Greenhouse gas emissions from dairy industry in Northern China using holistic assessment approach

Abstract: The objective of this study was to quantify greenhouse gas (GHG) emissions from dairy production system in northern China using a holistic assessment approach. To illustrate the impact of an increase in dairy production efficiency on GHG emissions, it is important to estimate the combined methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions per unit of production. In this study, the holistic approach was used to assess the greenhouse gases emissions in milk production and the intensity per milk unit in Northern China (include 5 districts which are Beijing, Tianjin, Hebei, Shanxi and Inner Mongolia) in 2012. The GHG emission sources estimated included farm fieldwork for dairy cattle consuming, relevant machinery supplying, the energy consuming corresponds to animal feeding, fertilizer production and supplying, enteric fermentation and manure management system. The functional unit (FU) was defined as one kg milk production. GHGs involved in agriculture (CO2, CH4 and N2O) are different in trapping heat and the turnover rates in the atmosphere. The global warming potential (GWP) of CH4 and N2O were 25 and 298 times to CO2 respectively. And total greenhouse emissions were expressed as kg CO2 equivalents. The holistic assessment approach is to account for the environmental impacts from all stages of agricultural production which can be a useful tool for evaluating the potential environmental impacts during the entire life cycle of a product, by compiling the inputs and outputs of a production system. It is composed of three major parts which are: To define the goal FU as well as system boundary; The system boundary of typical milk production system included not only the physical limits and its activities of milk production, but also the relative activities such as the crop production and fertilizer application. To draw up life cycle inventory and to assess the GHG emission per milk unit, holistic assessment approach has frequently been used to assess the impacts of livestock systems in different countries, it should be also valuable to do such analyses on GHG emissions of the dairy production systems in northern China. The Intergovernmental Panel on Climate Change (IPCC) assessment methodology and relevant literature were adopted for calculating CH4, N2O and CO2 emissions. Data collected from the literature was used for specific activities for the milk production system. Through this study, it indicated that the total GHG emission was 22 437.85×103 t in dairy production systems (DPS) in North China during 2012. Methane (CH4) is the major source, approximately 8 516.53×103 t, 84% coming from enteric fermentation and 16% coming from manure management system. The emissions of nitrous dioxide（N2O）were 6 240.27×103 t and the carbon dioxide（CO2）were 7 681.05×103 t. Based on the emission intensity, average GHG emissions were 1.3 kg/kg.