Ohio State University (OSU) and University of Minnesota researchers have received a $599,836 U.S. Department of Agriculture National Research Initiative grant to study the feasibility of capturing and recycling ammonia emissions from manure to reapply as fertilizer.
“Large amounts of ammonia emissions from animal feeding operations have caused significant environmental and health concerns,” says Lingying Zhao, an OSU Extension specialist in agricultural air quality and bioenvironmental control. The Environmental Protection Agency estimates in 2002 that 2.4 million tons of ammonia were emitted into the air.
This project intends to offer livestock producers an innovative tool to reduce air emissions, while generating an alternative product to commercial nitrogen fertilizer.
The grant calls for developing a wet scrubber for trapping ammonia emissions from manure storage facilities and evaluating their performance in conversion into nitrogen fertilizer.
Zhao comments wet scrubber technology isn’t new – but this type of wet scrubber is. Most wet scrubbers for removing gaseous pollutants are known as packed towers in which vapors are absorbed by liquids over the surface of packing material.
“Packed towers, however, cause significant pressure drop and energy consumption and don’t operate well with agricultural ventilation fans, which normally move large amounts of air at lower pressures,” says Zhao. The technology isn’t feasible for large animal facilities.
Zhao and her colleagues have been focusing on a spray-type of wet scrubber that operates by capturing gas in water/acid liquid droplets normally sprayed in the device. The ammonia gas is transferred to the liquid via air being passed through, and then recycled.
A prototype scrubber has been developed in the lab to be tested in the field.
“From our results in the lab, we see the potential that the scrubber has on an animal farming operation,” says Zhao. “Scrubber technology is complex. What we want to do is create a small-scale scrubber applicable to a farm. If a composting facility generates approximately 100 tons of ammonia annually, and the scrubber is efficient, even at only 70% collection efficiency, 70 tons of ammonia can be collected and recycled for use on the farm.”
The three-year grant is part of USDA’s Cooperative State Research, Education and Extension Service air quality grants program. In all, USDA has awarded $5 million to 11 universities to conduct air quality projects aimed at developing and evaluating emission control technologies.