Techno-economic comparison of process technologies for biochemical ethanol production from corn stover

This techno-economic study compares several process technologies for the production of ethanol from lignocellulosic material, based on a 5- to 8-year time frame for implementation. While several previous techno-economic studies have focused on future technology benchmarks, this study examines the short-term commercial viability of biochemical ethanol production. With that goal, yields (where possible) were based on publicly available experimental data rather than projected data. Four pretreatment technologies (dilute-acid, 2-stage dilute-acid, hot water, and ammonia fiber explosion or AFEX); and three downstream process variations (pervaporation, separate 5-carbon and 6-carbon sugars fermentation, and on-site enzyme production) were included in the analysis. Each of these scenarios was modeled and economic analysis was performed for an nth plant (a plant with the same technologies that have been employed in previous commercial plants) to estimate the total capital investment (TCI) and product value (PV). PV is the ethanol production cost, including a 10% return on investment. Sensitivity analysis has been performed to assess the impact of process variations and economic parameters on the PV. The dilute-acid pretreatment process has the lowest PV among all process scenarios, which is estimated to be $1.36/l of gasoline equivalent [LGE] ($5.13/gal of gasoline equivalent [GGE]). Sensitivity analysis shows that the PV is most sensitive to feedstock cost, enzyme cost, and installed equipment costs. A significant fraction of capital costs is related to producing heat and power from lignin in the biomass. Cellulosic ethanol production has yet to be commercialized. Hence, a pioneer plant is expected to be more costly to build and operate than an nth plant. To assess the impact of technological maturity on pioneer plant cost, a cost growth analysis was performed. The estimated value of PV for the pioneer plant is substantially larger than for the nth plant. The PV for the pioneer plant model with dilute-acid pretreatment is $2.30/LGE ($8.72/GGE) for the most probable scenario, and the estimated TCI was more than double the nth plant cost. (C) 2010 Elsevier Ltd. All rights reserved.