Economic and environmental impacts of changes in culling parity of cows and diet composition in Japanese beef cow–calf production systems

The effects of changes in culling parity of cows and diet composition on economic and environmental outputs in Japanese beef cow–calf production systems were deterministically analyzed using a herd model simulation. The model simulated the annualized net revenue as an economic indicator and the overall environmental index derived from a life cycle assessment (LCA) as an environmental indicator. Biological factors (survivability, growth, reproduction, and feed requirements) and economic factors (returns from sales of live calves and cows’ carcasses and production costs) were included in the model. The model also included modified feed formulation methods, allowing us to analyze the effect of reductions in environmental loads caused by the change in diet compositions. The results of the present study indicated that later culling was economically and environmentally optimal under the current production system, which suggested that the selection of economically optimal culling parity of cows could result in environmentally optimization of the beef cow–calf production system. The difference in feed composition derived from the difference in feed formulation methods did not affect the determination of optimal culling parity, whereas the use of modified feed formulation methods could reduce environmental loads at a higher rate than that of economic benefits. However, the reduction rate of the environmental impact was much higher in the case of selection of the optimal culling parity than in the case of use of modified feed formulation methods, which stressed the importance of choosing the optimal culling parity of cows both from the economic and environmental points of view

Carbon footprint assessment of a whole dairy farming system with a biogas plant and the use of solid fraction of digestate as a recycled bedding material

Biogas generated from livestock manure is a renewable energy source and the digestate is used as a fertilizer. Moreover, dewatered biogas digestate can be used as a bedding material (recycled bedding material). The aims of the present study were to model a whole dairy system with a biogas plant using recycled bedding material and to assess the life cycle greenhouse gas (GHG) emissions. Emissions from the material flow of dairy cattle production, manure treatment and organic fertilizer application to on-farm crops were evaluated. In the emissions from organic fertilizer storage and recycled bedding material production, CH4 emission was decreased by 43.0%, and consequently the system with a biogas plant reduced total GHG emissions by 6.8% compared with conventional slurry storage and straw bedding. The use of recycled bedding material from a biogas plant has the potential to create a resource cycle and to be beneficial as a GHG mitigation strategy

Simulation of livestock biomass resource recycling and energy utilization model based on dry type methane fermentation system

International Conference of Biomass and Bioenergy 19-20 August 2019, West Java, IndonesiaThis study was aimed at investigating the local livestock biomass volume for dairy farms in Town A, located in eastern Hokkaido, Japan, and at presenting a model of a biogas plant that enables maximizing the use of the available livestock biomass. Using a dairy farm with 250 animals in Town A as a model for a biogas plant based on dry-type methane fermentation system (dry-type biogas plant), we set the operational conditions to an average hydraulic retention time of 20 days, digestion temperature of 55°C, and methane gas yield of 0.12 Nm3 CH4/kg VSA. We compared the biogas production of our presented model with that of a wet-type biogas plant with the same number of animals. The results showed that the dry-type biogas plant produced biogas at 859 Nm3/day, while the wet-type biogas plant produced biogas at 666 Nm3/day. These results indicate that introducing dry-type biogas plants in all dairy farms in Town A would potentially enable semi-solid livestock manure to be processed, which is not amenable to ordinary composting, in addition to the conventional processes being carried out through biogas plants, as well as lead to an increase in the amount of biogas production

ニホン ノ カチク セイサン システム ニ オケル ライフ サイクル アセスメント

京都大学0048新制・論文博士博士(農学)乙第12093号論農博第2653号新制||農||947(附属図書館)学位論文||H19||N4292(農学部図書室)UT51-2007-H697(主査)教授 廣岡 博之, 教授 今井 裕, 教授 久米 新一学位規則第4条第2項該当Doctor of Agricultural ScienceKyoto UniversityDA

Evaluation of the Nitrous Oxide Emission Reduction Potential of an Aerobic Bioreactor Packed with Carbon Fibres for Swine Wastewater Treatment

Nitrous oxide (N2O) is a potent greenhouse gas that is emitted from wastewater treatment plants. To reduce emissions of N2O from swine wastewater treatment plants, we constructed an experimental aerobic bioreactor packed with carbon fibres (ca. 1 m3 bioreactor) as an alternative to conventional activated sludge treatment. The N2O emission factor for the aerobic bioreactor packed with carbon fibres (CF) was 0.002 g N2O-N/g TN-load and the value for the typical activated sludge (AS) reactor was 0.013 g N2O-N/g TN-load. The CF treatment method achieved more than 80% reduction of N2O emissions, compared with the AS treatment method. The experimental introduction of a CF carrier into an actual wastewater treatment plant also resulted in a large reduction in N2O generation. Specifically, the N2O emission factors decreased from 0.040 to 0.005 g N2O-N/g TN-load following application of the carrier. This shows that it is possible to reduce N2O generation by more than 80% by using a CF carrier during the operation of an actual wastewater treatment plant. Some bacteria from the phylum Chloroflexi, which are capable of reducing N2O emissions, were detected at a higher frequency in the biofilm on the CF carrier than in the biofilm formed on the AS reactor