Abstract
The purpose of this study is to evaluate biomass energy systems based on both material and energy flows. The biomass energy system consists of 4 processes such as harvesting and collection, preprocessing, energy conversion, and waste treatment. As the conventional evaluation such as energy return on investment (EROI) is based on the amount of fossil fuel consumption, it shows the efficiency of inputted fossil fuel to form biomass derived fuels without biomass material flow. In this study, the effective utilization rate of resource is defined as the ratio of the difference between produced bio-fuel energy and consumed fossil fuel energy to the biomass resource energy, and the fossil fuel substitution rate is defined as the ratio of net substituted fossil fuel energy by the bio-fuel to the biomass resource energy. As a case study, the woody biomass utilization systems considering 7 preprocessing technologies and 4 energy conversion technologies are evaluated by using EROI and suggested values. It is shown that the effective utilization ratio of resource and the fossil fuel substitution rate can be small even if EROI is enough high.
