ARIS NC-26001

Optimisation of the Hydrothermal Liquefaction Pathway for Biofuel Production from Microalgae

Principal investigator: dr. Filipa A. Andre Vicente

Content description of the project

Microalgae have long been recognised as one of the most promising natural tools for capturing CO₂ and converting it into renewable fuels and valuable chemicals. They grow rapidly, do not compete with agricultural land, and can efficiently convert carbon dioxide into biomass rich in proteins and lipids. However, despite their potential, microalgae-based biofuels are still not economically competitive. High cultivation costs, limited CO₂ utilisation efficiency, and the production of nitrogen-rich biocrude, which requires energy-intensive upgrading, remain key obstacles.

HYDROTHERMALG addresses these challenges by rethinking the entire process as an integrated and circular system. The project explores the use of deep eutectic solvents (DES) to capture CO₂ directly from industrial streams and improve its transfer to microalgae cultures. Instead of treating CO₂ as waste, the process turns it into a resource. By screening multiple DES formulations, the project aims to significantly improve carbon capture and biofixation efficiency.

At the same time, HYDROTHERMALG tackles one of the major technical limitations of hydrothermal liquefaction (HTL): the high nitrogen content in the resulting biocrude. As proteins are the primary source of nitrogen in microalgae, they are selectively extracted before fuel production. Using DES-based extraction and hydrolysis, the protein fraction is converted into peptides and amino acids, which are then catalytically upgraded into nitrogen-containing platform chemicals for applications in materials, feed, or fine chemicals. This approach not only reduces the need for severe fuel upgrading but also creates additional value streams.

The remaining lipid-rich biomass is converted into biocrude via HTL, while the nutrient-rich aqueous phase generated during the process is recycled back into cultivation. By aiming for full recycling of this stream, the project moves towards a genuinely closed-loop biorefinery concept.

By combining CO₂ capture, selective biomass fractionation, catalytic upgrading, and fuel production into a coherent strategy, HYDROTHERMALG demonstrates how industrial emissions can be transformed into sustainable energy carriers and valuable products. The project contributes to the development of carbon-efficient biorefineries and supports the broader transition towards climate-neutral energy systems.

The project is divided into 4 interconnected WPs, ensuring active cooperation between the two partners:

WP1: Sustainable CO₂ capture and biofixation

NIC will develop DES formulations for CO₂ capture, which CEA will test under simulated industrial conditions to evaluate CO₂ transfer methods in microalgae cultures.

WP2: Protein extraction and conversion

NIC will extract and hydrolyse proteins from the microalgae biomass supplied by CEA and convert the hydrolysates into nitrogen-containing or other high-value products through catalytic processes.

WP3: Valorisation of biomass and recycling of the aqueous phase

NIC will lead the conversion of biomass to biofuel via HTL, while CEA will focus on the adaptation of microalgae for growth using the recycled aqueous phase.

WP4: Project management and dissemination

Both partners will jointly manage the project, monitor progress, address risks and ensure effective dissemination of results.