A review of economic & energy analysis of the conventional and the modified dry grind ethanol process

Biofuels are one of many renewable energy technologies offering an opportunity to put our civilization on more sustainable ground. Ethanol currently constitutes 99% of all biofuels in the United States. To meet this demand, the current ethanol plant expansion in the industry is mainly based on the dry grind process. Over the past several years, this industry is suffering great pressure with currently fluctuating feedstock prices. Several modified dry grind processes have been developed aiming at increasing the profitability of the ethanol plant, and significant improvements have been observed on the process efficiency and the value of coproducts. Previous economic analyses suggest that corn, ethanol and energy prices and ethanol yield are the four major factors that will affect the profitability of the conventional dry grind plants. However, for the modified dry grind process, the composition of coproducts is another key factor. Thermal energy and electric power are two major forms of energy consumption in the ethanol plant. The amount of total energy consumption varies widely in previously published works, and those papers often lack detail on energy use at the unit process scale. For these reasons, computer simulation will be an alternative to better understand the energy flow and the composition of various processing streams in dry grind ethanol production, modified and otherwise. To evaluate the modified dry grind ethanol process, an engineering economic model should consist of two parts: a chemical process model illustrating the energy consumption and cost of the baseline plant and a user-friendly economic model, that chemical process model should be directly linked to the economic model. Thus, both models should be mass balanced and compositionally driven enabling economic analyses sensitive to the quality, quantity, and variability of available feedstocks.