About (the project)

The HyFlexFuel project is 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 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 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 large scale.


The central objective of HyFlexFuel is to advance the technical maturity of the hydrothermal liquefaction technology to provide truly sustainable fuels that are compatible with existing infrastructure (drop-in capable) and that can be produced at competitive costs.

The specific objectives are:

  • Demonstrating HTL conversion compatibility with diverse advanced biomass feedstocks
  • Maturing key subsystems of HTL-based fuel production from TRL 2-4 to TRL 5, including the upgrading of the intermediate product biocrude to final fuel products
  • Demonstrating drop-in capability of HyFlexFuel fuel products
  • Increasing process efficiency through enhanced heat integration and product recovery procedures
  • In-depth understanding of the relation between feedstock and process conditions vs. product yield and quality
  • Efficient valorization of residual process streams, particularly of the aqueous phase from HTL conversion
  • Quantification of technical, socio-economic and environmental performance potentials, risks and benefits
  • Identification of technology gaps and development of an R&D roadmap towards full-scale implementation

The strength of HyFlexFuel lies in the fact that its scope goes beyond the process step of hydrothermal liquefaction and also includes the upgrading of biocrude to fuel products and the energetic and material utilization of the aqueous phase as main residual process stream. Moreover, supply and utilization of a broad range of feedstock is studied in detail. HyFlexFuel will examine the key subsystems in continuous operation under relevant conditions. In combination with an in-depth assessment of environmental, economic and social potentials, the project will thereby generate technology solutions and insights as valuable basis for further developments of HTL-based fuel production towards industrial application.


In HyFlexFuel a threefold approach of experimental work, technology assessment and process modelling is pursued to meet the project’s objectives. All process steps, will be addressed in a holistic way, considering technical, economic, environmental and social risks and potential benefits. The fundamental chemistry of HTL, biocrude upgrading and catalytic hydrothermal gasification (cHTG) will be examined through application of established and novel analysis techniques in the laboratories of the project partners.

The principle relation of research levels in HyFlexFuel is illustrated in the following schematic.

HyFlexFuel Methodologies
The study of feedstock diversity and availability in the EU is performed to analyse the potential impact of HTL technology. The field validation of the HTL-based fuel production process comprises three main subsystems, (1) the HTL reactor, (2) the upgrading subsystem, (3) the valorisation of residual process streams with the cHTG subsystem, anaerobic digestion (AD) and nutrient recovery.

These subsystems are examined in a dual scale approach: Small-scale batch and continuous reactors will enable flexibility in researching the parameter space for optimum conditions. For the pilot-scale field validation in continuous operation mode, the subsystems will be studied in relevant operational environments, also enabling the production of significant volumes of products for downstream analysis, further processing and testing.

The holistic assessment of perspectives towards industrial application is performed for a full-scale model system. The full-scale analysis comprises techno-economic, environmental, and social aspects as well as a business case and risk assessment. These results are embedded in a roadmap towards successful future commercial exploitation.

The work plan

The HyFlexFuel project’s work plan is divided into a total of eight work packages. High-level interrelation between individual WPs is illustrated below:

Work package 01: Feedstock potentials, availability and supply

Objectives of the Workpackage

There is currently no detailed information on whether Europe has a biomass potential for the HTL process. Therefore, this work package represents a starting point for identifying which, where and how many biomass resources are available in Europe for the operation of the HTL process.
WP1 aims to

  • identify promising feedstock for the HTL process in Europe (EU28)
  • identify potential regions of feedstock for the HTL process in Europe
  • describe feedstock supply chains for the HTL process in Europe
  • analyse characteristics and suitability of the feedstocks under investigation for the HTL process

Workpackage Description

HTL processes can be applied to a wide range of biomass feedstock with different characteristics, costs, and regional availabilities. In this WP, promising feedstock for HTL process, their availability and location in Europe will be evaluated. The tasks involved are described in the following.

  • Identification of promising feedstocks (e.g. lignocellulosic biomass, algae, sewage sludge, municipal organic waste, etc.) for the HTL process and their potential assessment in European countries (EU28)
  • Regional assessment of promising feedstocks for the HTL process in the identified countries (EU28)
  • Set of exemplary supply chains to connect identified promising regions with feedstock (supply) and developed HyFlexFuel technology (demand)
  • Provide a comprehensive characterization of the feedstocks identified in the above tasks

Work package 02: HTL Conversion

Objectives of the Workpackage

The overall goal of WP2 is to optimise the production of high value biocrude from multiple feedstocks.

Specific objectives are:

  • to optimize pilot scale HTL system set-up in terms of heat and product recovery
  • to perform biocrude production campaigns
  • to improve HTL reaction parameters, such as water recycling, residence time and temperature
  • to provide a deeper understanding of biocrude composition and reaction pathways, as well as yields and quality

Workpackage Description

AU will use one of the most advanced pilot-scale continuous HTL reactor systems currently running in the world (about 100 L/h). In order to advance HTL-based fuel production to operation under industrially relevant conditions and with high energy and carbon efficiencies, the pilot-scale system will be optmised to integrate feedstock pre-treatment, HTL conversion and product recovery. Three biocrude production campaigns will commence immediately on the model feedstocks (Miscanthus, microalgae, and sewage sludge) in order to provide samples for upgrading and valorisation of side-streams. Fuel products will be thoroughly analysed in order to elucidate chemical reaction pathways. Advanced analytical equipment available at PSI will be employed in collaboration with AU to provide a full understanding of biocrude composition and yields as a function of process conditions and applied feedstock. AU will work closely with DBFZ in order to utilize the most promising feedstocks identified in WP1.

Work package 03: Biocrude upgrading and fuel production

Objectives of the Workpackage

The overall goal of WP3 is to identify and demonstrate the optimal upgrading pathway for HTL-derived biocrude and refining into transport-grade biofuels.
The specific objectives in relation with this goal are:

  • to determine and quantify the optimum process conditions for upgrading the HTL biocrude in terms of temperature, pressure, hydrogen consumption, catalyst type/loading
  • to demonstrate prolonged, continuous upgrading operations and to produce at least 10 to 30 L of upgraded bio-oil
  • to produce drop-in, transport grade biofuels and to test their technical suitability (e.g. testing in an actual engine)
  • to explore the alternative possibility of co-processing of biocrude with petro crude in existing refineries

Workpackage Description

HTL biocrude is a complex product with many different compound classes, highly dependent on the feedstock used for its production and on the process conditions. Biocrude is not suitable for direct use as a transportation fuel, unless proper upgrading is performed. In this WP, transport grade biofuels will be produced through a catalytic treatment with hydrogen. A deoxygenated, nitrogen and sulphur free bio-oil will be eventually obtained. Distillation of such product will give high quality transport-grade fuels. Additionally, an optional pathway will be also explored, where biocrude is used as a co-feed in fossil refineries. This will help using existing infrastructures in a more sustainable way.

Work package 04: Valorisation of residual streams

Objectives of the Workpackage

The overall goal of this WP is to develop a standard procedure for valorising the residual liquid and solid streams of HTL, increasing the overall process efficiency of HTL and minimizing its environmental impact.
Specific objectives are:

  • to analyse and characterize the organics in the HTL process water and map the nutrients
  • to concentrate and valorise the organics by conversion into synthetic natural gas
  • to develop and scale up a procedure for inorganics recovery as fertilizer
  • to provide the information base for the techno-economic and environmental assessment of the most efficient treatment and valorisation of the residual HTL streams including nutrient recycling

Workpackage Description

For a sustainable HTL process, it is of major importance to valorise the organic (30-50 % of starting C) and inorganic residues contained in the process water phase as well as the inorganics in the solid phase. The valorisation of the residual streams of HTL is an underdeveloped process step in the overall HTL conversion chain to date. Both catalytic hydrothermal gasification (cHTG) and anaerobic digestion (AD) are studied and linked to the organics composition of the HTL water phase. Quantitative descriptors of the process waters such as the amounts of organic compound classes are used to decide which valorisation path is best suited for a certain process water.
The three major tasks of WP4 are accordingly:

  • organics concentration in the water phase (Task 4.1),
  • further utilisation of the organics (Task 4.2 and 4.4) and inorganics (Task 4.3) contained in the water phase and solid phase,
  • providing a data set for the environmental and economic assessment in WP5

Work package 05: Performance potential, risk and implementation study

Objectives of the Workpackage

The overall goal of WP5 is to evaluate the techno-economic and environmental performance potential of HTL-based fuel production and to assess the risks associated with development and implementation of the HyFlexFuel technology.

Specific objectives are:

  • to evaluate application and market potentials for HyFlexFuel products
  • to identify technology gaps
  • to conduct a techno-economic and environmental system analysis
  • to assess the technical, economic, environmental and social risks

Workpackage Description

WP5 Performance potential, risk and implementation study concentrates all tasks related to the assessment of the HyFlexFuel technology in terms of economic performance, environmental and social impact, risks and technology gaps. It represents a focal point for results from the technical work packages and integrates these findings in a holistic picture of potentials, limitations and risks associated with the HyFlexFuel value chain.

The following tasks will be carried out in WP5:

  • Technology monitoring, analysis of application potentials and market opportunities
  • Process modeling and system design study
  • Techno-economic and life cycle assessment, environmental impact analysis
  • Assessment of risks and potential benefits
  • Development of a business case for an industrial production facility
  • Holistic, multiple-criteria assessment of techno-economic, environmental and social performance of the HyFlexFuel production pathway

Work package 06: Synthesis of results, recommendations and perspectives

Workpackage Description

WP6 combines and integrates the experimental and theoretical results achieved in all scientific WPs. Overarching conclusions are drawn and recommendations for future R&D efforts on HTL-based fuel production are developed.

Work package 07: Communication and promotion of the HyFlexFuel innovations

Objectives of the Workpackage

Achieve sustainable impact for HyFlexFuel results and innovations beyond the project horizon by

  • Providing the project with appropriate and effective communication media and tools,
  • Promoting the project results with customised contents to the scientific, industry and general public,
  • Community building, actively involving, both the scientific and user communities into a continuous dialogue and fostering the emergence of sustainable cooperation and partnerships beyond the project consortium and lifetime,
  • Mobilising leading experts from different business and industry sectors to participate and contribute to HyFlexFuel workshops, trainings and exploitation events,
  • Supporting the HyFlexFuel consortium in the proactive management of Intellectual Property generated by the project.

Workpackage Description

WP7 will provide appropriate infrastructure and measures enabling targeted communication towards the various stakeholders’ communities. Project IP management and results exploitation activities will be implemented under this WP.

Work package 08: Management and coordination

WP8 provides the project administration, thereby ensuring and facilitating strategic decision making as well as financial and contractual management of the project. WP8 also acts as interface with the European Commission as the funding authority. In terms of scientific coordination, proper interaction between all work packages and partners is ensured and the overall workflow according to the project work plan is coordinated and monitored.