Pyrolysis technologies for pomegranate (Punica granatum L.) peel wastes. Prospects in the bioenergy sector

An unpublished low-cost industrial biomass waste, pomegranate peel, as alternative and sustainable fuel source was studied. A horizontal tubular furnace of original design for conventional and flash pyrolysis was carried out. The bio-char yields from both processes were similar, but the bio-oil and bio-gas yields were higher in flash pyrolysis, depending on the temperature. The bio-char obtained show that it could be used as a fuel (higher heating values ≥ 28.0 MJ/kg) and as a potential precursor of activated carbon. It was also found that the lower temperature of the flash pyrolysis was, the greater the bio-oil yield (∼53%) and that the higher was, the greater the biogas yield (∼50%). The bio-oil from conventional pyrolysis has a predominantly furanic nature and contained significant amounts of the phenols and benzenes. In contrast, the bio-oil from flash pyrolysis is similar to that of “anthracene oil”, both of them being composed mainly of polycyclic aromatic hydrocarbons. The bio-gas obtained by flash pyrolysis is of a higher quality than that obtained by conventional pyrolysis because it has a lower CO2 content (32.4% vs 66.6%) and higher syngas content (CO + H2) (50.8% vs 26.8%). Flash pyrolysis is better in CH4 production (11.6% vs 4.6%).