Evaluation of Cost and Environmental Load of Bioethanol Production from Rice Straw that Considered Abandoned Cultivation Lands

Abstract

Objectives. It is important to design a biofuels production and utilization system which can reduce economic cost and environmental load from the viewpoint of global warming prevention and energy safety. In this study, we estimated suitable numbers of bioethanol plants, construction sites of bioethanol plants, transportation routes of rice straw orienting cost minimization and greenhouse gas (GHG) emissions minimization which considered the characteristics of region such as distribution and quantity of rice straw, road network and distribution of biogasoline stations in Chiba prefecture. Also, we examined influence that abandoned cultivation lands use gave to the cost and GHG emissions of the bioethanol production utilization system. Furthermore, we performed sensitivity analysis about factors that influenced bioethanol production cost.
Results and Discussion. We analyzed cost minimization, GHG emissions minimization, and total cost minimization for current condition scenario (scenario 1) and abandoned cultivation lands use scenario (scenario 2). The construction sites of bioethanol plants, transport routes of rice straw, the cost and GHG emissions were calculated in each scenario. The result shows that plants construction sites and rice straw transportation routes were different in the cost minimization and in GHG emissions minimization. The bioethanol production cost were estimated to be 133 JPY/L in the scenario 1 and 140 JPY/L in the scenario 2. The ratio of collection and transportation costs of the rice straw occupied about 30% of the total cost and was the biggest. The GHG emissions were estimated to be 1.31 kgCO₂-eq/L in the scenario 1 and 1.41 kgCO₂-eq/L in the scenario 2. The GHG emissions in bioethanol conversion process occupied about 70% of the total GHG emissions. GHG reduction effect was evaluated in the scenario 1 but was not evaluated in the scenario 2. The rice straw collection and transportation unit price influenced the bioethanol production cost most.
Conclusions. The bioethanol production was unprofitable in each scenario. The finance supports from country/government and tax break are necessary for the bioethanol to be profitable. Since the rice straw collection/transportation cost accounts for a large part of the total cost in the bioethanol production system, it is significant to make the price competitive. The development of low cost technologies to collect rice straw and bioethanol conversion as well as a financial support system is needed. In comparison with the gasoline, the GHG emission reduction effect of the bioethanol was evaluated in the scenario 1. But the GHG emission reduction effect of the bioethanol was not shown in the scenario 2 because GHG emissions of cultivation stage are considered.