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wood chips from poplar trees, which are mainly used today for paper and pulp. The biomass goes through a separation process called fractionation. Sugars from the wood are filtered out and sent through a fermentation process. A natural microorganism from soil, called an acetogen, then converts the sugars into acetic acid without creating carbon dioxide as a byproduct—which other ethanol-making processes do. The acetic acid is converted into a chemical intermediate called an ester, which then goes through an industrial hydrogenation process in order to become ethanol.
That could be the end of the process, but it isn’t. One of the byproducts of the fermentation process is lignin, the tough glue-like material in wood and other biomasses that can’t be broken down efficiently. Part of the key to ZeaChem’s plan is to capture this lignin residue and run it through a high-heat industrial gasification process that creates a rich stream of hydrogen that’s needed for hydrogenation, and which produces power for the factory.
At the end, about two-thirds of the energy stored up in the ethanol comes from the sugar fermentation process, while the rest comes from lignin residue.
“The neat thing about is that you get all the fractions of the wood into the product,” Verser says.
So far, ZeaChem has only performed this process in 5,000 liter fermenters—too small for commercial scale. It has run various parts of the process at different facilities, and has never really done it in a true closed-loop system like it intends to at commercial scale. That’s what it plans to do at the plant in Boardman, OR.
Oregon was chosen to be the proving ground for this cellulosic ethanol process for a number of reasons, Verser says. For one, ZeaChem found a steady, reliable supply of raw material in the form of poplar trees from Greenwood Resources, which runs a 28,000-acre tree farm nearby. The trees grow fast—reaching maturity in about three years—and they can re-sprout when they are cut off at the ground, meaning there’s no need to re-plant them, Verser says. The farm is located near a deepwater port on the Columbia River, providing easy access to the Pacific Ocean and major West Coast shipping ports. And the state of Oregon has a tax credit program, mainly used for wind farms, that is expected to pay for about $6 million to $7 million of the construction costs of the $50 million ethanol demonstration plant in Boardman, Verser says. (About half of the construction costs will be paid for by the U.S. Department of Energy, with the rest coming from ZeaChem, he says.)
Once up and running, the Boardman plant should … Next Page »
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