Accessing the Efficacy of Sargassum-Based Aqueous Phase Products Derived from Hydrothermal Carbonisation and Hydrothermal Liquefaction on Plant Growth

James Smith, Amy Pilsbury, Vinod Kumar, Eleni E. Karamerou, Christopher J. Chuck, Leopoldo Herrera-Rodriguez, Julio V. Suarez, Michael J. Allen

Research output: Contribution to journalArticlepeer-review


Mass Sargassum inundations have created opportunities for readily available biomass to be used as a crop enrichment application. However, the heavy metal contents of Sargassum pose serious concerns for crop administration and subsequent human consumption. Hydrothermal processing can break the feedstock components, allowing heavy metals to be partitioned, through the utilisation of high temperatures and pressures. As a result, seemingly nutrient-rich phases can be produced. Elemental analyses showed that Sargassum-derived fractions contain important macro- and micronutrients for plants, particularly ammonium, orthophosphate, and potassium, making them potential nutrient sources for plant growth. To date, no research has investigated the plant growth potential of hydrothermally processed Sargassum products from a bioavailability or biotoxicity perspective. We seek to determine if the aqueous phase products derived following Sargassum processing by hydrothermal carbonisation and liquefaction are toxic to higher plants, and if they can support plant growth. Aqueous phase products in ≥1% concentrations inhibit root growth and lateral root formation in Arabidopsis plants, likely from the presence of inhibitory compounds. However, aqueous phase products in ≤0.1% concentrations paired with an established nutrient mix may provide improved leaf and root growth. Both HTC and HTL were capable of eliciting improved foliage growth, while only HTC induced improved root growth. Conclusively, aqueous phase products lack nutrient potency to allow high dilutions for fertiliser application on their own and may contain inhibitory compounds that deter plant growth at high concentrations. However, they might have a purpose as an additive extract. The recovery of important elements needed for plant growth draws a promising path for future applications of hydrothermal processing with different feedstocks.

Original languageEnglish
Pages (from-to)53-64
Number of pages12
Issue number1
Early online date18 Jan 2024
Publication statusPublished - 31 Mar 2024

Data Availability Statement

The data presented in this study are available on request from the corresponding author.


  • feedstock
  • fertiliser
  • heavy metals
  • HTC
  • HTL
  • hydrothermal carbonisation
  • hydrothermal liquefaction
  • macroalgae
  • phytohormones
  • Sargassum
  • seaweed

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)

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