The Catalytic Process Engineering (CPE) group at PSI participates in a new project dedicated to the development of an entire process chain to produce sustainable liquid fuels based on hydrothermal liquefaction of a broad range of biomass feedstocks. The project was launched in October 2017. Ten partners, including the PSI, from six different European countries collaborate to reach the project objectives. The EUR 5 million project is funded under the European Union’s Horizon 2020 Research and Innovation Action program for a total duration of 48 months.

Need for the HyFlexFuel project

The European Union has set out ambitious targets for renewable fuels and stipulated that they should cover 10% of the final energy consumption in transport in 2020 (Directive 2009/28/EC). Decarbonisation of the transport sector is highlighted as a major challenge in the Energy Roadmap 2050.

Hydrothermal liquefaction (HTL) has recently received increasing attention as a technology option to convert essentially any type of biomass feedstock into liquid fuels without the requirement of prior energy-intensive drying. HTL holds the potential of truly sustainable and cost-efficient production of drop-in capable biofuels at a large scale.

The production of bio-crude from biomass is a well-known process that will benefit from some additional research to understand the relations between different feed stocks, process conditions, yield and quality. In contrast, the upgrading of bio-crude to fuel and the management of residual process water and salts are less mature processes that require basic parametric studies of processing conditions, targeted catalyst development, a novel continuous processing system and development of a process for the catalytic hydrothermal gasification of the soluble organics present in the residual aqueous stream.

The techno-economic performance of the entire HyFlexFuel production chain must be evaluated in order to make comparisons to alternative fuel production processes. Additionally, the social, technological, economic and environmental risks and benefits of the process must be assessed.

A new process to produce sustainable liquid fuels from biomass feed stocks

Liquid biofuel will be produced in a 3-step continuous process comprising 1) hydrothermal liquefaction (HTL) to convert raw biomass to high value bio crude oil followed by 2) upgrading to a deoxygenated, nitrogen and sulfur free bio-oil produced through a catalytic treatment using hydrogen and 3) final fuel production by distillation of the bio-oil or by co-feeding in fossil fuel refineries.

The known advantages of HTL are feed stock versatility and the ability to convert wet materials. Feed stock conversion will be studied during production campaigns using diverse model feed stocks namely Miscanthus, microalgae, and sewage sludge.

Compared to existing technologies to transform biomass to liquid fuels, the HyFlexFuel process improves process economic return through enhanced heat integration and the recovery of residual streams. In particular, standard procedures to recover value from the residual aqueous stream by converting organics (30-50% of starting C) to synthetic natural gas and recovery of inorganics for sale as fertilizer will be developed and assessed in terms of economic and environmental costs and benefits.

The HTL conversion and the bio-crude upgrading steps will be demonstrated in continuous operations. The less mature residual stream valorization processes will be studied to provide the information base for their technical and environmental assessment. An entire work package is dedicated to the holistic assessment of the HyFlexFuel process with the specific objectives of evaluating the applications and market potentials, identifying the technology gaps, conducting systems analysis and assessing technical, economic, environmental and social risks.

Role of the Paul Scherrer Institut

The PSI-CPE has received EUR 750’000 to lead work package n°4 “Valorization of residual streams” and contribute to product characterization in work package n° 2 “HTL Conversion”. The CPE group will convert the organic residues of the HTL process water phase to methane by their catalytic hydrothermal gasification process. The salts contained in the water phase will be separated and collected as concentrated brine, generating an additional value through the possibility of nutrient recovery. Furthermore, PSI-CPE will characterize the aqueous and bio-crude HTL process phases.

Industrial and economic impact

The results of simulation studies conducted Tzanetis et. al. (2017) showed that the lowest cost of jet fuel production from biomass by HTL is 25.1 €/GJ biojet fuel. This benchmark value is approximately twice the cost of conventional jet fuel. Greenhouse gas emissions from bio jet fuel production and use were shown to be only 15% of those from fossil based jet fuel. Improved liquefaction, heat integration and residue recovery processes to be developed during the HyFlexFuel project are expected to improve the process economics. The energy company ENI S.P.A. will contribute to the development of a business case for a fuel production facility based on HyFlexFuel technology.

About the Catalytic Process Engineering (CPE) group at PSI

In the Catalytic Process Engineering group 18 team members, including 4 PhD students, are working to develop new processes to recover energy from biomass and to provide liquid and gaseous energy carriers including transportation fuels. The lab is well equipped with analytical instruments and test rigs for thermal and catalytic treatment of biomass and for separation and precipitation of ionic species. It is one of the leading groups in the field of catalytic hydrothermal gasification. CPE’s research activities range from molecular-level to pilot-scale investigations. Fundamental phenomena in hot compressed water are addressed by, for instance, advanced Raman, EXAFS, or neutron radiography in-situ studies. They have an advanced analytics platform with state-of-the-art high resolution mass spectrometry. A prototype salt separator designed for a throughput of 50 kg/h has been successfully tested in collaboration with KIT on residues from anaerobic digestion in July 2015.

Link to the project web site:


Prof. Dr. Frédéric Vogel, Head, Catalytic Process Engineering Group

Paul Scherrer Institut, OVGA/113, 5232 Villigen PSI, Switzerland

Telephone: +41 56 310 21 35, E-Mail:

Web site:

Text: HyFlexFuel project and PSI-CPE web sites and Mark McCormick