Engineering economic analysis of the quick-germ/quick-fiber modified dry grind ethanol fractionation process

It has been widely debated whether producing ethanol from corn is sustainable in the long term. Environmentally, the major concern is that producing ethanol from corn involves intensive water and energy consumption. Economically, recent fluctuations in petroleum, ethanol, and corn prices have driven several large producers of ethanol into bankruptcy. The ethanol industry is vulnerable to periods of economic weakness because its product value varies with oil prices but its raw material (corn) varies with food prices. To improve the economic sustainability of corn-to-ethanol production, several modified dry grind processes had been developed at the lab scale. The Quick-germ / Quick-fiber (QQ) process is one of them. However, there has been no analysis of the QQ process that provides detailed information related to the energy, water, and economic performance at a commercial scale. To determine the both environmental and economic performance, a process simulation model was developed on the SuperPro Designer® platform to simulate the QQ process, and compared to the conventional dry grind model. Results indicate that germ and fiber recovery as done in the QQ process improves the process capacity of a conventional dry grind ethanol facility by approximately 24%. Because of germ and fiber recovery at the front end, the ethanol concentration has been increased to 15% (w/w) as compared to 10.9 (w/w) in the conventional dry grind process. The QQ process reduces the energy and water consumption by 32% and 17.8%, respectively. The QQ process produces more value-added coproducts, including corn germ, corn fiber, and a modified distillers dried grains with solubles (DDGS), but has a lower ethanol yield rate due to some starch losses to the recovered germ and fiber fractions at the front end. A detailed cost and benefit analysis of the QQ process, based on the market prices in April 2009, shows that despite its higher capital investment costs, the QQ process reduces the payback period to 6.5 years, compared to 9.2 years for the conventional dry grind process. Increased ethanol production, more value-added coproducts, as well as significant reduced utility costs are three major contributors to improve the economic performance of the QQ process. This work lays the foundation for the similar studies on the sustainability performance for other modified dry grind ethanol processes