Evaluation of Different Techniques to Control Hydrogen Sulfide and Greenhouse Gases from Animal Production Systems

The livestock manure management sector is one of the prime sources for the emission of greenhouse gases (GHGs) and other pollutant gases such as ammonia (NH3) and hydrogen sulfide (H2S), which may affect the human health, animal welfare, and the environment. So, worldwide investigations are going on to mitigate these gaseous emissions. The overall objective of this research was to investigate different approaches (dietary manipulation and nanotechnology) for mitigating the gaseous emissions from livestock manure system. A field study was conducted to investigate the effect of different levels of dietary proteins (12 and 16%) and fat levels (3 to 5.5%) fed to beef cattle on gaseous emission (methane-CH4, nitrous oxide-N2O, carbon dioxide-CO2 and hydrogen sulfide-H2S) from the pen surface. To evaluate the effects of different nanoparticles (zinc oxide-nZnO; and zirconium-nZrO2) on these gaseous emissions from livestock manure stored under anaerobic conditions, laboratory studies were conducted with different treatments (control, bare NPs, NPs entrapped alginate beads applying freely and keeping in bags, and used NPs entrapped alginate beads). Field studies showed no significant differences in the GHG and H2S emissions from the manure pen surface. Between nZnO and nZrO2, nZnO outperformed the nZrO2 in terms of gases production and concentration reduction from both swine and dairy liquid manure. Application of nZnO at a rate of 3 g L-1 showed up to 82, 78, 40 and 99% reduction on total gas production, CH4, CO2 and H2S concentrations, respectively. The effectiveness of nZnO entrapped alginate (alginate-nZnO) beads was statistically lower than the bare nZnO, but both of them were very effective in reducing gas production and concentrations. These gaseous reductions were likely due to combination of microbial inhibition of microorganisms and chemical conversion during the treatment, which was confirmed by microbial plate count, SEM-EDS, and XPS analysis. However, further research are needed to understand the reduction mechanism and to transfer the technology in a real life application.