In a study of energy use on Iowa hog farms, Iowa State University (ISU) researchers found a huge drop in the use of nonrenewable energy for pig production over the last 35 years.

“This study showed a reduction of nearly 80% in nonrenewable energy use to produce one market pig in Iowa today, compared to 1975, which was the last time this topic was examined,” says Mark Honeyman, animal science professor and coordinator of Iowa State’s research farms.

ISU researchers used the life cycle assessment concept first applied to manufacturing processes to estimate the amount of nonrenewable energy needed to produce pigs in Iowa. The project was supported by a two-year grant from ISU’s Leopold Center for Sustainable Agriculture and a U.S. Department of Agriculture Sustainable Agriculture Research and Education grant.

The research accounted for all direct and indirect energy inputs in the construction and operation of a pig facility and the growing and processing of feed ingredients.

Energy use was compared between a conventional confinement system with mechanical ventilation and liquid manure handling, and one that uses bedded hoop barns for grow-finish pigs and gestating sows.

The two housing systems required similar amounts of nonrenewable energy, but each used energy differently, according to Pete Lammers, a former ISU doctoral candidate in animal science. Lammers is currently a livestock specialist for the National Center for Appropriate Technology in Des Moines.
Raising pigs in conventional confinement facilities requires more energy to heat and ventilate the buildings. “Using bedded hoop barns for gestation and grow-finish reduces this energy use by almost 70%,” he says.

But pigs in hoop barns require more feed, so the two systems balance out in terms of energy use. “Earlier ISU research showed a hoop barn-based system requires 2.4% more feed. In addition, the nitrogen value in the solid manure is less than what’s available in liquid manure collected at a confinement facility. That means more fertilizer nitrogen must be applied to corn fields,” Lammers says.

The greatest use of nonrenewable energy in pig production comes from growing the feed, researchers found. About 50% of the nonrenewable energy associated with growing and processing a typical corn-soybean meal diet is due to synthetic nitrogen fertilizer for corn production.

In short, although conventional facilities take more energy to operate fans, lights and heaters, the amount of energy related to crop production is slightly less when compared to hoop barn-based pig production.

Honeyman says the research indicated the way to further reduce nonrenewable energy use for Iowa pig production is nitrogen management. “Strategies to optimize nitrogen stocks and flows among crops, livestock, manure and soil should be a priority for future research,” he states.

This and other related articles are posted on the Web for Iowa State University College of Agriculture and Life Sciences at http://www.ag.iastate.edu/news/.