Effect of pre-pyrolysis biotreatment of banana pseudo-stem (BPS) using synergistic microbial consortium: Role in deoxygenation and enhancement of yield of pyro-oil

Essentially non-edible banana pseudo-stems (BPS), an abundant agro-waste, can be pyrolytically converted to bioenergy vectors namely; pyro-oil and pyro-gas and a valuable biomaterial, biochar. The study of thermo-chemical behavior of BPS is essential to assess its potentiality as a pyrolysis feedstock. The present article focuses on the studies of the generation of pyro-oil from BPS, enhancement of yield and on the improvement of its fuel quality through a novel biochemical pre-pyrolysis treatment. A semi-defined synergistic microbial consortium comprising baker's yeast and the native fungal sp. of BPS has been utilized in the pretreatment process. The thermogravimetric analysis (TGA) of native and biochemically treated BPS (BBPS) obtained after different pretreatment time (24 h, 36 h and 48 h) has been performed and their lignocellulosic composition has been determined through deconvolution of derivative thermogravimetry (DTG). while DTG analysis indicates overall increase in the fraction of thermally degradable cellulose forms and decrease in lignin content, FTIR analysis confirms decarboxylation of BPS through the increase in biochemical treatment period. The elemental analysis of pyro-oil obtained from BBPS-48 indicates gradual decrease in oxygen content as the pretreatment time is increased. At the pyrolysis temperature of 773 K, the maximum yield (53.54% (w/w)) of pyro-oil from 48 h bio-pretreated BPS (BBPS-48) is two-fold higher than that obtained from native BPS (24.5%), the oxygen contents of the former and latter being 53.75% and 64.1%, respectively. This effectively leads to almost two fold increase in higher heating value (HHV), of pyro-oil from BBPS-48 (12.97 MJ/kg) in comparison to its BPS counterpart (7.77 MJ/kg). The overall increase in yield and quality of pyro-oil due to bio-pretreatment has been explained in the article.