Energy balance for biodiesel production processes using microbial oil and scum.

Graphical abstract Highlights • Biodiesel production from scum is more favorable than methane production. • Lipid extraction using organic solvents makes process energy intensive. • Sludge fortified crude glycerol reduces energy input at fermentation for microbial lipid production. • Lipid extraction using N-LS and Petroleum diesel is quick and less energy intensive. Abstract Biodiesel production using microbial oil is a promising technology. The main aim of this study is to check practical feasibility (in terms of energy balance) of different biodiesel production processes. Mass and energy balance of biodiesel production have been performed for 3 separate processes: (1) microbial lipid production from T. oleaginosus using waste substrates followed by INRS downstream process (2) microbial lipid production from pure substrate using R. toruloides followed by traditional and INRS downstream process and 3) oil extraction from scum and conversion to biodiesel. It was found that employing waste substrates like crude glycerol and municipal sludge in fermentation reduced the energy input by 50%. While employing biodegradable surfactants and petroleum-diesel as solvent (PD) for lipid extraction and recovery significantly reduced the energy input at cell wall disruption step. Biodiesel production from scum is a two-step process which is fast and energetically favorable. [ABSTRACT FROM AUTHOR]