ZeaChem Begins Construction of Cellulosic Biorefinery; Combined Biochemical and Thermochemical Process to Produce Ethanol
ZeaChem Inc. has begun construction of its semi-works scale facility. The facility will have capacity to produce 250,000 gallons of biofuel per year. ZeaChem’s process combines the outputs of two traditional ethanol production pathways (fermentation of sugars and gasification of biomass) into a third catalytically-driven step—hydrogenation—to produce ethanol. (Earlier post.)
In the ZeaChem process, the biomass is chemically fractionated to produce a sugar stream containing both xylose (C5) and glucose (C6) sugars, and a lignin residue stream. The sugars are fermented by a carbon-efficient acetogen—Clostridium thermoaceticum, found in termites—to acetic acid without CO2 as a by-product. (Conventional yeast fermentation creates one molecule of CO2 for every molecule of ethanol.) The acetic acid is converted to an ester which is then be reacted with hydrogen to produce ethanol. The hydrogen is produced by the gasification of the lignin residue to produce syngas.
The front-end fermentation unit scales up production of the naturally occurring acetogen. ZeaChem has successfully produced acetogens at the lab scale for more than 1,000 fermentation trials of sugars as well as hydrolyzate derived from cellulosic biomass.
Hazen Research, an industrial research and development firm, will construct and host the initial process unit and provide infrastructure and operations support. ZeaChem is constructing the semi-works scale biorefinery utilizing skid mounted design, which allows construction of individual process units more quickly in fabrication shops.
The skids act like modular building blocks, each approximately the size of a cargo shipping container, and will be integrated together at the final biorefinery site, proposed in Boardman, Oregon. Key advantages of skid mounted design include the ability to optimize unit operations earlier in the process and the flexibility to bolt on and phase in additional skids as the biorefinery is deployed in stages. These steps significantly reduce the risk of individual process operations and ultimate integration.
ZeaChem intends to scale to a commercial biorefinery upon successful operations at the semi-works scale facility. The core technology of such a facility will come online in 2010.