Researchers Claim 20x Boost in Biofuel Energy Recovery

Two researchers at Michigan State University says it has developed a biofuel production process that can recover at least 35% of feedstock energy 20 times the result for other techniques.

The team, which consists of MSU microbiologist Gemma Reguera and graduate student Allison Speers, reports its lab results in the current issue of Environmental Science and Technology. The entire paper can be downloaded HERE.

The MSU team started with microbial electrolysis cells, which use bacteria to turn agricultural waste into ethanol. Traditional MECs recover 3.5% of energy available in corn stover, agricultural waste that is a common feedstock biofuel production.

Reguera and Speers boosted energy recovery in part by pretreating corn stover with an ammonia fiber expansion process (AFEX) that was developed earlier at the university. Doing so helped boost energy recovery to 35%-40%, despite the energy used by the AFEX pretreatment.

The researchers were then able to nearly double the energy recovery rate to 73% by adding a second bacterium in the fuel cells. Called Geobacter sulfurreducens, it generates electricity that is then used to form hydrogen gas.

Reguera says she selected a bacterium for the MEC fermentation not just to produce ethanol but also to generate byproducts that could be metabolized by the electricity-producing bacterium. Thus the second batch of bacterium helps remove waste created by the first batch, improving overall fermentation efficiency.

The tandem system helps remove the waste products of fermentation, thus helping the fermentative bacterium to grow and metabolize.