Wood oil biodegradation in the marine environment: Behavior, mechanism, and impact

The demand for biomass pyrolysis oil (e.g., wood oil) is increasing with global carbon neutrality. As shipping of such oils expands, the risk of accidental spills also rises, posing threats to the marine ecosystem. Biodegradation represents the ultimate fate of spilled oil in marine environments; however, the biodegradation behavior and mechanism of wood oil spills and the associated environmental impacts remain largely unexplored. In this study, we assessed the biodegradation of fresh, weathered, and chemically dispersed wood oil under northern Atlantic Ocean conditions (4 °C and 20 °C), comparing it with conventional crude oil Alaska North Slope (ANS). Oil component changes and suspended aggregate formation during biodegradation, and the toxicological impacts of oil post-biodegradation were systematically investigated. Phenols and aldehydes were predominant biodegradable constituents (27 %-56 %) in wood oil, undergoing mineralization and ring-opening. Two oil-degrading indigenous bacterial strains Alcanivorax. sp and Exiguobacterium. sp exhibited similar pathways when degrading wood oil. Wood oil biodegradation formed lignin-based aggregates and altered marine snow structure, increasing benthic exposure potential. Chemical dispersant Corexit 9500A facilitated wood oil biodegradation but showed low dispersion efficiency. Despite faster biodegradation, wood oil residues exhibited tenfold higher toxicity than crude oil. Diminished biodegradation rates at the lower temperature intensified toxic effects, increasing risks to northern communities and the fragile marine ecosystem. This study provides previously undocumented insights into the wood oil spill behavior in marine environments, expanding the knowledge base needed to support marine biofuel spill response planning and associated risk management strategies.