Estimation of greenhouse gas emissions from dairy farming systems based on LCA

In order to find the effective mitigation means and lead dairy farming systems to low-carbon development, it is important to estimate greenhouse gas (GHG) emissions from dairy farming systems accurately. The paper developed an methodology to estimate the GHG emissions from dairy farming systems based on the life cycle assessment (LCA), combined with the specific situation of China's dairy farming systems, and the method was applied to estimate GHG emissions of a typical large-scale dairy farming system at the suburb in Xi'an city. The results showed that the large emission sources were enteric fermentation, feed production and processing, waste storage, accounting for 48.86%, 18.97% and 16.39% of the total emissions, respectively. The main compositions of greenhouse gas were CH4, N2O, accounting for 55.56% and 26.9% of the entire system. The emission per kg of raw milk corrected by protein and fat (FPCM) was 1.52 kg CO2-eq, which is lower than the average global emissions from mixed feeding systems, but higher than that of the European countries. So, there was big potential possibility to mitigate emissions. Emissions from individual sources could be reduced by improving the feed, manure management, field management and other measures, but the contribution to emission reduction of the entire system should be evaluated based on LCA. It is suggested to evaluate mitigation measures based on LCA to obtain the more effective emission reduction measures for the system.