Torrefaction of fruit waste seed and shells for biofuel production with reduced CO2 emission

This study investigated the torrefaction of fruit waste of Mangifera indica seeds (MIse) and Passiflora edulis shells (PEsh) at different temperatures (210-300 degrees C) and reaction times (30 and 60 min) to produce biochar as an ecofriendly renewable energy resource. The results confirmed that the torrefaction temperature had a greater influence on the torrefied biomass than the torrefaction times. With the increase in the torrefaction temperatures and times, the H/C and O/C atomic ratios of both biochar were comparable to those of lignite. The thermal stability of PEsh was considerably higher than that of MIse. Moreover, both biochar samples exhibited an increased fuel ratio (FR = 0.02-0.17) and a high energy return on investment (EROI = 11.5-28.5). The greenhouse gas (GHG) emissions caused by the combustion of the obtained biochar were considerably lower than those caused by the combustion of coal. Cofiring 10%-20% biochar with coal yielded FRs close to that of bituminous coal and effectively mitigated GHG emissions. In sum, PEsh as a bioenergy feedstock is a feasible partial substitute for bituminous coal in power plants because of its higher fixed carbon content, energy density, FR, and EROI as well as lower GHG emissions compared to MIse. (C) 2021 Elsevier Ltd. All rights reserved.