Manure management is the primary source of greenhouse gas （GHG） emissions from pig farming, which in turn accounts for 18% of the total global GHG emissions from the livestock industry. In this review, GHG emissions...Manure management is the primary source of greenhouse gas （GHG） emissions from pig farming, which in turn accounts for 18% of the total global GHG emissions from the livestock industry. In this review, GHG emissions （N20 and CH4 emissions in particular） from individual pig manure （PGM） management practices （European practises in particular） are systematically analyzed and discussed. These manure management practices include manure storage, land application, solid/liquid separation, anaerobic digestion, composting and aerobic wastewater treatment. The potential reduction in net GHG emissions by changing and optimising these techniques is assessed. This review also identifies key research gaps in the literature including the effect of straw covering of liquid PGM storages, the effect of solid/liquid separation, and the effect of dry anaerobic digestion on net GHG emissions from PGM management. In addition to identifying these research gaps, several recommendations including the need to standardize units used to report GHG emissions, to account ~br indirect N20 emissions, and to include a broader research scope by conducting detailed life cycle assessment are also discussed. Overall, anaerobic digestion and compositing to liquid and solid fractions are best PGM management practices with respect to their high GHG mitigation potential.展开更多
This study assessed the effects of reducing hydraulic retention times （HRTs） from 21 days to 10.5 days when anaerobically co-digesting pig manure and food waste. Continuously stirred tank reactors of 3.75 L working ...This study assessed the effects of reducing hydraulic retention times （HRTs） from 21 days to 10.5 days when anaerobically co-digesting pig manure and food waste. Continuously stirred tank reactors of 3.75 L working volume were operated in triplicate at 42℃. Digester HRT was progressively decreased from 21 to 15 days to 10.5 days, with an associated increase in organic loading rate （OLR） from 3.1 kg volatile solids （VS）·m^-3.day^-1 to 5.1 kg VS·m^3.day-1 to 7.25 kg VS.m^-3·day^-1. Reducing HRT from 21 days to 15 days caused a decrease in specific methane yields and VS removal rates. Operation at a HRT of 10.5 days initially resulted in the accumulation of isobutyric acid in each reactor. High throughput 16S rRNA gene sequencing revealed that this increase coincided with a shift in acidogenic bacterial populations, which most likely resulted in the increased isobutyric acid concentrations. This may in turn have caused the increase in relative abundance of Clocamonaceae bacteria, which syntrophically degrade non-acetate volatile fatty acids （VFAs） into H2 and CO2. This, along with the increase in abundance of other syntrophic VFA oxidizers, such as Spiorchatetes, suggests that VFA oxidation plays a role in digester operation at low HRTs. Reducing the HRT to below 21 days compromised the ability of the anaerobic digestion system to reduce enteric indicator organism counts below regulatory limits.展开更多
文摘Manure management is the primary source of greenhouse gas （GHG） emissions from pig farming, which in turn accounts for 18% of the total global GHG emissions from the livestock industry. In this review, GHG emissions （N20 and CH4 emissions in particular） from individual pig manure （PGM） management practices （European practises in particular） are systematically analyzed and discussed. These manure management practices include manure storage, land application, solid/liquid separation, anaerobic digestion, composting and aerobic wastewater treatment. The potential reduction in net GHG emissions by changing and optimising these techniques is assessed. This review also identifies key research gaps in the literature including the effect of straw covering of liquid PGM storages, the effect of solid/liquid separation, and the effect of dry anaerobic digestion on net GHG emissions from PGM management. In addition to identifying these research gaps, several recommendations including the need to standardize units used to report GHG emissions, to account ~br indirect N20 emissions, and to include a broader research scope by conducting detailed life cycle assessment are also discussed. Overall, anaerobic digestion and compositing to liquid and solid fractions are best PGM management practices with respect to their high GHG mitigation potential.
文摘This study assessed the effects of reducing hydraulic retention times （HRTs） from 21 days to 10.5 days when anaerobically co-digesting pig manure and food waste. Continuously stirred tank reactors of 3.75 L working volume were operated in triplicate at 42℃. Digester HRT was progressively decreased from 21 to 15 days to 10.5 days, with an associated increase in organic loading rate （OLR） from 3.1 kg volatile solids （VS）·m^-3.day^-1 to 5.1 kg VS·m^3.day-1 to 7.25 kg VS.m^-3·day^-1. Reducing HRT from 21 days to 15 days caused a decrease in specific methane yields and VS removal rates. Operation at a HRT of 10.5 days initially resulted in the accumulation of isobutyric acid in each reactor. High throughput 16S rRNA gene sequencing revealed that this increase coincided with a shift in acidogenic bacterial populations, which most likely resulted in the increased isobutyric acid concentrations. This may in turn have caused the increase in relative abundance of Clocamonaceae bacteria, which syntrophically degrade non-acetate volatile fatty acids （VFAs） into H2 and CO2. This, along with the increase in abundance of other syntrophic VFA oxidizers, such as Spiorchatetes, suggests that VFA oxidation plays a role in digester operation at low HRTs. Reducing the HRT to below 21 days compromised the ability of the anaerobic digestion system to reduce enteric indicator organism counts below regulatory limits.
