Scenario comparisons of gasification technology using energy life cycle assessment for bioenergy recovery from rice straw in Taiwan

This study uses different scenarios to evaluate, by means of energy life-cycle assessments (ELCAs), the energy balance of potential gasification technology and limitation boundaries in Taiwan. Rice straw is chosen as the target material in this study because it is the most significant agriculture waste in Taiwan. Energy products include syngas (CO + H2), methane, carbon dioxide and carbon black residue. The scenarios simulate capacities of 50,000–200,000 tons/year. The distances of collection and transportation are calculated by a circular area 50–100 km in diameter. Also, the on-site and off-site pretreatments of rice straw are evaluated. For this optimum scenario case, the average of the total input energy for the assessed systems is about 15.9% of the average output energy; the value of the net energy balance (NEB) is 0.841. Every technological process has positive energy benefits at all on-site scenario cases. As the capacity is increased, the energy consumption required for transportation increases and the values of the energy indicators decrease. According to the limitation boundaries from the tendency model at on-site cases, the suggested transportation distance and treatment capacity are below 114.72 km and 251,533 tons/year, respectively, while the energy return on investment (EROI) value is greater than 1.