Novel Biofuels Derivation and Characterisation From Macadamia Integrifolia, Undaria Pinnatifida and Tree Mulch via Advanced Pyrolysis

Price hikes, stringent emission regulations and the global demand for sustainable energy use have forced fuel researchers and vehicle manufacturers to explore sustainable fuels for internal combustion engines. In recent years, the exploration of waste-to-energy (WtE) derivations has attracted increasing interest. This study explored the derivation of pyrolysis oil from three waste biomasses: waste macadamia nutshell (WMN; macadamia integrifolia), waste tree mulch (WTM) and waste marine biomass (WMB; Undaria pinnatifida). The waste biomass-derived pyrolysis oils were characterised by key fuel properties with a target to recommend them for use as fuels in internal combustion engines. Simultaneous and detailed characterisation of three unique biomass-derived oils has not been widely examined and reported earlier in the literature. All tested properties of the three waste biomass-derived oils were compared with those of the American Society for Testing and Materials (ASTM), European (EN), Australian diesel and EN biodiesel standards. The properties of the three oils were aligned with diesel and biodiesel fuel standards. Fourier transform infrared (FT-IR) and gas chromatography–mass spectrometry (GC–MS) data indicate that all three pyrolysis oils contain aliphatic (alkanes and alkenes) and aromatic (mono-, di- and polyaromatic) compounds. Among the three biomasses, a maximum of 53% bio-oil was produced with WTM, followed by 52% with MNS and 44% with WMB. The cetane index, density, viscosity and boiling range of the three pyrolysis oils were comparable to those of traditional diesel fuel and EN biodiesel standards. It is interesting to note that the bio-oil from WTM showed the highest cetane index of 55 among all the tested fuels and biodiesel and diesel standards. However, the other properties, including sulphur, carbon and ash content, indicate that the oils need upgradation before they can be used as a replacement for diesel fuel in internal combustion engines.