Valorization of Palm Biomass Waste for Sustainable Production of Lipase-Carbon Matrices And Biodiesel

The conversion of arable land to produce plant-based biofuels can produce more greenhouse gas (GHG) emissions than the displacing effect that is expected from the use of biofuels instead of fossil fuels. Utilizing agricultural waste offers an alternative pathway to reducing GHG emissions. Typical palm oil mills, for instance, produce palm kernel shells (PKS) and palm oil mill effluents (POME) as wastes in enormous amounts which accounts for > 60% of solid and liquid waste from the mill. Here, we explore the feasibility of a circular palm bioeconomy where waste PKS was directly converted to activated carbons (AC) in a technique (550 °C, under N 2 ) that departs from the conventional two-step (carbonization and activation) AC synthesis route. Using FT-IR, FE-SEM, and EDX as surface analysis tools, the synthesized carbons, PKAC, showed excellent morphological and surface functionalities similar to bituminous coal-derived activated carbons. The 1 – 10 μm pore diameters of PKAC were relevant in the immobilization of Aspergillus oryzae whole-cells expressing recombinant Fusarium heterosporum lipase. For biodiesel synthesis, the higher specific activity of the PKAC-immobilized whole-cell lipase (81.6 IU/mg BSP) ensured the conversion of POME to ≥97.5 wt. % fatty acid methyl ester (FAME). Whilst offering the benefits of cheap immobilization carriers and greener synthesis routes, the produced FAME showed properties (48.8 cetane number) that conform to ASTM and EN specifications. This study thus serves as a framework for the design of hydrocarbon synthesis platforms for a future palm bioeconomy.