— PhD Thesis —
In the Special Report of Climate Change and Land (SRCCL) issued by IPCC in 2019, it was pointed out that as Greenhouse Gas (GHG) emissions emitted from the food system accounted for 21-37% of the total anthropogenic GHG emissions. Accounting for GHG emissions from the food system has also become the basis for assessing the impact of climate change on regional food systems. Although the European Commission Joint Research Centre (JRC) calculated the GHG emissions of the food system according to the decomposition method of the IPCC emission inventory, the inventory only calculated the GHG emissions of the food system at the national level by sectors, and the results are not able to guide the regional food system emission reduction policies.It is also difficult to identify the impact of food types at key stages of the life cycle.
Due to the rapid development of China’s economy, population and urbanization, the total amount of food consumption and its consumption structure are undergoing tremendous changes. The rising GHG emissions has become a major challenge for China to mitigate climate change and ensure food security.The spatial separation of production and consumption in China’s food system not only leads to the obvious spatial-temporal differentiation of GHG emissions caused by food consumption in China, but also leads to the corresponding transfer of emission responsibility and transfer efficiency differences due to the inter-regional flows of food trade. In view of this, based on the input-output cost-benefit survey data of food And food consumption statistics in China, using Meta analysis, life cycle analysis and other methods, this study constructed a “bottom-up” multi-type, multi-regional and multi-stage GHG emissions inventory of major food in China, calculating the entire life cycle GHG emissions of China’s food system from 1990 to 2018. And through factor decomposition analysis to explore the “Supply – Demand – Economy” influence mechanism of its change.Through scenario analysis and simulation, the GHG emission reduction potential of the food system under the scenarios of production technology upgrading, consumption structure transformation, production space optimization and international production space utilization was explored, and the main conclusions were as follows:
(1) The GHG emissions of China’s food system has obvious spatio-temporal characteristics and life cycle stage characteristics. From the spatio-temporal perspective, both the total amount and per capita emissions of GHG in the entire life cycle of China’s food system showed a trend of decreasing first and then increasing. In 2018, China’s food system emitted 1.55 [1.13, 1.97] billion tons of CO2eq, accounting for 11.7% of China’s GHG emissions this year, and per capita emissions were 1.11 tons of CO2eq. The emission ratio of grain food was relatively high (66.0%) but continued to decrease, while the emission of fruits, vegetables, meat, protein products and aquatic products continued to increase.The GHG emissions from China’s food system are mainly concentrated in the south (75.4%), but the growth rate is faster in the north. The emissions from milk, beef, eggs, aquatic products and pork in the south are gradually increasing, while the emissions from poultry, vegetables, rice and corn in the north are gradually increasing. From the perspective of life cycle stages, the GHG emissions of food system are mainly concentrated in the production and consumption stage, the production stage accounts for 46.9% of the entire life cycle of food emissions, the consumption stage accounts for 31.0%, processing, transportation and retail accounted for 4.0%, 4.3% and 12.9% of the entire life cycle emissions, respectively. Different types of food contribute different amounts of GHG emissions at different stages of their life cycles. In the production stage, rice, wheat, beef and mutton accounted for more than 50%, while pork and milk accounted for more in the processing stage, transport emissions from maize and fruit accounted for more, and GHG emissions in the consumption stage mainly came from the storage and cooking of meat and vegetables (75.6%).
(2) China’s food system has a high efficiency of inter-regional emission transfer and reduces emission pressure through net imports of food. The spatial distribution of food also leads to the redistribution of GHG emissions due to food production and consumption separation. From the perspective of the “dual circulation” development pattern, both domestic and international food trade of agricultural products have played a positive role in GHG emission reduction of China’s food system. From the national and regional level of food emission transfers, emissions of rice transfer relatively inefficient but emissions of wheat and maize transfer efficiently. Overall grains present efficient economical situation, but regional emissions fade out the high efficiency transfer. ” North Milk to the South ” supply and demand pattern makes the milk cross-regional transfer efficiently. Through making full use of international production space, China imports the poultry from South America as well as soybeans, and wheat, soybeans, pork imported from North America, beef, mutton, milk and wheat from Australia, rice and pork from southeast Asian countries, and milk from Europe. As a result, China’s net imported food has an implied emission of about 119 million tons of CO2eq, accounting for about 7.7% of the total emissions in the year.
(3) The GHG emissions of China’s food system are affected by supply side, demand side and economic and social factors with large spatio-temporal differences. Overall, the reduction impact of demand side is higher, contributing 319.5% of the reduction from 1990 to 2018. The influencing factors were explored comprehensively from the supply side, demand side and social economy of food, and the spatio-temporal and type characteristics of the impacts of these factors on the GHG emissions of the food system were summarized. The “Supply-Demand-Economy” influence mechanism model of GHG emissions of the food system in China was established. The results show that since 1990, the transformation of the energy structure of food production in China has significantly reduced GHG emissions at the production stage, especially the reduction of the demand for coal. Different driving factors have different impacts on different regions, which are mainly reflected in emission intensity, consumption structure and urbanization. The emission intensity of most regions are weakening, while the northern regions such as North China and Northwest China have a trend of increasing emissions due to the increase of emission intensity. The transformation of consumption structure has contributed to the growth of emissions in most regions, with South China and Southwest China being the most affected by the transformation of consumption structure and showing a trend of continuous increase in emissions. Urbanization has continuously increased GHG emissions from the food system in Northwest and North China, and reduced to increased GHG emissions from the food system in Northeast, East and South China. However, the continuous urbanization has reduced GHG emissions from the food system in Southwest and Central China. The trends of GHG emissions from food systems in developed and derdeveloping regions of China are significantly different. The GHG emissions of food system in developed regions are gradually increasing, mainly due to the contribution of economic development and population growth, while the GHG emissions of food system in developing regions show a trend of decreasing first and then increasing. The earlier reduction is mainly due to emission intensity, price, Engel coefficient. However, the increase of emissions after 2010 is mainly due to the insufficient emission intensity reduction effect in developing regions and the increase of GHG emissions from the food system caused by the consumption structure shifts.
(4) The GHG emission reduction of China’s food system in the future can be achieved to a large extent through production technology and management collaboration, production-consumption interaction and domestic and international dual cycle support. Five scenarios, including baseline scenario, production technology upgrading, consumption structure transformation, domestic production space optimization and international production space utilization, were constructed, and the combined effects of these scenarios were analyzed. The results show that the transformation of the consumption structure has the highest potential for food system emission reduction, which can reduce the emission by about 14.9% [-43.0%, 7.3%] by 2060. However, due to the lack of food consumption guidelines based on “healthy-sustainable”, the emission reduction potential of consumption structure shifts are highly uncertain. In addition, the food production scenario also has a high potential to reduce emissions by about 12.1% [-16.3%, -7.9%] by 2060. The domestic food production space optimization scenario and the international food imports scenario have similar emission reduction potential, which can reduce emissions by 3.5%[-3.9%, -3.0%] and 4.4%[-5.7%, -3.2%], respectively. Through the emission reduction scenario combination results, it can be seen that the emission reduction effect of the production side can be further enhanced through the technology and space optimization at the production side, the combination of emission reduction measures at the production side and the consumption side can play a systematic role in emission reduction, and the comprehensive utilization of domestic and international production space can increase the national emission reduction effect.
In this study, a “bottom-up” GHG emission inventory of the entire life cycle of China’s food system was constructed to systematically evaluate the spatio-temporal characteristics of GHG emissions from 1990 to 2018. Compared with the current EU GHG emissions inventory based on sector downscaling, this inventory can further reveal the spatio-temporal characteristics of GHG emissions of different types of food. This study is to explore to construct the “Supply-Demand-Economy” factor decomposition model, a systematic analysis of the Chinese food system mechanism, the influence of GHG emissions change proposed the field of food energy consumption structure shift is the important reason for the early stage of the food system emissions, economy, population, consumption structure and urbanization is the main cause of GHG emissions affecting food system. Although, there are large differences in time and space and food types. Appropriate price mechanism can greatly affect the emission reduction of food system.This research set scenarios by technology progress, consumption transformation, structure optimization, the food imports, showing the supply side and demand side synergy is the best path to reduce emissions reductions in GHG emissions. While production space optimization and international food impors for food systems reduction are equally authentic.
