|Elements of the ZeaChem process. Click to enlarge.|
ZeaChem, Inc. and GreenWood Resources, Inc. (GWR) signed a non-binding Letter of Intent for the supply of poplar tree (Pacific Albus) feedstock under a long-term agreement to support the operation of an initial 1.5 million gallon per year (MGPY) ZeaChem cellulosic biorefinery near one of Greenwood’s Pacific Albus tree farms in the Columbia River Basin.
The ZeaChem biofuel process combines the outputs of two traditional fuel production pathways (fermentation of sugars and gasification of biomass) into a third catalytically-driven step—hydrogenolysis—to produce cellulosic ethanol fuel and cellulose-based intermediate chemicals. ZeaChem’s technology will produce 50% more ethanol per ton of feed than the current best-in-class technology. (Earlier post.)
The biochemical processing step converts sugars in the cellulosic biomass into acetate via bacterial fermentation. The conversion can be either direct in a one-step fermentation process or via lactic acid to acetic acid in a 2-step process. (The production of lactic acid can provide an additional revenue source.) After fermentation, the acetic acid is extracted from the fermentation broth in an acid recovery stage and esterified.
The thermochemical processing step converts lignin and other non-fermentable materials in the cellulosic biomass into a syngas. The acetate ester from the fermentation pathway and the hydrogen from the syngas combine in a hydrogenolysis reaction to produce the ethanol.
An analysis of the ZeaChem process included in a report on ethanol by the University of Illinois, published in November 2007, notes that:
In this process, 3 moles of ethanol are produced from 1 mole of glucose resulting in a 50% improvement over the conventional route where 2 moles of ethanol are produced from 1 mole of glucose. The energy for the third mole of ethanol is supplied by hydrogen, which can be generated by the gasification of the lignocellulosic biomass.
Zeachem also uses the thermochemical processing stage to provide steam and power for the plant.
Additionally, ZeaChem and GWR agreed to explore increasing the scope of the relationship to accommodate additional capacity at this biorefinery and other future sites through the potential development of short-rotation poplar biomass energy tree farms integrated with ethanol conversion technology.
ZeaChem will be responsible for financing, constructing and operating the biorefinery. Initial engineering for the site has already begun.
GreenWood Resources (GWR) is a leader in the development and management of short-rotation, high-yield hardwood tree farms for a range of products and end uses. The GreenWood Tree Farm Fund, LP (GTFF), a $175-million fund organized by GWR, has invested in the consolidation of existing high-yield, fast-growing tree farm assets in the Pacific Northwest.
GTFF currently owns 35,000 acres of sustainable tree farms certified under FSC in the Columbia Basin in Oregon and Washington.