Anaerobic Digesters Provide Green Energy

Comment from the UK

By Charlie Brooks, Daily Telegraph 2/10/09
Oct 3, 2009 - 11:39:09 AM

I keep having nightmares about Ed Miliband, the Secretary of State for Energy and Climate Change. It's been going on since he told us that "it is socially unacceptable to be against wind turbines in your area". It isn't.

The idea that onshore wind farms, which are defacing our countryside in increasing numbers, are the be-all and end-all of renewable, green electricity has been a very successful con and the idea that you are irresponsible if you object to them is environmental blackmail. Because there are alternatives which are much more environmentally friendly.

If Mr Miliband were to announce, for example, that "it is a criminal offence to be against an anaerobic digester in your area", I would carry him around the country on my shoulders. As listeners to The Archers know, thanks to a controversy over whether to install one on Home Farm in Ambridge, an anaerobic digester works a bit like your stomach: it uses bacteria to break down organic material, while giving off a vast amount of methane which is converted into electricity. In Britain, they are relatively few and far between, but our European cousins have got their act together. The Germans, for example, have 4,000 digesters, generating 10.9 per cent of their renewable energy. In India, there are 300,000.

The advantages of digesters are clear. They produce electricity 24 hours a day, whereas wind farms produce electricity when the wind blows. Because the grid cannot rely on the wind blowing during periods of peak demand, power stations are needed to back up the turbines. Not so with digesters, which also produce heat and organic fertiliser and consume waste.

This latter point is particularly important. Sainsbury's alone produces 56,000 tons of food waste a year. By the end of this year, all of it will end up in digesters, rather than landfill sites. Yet the country as a whole generates between 20 and 30 million tons of food waste, which could become a valuable resource rather than a toxic liability if we developed a network of digesters on the German scale.

Although we are well off the pace as a nation, we do have some innovative pioneers who have seen the light. Owen Yeatman, a farmer in Dorset, is now converting silage and cattle slurry into electricity. In Bedfordshire, Biogen Greenfinch have adapted and improved German technology. Initially, the variety of the waste they processed was corroding their digester and causing it to behave in a rather volatile manner (if you think about what would happen if you scoffed a box of figs and a chicken tikka, you'll get the drift).

The heat generated by digesters is harder to distribute than the electricity, but not impossible. Insulated pipes are becoming more efficient. In Copenhagen, for instance, there is now an 80-mile grid distributing hot air. But it is the fertiliser produced that completes the virtuous circle, returning to the soil the nutrients that grew the food in the first place.

So given that anaerobic digesters kill three birds with one stone - as opposed to wind farms, which only kill one (or rather, wound it) - you would expect government incentives to match those given to the vandals slapping up wind farms. But you would be wrong. After a consultation period which is set to end on October 15, the Government proposes to set a feed-in tariff (the guaranteed price of electricity generated) of nine pence per kilowatt for a farm-based digester. If, however, a farmer were to erect an 80ft wind turbine, he would get double that, even though it would deliver one third of the amount of electricity, and that unreliably.

This is clearly insane. Flatulence, not wind, is the way to go.

http://www.ocnus.net/artman2/publish/Research_11/Anaerobic-Digesters-Provide-Green-Energy.shtml