Evaluation of the potential of activated sludge biomass from Nigeria as a feedstock for biodiesel production

Abstract

Depleting fossil fuel reserves and the effects of greenhouse gases on climate change have led to the investigation of alternative energy sources such as biofuel, including biodiesel and renewable diesel. Unfortunately, the cost of the feedstock exceeds 70% of the total production cost. The current work investigates the potential of utilizing a waste product (activated sludge biomass) from wastewater treatment, as an alternative feedstock for biodiesel production. The activated sludge biomass was pretreated with subcritical water to enhance the lipid yield before extracting the lipid using solvent extraction. The result showed that lipid yield from the activated sludge was 4.73–8.58%. After subcritical water pretreatment with varying residence time, temperature, and biomass loading, the lipid yield increased by 158.04–400%. Gas chromatography–mass spectrometry (GC–MS) analysis of the fatty acid methyl esters (FAME) from the transesterification of the lipid extract using calcined egg shell as a catalyst identified the following lipids: triglyceride, fatty acids, sphingolipid, phospholipid, glycerolipid, glycerophospholipid, steroid, and cholesterol. The predominant lipid was triglyceride, and the high percentage of unsaturated fatty acids, including arachidonic acid (23.54%), eicosadienoic acid (8.37%), and oleic acid (6.23%) suggest that the lipid extract is a potential feedstock for biodiesel production.