为了研究奶牛产业生产效率对温室气体排放的影响,对单位牛奶产量所产生的温室气体(甲烷、氧化亚氮和二氧化碳)进行科学的评估是非常重要的。在该研究中,利用整体分析方法评估了2012年华北地区奶牛产业的总温室气体排放以及单位牛奶的温室气体排放。估算的排放源包括奶牛胃肠道发酵以及粪便管理系统产生的温室气体(greenhouse gas,GHG)排放、奶牛饲养过程中耗能所带来的GHG排放、饲养奶牛所需作物种植管理过程中以及所需农业机械设备制造所产生的GHG排放、化学肥料生产和施用所来的GHG排放。估算方法采用政府间气候变化专门委员会(IPCC,Intergovernmental Panel on Climate Change)评估报告中的方法学以及相关文献的研究成果。研究结果表明:在华北地区奶牛产业系统中总温室气体排放量为22437.85*10~3t。甲烷(CH_4)是主要的排放源,为8516.53*10~3 t,其中奶牛胃肠道排放占84%,粪便管理系统占16%;氧化亚氮(N_2O)排放为6240.27*10~3 t,二氧化碳(CO_2)排放为7681.05*10~3 t。基于排放强度,得出单位牛奶的平均温室气体排放量为1.3 kg/kg。
英文摘要:
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 (CH_4), nitrous oxide (N_2O) and carbon dioxide (CO_2) 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 (CO_2, CH_4 and N_2O) are different in trapping heat and the turnover rates in the atmosphere. The global warming potential (GWP) of CH_4 and N_2O were 25 and 298 times to CO_2 respectively. And total greenhouse emissions were expressed as kg CO_2 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 CH_4, N_2O and CO_2 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*10~3 t in dairy production systems (DPS) in North China during 2012. Methane (CH_4) is the major source, approximately 8 516.53*10~3 t, 84%coming from enteric fermentation and 16%coming from manure management system. The emissions of nitrous dioxide (N_2O) were 6 240.27*10~3 t and the carbon dioxide (CO_2) were 7 681.05*10~3 t. Based on the emission intensity, average GHG emissions were 1.3 kg/kg.