UNRAVEL – UNique Refinery Approach to Valorise European Lignocellulosics

The UNRAVEL project aims to develop advanced pre-treatment, separation and conversion technologies for complex lignocellulosic biomass. The technology relies on pre‑extraction, fractionation using low-temperature acetone and subsequent downstream processing to isolate and convert the lignocellulosic constituents into high-value applications. This will produce usable lignin fragments and monomeric sugars from the cellulose along with a hemicellulose fraction suitable for biochemical conversions.

It will bring together specialists with expertise of the entire value chain from feedstock composition, chemical pulping and pre-treatment, enzymes production, polymer chemistry, separation and reactor engineering, techno-economic and sustainability assessments and knowledge dissemination, exploitation and communication.

Unraveling flexible fractionation of lignocellulose

Lignocellulose represents a large proportion of the renewable raw materials on earth. The full utilization of lignocellulose as a raw material in the bioeconomy requires efficient and flexible processes of fractionation into the components cellulose, hemicellulose and lignin. In the BBI-EU project UNRAVEL, the novel FABIOLA™ organosolv digestion of lignocellulose was piloted for the first time. Acetone is used as the solvent. Compared to ethanol, it can be used at milder temperatures and the energy required for solvent recovery is reduced.

Birch as raw material for use in the pilot plant.
© Fraunhofer CBP
Birch as raw material for use in the pilot plant.

Successful scale-up of the flexible process

The concept was scaled up using the unique integrated pilot plant at Fraunhofer CBP. By integrating a pre-extraction step, it was possible to use complex feedstocks and residual materials such as birch wood with bark and branches or wheat straw. A mix of these raw materials was successfully processed as well. This demonstrated the flexibility of the process, which is a major advantage for industrial implementation.


Reprocessing and utilization of all three fractions

For the precipitation of lignin from the fractionation liquid, a process for continuous precipitation by evaporation of the solvent, patented jointly with the Max Planck Institute for Dynamics of Complex Technical Systems, was successfully transferred to the acetone process. After enzymatic hydrolysis of the cellulose, fermentation of the resulting glucose to acetone was successfully demonstrated on a 100-liter scale. The hemicellulose was fermented to xylic acid. The lignin was tested by the project partners CNRS and Soprema for applications in polyurethane foams and bitumen.



The demonstration of the FABIOLA™ process at the CBP pilot plant provided promising results. If the techno-economic evaluation and life cycle assessment of the concept in the project are successful, the stage is set for industrial implementation.

fractionation of lignocellulose
© Fraunhofer IGB
Equipment for the scale up of lignocellulose fractionation processes at Fraunhofer CBP
Recovered lignin on the filter press.
© Fraunhofer CBP
Recovered lignin on the filter press.
Hemicellulose filtrate after lignin precipitation.
© Fraunhofer CBP
Hemicellulose filtrate after lignin precipitation.


[1] Smit, A.; Huijgen, W. (2017) Effective fractionation of lignocellulose in herbaceous biomass and hardwood using a mild acetone organosolv process, Green Chemistry 19, (22), 5505-5514

[2] Schulze, P.; Leschinsky, M.; Seidel-Morgenstern, A.; Lorenz, H. (2019) Continuous separation of lignin from organosolv pulping liquors – combined lignin particle formation and solvent recovery, Ind. & Eng. Chem. Res., 58, (9), 3797-3810

Project information

Project title

UNRAVEL – UNique Refinery Approach to Valorise European Lignocellulosics


Project duration

June 2018 – May 2021


Project partners

  • Netherlands Organisation for Applied Scientific Research TNO, Petten, The Netherlands (Coordination)
  • Fraunhofer Center for Chemical-Biotechnological Processes CBP, Leuna, Germany
  • Celignis Ltd, Limerick, Ireland
  • Metgen OY, Kaarina, Finland
  • Soprema, Strasbourg, France
  • Institut für Energie- und Umweltforschung Heidelberg GmbH, Heidelberg, Germany
  • Rita Clancy (EURIDA), Berlin, Germany
  • Centre national de la recherche scientifique CNRS, Paris, France
  • Sappi, Lanaken, Belgium
  • Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V., Germany


The project “UNRAVEL“ has received funding from the Bio Based Industries Joint Undertaking (JU) under grant agreement n° 792004. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Bio Based Industries Consortium.