I. Kruger, Inc.

Jun 17, 2019
Michele Kline

EXELYS is an innovative technology for sludge thermal hydrolysis. Thermal sludge hydrolysis has been recognized as being one of the most effective ways to enhance biogas production and solids destruction in anaerobic digestion systems. Through its design and continuous operational configuration, EXELYS is an energy-efficient technology for thermal sludge hydrolysis. Due to the unique characteristics of the hydrolyzed sludge product, EXELYS provides a solution for significantly increasing the capacity of existing digestion systems. EXELYS can help utilities achieve the full potential of renewable sludge energy.

EXELYS Overview

The EXELYS process is a continuous thermal hydrolysis system that operates in a temperature in excess of 130°C and at pressures greater than 130 psi. Thermal hydrolysis breaks down a fraction of the organic matter and results in a sludge form that is more biologically available. This means that biogas will be formed at a higher rate during digestion. The process requires energy, but the majority of this comes from waste heat utilization. The EXELYS system is heavily insulated, resulting in minimal heat losses and also allows the flexibility to place the system outdoors.

What are the benefits to implementing your technology?

EXELYS offers the following advantages over conventional anaerobic digestion:

  • Lowers sludge viscosity, increasing existing digester capacity up to 100% and enhancing mixing. This offers municipalities a streamlined plant design, reduced capital, and lower operations and maintenance expenses.
  • Improves biodegradability, increasing volatile solids reduction up to possibly 65%. This increases biogas production, allowing for greater energy production to be used onsite or exported.
  • Meets Class A requirements which create a pathogen-free end product. EXELYS opens disposal routes for municipalities, decreasing risks associated with sludge removal.
  • Improves dewaterability producing from 28-40% dry solids, reducing hauling costs in sludge disposal and decreasing a plant’s environmental impact by reducing truck traffic and carbon emissions relating to transportation.

Has the technology been tested, demonstrated, or implemented to date?

Testing, demonstration, and implementation of the EXELYS process has been and is being performed at the following locations:

  • Holbaek, Denmark
  • Hillerod, Denmark
  • Bonnueil, France
  • Lille, France
  • Versailles, France
  • Billund, Denmark
  • Ljublanda, Slovenia

Small-scale pilot testing was performed at the Holbaek, DK WRRF. The pilot testing operated over a nine month period in 2009 and proved EXELYS concept by achieving the required hydrolysis process conditions and similar results as batch type systems while under continuous operation.

A full-scale demonstration facility was constructed in Hillerod, DK. The demonstration plant proved the concept of the DLD process configuration, along with its ability to be integrated within an existing sludge treatment process. It also proved that EXELYS could operate continuously and effectively for an extended period of time. Kruger presented papers at WEFTEC with results from this demonstration plant. These papers are available upon request.

Four EXELYS projects have been sold and implemented in Europe. One project has started and is almost fully operational. Three other installations are in the design or construction phase. All of these are expected to be in operation by mid-2016.


The next step to really advance the technology would be the installation of a full-scale EXELYS project within the U.S. Although widely accepted within Europe, thermal hydrolysis is relatively new to the U.S. market and needs to be further proven at multiple size municipalities allowing operators to personally experience the thermal hydrolysis process.
Michele Kline
Vice President of Product Delivery
I. Kruger Inc.



Michele Kline
Vice President of Product Delivery
I. Kruger Inc.