Purdue University researchers have found that soybean oil reduces greenhouse gas emissions when sprayed inside hog finishing barns.

Purdue agricultural engineers Al Heber and Jiqin Ni and University of Missouri researchers conducted a year-long project to monitor the effectiveness of soybean oil on dust and odor levels within hog facilities.

“This project provided baseline measurements of the greenhouse gas contributions of swine finishing barns,” Heber reports. “In addition to the baseline measurements, we now have data on an abatement technology to reduce the carbon footprint contribution of a pound of pork.”

Greenhouse gases contribute to the greenhouse effect by causing heat to be trapped in the lower atmosphere, producing global warming. The Environmental Protection Agency says agricultural practices were responsible for 7.4% of total greenhouse gas emissions in the United States in 2005.

The Purdue study at a northern Missouri hog farm involved spraying oil in one of two, 1,100-head barns. The treated barn was sprayed for one minute per day, similar to the spray technology used to treat fields with pesticides.

“We tested three different methods of pollution mitigation: soybean oil sprinkling, misting with essential oils and misting with essential oils and water,” Ni says.

“Our original intent was to see if those three methods would control dust, as well as odor emissions, ammonia, hydrogen sulfide, methane and carbon dioxide emissions.”

Compared with the unsprayed barn, the oil-treated barn achieved an average 20% reduction in methane emissions and a 19% average drop in carbon dioxide emissions, both greenhouse gases.

Dust reduction was even more striking. The treated barn emitted about 65% less particulate matter than the untreated barn. Researchers believed controlling dust also would lead to reduced greenhouse gas emissions, Heber says.

“The spray takes out dust, and since dust carries odor and it absorbs other gases, there was a scientific reason why it might take out those greenhouse gases,” Heber adds.

“We saw a reduction in odor but it wasn’t statistically significant,” he adds. “That may be because we didn’t take enough air samples. All we can say is that there was a trend in odor reduction.”

Challenges to using soybean oil in swine barns include safety, cleaning and the cost of application, according to Heber.

“First of all, soybean oil is more expensive now than it was when we did the study,” he explains. “Whereas, we thought it would cost less than a dollar per pig marketed to treat the barn – around 60 cents – since then the price of soybean oil has increased dramatically, and so the economics are not as good. Also, the application of oil can create a safety hazard for the producer.

“In addition, some of the oil ended up on the floor, the pigs, the feeders and fans. This makes the cleaning process more difficult. The producer we worked with indicated it took an additional day of power washing to clean that barn. That’s an extra expense.”

Although soybean oil shows promise to control greenhouse gases, it’s too early to declare the findings conclusive, Heber and Ni agree.

“There are technical problems with this practice, but those may be overcome through good engineering,” Heber says.

“We need to do more research to get a better idea of the effectiveness of this technology and its benefit on environmental protection,” Ni says.

Click here to read the full paper, “Methane and Carbon Dioxide Emission from Two Pig Finishing Barns,” in the Journal of Environmental Quality.