A review on the production and application of tall oil with a focus on sustainable fuels

The world's rapid energy demand through overpopulation and industrial development, coupled with environmental trends to reduce fossil fuel reliance, has created a global need for renewable and sustainable fuel sources. As researchers, governments, and industries look towards non-edible oils as a source for biofuels, the pulping industry by-product, tall oil, has promise as a feedstock. This review provides an overview of tall oil production from woody biomass, tall oil purification, and treatment of refined tall oil for biochemistry, bioenergy, and miscellaneous applications. Further, this review investigates the recent trends and barriers toward tall oil-derived biofuels. Tall oil and its components currently contribute to the circular bioeconomy through several applications, primarily being biochemicals. Recent commercialization of stand-alone tall oil biorefineries has demonstrated that biodiesel is the main pathway for tall oil-derived fuels, however, experimental gasoline and jet fuel pathways have shown promise in meeting fuel standards. Limited studies have co-processed tall oil biocrude with petroleum intermediates, facing challenges to stay within fuel specifications. Showing technical feasibility as a fuel source, tall oil's by-product nature has an economic and legislature-supported advantage over other biofuel sources, being closer to competing with fossil fuels. Yet tall oil's inflexible global supply as well as demand from biochemical industries may cause future supply chain challenges. The lack of political commitment and scaling uncertainty pose further barriers for tall oil-derived fuels that must be overcome to contribute to biofuel demand in future years.