Recovery of ammonia nitrogen in livestock and industrial wastes using gas permeable membranes

New waste management methods are needed that can protect the environment and allow manure management to switch back to a recycling view of manure handling. We investigated the use of gas-permeable membranes as components of new processes to capture and recover the ammonia in the liquid manures or in the air of poultry houses and other livestock installations. The basic process includes the passage of gaseous ammonia contained in the contaminated air or liquid through a microporous hydrophobic membrane and capture and concentration with circulating diluted acid or water on the other side of the membrane. The membranes can be assembled in modules or manifolds and can be tubular or flat. For liquid manure applications, the membrane manifolds are submerged in the liquid and the ammonia is removed from the liquid matrix in barn pits or storage tanks before it goes into the air. The concept was successfully tested using concentrated swine and dairy manure effluents containing 140 to 1400 mg/L ammonia-N. For the removal of ammonia in air, the technology captured and recovered 96% of the ammonia lost from poultry litter. The membrane manifolds can be placed close to the poultry litter surface (above or below), thus reducing the exposure of the birds to ammonia. The results obtained show that the use of gas-permeable membrane technology could be an effective approach to recover ammonia from livestock wastewater and from the air in poultry barns and other livestock operations. The final products are (1) reduced environmental emissions from livestock facilities, (2) cleaner air inside the poultry and swine houses with benefits to bird/animal health, and (3) concentrated liquid nitrogen that can be re-used in agriculture as a valued fertilizer. Key-words – Nutrient recovery, swine manure, poultry litter, ammonia emissions control. Introduction New waste management methods are needed that can protect the environment and allow manure management to switch back to a recycling view of manure handling (Martinez et al., 2009). One of the largest environmental concerns associated with livestock and poultry production is the loss of ammonia (NH3) gas from the manure (Aneja et al., 2001, Paerl, 1997). The Research Triangle Institute International (RTI, 2003) estimated the monetized economic benefits to North Carolina households of changes in environmental quality resulting from the generalized adoption of alternative waste technologies (2,300 swine operations). Results indicated that adoption of technologies that provides a 50% reduction of NH3 emissions account for an estimated benefit of $190 million/year in avoided human health impacts (RTI, 2003). Similarly, volatilization of NH3 inside poultry barns often results in an excessive accumulation of NH3 in air, which can negatively affect the health of both workers and birds (Ritz et al., 2004). Although increased ventilation can lower the NH3 in poultry houses to safe levels, it is expensive due to energy costs during winter months (Moore et al., 1995). Conservation and recovery of nitrogen (N) is also important in animal agriculture because of the high cost of commercial NH3 fertilizers. Thus, there is major interest from producers and the public on implementing best control technologies that would abate NH3 emissions from confined livestock and poultry operations by capturing and recovering N. In this work we investigated the use of gas-permeable membranes as components of new processes to capture and recover ammonia from liquid manures as well as from the air in poultry houses and other livestock installations. Materials and Methods The basic process includes the passage of gaseous NH3 through a microporous hydrophobic membrane and capture and concentration with circulating diluted acid on the