Optimization of acid pretreatment and enzymatic hydrolysis on the production of ethanol fuel from waste banana peels

This study investigated the application of waste banana peels as feedstock for the production of ethanol fuel as a second-generation biofuel. First, acid pretreatment followed by enzymatic hydrolysis converted both the cellulosic and hemicellulosic biomass of the peels into fermentable sugars, which eventually produced ethanol by yeast fermentation. The optimal conditions for the production of ethanol fuel were determined by orthogonal experimental design method. The results showed that 100 g of fresh banana would produce 31.4 g of banana peel which could be turned into 2.8 g dried peel powder. Under optimal conditions of acid pretreatment with 0.2% tartaric acid, enzymatic hydrolysis by cellulase and yeast fermentation, 115 mg of ethanol (95% purity) could be recovered by distillation from the fermentation broth, which was approximately 4% by weight of the dried peel powder. This study concluded that banana fruit, after the removal of peels for consumption or food processing, the discarded peels will no longer pose an organic waste problem to the environment if they could be recollected and converted into value-added products like ethanol fuel. We also demonstrated that tartaric acid, an organic acid used in the acid pretreatment, for the first time to our knowledge, outperformed the traditional sulfuric acid used commonly in other studies.