WANG Wen

This thesis is an assessment of the overall technical and economic mitigation potential in Chinese agriculture and the conditions necessary for the formation of a carbon price in this sector. The scope of the research includes emissions from croplands and in particular those related to the use of synthetic nitrogen fertilizers. It is based on the construction of a marginal abatement cost curve (MACC), which provides a rational framework for combining biophysical and economic data to reflect mitigation costs. This tool aggregates the mitigation potential from applying a subset of cost-effective measures above a designated baseline. An analysis of China's climate policies reveals that agriculture is almost absent from the national mitigation strategy. We therefore intend to examine the feasibility, from a technical, economic and political perspective, of integrating agriculture into domestic mitigation policies. First, the trend and methods of calculating emissions are assessed to determine a rigorous approach to constructing baseline scenarios from business-as-usual projections for 2020. Second, we identify nine mitigation measures for cultivated soils, assess their abatement rates and future applicability beyond the baseline scenario to obtain a total technically feasible mitigation potential. Their translation into economic potential is then made by comparing the implementation costs of different mitigation options relative to conventional agricultural practices. The MACC results show that agriculture offers a significant mitigation potential, which could offset about one third of the baseline emissions and of which one third could be achieved at negative cost to farmers. Finally, we examine the use of economic instruments to reduce emissions at least cost in the agricultural sector. Given the institutional, behavioral, and social barriers, we strongly suggest reforming the fertilizer subsidy system to send a clear policy signal to farmers. The use of carbon intensity as a standardized benchmark is recommended to improve and broaden access to offset projects, and may also set the stage for a possible experimental emissions trading program in agriculture. Consistent with the priority of protecting food security in China, case studies of regional grain production are introduced in all these steps, including analysis of the greenhouse gas intensity of production in each province, the regional potential for reducing emissions from nitrogen fertilizer use, as well as the disparity in implementation costs in some regions.

China faces significant challenges in reconciling food security goals with the objective of becoming a low-carbon economy. Agriculture accounts for approximately 11 % of China’s national greenhouse gas (GHG) emissions with cereal production representing a large proportion (about 32 %) of agricultural emissions. Minimizing emissions per unit of product is a policy objective and we estimated the GHG intensities (GHGI) of rice, wheat and maize production in China from 1985 to 2010. Results show significant variations of GHGIs among Chinese provinces and regions. Relative to wheat and maize, GHGI of rice production is much higher owing to CH4 emissions, and is more closely related to yield levels. In general, the south and central has been the most carbon intensive region in rice production while the GHGI of wheat production is highest in north and northwest provinces. The southwest has been characterized by the highest maize GHGI but the lowest rice GHGI. Compared to the baseline scenario, a 2 % annual reduction in N inputs, combined with improved water management in rice paddies, would mitigate 17 % of total GHG emissions from cereal production in 2020 while sustaining the required yield increase to ensure food security. Better management practices will entail additional gains in soil organic carbon further decreasing GHGI. To realize the full mitigation potential while maximizing agriculture development, the design of appropriate policies should accommodate local conditions.

China is now the world's biggest annual emitter of greenhouse gases with 7467 million tons (Mt) carbon dioxide equivalent (CO2e) in 2005, with agriculture accounting for 11% of this total. As elsewhere, agricultural emissions mitigation policy in China faces a range of challenges due to the biophysical complexity and heterogeneity of farming systems, as well as other socioeconomic barriers. Existing research has contributed to improving our understanding of the technical potential of mitigation measures in this sector (i.e. what works). But for policy purposes it is important to convert these measures into a feasible economic potential, which provides a perspective on whether agricultural emissions reduction (measures) are low cost relative to mitigation measures and overall potential offered by other sectors of the economy. We develop a bottom-up marginal abatement cost curve (MACC) representing the cost of mitigation measures applicable in addition to business-as-usual agricultural practices. The MACC results demonstrate that while the sector offers a maximum technical potential of 402 MtCO2e in 2020, a reduction of 135 MtCO2e is potentially available at zero or negative cost (i.e. a cost saving), and 176 MtCO2e (approximately 44% of the total) can be abated at a cost below a threshold carbon price ≤¥ 100 (approximately €12) per tCO2e. Our findings highlight the relative cost effectiveness of nitrogen fertilizer and manure best management practices, and animal breeding practices. We outline the assumptions underlying MACC construction and discuss some scientific, socioeconomic and institutional barriers to realizing the indicated levels of mitigation.