Carbon footprints, mitigation effects and economic performance of dairy farm systems in Inner Mongolia

CONTEXT: Reducing the GHG emissions intensity of milk production has become a key sustainability challenge for the dairy sector. Addressing this challenge requires thorough understanding of the current GHG emission levels of individual farms, the practices influencing GHG emissions, and the economic trade-offs associated with reducing those emissions.OBJECTIVE: Quantify the carbon footprint (CF) and economic performance of milk production in Inner Mongolia (the main dairy farming region in China), and understand the main contributing factors to them. The effects of potential mitigation options at dairy farm system level were evaluated.METHODS: Life cycle assessment methodology was used to analyze the CF of 15 dairy farms (with year-round cow housing and crop feeding) selected for different milk production levels, herd structures and diet composition.RESULTS AND CONCLUSIONS: The average CF per kg of fat and protein corrected milk (FPCM; after allocation to milk) was 2.3 kg carbon dioxide equivalents (CO2-eq) (1.5-3.4 kg CO2-eq). Emissions related to feed production, manure management and enteric fermentation were the top three GHG emission sources and contributed an average of 27% (5%-46%), 28% (19%-38%) and 18% (14%-25%), respectively, to total emissions. The average cost of the farm system per ton FPCM was USD 540 per year. Feed costs dominated at 70% of the total costs. The CF of milk was negatively correlated with profit per kg FPCM. Mitigation potential of the CF of dairy production for single mitigation strategies ranged from 2.3% to 20.0% compared with business as usual, and combined mitigation measures could reduce emissions by 48.3%. The most effective mitigation measures should focus on decreasing N-fertilizer use per ha for feed crop production and increasing feed crop yield, adjusting herd structure for milk productivity and using localized feed inputs. All mitigation measures had a positive impact on farm profit, except for the improved manure management (changing the farms using manure composting to a static compost system and changing natural storage to direct land application). Therefore, the combination of crop and dairy production and manure management offer the greatest potential to reduce the GHG emissions from Inner Mongolia dairy farm systems. Economic subsidies and extension of findings to farmers might encourage more rapid adoption of these technologies.SIGNIFICANCE: The insights from our study can provide guidance for defining and prioritizing mitigation strategies for dairy production to reduce GHGs emission in other rapidly developing countries and regions with crop-based housed-cow dairy production.