Combating PFAS and Utilizing Phosphorus with Pyrolysis

Excess sludge from wastewater treatment and digestate from biogas production is utilized as fertilizer in farming due to its high phosphorus content. However, this type of sludge may contain harmful PFAS. For this reason, Danish district-heating company – DIN Forsyning – decided to combat this issue by establishing a large-scale pyrolysis plant from local partner, Dall Energy. With this solution, they aspire to achieve 16,500 tons in CO2-reductions and produce 8,000 tons biofertilizer, annually. A technology that is ready to be exported to the UK and EU.

Near the Danish west coast, district-heating company DIN Forsyning operates 16 treatment plants in Esbjerg and Varde municipalities which treat about 22 million m3 of wastewater in total, each year.

In the treatment process, 15,000 tons of excess sludge with high phosphorus content are produced, and its high nutrient value makes it a valuable fertilizer for UK and EU-agriculture.

Significant CO2-Reductions for Agriculture

Unfortunately, there is a risk that the sludge may contain PFAS and other environmental contaminants – adding to the agricultural industry’s CO2-emissions and potentially polluting the soil and groundwater.

Given the substantial amount of sludge involved, it was crucial for DIN Forsyning to ensure that the sludge’s positive effects were not wasted, but instead could continue to contribute to the community.

“We decided to solve this issue with pyrolysis technology. During pyrolysis, sludge is heated to 650°C, followed by combustion of the pyrolysis gases at over 1,000°C. Studies have shown that compounds such as PFAS breaks down under the intense heating. Furthermore, we preserve the sludge’s important phosphorus content. The residue after sludge pyrolysis is biofertilizer. The biofertilizer binds carbon from the sludge instead of emitting it as CO2. So, we also expect that CO2-emissions from our wastewater sludge could be reduced by up to 16,500 tons a year, which is quite significant,” explains Project Manager and Business Developer Kim Stenholdt Madsen from DIN Forsyning.

Forward-Looking Technology with Enormous Potential

The Danish biomass and pyrolysis-technology company, Dall Energy, will deliver the plant, while the development project is supported by the Danish Energy Agency (in Danish: Pyrolysepuljen).

It is an entirely unique solution and facility. It is expected to be operational by 2026, and furthermore it is expected to be the first of its kind, globally – breaking ground for others to follow.

“Dall Energy is incredibly proud of this project for DIN Forsyning and the support from Pyrolysepuljen. We have developed a technology that converts waste streams into energy and other useful products. This solution for the DIN Forsyning-plant is an excellent example of how we can turn waste-water sludge into an environmentally friendly and efficient solution for agriculture. Credit to DIN Forsyning for being forward-looking and for embracing the value of pyrolysis technology. A technology with enormous potential – not only in terms of wastewater sludge, but also for CCS and for the utilization of excess fibers from biogas production”, Managing Director from Dall Energy, Jens Dall Bentzen states.

“In addition to wastewater sludge, the pyrolysis plant will also be able to utilize by-products from farms as an auxiliary fuel. This increases the amount of biofertilizer which contributes to CO2-reduction in agriculture. Moreover, the plant will be able to produce a considerable amount of process heat, which can replace fossil fuels for industrial purposes or district heating,” Kim Stenholdt Madsen adds.

Facts and figures

  • DIN Forsyning produces 15,000 tons of excess sludge with wastewater treatment, annually.
  • CO2-emissions from wastewater sludge to be reduced by up to 16,500 tons per year.
  • The plant is expected to produce approximately 8,000 tons of biofertilizer, annually.
  • The biofertilizer has a Carbon, Capture & Storage effect, positively impacting CO2-reduction.
  • The plant will be capable of producing process heat, which can replace fossil fuels.
  • The process is designed to process biogas fibers, sewage sludge, and farm waste.