Life-cycle energy and environmental analysis of Bio-oil production from rice straw and leucaena leucocepphala in Thailand

Abstract

In this study, the life-cycle energy and environmental assessment was conducted for bio-oil production from fast pyrolysis process using rice straw and leucaena leucocepphala in Thailand. The bio-oil product was targeted to be used as green crude for the refinery. The system boundary covered four stages: raw material plantation and harvesting, transportation, pyrolysis, and upgrading process. The input-output data of plantation were collected at actual plantation sites. For rice straw, it was considered in 2 cases: as waste and as a by-product where economic allocation was required. Since there is no commercial plant in Thailand, data for fast pyrolysis and bio-oil upgrading processes were retrieved from literature and pilot plant. The results were compared with conventional fuels and biofuels based on 1ton oil equivalent (toe). From the energy analysis, net energy ratios (NER) indicated a net energy gain for both feed stocks with an energy ratio higher than 1. In addition, the NER would be even higher (> 5.0) if heat integration and heat recovery could be applied to the upgrading process. For the environmental performance, the cradle-to- gate results show that the upgrading stage contributes most to the environmental impact which is due to the intensive use of electricity and steam in the process.