Germany boosts biogas from new sewage treatment plant
Processing sewage sludge is becoming ever faster as scientists optimise the digestion stages. Now German engineers have developed a high-rate processing plant that generates biogas from sewage in under five days.
“We have combined an excellent biological process with excellent biochemical engineering,” Professor Walter Trösch from the Fraunhofer Institute told edie. “Of the electricity generated from the biogas produced, only a third is used in the process, leaving two-thirds to be sold to the grid or diverted to other areas of the plant.” Thus the city of Heidelberg runs off its own sewage.
The new method has the added advantage of reducing the organic content of sewage by 50 to 60% compared with an average 40% in normal decomposition, resulting in fewer residues to dispose of. But although some processing plants could be updated to incorporate the new procedure, for older plants in Germany the cost of conversion is too high. “Old-fashioned plants would need to be re-built, so their conversion is not yet possible,” says Professor Trösch.