Sludge mono-processor will recover energy and resources from the waste water of 4 million Flemish citizens

With our sludge strategy, we will take major steps towards the circular economy in the coming years. By 2040, we want to process all sewage sludge with maximum recovery of energy and phosphorus. A new mono-processor to be built in Ghent is the engine for this.

At our more than 300 WWTPs, we produce 95,000 tonnes of dry matter of sludge every year. The activated sludge grows continuously, which is a side effect of waste water treatment. Hower, the sludge that we do not reuse in the treatment process is not waste but a valuable form of biomass. Sludge is rich in nutrients that it stores from the waste water. It is perfectly possible to recover these nutrients and reuse them as resources.


New final processing route from 2040

Today we dry a third of the sludge into pellets that are used as co-fuel in the cement industry. A third is dewatered and burned without extra fuel in the sludge processor in Bruges. The remaining third is also dewatered and incinerated by an external party, along with industrial waste. That will change in a few years. On the ArcelorMittal site in the port of Ghent there will be built a brand new mono-processor.

This new installation will be designed, built, financed and maintained by the BESIX-Indaver consortium. That assignment runs until 2046. In 2026, the sludge mono-processor must be operational and be able to use the biomass from the sludge even more than is currently the case. In a mono-processor, the sludge will not be diluted with other substances, enabling maximum recovery of energy and resources.

Reuse of produced steam

In determining the ideal location of the mono-processor, the ecological arguments were decisive. We took as our staring point a model in which we could see, for each potential location, the CO2-impact of all sludge transportation in Flanders. Also important were the possibilities to make optimal use of the energy produced at and around potential sites, with a view on optimal solution for Flanders as a whole. The initiatives for carbon capture that are in the pipeline in the port of Ghent furhter strengthened ArcelorMittal's position.

In cooperation with Fineg, ArcelorMittal will use 100% of the high-pressure steam produced by the sludge processor. For the steel company, this is an additional energy source for their internal steam network, further reducing the use of fossil fuels.

Sustainable recovery of phosphorus

In a follow-up phase, Aquafin is planning to start up full-scale phosphorus recovery, representing some 2,000 tonnes of pure phosphorus a year. That's a substantial share of the annual consumption in Belgium. Phosphorus is an essential building block for life, being among other things an important component of our DNA, our cell walls and our bones. We ingest it via our food, and it is also a basic component in mineral fertilisers for agriculture and horticulture. Phosphate ores are, however, a finite resource, and with only limited supplies naturally present in Europe. Via our food, phosphorus finds its way into domestic waste water, form where Aquafin will recover it with this new sludge mono-processor.

Expanding to 2040

The sludge mono-processor will initially treat two-thirds of the sludge. By 2040, we want to evolve to 100%. The project is fully in line with Aquafin's ambition to no longer use fossil fuels by 2030 and to evolve towards climate-neutral business operations in the long term.



Sam Geerts

manager Process Engineering