The prospect of bamboo and non-fodder rice husk for sustainable bioethanol production

Due to the rapid industrialization globally, there is a constant increase in demand for energy, which drives up fuel prices and contributes to the depletion of fossil fuels. The rise in the use of fossil fuels results in increasing greenhouse gas emissions contributing to biodiversity loss. Thus, the development of alternative green biofuel (e.g., bioethanol) from renewable and surplus biomass resources has taken center stage as our attention is drawn to environmental concerns and energy security. However, till now, the studies pertaining to the process optimization and techno-economic analysis of bioethanol production using indigenous non-conventional biomass resources are scarcely reported for the industrial application. Henceforth, this study employed Bambusa bambos (BB) culm and non-fodder rice husk (NFRH) as the raw material due to its high holocellulose content (60-70%) for bioethanol production and based on its biomass availability in the agrarian state of Karnataka (India). Thereupon, the statistical design of experiment (DoE) method was applied for the thermo-chemical pretreatment optimization of the collected biomass resources, and the fermentation was performed using osmotolerant Angel™ yeast for the bioethanol production. Overall, the maximum reducing sugar (RS) concentration of 70.7 ± 2.6 g/L under optimal condition of 10% (w/v) loading at 121 °C for 30 min using 0.3 M sulfuric acid and bioethanol concentration of 4.7 ± 0.8 g/L (0.42 g/g RS) with conversion efficiency of 70% was obtained from the indigenous BB biomass, whereas the NFRH biomass yielded the maximal concentration of RS around 91.5 ± 2.2 g/L as per optimized conditions [15% w/v loading at 121 °C for 30 min using 0.5 M sulfuric acid] with 61% saccharification efficiency and bioethanol productivity of 5.3 ± 0.4 g/L (0.10 g/g RS). Conclusively, 61-101 L of bioethanol is estimated from 1 tonne of BB and NFRH biomass resources from the study with net energy ratio of greater than 1.0, low carbon footprint (0.14-1.97 kg carbon dioxide equivalent), bioconversion of 10-40% as per the mass-balance analysis, and production costing of less than 100 ₹/L; hence, this result provides a cost-effective sustainable solution for bioethanol production that can raise farmers income as well as enables the rural development.