Understanding gaseous reduction mechanisms in swine manure resulting from nanoparticle treatments under anaerobic storage conditions

Authors: SARKER, NILOY - North Dakota State University; BORHAN, MOHAMMED - North Dakota State University; Fortuna, Ann Marie; RAHMAN, SHAFIQUER - North Dakota State University

Submitted to: Journal of Environmental Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2019
Publication Date: 3/18/2019
Citation: Sarker, N.C., Borhan, M., Fortuna, A., Rahman, S. 2019. Understanding gaseous reduction mechanisms in swine manure resulting from nanoparticle treatments under anaerobic storage conditions. Journal of Environmental Science. https://doi.org/10.1016/j.jes.2019.03.005.
DOI: https://doi.org/10.1016/j.jes.2019.03.005

Interpretive Summary: Due to increasing feed costs and environmental concerns livestock production facilities are employing technologies to improve feed efficiency and reduce their environmental impact. In furtherance of this aim silver and zinc nanoparticles (NPs) are added to animal feeds to control microbial proliferation and promote animal growth, respectively. These nanoparticles are excreted and their impact on livestock manure management is unknown. Digestion of manures is dependent on microbial populations that can be adversely effected by the presence of these metals. Microorganisms exposed to metals associated with NPs, particularly ones coated with polymers have reduced exposure response relative to metals and uncoated NPs. Such novel technologies are capable of reducing gaseous emissions during anaerobic storage of manure due to their adsorption of H2S. Few published studies address the transformations NPs undergo in waste systems and or the exposure response of bacteria to NPs in these systems. The aims of our research were to: design and employ permeable polymers to entrap nanoparticles that adsorb hydrogen sulfide from manure and reduce the NPs biocidal properties and to quantify gaseous emissions while determining the chemical and biological reactions controlling such emissions during anaerobic storage of manure containing NPs. Nanoparticles tested in this study reduced the cumulative gas volume compared to the untreated control. Reductions in H2S concentrations ranged from 87 to 97%. Gaseous reductions were likely due to measured decreases in the activity and numbers of specific gas producing microorganisms, methanogenic archaea and sulfate reducing bacterial species.

Technical Abstract: Manure is an impending source of carbon (C), sulfur (S) and water (H2O). Consequently, microbial populations utilize these constituents to produce methane (CH4), carbon dioxide (CO2), greenhouse gases (GHGs), and hydrogen sulfide (H2S). Application of nanoparticles (NPs) to stored manure is an emerging GHG mitigation technique. In this study, two NPs: nano zinc oxide (nZnO) and nano silver (nAg) were tested in swine manure stored under anaerobic conditions to determine their effectiveness in mitigating gaseous emissions and total gas production. The biological mechanisms of gas production i.e. microbial populations were characterized via Quantitative Polymerase Chain Reaction (qPCR) analysis. Each treatment of the experiment was replicated three times in 1-L Erlenmeyer flasks with a working volume of 500 mL of swine manure to which NPs were applied at a dose of 3 g L-1 of manure. Headspace gas from all treatment replicates were analyzed for CH4 and CO2 gas concentrations using an SRI-8610 Gas Chromatograph and H2S concentrations were measured using a Jerome 631X meter. Nanoparticles tested in this study reduced the cumulative gas volume by 16 to 79% compared to the control. Among the NPs tested, only nZnO consistently reduced GHG concentrations by 37 to 97%. Reductions in H2S concentrations ranged from 87 to 97%. Gaseous reductions were likely due to decreases in the activity and numbers of specific gas producing methanogenic archaea and sulfate reducing bacterial (SRB) species.