Optimizing biomass supply for cofiring at power plants to minimize environmental impact: A case of oil palm empty fruit bunches in West Java

Abstract

This study addresses the supply flow optimization to reduce global warming in a cofiring system, using the example of oil palm empty fruit bunches converted into pellets for use in power plants in Indonesia. Four oil palm mills, seven pellet plants and five coal power plants in the West Java Region were considered in this study to select the optimal supply chain. The study was performed using a life cycle assessment (LCA) for evaluating impact of single firing of coal and linear programming (LP) for optimizing the impact reduction of cofiring of coal and pellets. Our study indicates that the optimal environmental reduction can be achieved by constructing six of the seven pellet plants, which can substitute up to 1 % of the coal supply in five power plants. Accordingly, the emissions could be decreased by an average of 0.018 kg CO2eq/kWh for the power plants, which is equal to 0.2 Mt CO2eq/y or a 1.57 % reduction per year. By varying the emission factor of the pellet plants, our analysis showed a tolerable range in which the supply would not be affected. The sensitivity analysis at a 1 % cofiring rate showed that the increase in biomass supply from the oil palm mills had the highest reduction, whereas the reduction in transportation emissions provided much less impact. By adjusting the cofiring rate, the impact would not change after the 3 % cofiring rate because of the limited availability of Empty Fruit Bunch (EFB) feedstock. However, if sufficient supply could be provided, the environmental impact would be further reduced significantly. Furthermore, the scenario expansion indicated that only three pellet plants would be required for the minimum economic scale of production, although the environmental impact increased by 0.47 % compared to using six pellet plants. Therefore, this study can be used to determine the optimal supply chain scenarios by constructing an appropriate number of economically feasible pellet plants according to the biomass demand and cofiring rate of the power plant.