Biodiesel, a mixture of fatty acid methyl esters (FAME), is a clean and renewable energy industrially produced from the relatively expensive and edible vegetable oils via methanolysis. Waste grease such as brown grease has been considered as an attractive feedstock for biodiesel production, since it is cheap (0.19 USD L-1) and non-edible. However, there is a significant technical challenge in converting grease to biodiesel: the traditional base catalysis is not applicable due to the high content (15-40 wt%) of free fatty acid (FFA) in grease. In our recent research, we have developed several different methods for the high-yielding production of FAME from waste grease. One-pot conversion of grease to biodiesel via simultaneous esterification of FFA and transesterification of triglycerides with methanol was achieved by using recombinant E. coli cells expressing an intracellular lipase SML as well as recombinant Escherichia coli cells co-expressing tandem lipases CALB and TLL, respectively. Wet cells were also developed as simple and cheap biocatalyst for the one-pot production of biodiesel from grease. The yields of FAME were high and the cells showed good recyclability. In addition, highly active and easily recyclable magnetic nano-size solid acid catalysts were developed as greener acid catalysts for the esterification of FFA in grease as the efficient first step in the acid-base two-step transformation of waste grease to biodiesel. Most recently, new type of magnetic nano-size solid acid catalysts were also developed for one-pot conversion of grease to biodiesel via simultaneous esterification and transesterification. These technologies developed in our lab provide with application potential in industrial production of biodiesel from grease.

Production of biodiesel from waste grease using whole cell biocatalysts or nanosize solid acid catalysts

247th National Meeting (2014)

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