CO₂ Emission Reduction by Cellulosic Ethanol Production via Syngas

Abstract

This study evaluates three bioethanol production pathways that are composed by saccarification and fermentation process (SFP), gasification and chemical synthesis process (GCP), gasification and biosynthesis process (GBP). These pathways are designed by process simulator PRO/II, and these material and energy balances are calculated. From the simulation results, the CO₂ emission reduction of each process is evaluated. It becomes clear that the CO₂ emission reduction of the process via syngas is larger than that of the process via sugars. The ethanol yield of GBP is the maximum, and GBP can support oneself a power and thermal energy in the process. In three processes, therefore, the CO₂ emission reduction of GBP is the largest. The ethanol yield of SFP and GCP is almost the same. Because the residue including lignin contains moisture, the thermal energy from which SFP can be recovered is not large. On the other hand, GCP can use the thermal energy generated by chemical synthesis for the power production. It is indicated that GCP has the possibility of increasing the CO₂ emission reduction more than SFP.