Ethanol Plant Is Switching to Butanol

Green: Business

High oil prices are generally bad news for American companies, but one, Gevo of Englewood, Colo., says that $100-a-barrel oil is opening up a niche.

The company bought a factory in Luverne, Minn., that makes ethanol from corn. Ethanol replaces some petroleum but has only one main use, vehicle fuel, and it yields less energy per gallon than gasoline. Gevo will convert the plant to make a different chemical, isobutanol, one of a number of new pathways to butanol, a chemical that can be used for fuel for many other purposes.

Butanol can go into rubber and plastics, and in that role it not only replaces oil but also becomes a “carbon sink,” a place where carbon dioxide, a greenhouse gas, can be stored after it is pulled out of the atmosphere. The rubber or plastic is indistinguishable from the rubber made with oil. But the carbon dioxide in oil came from deep underground; the carbon in the butanol was pulled out of the atmosphere by a corn plant.

And it can be done at a profit, Gevo says.

Ethanol is made by feeding sugar to yeast, which secretes the ethanol. But the same yeast ordinarily convert some of the sugar to isobutanol. Gevo tinkered with the yeast to turn off its ability to make ethanol and increase its production of isobutanol.

Gevo already makes isobutanol in a pilot plant. The Luverne plant will make 18 million gallons a year, the company says.

Why isobutanol? Both ethanol and isobutanol are made up of just three kinds of atoms: carbon, hydrogen and oxygen.
But ethanol is useful mostly as a motor fuel, whereas isobutanol is a building block for many other chemicals. Notably, it is easily converted into commodity chemicals called butylene, which have four carbon atoms and are in relatively short supply right now.

Butylenes are ordinarily made from oil along with various other basic chemicals. When oil is expensive and natural gas is cheap, chemical companies start making those chemicals from natural gas instead and from other chemicals that come out of natural gas wells.

That works fine, but using natural gas and related chemicals turns out a different mix of materials than using petroleum does; one class of chemicals that does not get produced in abundance is butylene.

Enter Gevo. Isobutanol is easily converted to butylenes, according to Patrick Gruber, the company’s chief executive. From there, it can be turned into a drop-in component of gasoline, diesel or jet fuel. Or it can be turned into a component of synthetic rubber or plastic.

The company recently raised over $100 million in an initial public offering and plans to use it to buy more ethanol plants. Mr. Gruber said that because of the product’s flexibility, he expects the company to do well selling butanol for conversion to fuel when fuel prices were high, or for other chemical uses.

Some of those uses could be considered carbon dioxide sinks, Mr. Gruber said. For example, when butanol goes into making synthetic rubber, carbon dioxide stays in the rubber — even if the product is a pair of sneakers that eventually gets buried in a landfill.

Motor fuel from butanol could also qualify as an advanced biofuel, under a federal law that sets aside a quota for such fuels. For that to happen, it would have to be produced with fewer carbon dioxide emissions, which could be accomplished by drawing the energy from the burning corn wastes, for example, said Jack Huttner, the company’s executive vice president.

Gevo is not alone in butanol work. BP and DuPont have a partnership to make butanol. And researchers at the University of California, Berkeley, reported last week that they were producing butanol by using a bacterium that was fed glucose.

This is a well-known technology, but the enzymes that actually do the conversion also tend to change some of the butanol back into the raw materials it came from, according to Michelle C.Y. Chang, an assistant professor of chemistry there.

So the researchers altered the genes of an E. coli bacterium. Their new bacterium produces 10 times as previously engineered bacterium produce, she said.