Tuesday, May 01, 2007Petroleum and Natural Gas Watch
by Michael Vickerman, RENEW Wisconsin
April 30, 2007, Vol. 6, Number 7
Discussions of the net energy balance of grain ethanol tend to gravitate toward the fossil fuels used for growing and shipping corn. Somewhat overlooked in the net energy return debate are the quantities of natural gas and electricity consumed at ethanol refineries, which are substantial.
An ethanol refinery that produces 50 million gallons a year burns about 50,000 therms of non-renewable natural gas a day for process heat. This is no trivial expense. Using today’s prices, a refinery operator would need to budget at least $15 million over the next 12 months to secure enough fuel to keep that plant running nearly every hour of the year. After corn, natural gas is the second-largest cost component of ethanol production.
That plant also exerts, on average, a 5 megawatt load on the electrical grid. The quantity of electricity consumed at that plant could support nearly 6,000 households in Madison, Wisconsin. About 75% of the electricity from Wisconsin’s power grid comes from coal combustion.
Whether the goal is to reduce greenhouse gas emissions or enhance energy security, it makes little sense to pin our hopes on an agricultural commodity that has such an outsized appetite for fossil fuel-derived energy. When all is said and done, what this biofuel represents is the repackaging of stored energy (coal, petroleum and natural gas) into a land-intensive flow product (corn). Even though several months’ worth of sunshine goes into the production of corn, the amount of usable energy contained in ethanol is barely higher than would have been available from using the fossil energy directly.
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