Aarhus Universitets segl



The Sludge2Fuel project is funded by the Energy Technology Development And Demonstration Programme – EUDP Fund Denmark 2021-2024. The project will in collaboration with Crossbridge Energy A / S, Fredericia Spildevand & Energi, Circlia Nordic, Krüger and Aarhus University establish a demonstration plant based on HTL technology developed by Circlia Nordic. The plant is set up at Fredericia Spildevand & Energi, where wastewater sludge will be processed into an oil base, which will be refined at the Crossbridge Energy A / S refinery in Fredericia.


Sludge2Fuel is a comprehensive demonstration project to validate the world’s first full scale implementation of the direct conversion of wet wastewater sludge to sustainable fuels. Key is an innovative modular technology for decentralized Hydrothermal Liquefaction (HTL) of wastewater sludges to produce liquid fuels and fertilizer. Sludge2Fuel spans the full value chain from wastewater sludge to the use of the refined fuels. Innovative new solutions to integrate the HTL technology into existing fuel refining operations are implemented at full scale thereby fast tracking the launch of the technology to the commercial market and allowing modern fuel refineries to become a key part of the green transition.

HTL conversion of wet waste streams, e.g. wastewater sludge, into a renewable biocrude, is a key step towards implementing a circular economy and will contribute to making Denmark independent of fossil fuels. At the same time, the technology can prevent harmful substances such as microplastics pathogens and residual pharmaceutical compounds entering the environment. The production of liquid fuel using HTL is favorable to competing technologies. The resulting biocrude contains 7-8 times the amount of energy that is consumed to produce it, has a >80% reduced carbon intensity compared to fossil fuels, and are cost competitive in many cases even to fossil fuels. HTL implementation at the wastewater treatment plants (WWTP) will be commercially favorable due to reduced sludge disposal costs as well as providing an income in sale of the biocrude to the refinery, which will benefit financially from the price premium for green fuels to customers. Furthermore, the project will show how this product is upgraded to transportation fuel in a modern refinery using green hydrogen, thereby providing a commercially attractive pathway to operate renewable oil refineries.

The project will create the foundation for the commercialization of this technology both in Denmark and internationally. Modular, decentral HTL plants will be produced and sold by Bio2oil either directly or via service providers. The produced biocrude will provide the sustainable feed for the next generation refineries like Shell, who see a large potential in upgrading with green hydrogen to provide sustainable fuels for the market, and thus help to meet the meet the requirements set forward in the EU RED II agreements. Implementation and integration knowhow of the HTL technology at WWTP’s will be a major future business opportunity for Krüger both nationally and abroad through the global distribution of Veolia Business units