Integral approach for second-generation bio-ethanol production and wastewater treatment using peanut shell waste: yield, removal, and ANN studies

Ethanol production from lignocellulosic feedstock is regarded as one of the most promising options for developing a sustainable energy system. Herein, the paper investigates the use of peanut shell biomass along with Saccharomyces cerevisiae and Zymomonas mobilis strains for bioethanol production under aerobic as well as anaerobic fermentation conditions. Furthermore, the waste left after ethanol generation is converted into a potential adsorbent. Results revealed that the maximum sugar yield of 3.10 mg/ml was obtained using 3% (NaOH) assisted by 1% H₂SO₄ pre-treatment technique. Anaerobic environment was more preferable by both the strains for fermentation with the maximum productivity of 1.96 g/g ethanol by S. cerevisiae and a production of 1.79 g/g when Z. mobilis is used. To the best of our knowledge, such comparative study of aerobic and anaerobic fermentation on bioethanol production from peanut shell has not been reported. Artificial neural network (ANN) was successfully applied to optimize the total fermentable sugar production in the saccharification stage. The model represents an excellent regression coefficient (R² 0.929) indicating that the experimental data have a good fit with the predicted result. To sustainable reduce the waste produced after bioethanol production, the discarded substrate was pyrolyzed to carbonized biochar. The biochar was utilized for methylene blue dye removal from waste effluent with 99.65% removal at (5 mg/l) initial dye concentration, (6) pH, and (0.3 g/l) substrate dose within 150 min. Results revealed that peanut shell is a potential candidate for use in the bioethanol industry especially when integrated with adsorbent production process.