New Biogas production landmak for Municipal Sludge

Scottish Water's Nigg wastewater treatment centre in Aberdeen has become a centre of excellence for biogas production, thanks to its dedicated team that focuses on improving efficiencies. Nigg is the first wastewater treatment plant in the UK to successfully co-digest. The site, built in 2002, has made significant progress since Scottish Water took over ownership and operation in 2018, upgrading the existing thermal hydrolysis process and installing a new digester mixing system from Landia. Previously producing 250 cubic metres of gas per tonne of dry solids, the plant now produces 400-420 cubic metres, without requiring costly power. The clean-out of the digesters for the upgrade revealed that 45% of the volume had been lost to grit and heavily compacted sludge. Further evidence of Nigg's success is its use of the biogas and heat from the combined heat and power units for the site's new boiler, which saves £0.5m per year on fuel oil. Since the introduction of the Landia digester mixing system and the upgrade of the Cambi THP, CO2 emissions have more than halved, and the amount of biogas being produced has risen by more than 30%. Based on Nigg's success, Scottish Water is considering the development of a further six sludge-to-energy facilities, which would represent a giant leap towards achieving the net zero target by 2040, five years earlier than the Scottish Government's goal.