Bio-oil production from pyrolysis of oil palm biomass and the upgrading technologies: A review

Oil palm biomass (OPB) represents major portion of the lignocellulosic waste in Malaysia that can be converted into bio-oil. This review aims to provide important insights in OPB-derived bio-oil production by first discussing the chemical compositions of different OPB and their effects to the bio-oil yield and quality obtained from pyrolysis process, followed by discussing the addition of plastics and catalysts into the pyrolysis for bio-oil upgrading, and lastly summarizing the existing technoeconomic and environmental studies and the potential use of process integration and intensification in this topic. Polypropene (PP), low density polyethylene (LDPE), and high density polyethylene (HDPE) have been commonly used in co-pyrolysis of OPB, which can effectively increase the heating value of bio-oil up to 80 % that of diesel. Likewise, acidic, basic, and neutral catalysts have been applied to increase the amount of hydrocarbon and phenol in the bio-oil, further improving the heating value to be comparable to diesel. The bio-oil production from OPB is currently still limited to demonstration scale despite the favorable environmental compatibility and technoeconomic feasibility shown by studies focused on empty fruit bunch (EFB). Several promising advanced pyrolysis processes that integrate other processes such as anaerobic digestion, hydrogen production process, and heat and power generation units as well as the advanced reactor designs are also overviewed here as future innovation of the bio-oil production from OPB, which may play more significant role as the technology matures.