PAPERS OF THE 24TH EUROPEAN BIOMASS CONFERENCE: SETTING THE COURSE FOR A BIOBASED ECONOMY

Wastewater treatment (WWT) plants consume up to 180 MJ and produce 10-85 kg dry sludge per person every year. This will continue to increase due to more rigorous effluent quality regulations and demands. Sludge management and disposal can increase energy requirements and the carbon footprint of the plant. Anaerobic digestion (AD) offers an alternative to reduce sludge volume and improve energy efficiency; however, its performance is limited. Sludge digestate gasification represents a potential route for sludge disposal and energy recovery via CHP generation. This study evaluated the energetic integration of gasification as sludge management technology, following either AD and or drying. Emphasis was given to the effects of process parameters and sludge properties on the system performance. Intermediate equivalence ratios (ER= 2-3) and moisture contents between 30 and 40 wt% allowed the coverage of on-site energy demands. However, efficient and technically feasible operation led to high electricity generation with insufficient heat recovery. Integration of gasification with AD, co- processing and co-digestion were also evaluated as alternatives to overcome energy balance limitations. The proposed concept represents an energy-efficient alternative for sludge management when sludge transportation or landspreading is unfeasible, and highlights the effects that sludge properties and production have on the performance of the system.