Thursday, 26 August 2010

Concrete Cow' Becomes First Commercial Power Plant Fed on Crops in U.K. - Bloomberg

Severn Trent Plc started generating electricity from the U.K.’s first commercial-scale crop-fed power plant as the utility seeks to lower its carbon emissions and tap a new form of renewable power.

The company’s Severn Trent Water unit began feeding the power grid with electricity from a gas-fueled turbine at a site near Nottingham, Gill Dickinson, a company spokeswoman, said in a telephone interview. The gas comes from anaerobic digestion towers, which use micro-organisms to break down corn and wheat.

Rising oil prices since the 1990s has led to growth of the previously uneconomical technology in Europe. Severn Trent, which plans to use government incentives to earn money from the 15 million-pound ($23 million) plant, is tapping crops to produce energy after exhausting sewage waste as a fuel.

“We’ve maxed out and have sewage-fueled combined heat and power plants deployed at all our major sites,” Renewable Energy Development Manager Martin Dent said in an interview at the Stoke Bardolph site near Nottingham. “This means we need to start going into new areas we haven’t gone to in the past.”

Anaerobic digestion is also used to make gas from food waste, animal slurry and sewage. Severn Trent already has power plants at 34 sites fed by sewage instead of crops. The new plant is fitted with two engines from General Electric Co.’s Jenbacher unit and will help the utility come close to a company target of getting 30 percent of its power from renewable power by 2015.

Concrete Cow

One of the two turbines began to power the sewage works and feed some energy to the grid on Aug. 16, Dickinson said. The generator is producing about 880 kilowatts of electricity, she said, adding that the quantity exported to the grid varies daily depending on the site’s energy needs. When both engines are generating at capacity, the plant will produce 2 megawatts of power, enough power for more than 4,000 homes.

“We don’t expect to be at maximum capacity with both engines until the end of the year,” Dickinson said.

There are about 25 anaerobic digestion plants on U.K. farms, running mainly on animal slurry, and 220 anaerobic digesters run by water companies using sewage, according to the government’s Department for Environment, Food and Rural Affairs. In the U.K., there are no crop-fed plants of the scale as the Severn Trent project, a department spokesman said.

In the digestion towers, micro-organisms that occur naturally in the crops break them down into gas aided by a temperature of about 40 degrees Celsius (104 degrees Fahrenheit) and air that’s low in oxygen.

“What we’re actually doing is building a concrete cow,” Dent said. “We need to keep it fed, we need to keep the temperature inside constant, and we want gas out of the end.”

Government Incentives

At present, it wouldn’t be viable to build such a plant without government incentives, Dent said. Severn Trent hasn’t yet decided which incentive plan to use -- the government’s feed-in tariffs, guaranteeing a set rate per unit of electricity generated, or the renewables obligation that awards sellable certificates for energy from renewable sources.

“The asset life of the mechanical plant and equipment is 20 years, and that’s 50 percent of the build cost,” Dent said. “Anything beyond a 20-year payback, you wouldn’t do it.”

To contact the reporter on this story: Alex Morales in London at

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