The concept of “life cycle assessment” was first applied to manufacturing processes but is increasingly being used to examine agriculture. It's a technique to analyze the environmental impacts associated with a product, process or service. Iowa State University researchers used the life cycle assessment concept 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 took into account all direct and indirect energy inputs in the construction and operation of a pig facility, plus the growing and processing of feed ingredients.
Conventional confinement system/ mechanical ventilation and liquid manure handling
Comparisons were made 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 uses energy differently according to Pete Lammers, a former ISU doctoral candidate in animal science. Lammers now is a livestock specialist for the National Center for Appropriate Technology in Des Moines.
Lammers said raising pigs in conventional confinement facilities requires the use of more energy to heat and ventilate the buildings. “Using bedded hoop barns for gestation and grow-finish reduces this energy use by almost 70 percent,” he said.
However, pigs raised in hoop barns require more feed, which ultimately leads to the two systems performing similarly in terms of energy use. “Earlier ISU research showed a hoop barn-based system requires 2.4 percent 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 said.
The researchers found the largest single use of nonrenewable energy in pig production is growing the feed. Approximately 50 percent of the nonrenewable energy associated with growing and processing a typical corn-soybean meal diet can be attributed to synthetic nitrogen fertilizer for corn production.
So although conventional facilities require 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.
Mark Honeyman, animal science professor and coordinator of Iowa State's research farms, said the research showed a huge drop in the use of nonrenewable energy for pig production over the past 35 years.
“This study showed a reduction of nearly 80 percent in nonrenewable energy use to produce one market pig in Iowa today, compared to 1975, which was the last time this topic was examined,” Honeyman said. “This can be attributed to improved genetics and nutrition, changes in housing and ventilation systems and an overall increase in production efficiency.”
Honeyman said the research shows the key to further reducing 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 said.
Peer reviewed papers on the research have appeared in “Applied Engineering in Agriculture,” “Journal of Animal Science” and “Agricultural Systems.”