Life cycle assessment of optimized cassava ethanol production process based on operating data from Guangxi factory in China

In cassava ethanol studies, few studies have combined production data from plants with simulation models, and further investigated the environmental emissions caused by different production processes. In this paper, based on the survey data of cassava ethanol plants in Guangxi, we established an ethanol production process model and conducted a life cycle assessment of the raw meal fermentation (RMF) process and traditional clinker fermentation (CF) process. The impact of fermentation broth alcohol concentration on the environmental emissions of the whole process was also investigated based on the conventional CF process. The results showed that the RMF production process had more advantages than the CF production process in terms of energy savings, with 633 MJ per ton of ethanol and 37.39 kg eq/t ethanol of CO2 reduction. Increasing the alcohol concentration of the fermentation broth facilitated the removal of environmental emissions from the process. All cassava ethanol production models exhibited net energy ratios of no less than 2.74. Of these, the RMF 15% showed the most competitive net energy ratio of 2.97, the highest renewability of 4.52, and the lowest environmental emissions. A detailed analysis of the environmental impacts by the ethanol production phase showed that the distillation section was the critical point for energy saving and emission reduction. Sensitivity analysis showed that fertilizer and natural gas consumption could not be ignored.