A more accurate comparison is with the early corn

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lignocellulose conversion process. A more accurate comparison is with the early corn ethanol industry. The cost of corn ethanol plants has dropped since the industry°s inception, and it is realistic to assume that the lignocellulosic ethanol plant costs would also be reduced as more plants are built. For the lignocellulose process, elimination of some of the capital-intensive areas, through purchase of the materials, could significantly reduce the capital cost. For example, in this analysis enzyme is produced on-site for the lignocellulose process and purchased for the starch process. This contributes about $0.70 per gallon in capital costs. Another area is steam production. The lignocellulose plant produces steam from lignin-rich solid residue, which requires a more expensive boiler than natural gas combustion for the starch process. The solids boiler system contributes about $1.40 per gallon in capital costs to the lignocellulose process. If the lignocellulose plant were able to locate next to a power generator, steam and electricity could be purchased rather than produced. For a larger capacity plant, the capital cost per gallon decreases due to the fact that capital costs are not linear with plant capacity. A plant with two times the capacity, or 50 million annual gallons, would have closer to $4.30 per gallon in capital costs. The cost to transport feed from a longer distance to supply the larger plant might offset some of these savings. In contrast, one could model the lignocellulosic ethanol plant as a pioneer plant, the first of its kind, in which case the costs would be significantly higher due to the higher level of uncertainty in the design and costing. There are methodologies discussed in literature to build this type of model which might provide a more accurate cost estimate in the design and construction phases of the first plants. 14 The method compares a fledging technology with an established similar one, taking into account how much of the technology is new and how much is proven. Depending on this ²new to proven³ ratio, a factor is applied to the cost estimates to account for the additional costs associated with the new technology. Applying these factors, while increasing the cost estimate, may provide a more accurate estimate earlier, and help avoid cost creep during the construction and startup phases.
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6 III Process Descriptions Each process has the same general flow, from feedstock handling through fermentation to product and co-product recovery. The process details are outlined below. III.1 Corn Starch Feedstock-to-Ethanol Process Description Figure 1 depicts the dry mill process. The majority of the flowsheet information was provided by Delta-T Corporation, which designs, constructs, and operates corn ethanol plants. 15 Figure 1. Corn starch-to-ethanol dry mill process flow Corn is received and conveyed to two storage silos, having a combined capacity of 10 days. Stored corn is conveyed to grain-cleaning equipment where trash such as tramp metal and rocks (0.3%) is removed, and then to hammer mills (two operating mills, plus one standby). The corn meal is metered to a continuous liquefaction tank, where it is
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