Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.iii Executive SummaryThe U.S. Department of Energy (DOE) promotes the production of ethanol and other liquid fuels from lignocellulosic biomass feedstocks by funding fundamental and applied research that advances the state of technology in biomass collection, conversion, and sustainability. As part of its involvement in the program, the National Renewable Energy Laboratory (NREL) investigates the production economics of these fuels.This report describes in detail one potential biochemical ethanol conversion process, conceptually based upon core conversion and process integration research at NREL. The overarching process design converts corn stover to ethanol by dilute-acid pretreatment, enzymatic saccharification, and co-fermentation. Ancillary areas-feed handling, product recovery, wastewater treatment, lignin combustion, and utilities-are also included in the design. Detailed material and energy balances and capital and operating costs were developed for the entire process, and they are documented in this report and accompanying process simulation files, which are available to the public.As a benchmark case study, this so-called technoeconomic model provides an absolute production cost for ethanol that can be used to assess its competitiveness and market potential. It can also be used to quantify the economic impact of individual conversion performance targets and prioritize these in terms of their potential to reduce cost. Furthermore, by using the benchmark as a comparison, DOE can make more informed decisions about research proposals claiming to lower ethanol production costs.Building on design reports published in 2002 and 1999, NREL, together with the subcontractor Harris Group Inc., performed a complete review of the process design and economic model for the biomass-to-ethanol process. This update reflects NREL's current vision of the biochemical ethanol process and incorporates recent progress in the conversion areas (pretreatment, conditioning, saccharification, and fermentation), optimizations in product recovery, and an improved understanding of the ethanol plant's back end (wastewater and utilities). The major process updates in this design report are the following:• Feedstock composition is updated to a carbohydrate profile closer to the expected mean.• Pretreatment reactor configuration is revised with significant new detail.• Whole-slurry pH adjustment of the pretreated biomass with ammonia replaced the previous conditioning practice of overliming, eliminating a solid-liquid separation step.

Off-gas 10% of total Carbon AHTL Oil 72% of total Carbon (77% algal carbon recovery) Natural Gas 3.5% of total Carbon in Water & Solids Recycle to Ponds 8% of total Carbon as dissolved CO2 (9% of algal carbon) Reformer & Heater Exhaust 23% of total Carbon (Includes 21% of algal carbon) Natural Gas Drier & Exhaust 3.5% of total Carbon in

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from the National Renewable Energy Laboratory (NREL) for helpful discussions, comments, and shared insights during the development of this report. We appreciate all of the help from Kathy Cisar for her technical editing and support in publishing this report. Finally, we thank Billie Christen from the NREL for her help in formatting this report and for developing the U.S. bioproduct facilities map.