Phosphorus recovery in algae-based biofuels

About the project

Replacing fossil fuels with sustainable fuel from biomass requires both innovative technological solutions and a feedstock that does not put too much strain on food production and land use. Hy­drothermal liquefaction, HTL, is a technology for producing biofuels that has been gathering increasing interest, and by using seaweed (macroalgae) as a feedstock it is a promising option that fulfils both previously mentioned criteria. Using macroalgae has the added benefit of remediating eutrophic coastal waters since the macroalgae during marine cultivation absorb some of the excess nutrients from the surroundings.

The main culprit in eutrophication is phosphorus, which is primarily used in fertilizers and ends up in the environment from agricultural runoff. After the HTL of the macroalgae, the phosphorus can be recovered and used to produce struvite, a natural fertilizer that can replace the conventional mineral fertilizer.

The purpose of this study has been iden­tify profitable and environmentally friendly technological solutions connecting phosphorous recov­ery with macroalgae processed with HTL and at the same time diver­sify the products outcome of biofuel production.

The project consisted of a comprehensive analysis of available phosphorus recovery technologies through a literature review and citation network analysis as well as modelling of one phosphorus recovery technology. Three different options of the chosen phosphorus recovery were assessed where the economic performance was evaluated by comparing the operating cost for the different options and the environmental im­pact was evaluated by comparing cumulative energy demand (CED), global warming potential (GWP) and eco-indicator99 (EI99).