Life Cycle Emergy Based Research For The Sustainable Development Of Straw Bioenergy

As one kind of abundant renewable energy, bioenergy is favorable to replace fossil fuels, ease energy crisis and reduce environmental damage, which have been caused by fossil fuel use. The collection and utilization of straw as energy, not only to avoid a waste of resources, but also can reduce the pollution caused by the random stacking and burning. However, the production and use of straw as bioenergy also will consume energy and pollute the environment. In addition, the different ways of straw utilization bring about different environmental, economic performance. Therefore, it is significant to evaluate straw bioenergy systems scientifically and rationally and compare the pros and cons of different ways of utilizing straw for the sustainable development of the systems. Life cycle emergy analysis has been applied to the evaluation of two different kinds of Straw power generation systems. The results showed that:(1) Through life cycle emergy analysis of straw direct-fired power generation system, the life cycle emergy indices were obtained. The life cycle transformity (LC-Tr) was 4.98E+04 seJ/J. The life cycle emergy yield ratio (LC-EYR) was 1.17. The life cycle environmental loading ratio (LC-ELR) was 3.06. The life cycle renewable index (LC-RI) was 24.6%. The life cycle emergy sustainability index (LC-ESI) was 0.38.(2) The LC-Tr of straw briquette fuel power generation system was 3.45E+04 seJ/J, which was lower than straw direct-fired power generation system. The LC-EYR, LC-ELR, LC-RI and LC-ESI were 1.15,2.61,27.7% and 0.44, respectively. The comparative analysis of the indicators of two straw power systems, coal-fired power, and fuel power generation systems indicated that the straw power systems were more sustainable, especially the straw briquette fuel power generation system.(3) The emergy input of cropping stage accounts for 59.98% in the straw direct-fired power generation system, and 52.09% in straw briquette fuel power generation system; the emergy input of transportation stage in straw direct-fired power generation system was 8.92E+13 seJ, which was much more than straw briquette fuel power generation system (8.58E+12 seJ).(4) The CO2 emission indicator of straw briquette power was lower than straw direct-fired power, and is much lower than coal power, indicating that both straw power systems could make a considerable contribution to the reduction of greenhouse gases emission.(5) Bioenergy waste was evaluated by emergy analysis taking the straw-power wastewater and straw-alcohol vinasses as examples. The transformities were -5.06+05 seJ/g and -6.64E+06 seJ/g, respectively. And the EYR of straw-power wastewater and straw-alcohol vinasses treatment were 1.57 and 2.17, respectively, which were mainly affected by water qualities and treatment processes.Through life cycle emergy analysis of straw power generation systems, the contribution of natural environment can be measured. And the utilization patterns of straw bioenergy could be evaluated reasonably. The process emergy analysis could help to determine the best straw bioenergy industry solution. Life cycle emergy analysis played a positive role in promoting sustainable development of straw bioenergy.