Lipid extraction and biodiesel production from municipal sewage sludges: A review

Extensive research is being conducted all over the world to produce fuels from renewable biomass. Biodiesel, a renewable liquid fuel produced from lipid sources, is one of the most attractive among the options explored for alternative energy sources. However, 70–80% of the overall biodiesel production cost is associated with raw materials cost. Municipal sewage sludge is readily available at no cost. It contains various lipids and hence it is a promising raw material for biodiesel production. Lipids can be initially extracted from the sludge. Subsequently, the extracted lipid is converted to biodiesel by esterification and/or transesterification reaction. Biodiesel is also produced by in situ transesterification of dried sludge. This paper reviews the various lipid extraction techniques and biodiesel production processes from municipal wastewater sludge.