Carbon Footprint Assessment of a Large-Scale Pig Production System in Northern China: A Case Study

Abstract

Abstract. China raises 50% of global live pigs. However, few studies on the carbon footprint (CF) of large-scale pig production based on China’s actual production conditions have been carried out. In this study, life cycle assessment (LCA) and actual production data of a typical large-scale pig farm in northern China were used to assess the greenhouse gas (GHG) emissions or CF associated with the whole process of pig production, including feed production (crop planting, feed processing, and transportation), enteric fermentation, manure management, and energy consumption. The results showed a CF of 3.39 kg CO2-eq per kg of live market pig and relative contributions of 55%, 28%, 13%, and 4% to the total CF by feed production, manure management, farm energy consumption, and enteric fermentation, respectively. Crop planting accounted for 66% of the feed production CF, while feed processing and transportation accounted for the remaining 34%. Long-distance transport of semi-raw feed materials caused by planting-feeding separation and over-fertilization in feed crop planting were two main reasons for the largest contribution of GHG emissions from feed production to the total CF. The CF from nitrogen fertilizer application accounted for 33% to 44% of crop planting and contributed to 16% of the total CF. The CF from the transport of feed ingredients accounted for 17% of the total CF. If the amount of nitrogen fertilizer used for producing the main feed ingredients is reduced from 209 kg hm-2 (for corn) and 216 kg hm-2 (for wheat) to 140 kg hm-2 (corn) and 180 kg hm-2 (wheat), the total CF would be reduced by 7%. If the transport distance for feed materials decreased from 325 to 493 km to 30 km, along with reducing the number of empty vehicles for transport, the total CF would be reduced by 18%. The combined CF mitigation potential for over-fertilization and transport distance is 26%. In addition, the use of pit storage, anaerobic digestion, and lagoon for manure management can reduce GHG emissions from manure management by 76% as compared to the traditional practice of pit storage and lagoon. This case study reveals the impact of planting-feeding separation and over-fertilization on the CF of the pig supply chain in China. The manure management practice of pit storage, anaerobic digestion, and lagoon is much more conductive to reducing the CF as compared to the traditional practice of pit storage and lagoon. Keywords: Greenhouse gas, Life cycle assessment, Mitigation, Pig.