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Executive SummaryThe ZeaChem indirect method is a radically new approach to producing fuel ethanol from renewable resources. Sugar and syngas processing platforms are combined in a novel way that allows all fractions of biomass feedstocks (e.g. carbohydrates, lignins, etc.) to contribute their energy directly into the ethanol product via fermentation and hydrogen based chemical process technologies.The goals of this project were: 1) Collect engineering data necessary for scale-up of the indirect route for ethanol production, and 2) Produce process and economic models to guide the development effort. Both goals were successfully accomplished.The projected economics of the Base Case developed in this work are comparable to today's corn based ethanol technology. Sensitivity analysis shows that significant improvements in economics for the indirect route would result if a biomass feedstock rather that starch hydrolyzate were used as the carbohydrate source.The energy ratio, defined as the ratio of green energy produced divided by the amount of fossil energy consumed, is projected to be 3.11 to 12.32 for the indirect route depending upon the details of implementation. Conventional technology has an energy ratio of 1.34, thus the indirect route will have a significant environmental advantage over today's technology. Energy savings of 7.48 trillion Btu/yr will result when 100 MMgal/yr (neat) of ethanol capacity via the indirect route is placed on-line by the year 2010. DE-FG36-03GO13010ZeaChem, Inc.ii 1 Project DescriptionExisting technologies for fuel ethanol production all rely on direct fermentation of carbohydrates derived from corn, sugar cane and other sources. All direct fermentation routes suffer from low carbon efficiency. For example, when the fermentable sugar is dextrose: two of the six carbon atoms in the substrate are converted into carbon dioxide, giving a maximum carbon efficiency of only 67%. From a chemical energy perspective, direct fermentation is actually quite efficient. The ratio of higher heating values for ethanol and dextrose is (2 x 1369 kJ/mol)/(2807 kJ/mol) * 100 = 98%, which means that most of the chemical energy stored in the starting dextrose is preserved in the final product. However, throwing away carbon in the form of CO 2 restricts the ability of direct fermentation processes to derive chemical energy from sources other than fermentable carbohydrates.What are the consequences of this limitation? Consider processing a typical lignocellulosic biomass such as corn stover into ethanol. Roughly one-third of the energy content of the feed is present in the form of cellulose, which can be converted into dextrose with appropriate pretreatment and hydrolysis of the feedstock and then fermented with traditional direct fermentation yeasts or similar micro-organisms. Lignin and other non-fermentable materials account for approximately 40% of the energy content of the feedstock. None of this energy can be used directly for ethanol production; it can only be burned and the heat released used to g...

Rising concerns over the use of fossil resources have generated renewed interest in the production of commodity chemicals via fermentation. Organic acids are a particularly attractive target because their functionality enables downstream catalytic upgrading to a variety of compounds. In this article, we survey how common technical issues are addressed in the recovery schemes for several organic acids. We present results for the recovery of acetate using a new method based on amine complexation. Our reactive separation scheme produces a high-purity product, is energy efficient, and avoids the coproduction of a waste salt coproduct, all prerequisites for a large-scale production process.

Heat and power systems commonly found in today's corn processing facilities, sugar mills, and pulp and paper mills will be reviewed. We will also examine concepts for biorefineries of the future. We will show that energy ratio, defined as the ratio of renewable energy produced divided by the fossil energy input, can vary widely from near unity to values greater than 12. Renewable-based utility systems combined with low-fossil input agricultural systems lead to high-energy ratios.

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