Evaluation of bio-oil/biodiesel production from co-pyrolysis of corn straw and natural hair: A new insight towards energy recovery and waste biorefinery

The present study evaluated the total energy output and economic feasibility of biodiesel production coupled with value-added nitrogen-containing compounds (NCCs) through co-pyrolysis of low- and high-protein biowaste. Corn straw (CS) and human hair waste (HW) were used at different blend ratios of 0%, 25%, 50%, 75%, and 100%, w/w. Individual pyrolysis of HW showed 20.7% higher bio-oil yield than CS due to higher volatiles in HW, while co-pyrolysis resulted in synergistic action which enhanced both bio-oil yield with higher fatty acids/esters proportion. The highest recorded bio-oil yield was 46.3% using 75% HW blend ratio, which showed insignificant difference with that of HW. In addition, co-pyrolysis resulted in reduction of NCCs by 13.7% comparing to HW, with simultaneous enhancement of fatty acids and esters contents by 67.8% and 13.2%, respectively. Therefore, transesterification of co-pyrolyzed bio-oil showed the highest biodiesel proportion of 20.7%, representing 4.7-times and 61.7% higher than CS and HW, respectively. In addition, transesterified co-pyrolyzed bio-oil showed 27.0% NCCs, which was 8.2-times higher than that of CS. Due to the higher calorific value of biodiesel compared to bio-oil, biodiesel of the co-pyrolyzed bio-oil showed the highest total energy output in the biorefinery route (3753 MJ/ton biomass), which was higher than the total energy output from the conventional route of bio-oil production from CS (3738 MJ/ton biomass). However, additional revenue of 39,860 US$/ton biomass was estimated in the biorefinery route due to NCCs fraction, which provides a new insight towards future industrial applications.