2008 Volume 4 Issue 2 Pages 135-140
Utilization of various biomass resources as energy is being promoted from the viewpoint of fossil fuel conservation and prevention of global warming. In order to foster its further utilization, it is important to evaluate the energy and environmental burden of biomass from a lifecycle perspective, incorporating upstream and downstream aspects such as cultivation, collection, transformation and use in preparing a comprehensive life cycle inventory (LCI). Indices such as EPR (Energy Payback Ratio) and EPT (Energy Payback Time) are frequently used for this purpose. In this paper, concepts of these indices are explained, and its application to evaluation of various bio-ethanol projects is conducted. Considerable difference (up to about five-fold) in EPR and EPT are found among various evaluation projects, which are attributed to setting range of LCI, setting of parameters, differences of background databases, and treatment of allocation among co-products (cornstarch in the case of corn, bagasse in the case of sugarcane, and lignin in the case of cellulosic resources).
