Integrated Analysis of Energy, Economic, and Environmental Performance of Biomethanol from Rice Straw in China

This paper focuses on a biomethanol from the rice straw process involving the thermodynamic, economic, and environmental performance in China. Based on the simulation of methanol synthesis via biomass gasification in interconnected fluidized beds using Aspen Plus software, the method of LCA (Life Cycle Assessment) is applied to evaluate the impact of pollutant emissions in the full life cycles of biomethanol. The integrated performance of biomethanol system is analyzed combining with energy utilization, economic cost, and environmental impact. The results show that the methanol yield can reach 0.308 kg/(kg rice straw), i.e., the energy efficiency of rice straw conversion to biomethanol is approximately 42.7%. For a biomethanol plant with an annual production of 50,000 tons, the real cost of biomethanol is evaluated at 2685 RMB/t, in which the economic cost is 2347 RMB/t, and the environmental cost is 337.6 RMB/t. Because of its high investment cost, presently the economic cost of biomethanol is higher than that of coal-based methanol in China. Nevertheless biomethanol will be becoming more competitive with the shortage of fossil fuel in the future. In the whole life cycle, the main pollutant emissions come from the biomethanol production process and biomethanol end-use by automobiles, whereas the net environmental effect is negative during the rice cultivation. Global warming is the most influential factor of the different impact categories. However, 1910 kg of CO 2 can be fixed for one ton of methanol by photosynthesis in the growth of rice, thus the effect of global warming is significantly reduced by biomass utilization compared with coal-based methanol. The integrated performance indicates that producing methanol from rice straw is beneficial to both the utilization of agriculture waste and in the improvement of environment.