北京市居民食物消费碳足迹

碳足迹作为一种评价碳排放影响的全新测度方法,已被用来衡量人类活动对大气环境和气候变化的影响。食物是人类的首要消费品,其消费的碳足迹反应维持一个区域人口的基本食物需求的碳排放以及对气候变化的影响。在碳足迹理论和模型的基础上,根据北京市食物的供应和消费现状情况,利用生命周期法(Life cycle analysis LCA),计算和分析了北京市居民食物消费的碳足迹。得到北京市居民食消费碳足迹为476.8×104t,约占北京市总碳足迹的6%,人均碳足迹为310.0kgCO2/人,占北京市家庭消费碳排放的23.3%,只占北京市能源消费人均碳排放量的5.96%,反映了居民食物消费对全球气候变化造成的影响有限。食物消费碳足迹最大的为粮食,其次为瓜果蔬菜豆类,总共占到65%以上,而在食物生命周期过程中,食物的再加工炊事过程碳排放最大,超过50%,合理减少食物加工炊事过程中碳排放将是减少食物消费碳排放的重要途径之一。其次为化肥农药施用,占到23.23%,减少食物生产过程中化肥农药使用,提高化肥农药的使用效率,或者进行生态农业尽量不使用化肥农药,北京市每年可减少135.1×104t CO2排放,人均87.84kgCO2/人,是有效的减排途径之一。

The carbon footprint of food consumption in Beijing

Carbon footprint has become an effective method for assessing carbon emission, aiming at measuring the influence of atmosphere environment and climate change caused by human activities across the whole life cycle of a product or an activity. With rapid urbanization, residents in cities are playing increasingly important roles in the alteration of environment. Meanwhile, consumption is one of the remarkable drivers of environmental pollution in city areas. With the perception that unsustainable consumption patterns are the major cause of the continued deterioration of the global environment, environmental concerns move to household sectors and related lifecycle activities. Food is the most important consumable of daily household life. The carbon footprint of food shows the carbon emission of the food provisions for the whole city and the contributions to the climate change. Based on the theory and model of carbon footprint, and using the life cycle analysis (LCA), we calculate and analyze the carbon footprint of food consumption according to the reality of Beijing city and the food supply plan. The result shows that the total carbon footprint of food consumption is 4.768×10⁶t, about 6% of the total carbon footprint of Beijing, corresponding to 310.0kg/cap, and accounting for 23.3% of the total emission of household consumption, which is only 5.96% of the total carbon dioxide emission in Beijing. This reflects the limited impact of food consumption on the environment, carbon emission, and climate change. If Beijing wants to achieve a goal of carbon reduction of more than 6%, it is not sufficient to take measures in the field of food consumption alone. The most important part of food consumption carbon footprint is from grain, and the second part is from fruits and vegetables. These two parts account for more than 65% of carbon footprint of food consumption. The most important process of food consumption carbon emission is from reprocessing and cooking of foods, which consume most of household energy, and result in almost 60% of the total carbon emission. One important reason for this phenomenon is that this process directly refers to energy using which serves as the most important action leading to carbon emission. The second important process is usage of chemical fertilizers and pesticides, which shares 23.23% of total food carbon footprint. Production and transportation are also important processes, which account for 8.35% and 6.98% of the total food consumption carbon footprint, respectively. Reduction of carbon emission in food reprocessing and cooking is the available process to reduce carbon emission from food consumption. And if we don't use chemical fertilizers and pesticides and promote ecological agriculture (or organic agriculture) in our food production or improve the used-rate, we can reduce 1.351×10⁶t CO₂ every year in Beijing, that is 87.84 kg CO₂ per capita per year. It is quite an efficient way to reduce carbon emission of Beijing city. We also compared the results of our improved method with the national average datum, and found that there are some reasonable differences attributed to the calculation method and parameters such as cropland area. The results also show that other parts of Beijing residents' consumption such as transportation, daily commodities and energy use have great contributions to carbon footprint. So further research need to be carried out on residents' other kinds of consumption in households to make an overview of total carbon footprint of residents.