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Bioresource-based energy: from energy vectors to molecules of interest

Wet Biomass

Published on 7 May 2019

Since 2011 Liten has been working on recycling very wet biomass—which contains more than 50% moisture—into energy or chemical molecules of interest. This biomass includes organic waste from the farming and food industries, urban waste, microalgae, and other high-moisture-content material that is not frequently recycled. And the benefits are both environmental and financial.

Our wet biomass recycling research looks at two methods:

  • Hydrothermal liquefaction, a bio-oil manufacturing process that leverages the moisture contained in organic waste to liquefy the material at high pressures and temperatures (30 bars to 200 bars and 250 °C to 350 °C).

  • Supercritical gasification, which takes place above 374 °C and 221 bars; the result is a combustible H2/CH4/CO2 gas blend.

These processes make use of both the organic and mineral components of wet biomass. However, several obstacles to industrial scale-up remain, one of which is cost (due to the need for high-pressure treatment, for example). The waste-to-energy industry is shifting rapidly, and these technologies are bound to play an important role.

Our researchers are developing pilot units for potential industrial applications. In 2015, a pilot continuous-liquefaction unit with a capacity of 2 liters/hour was built, enabling our labs to go beyond research previously conducted in closed autoclave-type systems. The process was successfully tested on microalgae and fruit residues from the food industry. The next step will be to test the process on other bioresources. Liten’s in-depth knowledge of processes under pressure, chemistry and petrochemistry (oxidation, hydrolysis, oil characterization), and analytical techniques have been crucial to this research.


Recycling wet biomass can help companies boost their bottom line while reducing their impact on the environment

  • Recycling wet biomass generates high returns—in terms of both environmental impacts and costs—and resources are in ample supply. In the farming and food industries alone, 20% of global production is wasted.

  • Hydrothermal liquefaction is high-yield and the energy produced is of a high quality. It also makes optimal use of resources. The reaction produces little residue and the water contained in the resource is used as the reaction medium. The process is therefore energy-efficient and offers better recycling of carbon-containing waste material.

  • The process can also be used to make high-added-value molecules that have the potential to substantially improve industrial facility profitability.


  • LiqHyd is researching ways of recycling fruit residues using hydrothermal liquefaction. Liten is expanding experimentation to fruits other than the blackcurrant, grape, and olive waste tested until now. The project also involves the Drôme Chamber of Commerce, A3I, and IRCELyon and is funded by the French National Research Agency (ANR).

  • Diesalg focuses on bio-oil production via hydrothermal liquefaction of microalgae at high pressure and at temperatures of around 300 °C. The oil obtained boasts an excellent higher calorific value. The process applied to microalgae offers real potential since algae grows 40 times faster than land-based biomass and offers very high yields. Liten is working with several industrial partners (GEPEA, Algo Source) on microalgae projects. Diesalg is funded by the French National Research Agency (ANR).

  • Vasco 2, which also involves Liten, aims to recycle the CO2 produced by plants in Fos-sur-Mer (near Marseille) by growing marine microalgae. The microalgae are transformed using hydrothermal liquefaction, producing refined raw materials for the bio-based chemical market. It is funded by the French National Energy Agency (ADEME).

  • Enerlig is looking at ways of recycling black liquor—a waste product from pulp and paper processing—using hydrothermal liquefaction or gasification. The process achieves higher energy yields than the leading evaporation-combustion process and produces molecules of interest like phenols, which manufacturers can use to make resins, glues, and plastics. This process can increase profitability in the paper industry, where 10% to 15% of process residues can be used to produce high-added-value molecules. Liten is working in conjunction with the Grenoble Institute of Technology Pagora Pulp and Paper Engineering School on this project, which is funded by the French National Research Agency (ANR) and the Instituts Carnot.

  • Two patent applications in progress on the hydrothermal liquefaction technique

  • Publications:

Huet M, Roubaud A, Lachenal D. January 2015. Conversion of sulfur-free black liquor into fuel gas by supercritical water gasification. Holzforschung 69 (6).
Hognon C, Delrue F, Texier J, Grateau M, Thiery S, Miller H, Roubaud A. February 2015. Comparison of pyrolysis and hydrothermal liquefaction of Chlamydomonas reinhardtii. Growth studies on the recovered hydrothermal aqueous phase. Biomass and Bioenergy 73(0): 23–31.
Delrue F, Li-Beisson Y, Setier P A, Sahut C, Roubaud  A, Froment K, Peltier G. May 2013. Comparison of various microalgae liquid biofuel production pathways based on energetic, economic and environmental criteria. Bioresource Technology 136: 205–212.