In Frielas, thermal hydrolysis transforms sludge into a resource

In Frielas, yesterday’s sludge becomes tomorrow’s energy.

In Frielas, near Lisbon, Luságua (Aquapor), a subsidiary of the Saur group, has just been awarded the contract to build Portugal’s first thermal hydrolysis plant. It will convert sludge from the wastewater treatment of 700,000 residents into green energy and agricultural biosolids — an investment of €28.7 million.

07.04.2026

This wastewater treatment plant operates 24 hours a day, 365 days a year, treating the wastewater of nearly 700,000 residents of Greater Lisbon, spread across six municipalities: Amadora, Lisbon, Loures, Odivelas, Sintra and Vila Franca de Xira. But this spring, something is changing. A contract has just been signed to build Portugal’s first thermal hydrolysis unit there.

What the eye does not immediately see is what remains after treatment: the sludge. Tons of concentrated organic matter, which treatment plants traditionally recover for use as agricultural fertiliser or for composting, but whose energy potential has remained largely untapped until now. With this new plant, the sludge will become a fully-fledged energy resource.

Result

The sludge produced at the end of any wastewater treatment process becomes a valuable energy resource in its own right.

So how does it work?

The principle is to subject the sludge to intense heat and controlled pressure to achieve deep disintegration. What was once waste is now a resource.

Up to 52% reduction in sludge volume for treatment

Up to +13.3 GWh/year of green energy produced through biogas recovery

Stabilized agricultural biosolids, suitable for direct land application.

António Cunha, CEO of Aquapor, states that this project represents a significant opportunity to implement innovative sludge treatment technology in Portugal, reinforcing our commitment to delivering sustainable and efficient solutions within the wastewater sector.

In just one year, Saur has deeply anchored its presence in Portugal through desalination in the Algarve, resource recovery in Albufera, and industrial water reuse.

These projects illustrate, site after site, a shared conviction.

"Water is no longer just a service. It is a strategic resource, at the heart of resilience, sovereignty, and sustainable growth. At Saur, we position ourselves across the entire value chain: where water, energy, and resource recovery converge. "

Luis de Lope

CEO of Saur International