Sewage sludge to bio-fuel: A review on the sustainable approach of transforming sewage waste to alternative fuel

Bio-fuels are gaining worldwide attention as an alternative fuel option replacing the usage of the mineral diesel derived from conventional fossil sources. However, the high cost attributed by the feedstock made it less competitive with the commercial diesel. A widespread research is going on worldwide for the production of fuels from renewable biomass replacing the currently used traditional sources. The high lipid-containing municipal sewage sludge (MSS) can be considered as a potential feedstock owing to its low cost and abundant availability. The lipids are transformed to biodiesel via transesterification or to bio-oil by pyrolysis. In this review paper, a comprehensive discussion on the various aspects of bio-fuel production from sludge derived lipids along with the key parameters affecting the process and its economics are presented. This review also emphasizes that future studies should focus on the usage of modern process intensification techniques for more efficient production of bio-fuel from renewable biomass.