Exploring a range of UK seaweed species for the production of fuels and fertiliser

Displacing crude oil in the fuel industry is vital for ensuring global energy security. Hydrothermal liquefaction (HTL) of macroalgae has been shown to generate bio-crude oils that can potentially be co-refined with mineral crude, or upgraded to hydrocarbon biofuels. HTL utilises water as one of the reactants, and produces four clear product phases which all have economic value and could potentially be used as a basis for a future biorefinery. Alongside the bio-crude oil, these comprise a gas phase (predominantly CO2), a solid residue containing carbon and most of the inorganic material, and a water phase. This contains a range of dissolved elements, including K, Mg, N and P, which are all classed as vital macronutrients for plant growth. The distribution of elements in each of the four phases is highly susceptible to the HTL operating conditions.
This project aims to examine a range UK-based macroalgae species to identify a suitable feedstock for a UK HTL biorefinery. HTL reaction conditions were optimised to give maximised bio-crude yields using the brown macroalga Ascophyllum nodosum. Aqueous phase macronutrient content was also considered, with a view to utilise the aqueous phase as an industrial fertiliser. A range of South West UK macroalgae species (belonging to all three major macroalgae classes: green, brown and red) were subsequently screened, with energy and nutrient balances carried out.
Ultimately, a biorefinery design incorporating macroalgae cultivation, harvesting and processing will be finalised, and a Life Cycle Assessment (LCA) carried out to quantify the system’s overall environmental impact.