Cette thèse est une évaluation du potentiel d'atténuation technique et économique global dans l'agriculture Chinoise et des conditions nécessaires à la formation d’un prix du carbone dans ce secteur. Le champ de recherche inclut les émissions venant de terres cultivées et en particulier celles liées à l'utilisation d'engrais azotés synthétiques. Il s'articule autour de la construction d'une courbe de coûts marginaux de réduction (MACC), qui offre un cadre rationnel pour combiner les données biophysiques et économiques afin de refléter les coûts d'atténuation. Cet outil permet d'agréger le potentiel d'atténuation découlant de l'application d'un sous-ensemble de mesures coût-efficacité en dessus d'un niveau de référence désignée. Une analyse des politiques climatiques chinoises révèle que l'agriculture est presque absente de la stratégie nationale d'atténuation. Nous avons donc l'intention d’examiner la faisabilité du point de vue technique, économique et politique, d’intégrer l'agriculture dans les politiques domestiques d’atténuation. En premier lieu, la tendance et les méthodes de calcul des émissions sont évaluées afin de déterminer une approche rigoureuse permettant de construire des scénarios de référence à partir de prévisions des activités ‘business-as-usual’ pour 2020. Deuxièmement, nous identifions neuf mesures d'atténuation des sols cultivés, nous évaluons leur taux d'abattement et leur applicabilité future au-delà du scénario de base pour obtenir un potentiel total d'atténuation techniquement faisable. Leur traduction en potentiel économique est alors faite en comparant les coûts de mise en œuvre des différentes options d'atténuation relatives aux pratiques agricoles conventionnelles. Les résultats des MACC montrent que l’agriculture offre un potentiel d'atténuation important, qui pourrait compenser environ un tiers des émissions de référence et dont un tiers pourrait être réalisé au coût négatif pour les agriculteurs. Nous examinons enfin l’utilisation des instruments économiques pour réduire les émissions au moindre coût dans le secteur agricole. Compte tenu des obstacles institutionnels, comportementaux et sociaux, nous suggérons fortement d’engager une réforme dans le système des subventions d'engrais afin d'envoyer un signal politique clair aux agriculteurs. L’utilisation de l’intensité du carbone comme référence normalisée est recommandé pour améliorer et élargir l'accès aux projets de compensation, et peut aussi préparer le terrain pour un possible programme expérimental d'échange de quotas d’émissions dans l'agriculture. En cohérence avec la priorité de protéger la sécurité alimentaire en Chine, des études de cas sur la production régionale de céréales sont introduites dans toutes ces étapes, y compris l'analyse de l'intensité des gaz à effet de serre de la production dans chaque province, le potentiel régional de réduction des émissions liées à l'utilisation d’engrais azotés ainsi que la disparité de coûts de mise en œuvre dans certaines régions. / This thesis is an evaluation of the overall technical and economic mitigation potential in China agriculture and the conditions of putting a carbon price in this sector. The research scope is cropland emissions and particularly those related to synthetic nitrogen fertilizer use. The thesis is articulated around the construction of a bottom-up marginal abatement cost curve (MACC) which offers a rational framework for combining biophysical and economic data to reflect mitigation costs. This tool allows the aggregation of the mitigation potential arising from the application of a subset of cost-effective measures above a notional baseline level. An analysis of Chinese climate policies reveals that agriculture is nearly absent in the current national mitigation strategy. We therefore intend to assess the technical, economic and political feasibility of integrating agriculture into domestic mitigation policies. In the first place, the emissions trends and calculation methods are assessed to determine a rigorous approach to build baseline scenarios from projected business-as-usual activities to 2020. Secondly, we identify nine cropland mitigation measures, evaluate their abatement rates and future applicability beyond the baseline scenario to conclude a total feasible technical mitigation potential. The translation to the economic potential is then made by comparing the implementation costs of different mitigation options relative to conventional farming practices. The MACC results show that agriculture provides significant mitigation potential to be able to offset about one-third of baseline emissions and realisation of one-third of the potential is cost-negative for farmers. We finally examine the conditions of using economic instruments to reduce emissions at the lowest cost for the agricultural sector. Given the institutional, behaviour and socials obstacles, we strongly suggest a reform in agriculture fertilizer subsidies to send a clear political signal from central planning. Scaling-up offset projects using carbon intensity as the standardized baseline is recommended and can prepare the grounds for a possible experimental emission trading programme in agriculture. In light with the top priority of safeguarding food security in China, cases studies on regional cereal production are carried out in all these steps, including the analysis of provincial greenhouse gas intensity of production, regional abatement potential related to synthetic nitrogen fertilizer use as well as implementation cost disparities in certain regions.

Whether it is based on current emissions data or future projections of further growth, the building sector currently represent the largest and singular most important contributor to greenhouse gas (GHG) emissions globally. This notion is also supported by the Intergovernmental Panel on Climate Change based on projection scenarios for 2030 that emissions from buildings will be responsible for about one-third of total global emissions. As such, improving the energy efficiency of buildings has become a top priority worldwide. A significant majority of buildings that exist now will still exist in 2030 and beyond; therefore the greatest energy savings and carbon footprint reductions can be made through retrofit of existing buildings. A wide range of retrofit options are readily available, but methods to identify optimal solutions for a particular abatement project still constitute a major technical challenge. Investments in building energy retrofit technologies usually involve decision-making processes targeted at reducing operational energy consumption and maintenance bills. For this reason, retrofit decisions by building stakeholders are typically driven by financial considerations. However, recent trends towards environmentally conscious and resource-efficient design and retrofit have focused on the environmental merits of these options, emphasising a lifecycle approach to emissions reduction. Retrofit options available for energy savings have different performance characteristics and building stakeholders are required to establish an optimal solution, where competing objectives such as financial costs, energy consumption and environmental performance are taken into account. These key performance parameters cannot be easily quantified and compared by building stakeholders since they lack the resources to perform an effective decision analysis. In part, this is due to the inadequacy of existing methods to assess and compare performance indicators. Current methods to quantify these parameters are considered in isolation when making decisions about energy conservation in buildings. To effectively manage the reduction of lifecycle environmental impacts, it is necessary to link financial cost with both operational and embodied emissions. This thesis presents a novel deterministic decision support system (DSS) for the evaluation of economically and environmentally optimal retrofit of non-domestic buildings. The DSS integrates the key variables of economic and net environmental benefits to produce optimal decisions. These variables are used within an optimisation scheme that consists of integrated modules for data input, sensitivity analysis and takes into account the use of a set of retrofit options that satisfies a range of criteria (environmental, demand, cost and resource constraints); hierarchical course of action; and the evaluations of ‘best’ case scenario based on marginal abatement cost methods and Pareto optimisation. The steps involved in the system development are presented and its usefulness is evaluated using case study applications. The results of the applications are analysed and presented, verifying the feasibility of the DSS, whilst encouraging further improvements and extensions. The usefulness of the DSS as a tool for policy formulation and developments that can trigger innovations in retrofit product development processes and sustainable business models are also discussed. The methodology developed provides stakeholders with an efficient and reliable decision process that is informed by both environmental and financial considerations. Overall, the development of the DSS which takes a whole-life CO2 emission accounting framework and an economic assessment view-point, successfully demonstrates how value is delivered across different parts of the techno-economic system, especially as it pertains to financial gains, embodied and operational emissions reduction potential.