Multicultural biofuel made from toughest part of the plant

Lignin is tough stuff, but Washington University has a way to turn at least some of it into fuel.

Researchers at Washington University in St. Louis have devised a technique for turning some of the harder parts of a plant into fuel, a breakthrough that could further bring down the cost of biofuels.

Two of the major components of plant material are cellulose and lignin. Lignin essentially turns fibers into wood. It hardens cell walls and binds cellulose fibers together. It's the reason we have coal. If ancient plants hadn't had lignin, microorganisms would have eaten them and thus, the plants would never have been transformed into rock. (There's your fun primordial fact for the day.)

Lignin is also the bane of many companies trying to make cellulosic ethanol. The first step in many cellulosic processes involves separating the cellulose from lignin and other materials with acid or heat. That takes quite a bit of energy.

Lars Angenent, assistant professor of energy, environmental, and chemical engineering at WU, has figured out a way to take a cellulose/lignin mix from pre-treated corn fiber and turn it into butyrate, a precursor of butanol, a less corrosive, high-energy liquid fuel. Conceivably, the process could result in a richer fuel than standard ethanol that exploits plant matter more efficiently. That's key for the corn industry; critics note that corn ethanol doesn't result in a huge net gain in energy over the amount of energy required to make it. Ethanol made from other materials does much better on that score.

How does it work? Angenent has created an environment where thousands of different types of bacteria munch away on the lignocellulosic mass. (Hence the multicultural part) and turn it into butyrate.

"The advantage of mixed cultures is that it can take just about any waste material and, through our manipulations, convert it into something valuable. For instance, I can alter the pH in this culture. By keeping it neutral, I can get methane gas, but when I lower the pH, I can get butyrate," he said in a prepared statement.

Angenent, of course, isn't the only person looking at lignin. ZeaChem, which makes chemicals to convert plant matter into ethanol precursors, takes lignin extracted in early parts of the process and introduces it at a later stage.

The multispecies approach is also being taken by a number of fuel start-ups.

 

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