USDA: Energy Efficiency of Corn-Ethanol Production Has Improved Significantly

A new report from the U.S. Department of Agriculture, “2015 Energy Balance for the Corn-Ethanol Industry,” examines the energy efficiency of corn ethanol production. According to the findings, the energy balance of ethanol has improved significantly over the past two decades. It has made a “transition from an energy sink to a moderate net energy gain in the 1990s, to a substantial net energy gain in the present.” In some areas of the Midwest, ethanol production creates more energy than it consumes by a factor of 4 to 1. Nationally, the average ratio of energy outputs to inputs for ethanol production is 2 to 1.

The report methodically examines the energy used for corn ethanol production over a nearly 20 year period. Energy inputs for ethanol range from fertilizer and chemical applications to the corn, the energy needed to harvest and transport the corn, as well as the energy used at the ethanol plant and for the distribution of the ethanol and its co-products. Energy outputs are the ethanol and its co-products, such as dried distillers grains (DDGS) or wet distillers grains, both used as livestock feed. Despite the energy required to grow, harvest and distill ethanol, the industry has been able to greatly improve the energy balance of ethanol since the industry’s earliest days, and continues to make improvements.

The report calls out numerous factors that have led to the increased efficiency of ethanol production, including: closer proximity of farms to ethanol plants, new storage facilities that match increased corn production, and the rail shipment of ethanol to local and long distance markets (instead of truck shipment, which is less efficient). Long term improvements to corn yields and reductions in fossil energy used for corn production have reduced energy inputs. More recent advancements to procurement and distribution logistics have also boosted the energy efficiency of the industry.

A few states, such as Iowa and Minnesota, stand out as having particularly energy efficient ethanol production. Iowa operates with a higher rate of energy efficiency for several reasons. First, it has the second lowest production energy for corn of the nine states surveyed. The state’s high corn yields and concentration of ethanol plants also significantly reduce energy use from transportation. A significant cattle feedlot industry located in western Iowa boosts sales of wet distiller grains (DG), which are more energy efficient than dry distillers grains (DDGS) because they do not require drying—a significant use of heat. Finally, a robust local ethanol market means the final product doesn’t have to be transported very far.

The report pointed out several areas for further improvements in the industry's energy efficiency. One is the use of renewable biomass, such as corn stover (leaves, cobs, stalks and husks) to power ethanol facilities, instead of the traditionally used fossil sources – primarily natural gas or sometimes coal. The cost of biomass feedstock is only slightly higher than that of coal, and it has a distinct price advantage compared to natural gas. Despite this price advantage, plant managers have historically favored easier-to-manage natural gas rather than the logistics of biomass power.

The report's authors note that policy changes, such as a carbon tax or advanced biofuel status under the Renewable Fuel Standard (RFS) for biomass-using corn ethanol plants, could provide economic incentives for a shift to biomass power, which could further improve energy balance in the industry.

Author: Taotao Luo

For more information see:

Statement from Agriculture Secretary Tom Vilsack on Research Showing Significant Improvement in Efficiency of Ethanol Production and Other Trends, USDA

2015 Energy Balance for the Corn-Ethanol Industry, USDA