To achieve a low-carbon economy, China has committed to reducing its carbon dioxide (CO₂) emissions per unit of gross domestic product (GDP) by 40%–45% by 2020 from 2005 levels and increasing the share of non-fossil fuels in primary energy consumption to approximately 15%. It is necessary to investigate whether this plan is suitable and how this target may be reached. This paper verifies the feasibility of achieving the CO₂ emission targets by energy and industrial structure adjustments, and proposes applicable measures for further sustainable development by 2020 through comprehensive simulation. The simulation model comprises three sub-models: an energy flow balance model, a CO₂ emission model, and a socio-economic model. The model is constructed based on input-output table and three balances (material, value, and energy flow balance), and it is written in LINGO, a linear dynamic programming language. The simulation results suggest that China’s carbon intensity reduction promise can be realized and even surpassed to 50% and that economic development (annual 10% GDP growth rate) can be achieved if energy and industrial structure are adjusted properly by 2020. However, the total amount of CO₂ emission will reach a relatively high level—13.68 billion tons—which calls for further sound approaches to realize a low carbon economy, such as energy utilization efficiency improvement, technology innovation, and non-fossil energy’s utilization.

Tianjin City in China is a typical area that suffers from a serious water resource shortage and pollution problems, and this situation has spurred the use of reclaimed water as an additional source of water and an efficient method of improving water quality. This study aims to assess the reclaimed water utilisation amount available and its potential impacts on the water environment and economy, and proposes applicable approaches to establish the optimal development for Tianjin. A water resources-environment-economic management model was constructed, which was accomplished by dynamic linear optimisation. Through scenario analysis, Tianjin's optimal reclaimed water recycle rate can reach 56%, with 475 × 106 tons of reclaimed water amount available (supporting 22% of the water supply), while bringing sufficient environmental and economic benefits, such as reducing 20% of water pollutants and maintaining 6.3% annual economic growth by 2020. This research also suggests that an integrated water management approach is preferable, including a proper introduction of technologies suited to the region's needs, a support system for construction, and control of water pollutant emission sources, especially in agriculture. The originally formulated water management system can be easily applied and extended to solve water issues, especially for water recycling.

The stockbreeding industry is growing rapidly in rural regions of China, carrying a high risk to the water environment due to the emission of huge amounts of pollutants in terms of COD, T-N and T-P to rivers. On the other hand, as a typical biomass resource, stockbreeding waste can be used as a clean energy source by biomass utilization technologies. In this paper, we constructed a dynamic linear optimization model to simulate the synthetic water environment management policies which includes both the water environment system and social-economic situational changes over 10 years. Based on the simulation, the model can precisely estimate trends of water quality, production of stockbreeding biomass energy and economic development under certain restrictions of the water environment. We examined seven towns of Shunyi district of Beijing as the target area to analyse synthetic water environment management policies by computer simulation based on the effective utilization of stockbreeding biomass resources to improve water quality and realize sustainable development. The purpose of our research is to establish an effective utilization method of biomass resources incorporating water environment preservation, resource reutilization and economic development, and finally realize the sustainable development of the society.