14 June 2002

Where theres muck theres

Biogas is becoming big

business in Germany –

there are now over 1500

units and plans for many

more. Susie Emmett

reports on how the biogas

revolution is taking the

country by storm

FOR a German farmer wanting a wife, there is an interesting alternative to seeking a partner on a popular TV dating show – it is to get a biogas digester.

Typical of a man who spends his working life with livestock, unmarried Karl Kuch is softly spoken and chooses his words carefully.

"Having a biogas digester must be like having a wife. I have to spend time with it every day to be sure it is happy and know its moods," he says.

As day breaks on the Kuch family farm in Weckelweiler in southern Germany, Karl and his mother move silently among their waiting 25-cow dairy herd to take the early milk. A winch system claws all the dung dropped in the channel running through the centre of the barn. It is pulled into a mixing pit where it is swirled by a long-axle mixer at 800rpm into a soup then pumped into a digester.

In the warm, damp, airless dark, anaerobic bacteria make a meal of this – and any waste you can think of – and burp out high-energy methane gas in the process. This gas is then piped into an engine room where it powers a 15kw engine generating electricity 12 hours a day which is sold to the national grid.

The investment – about £55,000 – will be covered by sales of power and savings in effluent treatment and the bonus is what the bacteria leave behind: A first-class fertiliser.

"We have nothing less than a biogas revolution underway," says Michael Kottner of German-based International Biogas And Bioenergy Centre of Competence. "Last year a record number of biogas plants were installed on German farms and now there are over 1500 and many more planned."

Renewed enthusiasm has been driven into the development of biogas, and other sources of renewable energies, by the new German policy which offers a good and guaranteed price for the power generated for the next 20 years. Suddenly, the sums add up and so biogas digesters – eligible for grants for 30% of the costs – are going up all over the country.

Twice a week, four pig and dairy farmers deliver slurry to the community biogas plant run by Godfried Groenbach.

"We need 60cu m of waste a week from farms and 10t of kitchen waste from the catering industry to feed this digester," he says. An underground holding tank is used to store waste from where, six times a day, it is pumped into the biodigester. Fed little and often, and kept warm by some of the power generated, the bacteria produce 3000cu m of gas. This is used to supply 5000kw hours of electricity a day to 500 households and a small industrial estate.

Biogas plants are getting bigger. On sloping ground up the hill from three long broiler houses, Roland Lipp proudly shows the kind of system his Tanhausen-based company supplies and installs.

"This is big business now," he says as he stoops to get inside the 12m diameter digester his workmen are building. "This one will take 1000cu m of manure from 100,000 broilers on two farms."

Of the 300kw of energy produced some will be used on farm, the rest sold to the grid. But, at a cost of £650,000, this scale of plant will not be the biggest for long. In China, Roland Lipp is designing systems to process the waste from units with 10,000 cattle or pigs or poultry farms with many millions of birds.

Animal waste is not the only raw material. Mindful of the target that by 2050 Europe aims to get half of its energy from renewable sources, other problematic wastes – from abattoirs, industry, sewage plants, landfill and more – are in line for biogas digestion. There are even plans to encourage "energy farming". This is not the production of biomass for burning, but where harvested crops are destined only for use with digesters.

To get energy out, a lot of energy has to go in. For the huge and automated systems computers can take the strain, but for smaller systems the responsibility falls on the farm. Day in, day out the digester has to be fed and attended to.

Back in Weikel Weiler the milking is almost over, but like the livestock the farms biodigester always needs attention.

"Sometimes I need a whole day to fix a problem," says Karl Kuch "The gas is very corrosive, so the engine needs changing every two years."

But like other German farmers worried about agricultural incomes biogas production has one over-riding advantage: While consumer demand for farm produce goes up and down, they can be sure that there will be steady demand for electricity. &#42