Carbonisation of sewage sludge

The combination of sewage sludge drying and pyrolysis/carbonisation (for example with PYREG®) converts dewatered sludge into valuable carbonate, also known as pyrolysate or "biochar". In several large-scale projects, we have demonstrated benefits that go far beyond simply reducing the volume of sewage sludge.

In contrast to dewatered sludge, biochar is a valuable fertiliser with plant-available phosphorus that is virtually free of organic pollutants such as microplastics. In addition, the carbon it contains is converted into biochar - therefore sequestering CO2.


Production of a high-quality product from sewage sludge

Drying and subsequent carbonisation produces a valuable material that can be used as a soil conditioner. Due to the operating temperatures in the range of 600 to 700 °C, the recovered phosphorus remains available to plants after carbonisation.

In several EU countries such as the Czech Republic, Denmark, Sweden and Australia, the carbonate is already officially approved as a soil conditioner and raw fertiliser material.

Elimination of organic pollutants from sewage sludge

Drug residues, microplastics, PFAS and pathogens are eliminated through thermal treatment in the carbonisation process. You can find evidence of PFAS elimination here.


The lower temperature in the treatment process compared to conventional incineration influences the end product properties. The carbon contained in the sewage sludge is converted into biochar - and therefore CO₂ is sequestered. When sewage sludge is carbonised, the carbon it contains is not released as CO2, but is instead stably bound in the biochar and removed from the atmosphere.

Compared to incineration, carbonisation can save greenhouse gas emissions of around 198 kg CO2 per tonne of sewage sludge. In relation to the amount of sewage sludge produced in Germany, this amount of greenhouse gas emissions is equivalent to the binding capacity of a beech forest with around 48 million trees or a square forest area measuring 97 km by 97 km (Korrespondenz Abwasser, Abfall - 2020 (67) - No. 3).

The production of biochar is one of the "Negative Emission Technologies" (NET) urgently needed for climate protection. If the biochar is permanently incorporated into so-called carbon sinks (e.g. arable soil, building materials, asphalt), the sustainable storage of CO2 is successful in the long term.


  • The dewatered sewage sludge is first dried in the ELODRY® belt dryer to approx. 90 % dry matter.
  • The dried sewage sludge is then converted into valuable biochar in the carbonisation plant.
  • The excess heat generated during the carbonisation process can be used for drying and covers a large part of the ELODRY®'s heat requirement. With the combined installation of both systems and a holistic heat utilisation concept, you can achieve operational savings and an ideal CO2 balance for your entire system.
ELODRY® and carbonisation (using PYREG® as an example)

We have several years of experience in drying and carbonisation projects with a focus on holistic heat utilisation. We can support you with design, planning, construction, commissioning and maintenance.

Contact us

* mandatory field

What is the sum of 6 and 5?
Data privacy declaration of consent*

Our Accomplishments

Total green energy generated in MWh to date

Total tons of avoided CO2 emissions to date

Total number of avoided truck transports to date

Number of patents for our technologies