Where there's muck there's megaWatts!!
Few farmers would turn down a chance to get three jobs done properly and all at the same time. This may well be one of the main reasons why more and more farmers around the world are tempted to install a biogas digester. Put farm waste into a tank where methane-producing bacteria thrive in the warm, damp and dark, and the owner gets rid of a waste problem, gets back a good fertiliser and gets gas to heat and light the home or fuel a generator for electricity.
Biogas production is believed to have begun in India two hundred years ago. The technology then caught on fast in China. For the last ten years, biogas has proved increasingly popular on farmsteads in Trinidad, Jamaica, Barbados and in Belize. Now it is catching on fast in the heart of Europe.
"Here we have nothing less than a biogas revolution under way," 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 offering 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.
From effluent to electricity
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| credit: Susie Emmett |
As day breaks on the Kuch family farm in Weckelweiler in southern Germany, Karl and his mother move silently between their 25 cow dairy herd waiting 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 800 rpm into a soup-like consistency and then pumped into the biogas digester. In the warm, damp, and airless dark, anaerobic bacteria digest the waste and give off methane gas in the process. The gas is piped into an engine room where it powers, for 12 hours a day, a 15 kilowatt engine generating electricity that is sold to the national grid. The investment, about £55,000 ($82,500), will be covered by sales of power and savings in effluent treatment.
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| credit: Susie Emmett |
Twice a week, four pig and dairy farmers deliver slurry to the community biogas plant in Germany run by Godfried Groenbach. The plant takes 60 cubic metres of waste a week from farms, and 10 tonnes of kitchen waste from the catering industry. Six times a day waste is pumped into the biodigester from an underground holding tank. Fed little and often, and kept warm by some of the power they generate, the bacteria produce 3000m3 of gas. In a co-generation plant this produces 5000 kilowatt hours of electricity a day serving 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 12 metre diameter digester his workmen are building. "This one will take 1000 cubic metres of manure from 100,000 broilers on two farms." Of the energy produced, some will be used on farm, the rest sold to the grid. Although costing £650,000, even 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 problem 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 the growing of crops specifically for feeding into digesters.
To get energy out, energy has to go in. For the huge and automated systems, computers can take the strain. For smaller systems the responsibility falls on the farm. Day in and day out, the digester has to be fed and attended to. Back in Weikelweiler the milking is almost over but, like the livestock, the farm's 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." All farmers worry about their agricultural incomes but biogas producers have one over-riding advantage: whereas incomes from farm produce can go up or down in response to demand, they can be sure there will be a steady demand for electricity.
Article submitted by Susie Emmett, freelance journalist.
