New Biofuel Gasification Process Doubles Production
A new "gasification" method of converting biomass feedstock into sustainable fuel reduces greenhouse gas emissions and doubles the amount of fuel that can be made from one acre, according to Paul J. Dauenhauer of the University of Massachusetts Amherst chemical engineering department.
Dauenhauer explained the new process in a recent story in Technology Review, published by the Massachusetts Institute of Technology. In the new approach, researchers gasify biomass in the presence of precisely controlled amounts of carbon dioxide and methane in a special catalytic reactor. The result is that all the carbon in both the biomass and the methane is converted to carbon monoxide.
This technique allows researchers to use 100 percent of the carbon in that biomass for making biofuels. That doubles the proportion of fuel-producing carbon produced by a conventional gasification process done in one reactor while converting biomass to biofuels.
When perfected in as few as two years, the new method would be a major step forward in the quest for a production-ready process to convert biomass to biofuel, Dauenhauer said. His colleagues at the University of Minnesota are Professor Aditya Bhan and Regents Professor Lanny Schmidt.
The drawback of current gasification, Dauenhauer explained, is that about half of the carbon in the biomass gets converted to carbon dioxide rather than into carbon monoxide, a precursor for fuels. The question for Dauenhauer and the research team was how to improve that technology. One way is to control the “breakdown environment.”
To increase yield from gasification, the researchers add carbon dioxide, which promotes a well-known reaction: the carbon dioxide combines with hydrogen to produce water and carbon monoxide. But adding carbon dioxide isn’t enough to convert all of the carbon in biomass into carbon monoxide instead of carbon dioxide. It’s also necessary to add hydrogen, which helps in part by providing the energy needed to drive the reactions. The new gasification process uses methane, the main component of cheap and available natural gas, to generate the hydrogen within the reactor. While it has long been possible to do each of these steps in separate chemical reactors, the researchers’ innovation was to find a way to combine all of these reactions in a single reactor, the key to making the process affordable, Dauenhaer said.
The researchers still need to demonstrate that the method works with biomass, not just with cellulose derived from biomass. Biomass contains various contaminants not found in pure cellulose. Those contaminants could have a negative effect on the catalyst, and this could make it necessary to reengineer the reactor. And there could be challenges scaling up the process, including ensuring that heat moves through the reactor the same way it does on a small scale.