Circular Economy and Me – Issue 19
Sustainable Transformation: Converting Biomass into Bio-oil and High-Value Chemicals by Samson Akpotu
Imagine a world where agricultural waste, forestry residues and lignocellulosic biomass are not discarded but transformed into platform chemicals and valuable fuels. This is no longer a distant vision. Through hydrothermal liquefaction (HTL), we can efficiently convert lignocellulosic biomass into biomass and bio-oil, a renewable and energy dense fuel creating a truly circular and sustainable circular economy. However, the produced fuel and chemicals can be improved upon, through catalytic upgrade of bio-oil, we can unlock a new generation of high value chemicals and olefins, which reduces our reliance on fossil fuels derived resources, while lowering environmental impact. This transformation will pave the way for a cleaner and more resilient future.
1. Transforming Biomass into Energy-Dense Bio-Oil: A Revolutionary Process in Green Chemistry
HTL is revolutionizing biomass valorisation by offering a unique advantage over traditional pyrolysis, which requires dry feedstocks. Unlike pyrolysis, HTL (Figure 1) operates in supercritical water, efficiently breaking down complex lignocellulosic structures such as cellulose, hemicellulose, and lignin into bio-crude. This eliminates the need for energy-intensive drying steps, reducing overall processing costs. Even more promising is the ability to recirculate the aqueous phase, enhancing bio-oil yield and quality while conserving water. This process does not only maximise energy recovery, but it also integrates seamlessly with existing refinery infrastructure, making bio-oil a viable alternative to fossil-based fuels. However, raw bio-oil contains high levels of oxygenates, acids, and unstable compounds, which limit its direct use as fuel. This is where catalytic upgrading is vital in transforming bio-oil into hydrocarbons, olefins, and industrially valuable chemicals through hydrodeoxygenation (HDO), catalytic cracking, and reforming. This innovative approach is revolutionising how biomass resources are being utilised, transforming agricultural waste into valuable energy carriers.
2. Catalytic Upgrading: From Bio-oil to High-Value Chemicals
As the global chemical industry shifts toward sustainability, catalytic upgrading of bio-oil has become a key enabler of this transition. The effectiveness of this process hinges on advanced catalytic systems, including transition metal-based catalysts, zeolites, and alkaline metal modifiers. These catalysts selectively deoxygenate bio-oil, stabilize reaction pathways, and improve compatibility with existing petrochemical processes. Thus, resulting into a cleaner, more refined bio-oil with reduced acidity and improved fuel properties. This approach does not only produce fuels, it also creates high-value chemicals like olefins, which serve as essential building blocks for plastics, lubricants, and synthetic materials. By replacing fossil feedstocks with renewable alternatives, catalytic upgrading bridges the gap between bio-based resources and the industrial-scale production of sustainable chemicals.
3. Circular Carbon Economy: Closing the Biomass Loop
The real importance of HTL technology and catalytic upgrade lies in its alignment with circular economy, where waste biomass and agricultural residues is not just discarded but repurposed into valuable products. Instead of allowing agricultural residues to decay or be burned, both of which contribute to CO₂ emissions, HTL captures their energy potential and transforms them into useful fuels and chemicals. This is the essence of the circular economy, with HTL and catalytic bio-oil upgrade at its core. Even beyond fuel production, HTL promotes sustainability by recycling water and recovering catalysts, further optimising the process. Furthermore, by recirculating the aqueous phase, carbon efficiency and bio-oil yields can be improved, while recovering valuable nutrients and reaction intermediates for further processing. The catalytic upgrading process ensures that bio-oil-derived hydrocarbons serve as drop-in replacements for fossil fuels, effectively lowering the carbon footprint of industrial operations. This is the foundation of a circular bioeconomy, where biomass waste is continuously repurposed into sustainable and high-value resources. Thus, breaking away from the linear fossil-based economy and create sustainable value chains.
4. Powering the Future: Biomass as a Sustainable Feedstock
Imagine a future where refineries run on renewable bio-crude instead of petroleum, where bio-based olefins replace fossil-derived plastics, and where chemical production operates with a net-zero carbon footprint. This transformative approach could revolutionise the chemical industry through the provision of renewable feedstocks and reducing greenhouse gas emissions. With continued advancements in HTL process optimisation, catalytic upgrading and integrated biorefinery concepts, we are on the path to scalable, cost-effective solutions for bio-based fuel and chemical production.
The future of bio-oil is driven by innovation. By leveraging catalysis and smart process engineering, we can transform lignocellulosic waste into one of the most valuable resources in the sustainable chemical industry. This is not just an alternative; it is a necessity. If we are to achieve a greener, more resilient future, we must embrace the transformation of waste biomass into sustainable fuels and chemicals. The path forward is clear: waste is no longer waste; it is the foundation of a sustainable and more resilient future.
Further Reading:
https://link.springer.com/article/10.1186/s40538-024-00710-w.
https://www.sciencedirect.com/science/article/pii/S1364032120304433.
https://onlinelibrary.wiley.com/doi/full/10.1002/marc.202200247.
https://link.springer.com/article/10.1007/s43621-024-00309-z.