On October 14th,2019 the anaerobic digestion plant delivered the first biomethane in the required quality to the UK gas distribution network From now on the plant will deliver c7.3 million m³/year biomethane which is sufficient to supply about 9,600 households with sustainable energy, 24/7. The sustainability of the project starts already with the input material. Food leftovers account for more than half of the 80,000 tpa of substrate. Additionally, there is cattle and chicken manure as well as grass silage and hybrid rye.
Under consideration of the substrate structure, the solids are fed through two walking-floor feed hoppers with 110 and 220m³, and two MULTIMix units, which removes foreign objects, liquefies, shreds and macerates incoming solids to make them into an easily pumpable, easily mixed, easily digested liquid. Liquids are fed in controllable volumes directly to digesters from five pre-storage tanks, of which two are equipped with a stainless steel bottom. The gas production takes place in four stainless-steel digesters with a height of 8.8 m and an above-average capacity of 6,848m³ each. WELTEC has decided to implement membrane upgrading to transform the biogas into high-quality biomethane. In a separation process comprising several stages, the raw biogas is refined efficiently without methane slip.
Additionally, the biomethane production yields digestate, which is used as high-quality fertiliser, returning organic material and nutrients to the land. For this purpose, it’s first be pasteurised and separated. For on-site electricity supply, WELTEC has integrated a 500 kilowatt CHP. The operator generates additional income from exporting excess electricity to the grid.
“This project will bring many benefits to the project developers Aqua Consultants as the technology is state of the art. Furthermore the fast construction time and the construction costs within the budget speak for themselves. We have to thank all involved parties for the good cooperation and hope that this project will be a role model for future waste-to-energy projects”, Wolfgang Bokern sums up the successful commissioning.