The challenge of nitrogen compounds in hydrothermal liquefaction of algae

• Published in: The Journal of supercritical fluids 2023-05, Vol.196, p.105867, Article 105867
• Main Authors: Matricon, L., Roubaud, A., Haarlemmer, G., Geantet, C.
• Format: Article
• Language: English
• Subjects: Amino acids reactivity; Biocrude oil; Biofuels; Catalysis; Chemical Sciences; Environment and Society; Environmental Sciences; Hydrothermal liquefaction; Microalgae; Nitrogenous compounds
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/j.supflu.2023.105867

There is a real interest in developing biofuels from microalgae. Their high productivity, lipid content and their capacity to capture CO2 make microalgae a competitive biomass for energy purposes and environmental concerns. Among various valorisation pathways of such biomass, hydrothermal liquefaction (HTL) process attracts interest. This process converts microalgae between 270 and 350 °C, in hot compressed water to produce a biocrude oil, which is then upgraded to produce biofuel. Biocrude oil is mainly composed of carboxylic acids and oxygenated compounds but also contains some cyclic nitrogen molecules or amides which are hard to upgrade and thus detrimental for biofuel quality. Therefore, in addition to the usual problem of oxygenated compounds in biocrude oils, the use of algae introduces another difficulty with the nitrogen compounds. The present review attempts to summarize the nature of the nitrogen compounds in algae, and their transformation during HTL conversion. [Display omitted] •Overview of amino acids degradation pathways during hydrothermal liquefaction.•There is a link between biomass and hydrothermal liquefaction products.•Nitrogen compounds in biocrude oil comes mainly from proteins degradation.•Each amino acid has a specific reactivity in hydrothermal liquefaction conditions.•Some pigments and lipid classes lead to nitrogen compounds in biocrude oil.