Study Looks at Converting Biomass and Electricity to Fuel |

In a collaborative effort between University of Wisconsin-Madison, University of Massachusetts-Amherst and Gwangju Institute of Science and Technology, a continuous process for converting biomass and electricity into renewable liquid transportation fuels has been developed. The researchers used a proton-exchange-membrane fuel cell to convert the model biomass compound acetone into isopropanol. This chemical compound can be used in a myriad of pharmaceutical and industrial applications and can also be used as a gasoline additive.

The project, led by George Huber, a UW-Madison professor of chemical and biological engineering, and other members of his research team, say the advance paves the way for researchers to convert biomass molecules such as glucose into hexanes, which are significant components of gasoline currently derived by refining crude oil.

“Essentially, we are making renewable liquid fuel that fits into the existing infrastructure,” said Huber, whose team published its results in the Sept. 7, 2012, issue of the journal ChemSusChem. Unlike other technologies that use large quantities of expensive hydrogen gas to convert biomass to biofuels, the team’s process is driven by electricity, which is inexpensive and readily available in rural areas. And, we’re storing the electrical energy as chemical energy.”

A fuel cell converts chemical energy into electrical energy, or vice versa. Reactions in a proton-exchange-membrane fuel cell, which consists of two “halves,”  require only water, electricity and the biomass-derived molecule. The chemical reaction is facilitated by a positive electrode coupled with a catalyst. The other side-the cathode-consists of a negative electrode and a catalyst.

The next step involves reducing biomass molecules into fuel. Water is fed into the anode side and passed through an electric current through the water to generate protons and electrons. The electrons run through a circuit and the protons pass through the proton-exchange membrane to the cathode side, where they generate hydrogen. The hydrogen reacts with the biomass molecule and reduces it to fuel, while oxygen exits the system.

The biomass-to-biofuel reduction process in a continuous-flow reactor, which continuously and efficiently moves reactants through the system. Another advantage, says Huber, is that the process yields 50 percent more liquid fuel over ethanol fermentation processes. At the production level, the process also could be modular.

“This is potentially a scalable technology where you could make these proton-exchange-membrane-type reactors in the field, close to the biomass, and run them at night when you have cheap electricity,” explained Huber.

In future work, Huber hopes to improve the catalysts and membranes in the fuel cell to make the process more efficient. In addition, one of Huber’s goals is to repeat the process with sugar, which could produce hexane and oxygen.


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