Why Study Ammonia Recovery from Livestock Wastewater?
This presentation shows a novel system that uses gas-permeable membranes to capture and recover ammonia from liquid manure, reducing ammonia emissions from livestock operations, and recovering concentrated liquid nitrogen that could be sold as fertilizer.
What Did We Do?
These systems use gas-permeable membranes as components of new processes to capture and recover the ammonia in liquid manures. The new process includes the passage of gaseous ammonia contained in the liquid manure through a microporous hydrophobic membrane and capture and concentration with circulating diluted acid on the other side of the membrane. The membranes can be assembled in modules or manifolds. For liquid manure applications, the membrane manifolds are submerged in the liquid and the ammonia is removed from the liquid manure in barn pits or storage tanks and lagoons before it goes into the air.
Cross-sectional diagram of ammonia capture using hydrophobic gas-permeable membrane. Ammonia gas (NH3) in the liquid manure permeates through hydrophobic membrane walls with micron-sized pores, where it combines with the free protons (H+) in the acid solution to form non-volatile ammonium ions (NH4+).
What Have We Learned?
The concept was successfully tested using concentrated swine manure effluents containing 140 to 1,400 mg/L NH4-N. The use of gas-permeable membranes to remove ammonia from liquid manure was effective, and the rate of N recovery by the gas-permeable membrane system was higher with higher ammonia concentration in the manure. While ammonia gas passed readily through the membrane pores, the soluble COD compounds did not pass. An average removal rate from 45 to 153 milligrams of ammonia per liter per day was obtained when ammonia concentrations in swine lagoon liquid ranged from 138 to 302 milligrams ammonia per liter. The rate of ammonia recovery was also increased with increased pH of the wastewater. With a natural pH of 8.3, the rate of N recovery was about 1.2% per hour. This rate was increased 10 times (to 13% per hour) at pH of 10 after alkali addition. In another study, we immersed the membrane module into raw liquid manure that had 1,400 milligrams of ammonia per liter, and after 9 days, the total ammonia concentration decreased about 50 percent to 663 mg per liter. The gaseous ammonia in the liquid (or free ammonia) linked to ammonia emissions decreased 95 percent from 114.2 to 5.4 milligrams per liter. The same process was used in 10 consecutive batches of raw swine manure and ended up recovering concentrated nitrogen in a clear solution that contained 53,000 milligrams of ammonia per liter. The new technology could help change on-farm nitrogen management: Livestock producers could use the technology to help meet air-quality regulations, save fuel, protect the health of livestock and their human caretakers, improve livestock productivity, and recover concentrated liquid nitrogen that can be re-used in agriculture as a valued fertilizer.
Diagram of ammonia recovery system using with gas permeable membranes
Recovery and concentration of ammonia from liquid manure using gas-permeable membrane system. Diagram and pictures show prototype testing, using the same stripping solution with repeated batches of liquid manure.
On-farm demonstration studies will be conducted in 2013-2014 in cooperation with Dr. John Classen, North Carolina State University, through an NRCS Conservation Innovation Grant (CIG) awarded in FY2012 “Ammonia recovery from swine wastewater with selective membrane technology”. The project will demonstrate recovery of ammonia from liquid manure effluents using the gas-permeable technology in three different manure collection systems: under floor belt system, scraper system, and anaerobic digester.
USDA seeks a commercial partner to develop and market this invention (US Patent Appl. SN 13/164,363) http://www.ars.usda.gov/business/docs.htm?docid=763&page=5
Matias Vanotti, USDA-ARS, Florence, South Carolina, firstname.lastname@example.org
Matias Vanotti, Ariel Szogi, Patrick Hunt
USDA-ARS, Coastal Plains Soil, Water, and Plant Research Center, Florence, SC
“Livestock Waste Management 2.0: Recycling Ammonia Emissions as Fertilizer“ published in the November/December 2012 issue of Agricultural Research magazine http://www.ars.usda.gov/is/AR/archive/nov12/livestock1112.htm
“Recovery of ammonia with gas permeable membranes” research update at USDA-ARS-CPSWPRC website http://www.ars.usda.gov/Research/docs.htm?docid=22883#ammonia
Vanotti,M.B., Szogi,A.A. “Systems and Methods for Reducing Ammonia Emissions form Liquid Effluents and for Recovering Ammonia”. US Patent Appl. SN 13/164,363, filed June 20, 2011. US Patent and Trademark Office, Washington, DC.
Vanotti, M.B., Szogi, A.A. 2010. “Removal and recovery of ammonia from liquid manure using gas-permeable membranes”. In: Proceedings of the 2010 American Society of Agricultural and Biological Engineers Annual International Meeting, June 20-23, 2010, Pittsburgh, Pennsylvania. 5 p. Paper No. 1008376.
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