Sludge biochar

Innovative solution for the treatment of your wastewater treatment sludge

Currently in Finland and Sweden, municipal wastewater treatment sludge is mainly composted or anaerobically digested in biogas plants to produce soil amendments and biogas. However, these technologies do not eliminate hazardous substances, such as PFAS, from the sludge, which then end up in the nature when the soil amendments are used in the fields. Therefore, innovative solutions, such as pyrolysis, are needed for sludge management. Pyrolysis turns sewage sludge into biochar and heat, which can both be utilized in a safe and environmentally sound manner.

What are the PFAS substances?

The per-and polyfluoroalkyl substances (PFAS) are a group of chemicals used to make fluoropolymer coatings and products that resist heat, oil, stains, grease, and water. These chemicals contain carbon-fluoride bondage, which makes them very persistent in the environment.


How does it work?

AquaGreen offers the world’s first integrated steam-drying and pyrolysis plant that upcycles wastewater sludge and wet biomass into biochar and heat. In short, HECLA® Setores-technology works like this:

  1. DRYING: First, the biomass is dried with 200°C superheated steam in an oxygen-free atmosphere. The process takes two hours and is free from malodor. The generated surplus steam is condensed, recovering the thermal energy for local- or district heating.
  2. PYROLYSIS: Next, 650°C pyrolysis for 20 minutes eliminates pollutants, while generating biochar and thermal energy.
  3. FLUE GAS TREATMENT: Finally, flue gases are treated according to environmental legislation.

With a highly stable carbon content, our biochar ensures effective carbon sequestration. It’s odorless, nutrient-rich, and versatile, and can be used for soil improvement, fertilization, and/or as activated carbon in wastewater filtration.

The benefits of pyrolysis

AquaGreen’s pyrolysis treatment

  • supports environmental protection. It removes harmful substances like microplastics, pharmaceuticals, pesticides, and PFAS from the sludge.
  • combats the climate crisis. It prevents waste from releasing greenhouse gases, captures atmospheric CO₂ and stores it in the biochar for millions of years.
  • plays an important role in resource preservation, recycling scarce minerals such as phosphorus.
  • reduces manpower and carbon footprint, offering an intelligent sludge management solution.

The AquaGreen technology is developed and patented jointly with the Technical University of Denmark.

HECLA® Setores systems are already in operation in Denmark, and several plants are currently being designed and built for projects in Sweden.

Produced biochar, with a highly stable carbon content, ensures effective carbon sequestration. It’s odorless, nutrient-rich, and versatile, and can be used for soil improvement, fertilization, and/or as activated carbon in wastewater filtration.

Co-operation between AquaGreen and GRK

GRK and AquaGreen are collaborating with sludge-based biochar plants in Finland, Sweden, and Estonia. We are offering a treatment of sewage sludge to biochar based on a service-based model as a turnkey solution.

What’s in it for you?

  • No need to make your own investment – we offer you a turnkey solution.
  • You reduce pollution and health risks.
  • You eliminate greenhouse gas emissions and capture CO2.
  • You recover energy and recirculate nutrients.

Would you like to know more? Please contact us.

Christian Wieth
Chief Marketing Officer

AquaGreen is a Danish Cleantech company that has developed a patented integrated steam-drying and pyrolysis solution treating wet biomass. Initially we focus on municipal wastewater sludge.

Anneliina Kupiainen
Business Development Director, Environmental Technology
+46 725 8437 40

Annika Sormunen
Program Development Manager, Environmental Technology
+358 44 331 8877

GRK designs, repairs, maintains, and builds roads, highways, tracks and bridges to make everyday life run smoothly, get people to meet each other and make the future more sustainable. Our expertise also includes environmental technology business. We have nearly 1,000 professionals in Finland, Sweden, and Estonia.