In terms of ethanol production cost share, the fractionated sludge-to-ethanol process had enzyme costs of 46 percent, energy costs of 16 percent and chemical costs of 6 percent of the total production cash cost (production cost minus noncash costs such as depreciation). In contrast, the nonfractionated process had enzyme costs of 48 percent, energy costs of 13 percent and chemical costs of 19 percent of the total production cash cost. The nonfractionated case has a much higher chemical share of the costs, mainly due to higher sulfuric acid use. The sludge-to-ethanol process can produce excess returns, assuming an ethanol wholesale price of $2.30 per gallon (average wholesale price of the past 16 months). The internal rate of return of this process is estimated at 28 percent and the modified internal rate of return at 19 percent with a reinvestment rate of 8 percent.