EnergyScientists resurrect process to convert sugar directly to diesel

Retooled bacterial fermentation process yields diesel fuel // Source: berkeley.edu

A long-abandoned fermentation process once used to turn starch into explosives can be used to produce renewable diesel fuel to replace the fossil fuels now used in transportation, UC Berkeley scientists have discovered.

Campus chemists and chemical engineers teamed up to produce diesel fuel from the products of a bacterial fermentation discovered nearly 100 years ago by chemist Chaim Weizmann who, in 1948, became the first president of Israel. The retooled process produces a mix of products that contain more energy per gallon than ethanol that is used today in transportation fuels and could be commercialized within 5-10 years.

A University of California, Berkeley release reports that while the fuel’s cost is still higher than diesel or gasoline made from fossil fuels, the scientists said the process would drastically reduce greenhouse gas emissions from transportation, one of the major contributors to global climate change.

“What I am really excited about is that this is a fundamentally different way of taking feedstocks — sugar or starch — and making all sorts of renewable things, from fuels to commodity chemicals like plastics,” said Dean Toste, professor of chemistry and co-author of a report on the new development that will appear in the 8 November issue of the journal Nature.

The work by Toste, coauthors Harvey Blanch and Douglas Clark, professors of chemical and biomolecular engineering, and their colleagues was supported by the Energy Biosciences Institute (EBI), a collaboration between UC Berkeley, Lawrence Berkeley National Laboratory, and the University of Illinois at Urbana Champaign, and funded by the energy firm BP.

The linkage between Toste, whose EBI work is in the development of novel catalysts, and Clark and Branch, who are working on cellulose hydrolysis and fermentation, was first suggested by BP chemical engineer Paul Willems, EBI associate director. The collaboration, Willems said, illustrates the potential value that can come from academic-industry partnerships like the EBI.

The late Weizmann’s process employs the bacterium Clostridium acetobutylicum to ferment sugars into acetone, butanol and ethanol. Blanch and Clark developed a way of extracting the acetone and butanol from the fermentation mixture while leaving most of the ethanol behind, while Toste developed a catalyst that converted this ideally-proportioned brew into a mix of long-chain hydrocarbons that resembles the combination of hydrocarbons in diesel fuel.

Tests showed that it burned about as well as normal petroleum-based diesel fuel.

“It looks very compatible with diesel, and can be blended like diesel to suit summer