Net energy analysis of small-scale producer gas production from Jatropha seed

摘要

Net energy analysis (NEA) of biodiesel production from Jatropha energy crop has been extensively studied. The commercialization of the Jatropha biodiesel, however, is not available yet due to high energy input for seed pressing and oil processing, which lowers the net energy balance (NEB) and the net energy ratio (NER) of the biodiesel production. Gasification technology is an alternative, which can bypass seed pressing and oil processing. This study aims to investigate the NEA of producer gas production from Jatropha seed per hectare of plantation for a 20-year lifetime, but the Jatropha shell and tree are not included in the studied system boundary. The energy output is the amount of diesel fuel replaced by producer gas for 1 kWeh electricity generation. 10 kg of gas replaced diesel fuel by 0.22 kg, or 46.9 MJ of gas replaced diesel fuel by 9.68 MJ. The results highlighted that the NEB and NER were 490.14 GJ and 5.45, respectively. The total CO2 emission was 296 tonnes (t). If the gasifier and gas cleaning system perform more efficiently, the NEB and NER become higher, and the CO2 emission decreases. If the energy input for introducing gasifying agent and cleaning producer gas is saved, the NEB and NER will increase up to 543.41 GJ and 9.57, respectively. Furthermore, the optimization of engine operation parameters can minimize CO2 emissions and improve the NEB and NER. Overall, the production of producer gas from Jatropha seed can be considered as a renewable system based on the findings of the renewability indicators of NEB and NER.