Multicriteria Analysis of Sewage Sludge-Based Biodiesel Production

There is increasing attention on developing efficient processes including circular economy principles, and obtaining fuels from wastewater treatment feedstocks is among the most promising. As a wastewater treatment byproduct, sewage sludge is a source of lipids that can be converted to biodiesel in a transesterification process. Using solvent extraction from wet sewage sludge, the high cost associated with the drying step is skipped. A multicriteria analysis has been applied to a plant (60 m3/h sewage sludge) considering both, dry and wet approaches. 32 different alternatives were analyzed from the economic and environmental perspectives. The wet alternatives with low amounts of solvent and acid usage depicted better performance compared to the dry ones. The case with 0.5:1 (v/v) of hexane to biomass ratio, 3-stage extractor, 60 min residence time and pH 4 was the optimum alternative in most criteria