Heat and Power (CHP), gas grid injection and vehicle fuel. In North West England United Utilities (UU) has teamed up with National Grid to inject methane from the wastewater treatment process into the local gas pipeline network and fuel for a fleet of sludge tankers. The ground-breaking initiative is centred on one of the country’s largest wastewater treatment plants at Davyhulme in Manchester.(4)
The Anaerobic Digestion and Biogas Association says the Government should be pushing for more green gas generated from waste as a sustainable alternative to shale gas. Green gas is something of a no-brainer, ticking boxes for energy policy, environment and the economy. It should lead the future of unconventional gas in Britain. Putting it at the centre of the Government’s energy strategy would deal with the hurdles to deployment, and allow gas to be part of energy decarbonisation rather than a challenge to it. Green gas has the potential to deliver £2-3bn of green gas a year and create 35,000 jobs. The maximum potential of biomethane from anaerobic digestion (AD) is equivalent to 10 per cent of domestic gas demand – not a dissimilar figure to that which the Institute of Directors suggests for shale gas potential in the UK alone.(5)
Alan Whitehead MP, a member of the House of Commons Energy and Climate Change Committee, compares the economics of the two methods of putting that gas into the grid. One shale gas well costs between £6 -10 million to drill and frack. It is difficult to assess total output of gas, but the average well in Texas at the moment is producing about 2 million cubic meters of gas per year for only about five years of production. One large farm size Anaerobic Digestion plant costs about £2million to build and then provides a steady stream of gas from then onwards, varying only to the extent that cows stop producing manure or people stop eating food. The first plant currently operational and injecting gas into the grid (the Poundbury plant in Dorchester) produces a bit more gas in a year than the average shale gas well.(6)
Cumbria County Council, in conjunction with the Borough Councils and Cumbria farming organisations should study the feasibility of food waste collections operating in tandem with a network of farm-based anaerobic digesters.