Biosolids--a fuel or a waste? An integrated appraisal of five co-combustion scenarios with policy analysis.

An integrated appraisal of five technology scenarios for the co-combustion of biosolids in the UK energy and waste management policy context is presented. Co-combustion scenarios with coal, municipal solid waste, wood, and for cement manufacture were subject to thermodynamic and materials flow modeling and evaluated by 19 stakeholder representatives. All scenarios provided a net energy gain (0.58-5.0 kWh/kg dry solids), having accounted for the energy required for transportation and sludge drying. Co-combustion within the power generation and industrial (e.g., cement) sectors is most readily implemented but provides poor water utility control, and it suffers from poor public perception. Co-combustion with wastes or biomass appears more sustainable but requires greater investment and presents significant risks to water utilities. Incongruities within current energy and waste management policy are discussed and conclusions for improved understanding are drawn.