The purpose of this design project is to examine the plant-scale economic viability of the anaerobic fermentation of crude glycerol to ethanol by a hypothetical wild strain of Escherichia coli. The manufactured ethanol, before being denatured with gasoline, has a purity requirement of 99.5% by weight. The capacity of the ethanol plant, as suggested by the problem statement, is 50 MM gallons per year. The process uses crude glycerol (a waste byproduct from the biodiesel industry) as a primary feedstock, so the manufactured ethanol can be considered a “green” or renewable fuel source. The process energy requirements must meet the current energy benchmark of 35,000 BTU/gallon of ethanol, typical for a modern corn-to-ethanol process of this scale according to the design problem statement. This goal is more than met, with an energy usage of 8,000 BTU/gallon of ethanol.
The process design consists of three main sections: upstream preparation of the glycerol feed for the E. coli, anaerobic fermentation of this glycerol feed to ethanol and succinic acid (a valuable specialty chemical and a side-product of fermentation), and downstream separation to recover the ethanol and succinic acid.
When performing the economic analysis, the plant was assumed to be a grass roots plant located in the Gulf Coast region of the United States. The total capital investment is 108million,includingaworkingcapitalof23.6 million. In the base case scenario, with crude glycerol priced at 0.05/lb,ethanolpricedat2.50/gallon, gasoline priced at 3.15/gallon,andsuccinicacidpricedat2.00/lb, the net present value (NPV) of the project is $95 MM based on an interest rate of 15%, and the investor’s rate of return (IRR) is 32.24%. The process profitability improves with increasing crude oil prices and decreasing crude glycerol prices, which we believe are highly likely scenarios based on our market research
