Abstract:

Rice is an important part of the food system in China and the world. It is of great significance to study the life cycle carbon footprint of rice food system from the perspective of food system for low-carbon transformation and green development. Based on statistics from 22 major rice-producing provinces in China in 2018, the cradle-to-market carbon footprint of Rice food systems in China, including its structural composition, regional differences and rice type differences was calculated and analyzed by using the life cycle assessment (LCA) method and the CF-Rice rice carbon footprint calculation tool developed by the International Rice Research Institute (IRRI). The results showed that 1) when comparing carbon footprint per unit production (CO₂ eq), the carbon footprint was in the order of late indica rice (2.31 kg?kg^-1), middle indica rice (1.32 kg?kg^-1), japonica rice (1.13 kg?kg^-1) and early indica rice (1.08 kg?kg^-1). When comparing carbon footprint per unit area (CO₂ eq), the carbon footprint was in the order of late indica rice (9.15×10³ kg?hm^-2), middle indica rice (6.34×10³ kg?hm^-2), japonica rice (5.56×10³ kg?hm^-2) and early indica rice (4.16×10³ kg?hm^-2); 2) Methane (CH₄) in paddy field was the most important component of the carbon footprint of rice food system, accounting for 36.2%-71.5%, followed by fertilization (8.69%-20.0%), harvest (8.41%-18.5%) and prenatal (4.97%-12.1%). Mechanical operations, storage, processing, packaging and transportation, although only accounting for less than 10%, were also significant sources of emissions; 3) early indica rice, middle indica rice and late indica rice showed no obvious spatial distribution pattern, while the main producing areas of japonica rice had a large spatial span and showed an increasing trend of carbon footprint from north to south, specifically as follows: except for Shandong, the carbon footprint of japonica rice in Northeast (Heilongjiang, Jilin, Liaoning) and North China (Inner Mongolia, Hebei) was lower than that in East (Anhui, Jiangsu, Zhejiang), central (Henan, Hubei) and southwestern China (Yunnan); 4) from the perspective of the composition of greenhouse gases, the contribution rate of CH₄ to the carbon footprint of rice food system was the highest, reaching 20.1%-76.4%, followed by that of CO₂ (21.1%-72.3%), and that of N₂O (1.76%-10.7%) was the lowest. The regional and type differences of rice food system carbon footprint were mainly related to climatic conditions, planting management measures and emission factors. Hence, in order to reduce the carbon emissions of rice food system, it is necessary to take overall consideration to reduce the CH₄ emission of rice field, improve water and fertilizer management, reduce energy consumption, and decrease food loss and waste.

Key words: rice food systems, carbon footprint, life cycle assessment, regional variation, type difference

摘要：

水稻是中国及全球食物系统的重要组成部分，以食物系统视角研究其生命周期碳足迹对实现水稻食物系统低碳转型和绿色发展具有重要意义。该研究基于中国2018年22个水稻主产省份的统计数据，结合生命周期评估（LCA）法和国际水稻研究所（IRRI）开发的CF-Rice水稻碳足迹计算工具，计算并分析了中国水稻食物系统“从摇篮到销售”的碳足迹及其结构组成、地区差异和水稻类型差异。结果表明：1）以单位产量碳足迹进行比较（以CO₂ eq计），晚籼稻 (2.31 kg?kg^-1)>中籼稻 (1.32 kg?kg^-1)>粳稻 (1.13 kg?kg^-1)>早籼稻 (1.08 kg?kg^-1)；以单位面积碳足迹进行比较（以CO₂ eq计），晚籼稻 (9.15×10³ kg?hm^-2)>中籼稻 (6.34×10³ kg?hm^-2)>粳稻 (5.56×10³ kg?hm^-2)>早籼稻 (4.16×10³ kg?hm^-2)；2）稻田甲烷（CH₄）是水稻食物系统碳足迹最主要的组成部分，占36.2%－71.5%，其次是施肥，占8.69%－20.0%，收获环节占8.41%－18.5%，产前环节占4.97%－12.1%，机械作业、仓储、加工、包装和运输环节虽占比较小（均<10%）但也不容忽视；3）早籼稻、中籼稻和晚籼稻没有表现出明显的空间分布规律，而粳稻呈现出自北向南碳足迹增加的趋势，具体表现为：除山东外，东北地区（黑龙江、吉林、辽宁）和华北地区（内蒙古、河北）的粳稻碳足迹低于华东地区（安徽、江苏、浙江）、华中地区（河南、湖北）和西南地区（云南）；4）从温室气体的构成来看，CH₄对水稻食物系统碳足迹的贡献率最高，达到20.1%－76.4%，其次为二氧化碳（CO₂），贡献率为21.1%－72.3%，氧化亚氮（N₂O）的贡献率最低，仅有1.76%－10.7%。水稻食物系统碳足迹的地区和类型差异主要与气候条件、种植管理措施和排放因子有关，因此，控制稻田CH₄排放，优化水肥管理，减少能源消耗及粮食损失和浪费可有效降低水稻食物系统碳足迹。

关键词: 水稻食物系统, 碳足迹, 生命周期评估, 地区差异, 类型差异