Gas-permeable membrane technology coupled with anaerobic digestion for swine manure treatment

Authors: MOLINUEVO-SALCES, BEATRIZ - Instituto Tecnológico Agrario De Castilla Y León (ITACYL); RIANO, BERTA - Instituto Tecnológico Agrario De Castilla Y León (ITACYL); Vanotti, Matias; GARCIA-GONZALEZ, MARIA - Instituto Tecnológico Agrario De Castilla Y León (ITACYL)

Submitted to: Frontiers in Sustainable Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2018
Publication Date: 6/6/2018
Citation: Molinuevo-Salces, B., Riano, B., Vanotti, M.B., Garcia-Gonzalez, M.C. 2018. Gas-permeable membrane technology coupled with anaerobic digestion for swine manure treatment. Frontiers in Sustainable Food Systems. 2:25. https://doi.org/10.3389/fsufs.2018.00025.
DOI: https://doi.org/10.3389/fsufs.2018.00025

Interpretive Summary: Anaerobic digestion (AD) of manure is a well-established stabilization technology by which organic matter is valorized into renewable energy. Additionally, AD contributes to greenhouse gas mitigation, odor and pathogen reduction. The present study is aimed at evaluating gas-permeable membrane technology for recovery of the ammonia coupled to AD for the treatment of swine manure. For this purpose, ammonia-nitrogen (N) from fresh swine manure was firstly recovered by a gas-permeable membrane module. The resultant effluent was evaluated as substrate for AD and its stabilization was studied. Firstly, 69% of the initial ammonia contained in swine manure was semi-continuously recovered as ammonium sulfate. The resultant effluent was stabilized by anaerobic digestion. A methane yield of 105 milliliters per gram of COD (chemical oxygen demand) was achieved. The results indicated that it is feasible to combine N-recovery by gas-permeable membrane technology and anaerobic digestion for the treatment of swine manure, contributing to ammonia emissions mitigation and sustainable livestock waste treatment. Moreover, a variety of valuable products is obtained, namely sustainable energy in the form of methane and fertilizers (i.e. ammonium sulfate and anaerobic digestate). Overall, this combined treatment for swine manure resulted in a 99% N-recovery and a 75% COD removal together with a possible reduction of AD equipment costs.

Technical Abstract: This study was aimed at evaluating gas-permeable membrane technology (N-recovery) coupled to anaerobic digestion for the treatment of swine manure. For this purpose, 69 percent (%) of the initial ammonium contained in centrifuged swine manure (SM) (i.e. 3.5 g N-NH4 per liter (L) was firstly recovered by a, ePTFE gas-permeable membrane as ammonium sulfate, a valuable fertilizer. The resultant manure effluent with reduced ammonia (ATM) was evaluated as anaerobic digestion (AD) substrate. It was compared with AD using the initial swine effluent (SM) without the ammonia recovery step (control). The AD process was done at increasing organic load rates (OLR) using both batch and semi-continuous operation. An OLR of 2.8 ± 0.5 g CODt (total Chemical Oxygen Demand) per L per day was established to ensure a stable process when working at semi-continuous mode. Regardless the operation mode, methane (CH4) yields of 105 ± 2 mL CH4 per g CODt were obtained for ATM. The combined treatment resulted in total ammoniacal nitrogen (TAN) and organic matter removal efficiencies of 99% and 75%, respectively. Initial TAN and CODt accounted for 3.36 and 54.69 g per L, respectively. From the removed TAN, 69% was recovered as ammonium sulfate fertilizer. The results prove that it is feasible to combine gas-permeable membrane technology and anaerobic digestion for the treatment of swine manure, contributing to ammonia emissions mitigation and sustainable livestock waste treatment. Moreover, by means of this technology combination, a variety of valuable products is obtained, namely sustainable energy in the form of methane and fertilizers (i.e. ammonium sulfate).