Severn Trent Water’s latest project moves away from their traditional sewage treatment works to create the UK’s largest energy from biogas plant run wholly on energy crops.
Clarke Energy supplied the 2 GE Jenbacher 1MW gas engines that work at the heart of the installation. The new plant based at Stoke Bardolph in Nottinghamshire is situated alongside the 1,750 acres of Severn Trent owned land that grows the feed stock of maize and wheat.
The digester comprises four pre-fermentation units from which material is fed into two secondary fermentation units and then finally to a single container where the last of the methane is extracted to feed the GE Jenbacher gas engines. Each day will see about 100t of maize silage being loaded into large hoppers which then slowly deliver the crop to four primary digesters. Inside, agitation is provided by a rotor having hot water pumped through its main shaft to maintain the temperature of the mix at the required 42OC.
About 30% of the gas is collected from the primary digester, with the bulk being collected after the mix has passed into the two secondary fermenters. It takes up to 90 days for material to pass through the digestion process from start to finish.
Utilising the heat from the engines to ensure correct temperatures in the digestion process further enhances the already high efficiency of the engines. High reliability, durability and the long service intervals of the GE Jenbacher engines provide Severn Trent with the security of mind to generate a stable income for years to come.
