Carbon Footprint Assessment Methodology Of Milk Production In Intensive Dairy Farm And Case Study

Livestock production is one of the most important sources of greenhouse gases (GHGs) emissions. Researches on carbon footprint methodology of milk production based on Chinese production practice intensive are insufficient. The objective of this study is to build China’s milk production carbon footprint assessment methodology for intensive dairy farm, and to evaluate a case study by using this methodology according to the carbon footprint assessment framework. This study also discusses the influence of different factors in the methodology on the milk carbon footprint, GHG mitigation options of milk production system were proposed, providing a theoretical support and scientific data for dairy farm GHG emissions accounting and practicing low carbon production. The main conclusions drawn in this study are as follows.(1) The system boundary is from feed production and processing to farm-gate, functional unit is one kg FPCM, and system allocation method is protein allocation. Methodologies for estimation GHG emissions from enteric fermentation, manure and land application of nitrogenous fertilisers are based on the 2006 IPCC National Greenhouse Gas Inventories Guideline Tier 2, Methodologies for estimation emissions from fertilisers, pesticides and agricultural film etc production and processing and energy consumption in dairy farm are based on GHG emission factor calculation methods. Compare with other models and methodologies abroad, this study adopted the emission factors of feed processing, agricultural material production, transportation and energy consumption of data from domestic researches. The parameters of agricultural materials input, feed consumption and manure management used in this study are from domestic statistics or field data. Therefore, emission factors and basic parameters are more in line with China’s production practice. This study also provides inventories and production parameters of crop planting of different farm scale in different provinces in China, which would provide help to users in GHG emission assessment.(2) A case study was analyzed by using dairy milk production carbon footprint assessment methodology. The results showed that an intensive dairy farm with stocks 5367 heads and milk yield of 7.7 t per cow per year. The manure management practice was anaerobic lagoon and compost treatment, and the system boundary was from feed production to farm-gate. GHG emissions from this dairy farm was 27093.83 t CO2-eq in 2013, and the average GHG emissions per cow was 5.05 t CO2-eq, with the method of protein allocation, the average carbon footprint per kg protein and fat correct milk was 1.34 kg CO2-eq.(3) The results showed that the largest GHG emissions sources was enteric fermentation, accounting for 41.18% of the total GHG emissions, following by feed production and processing, manure management, manure land application and energy consumption in dairy farm, accounting for 24.28,14.92,10.25 and 8.74% of the total emissions. This study also analyzed the key sources of three main emission sources by using the methodology, the results showed that the enteric fermentation of dairy cow contributes the maximum emissions, with 61.67% of the enteric fermentation source. The nitrogen fertilizer production and application contributes the maximum emissions, with 74% of the feed production and processing source. The N2O emission from manure management contributes the maximum emissions, with 57.1% of the manure management source. The main compositions of GHGs were CH4 and N2O, accounting for 48% and 32%, respectively. The result can provide support for determine GHG mitigation technology of key emissions sources.(4) This study quantitatively analyzed the influence of different functional units, allocation method, and GWP value on carbon footprint. Results showed that carbon footprints of milk production under different allocation methods had significant difference(P<0.05), except for the comparison between no allocation and mass allocation, protein allocation and economic allocation. Carbon footprint of milk production under different GWP value has significant difference (P<0.05). Comparison of the carbon footprint of milk production between raw milk and standard milk (FPCM and ECM) showed significant difference(P<0.05), except for the comparison between FPCM and ECM. Therefore, attentions should be paid to the influence of different factors when comparing the carbon footprints from different study results.