|GARCIA-GONZALEZ, M. - Instituto Tecnológico Agrario De Castilla Y León (ITACYL)
Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2015
Publication Date: 1/17/2015
Citation: Garcia-Gonzalez, M.C., Vanotti, M.B., Szogi, A.A. 2015. Recovery of ammonia from swine manure using gas-permeable membranes: Effect of aeration. Journal of Environmental Management. 152:19-26. doi:10.106/jenvman.2015.01.013.
Interpretive Summary: Ammonia (NH3) emissions from animal husbandry operations (dairy, beef, poultry and swine) in the USA were estimated at 2.4 million tons/year in 2010. Significant efforts are required to abate NH3 emissions from livestock operations. In addition, the costs of fertilizers have rapidly increased in recent years, especially nitrogen fertilizer such as anhydrous ammonia which is made from natural gas. Thus, new technologies for abatement of ammonia emissions in livestock operations are being focussed on nitrogen (N) recovery. Nitrogen recovery from swine manure was investigated using a new technology that uses gas-permeable membranes at low pressure. Membrane manifolds are submerged in the manure and the ammonia is removed from the liquid before it escapes into the air. The process involves manure pH control adding an alkali chemical. In this study a new strategy was tested to avoid the use of chemicals. Instead of the chemical we applied low-rate aeration to raise the pH. The new strategy worked quite well. When aeration was added to the gas-permeable membrane reactor, ammonium concentration in manure was almost depleted: it declined from 2270 milligram ammonium-N per litre to 20 milligram ammonium-N per litre. The ammonia was recovered efficiently (99% efficiency rate). Results obtained in this work indicate the low-rate aeration is an economical alternative to chemical to increase ammonia availability and the capture of ammonia by gas-permeable membrane systems. This conclusion is supported by the very high removal and recovery efficiencies obtained resulting in an overall capture of 97.5% of the initial ammonia in the manure.
Technical Abstract: Gas-permeable membranes can recover ammonia from manure, reducing pollution whilst converting ammonia into ammonium salt fertilizer. The process involves manure pH control to increase ammonium (NH4) recovery rate that is normally carried out using an alkali. In this study a new strategy to avoid the use of chemical alkali was tested applying aeration to the manure in order to raise pH. Results showed that aeration maintained pH above 8.5 allowing transformation of NH4+ in the manure into gaseous ammonia (NH3) that immediately permeated through the membrane and was captured by the acid solution. Due to this high level of NH3 in aerated manure 57% of NH4+ was recovered during the first 4 days of assays, while 37% of NH4+ was recovered in manure with alkali. Aeration was showed to be a successful strategy to recover 99% of NH4+ from manure; substituting chemical use (2.14 grams per Litre of sodium hydroxide) to increase pH in manure and to efficiently capture the ammonia with the gas-permeable system, avoiding NH3 emissions to the atmosphere.