ECLUSE tunnel under the Scheldt completed: Belgium's longest microtunnel now a reality

Technical feat

In March 2024, work began on the ECLUSE tunnel after years of preparation and meticulous planning. This tunnel, a technical feat, will enable ECLUSE to transport steam generated during waste incineration at the waste-to-energy plants in Doel to Evonik. The tunnel is a major extension of the existing ECLUSE network, which currently supplies process steam to five companies in the Waasland port.


With a length of 1,288 meters, this is the longest microtunnel ever drilled in Belgium. The tunnel has an internal diameter of three meters and provides space for the ECLUSE 2 pipes, a central maintenance path, and extra capacity for future pipes and cables. The tunnel was drilled using ‘microtunneling’. This is a technique for constructing underground tunnels without digging trenches in a wide variety of soil types. This technique is ideal for drilling under roads, railways, and rivers. The drilling itself took fourteen weeks and went entirely according to plan. Whereas an average progress of 70 meters per week was initially expected, an impressive 92 meters per week was ultimately achieved.

Waste incineration provides steam for chemical processes

When waste is incinerated in the waste-to-energy plants of Indaver and SLECO in Doel, the flue gases are used to generate steam. Since 2019, this steam has been supplied directly to five neighboring companies in the Waaslandhaven, which purchase the steam according to their needs for use in their chemical processes.

The steam is transported at a constant pressure of around 40 bar and a temperature of approximately 400°C. With the expansion to the right bank and the connection of Evonik to the ECLUSE network, the proportion of steam used directly will soon be significantly increased.

Evonik has a high demand for steam at its Antwerp site. Today, this demand is met in part by burning natural gas. By connecting to the ECLUSE network, Evonik can significantly reduce its use of natural gas. This reduction corresponds to the annual consumption of more than 38,000 households. By using steam from ECLUSE, Evonik also avoids the emission of around 100,000 to 150,000 tons of CO2 annually. In this way, ECLUSE is actively contributing to the energy transition in the port of Antwerp and the achievement of climate targets.

Ivan Pelgrims, Managing Director of Evonik Antwerpen NV: The connection to the ECLUSE network marks a turning point in our climate strategy. By meeting most of our steam requirements with low-carbon energy from waste incineration, we are taking a major step toward our goal of a 55% reduction in CO₂ emissions by 2030. This project shows how industrial cooperation and technological innovation go hand in hand to achieve the climate goals of Flanders and Europe. Evonik is proud to be the first customer on the right bank to help shape a more sustainable industrial ecosystem in the port of Antwerp.

"As Minister of Climate and Energy, I believe it is extremely important that companies actively participate in the energy transition. The ECLUSE tunnel under the Scheldt proves that investments in sustainable energy are good for both the climate and our industry. It makes companies less dependent on fluctuating natural gas prices in geopolitically unstable markets. And it anchors our energy-intensive industry towards a fossil-free future. That, in turn, is good for preserving our jobs. We will continue to encourage projects like this one," said Flemish Minister for Energy and Climate Melissa Depraetere.

Boudewijn Vlegels, chairman of Maatschappij Linkerscheldeoever, on behalf of ECLUSE: Thanks to its unique combination of public legitimacy and private clout, the ECLUSE network in Waaslandhaven is now being expanded to the port on the right bank, several years after the first steam delivery. In this way, the port of Antwerp, as the largest industrial cluster in the region, is actively contributing to the energy transition.

Next steps

The completion of the tunnel under the Scheldt is an important milestone, but the work is not yet finished. In the meantime, the second, shorter 185-meter bore under Scheldelaan towards Evonik on the right bank has also started. This bore will take approximately four weeks and will cross Scheldelaan and the railways, among other things. At the same time, preparations are underway for the installation of the support structures to which the pipes will later be attached. Completion of the entire project is scheduled for the end of 2026.

The ECLUSE tunnel is being built in a collaboration between private and public partners: Indaver, SLECO, FINEG, Maatschappij Linkerscheldeoever, and Port of AntwerpBruges, with support from the Flemish government.

About ECLUSE

ECLUSE is a public-private partnership between Indaver, FINEG, SLECO, Maatschappij Linkerscheldeoever, and Port of Antwerp-Bruges. The steam network that originated in the Waasland port was named ‘ECLUSE’, French for ‘lock’, because it channels steam from waste-to-energy installations to industry in the port. This ambitious, highly strategic project makes the energy supply in the port of Antwerp more sustainable and anchors industry in this region. www.ecluse.be

About Evonik

Evonik goes beyond the boundaries of chemistry thanks to a combination of innovative strength and leading technological expertise. The chemical company, which operates in more than 100 countries and has its headquarters in Essen, achieved sales of €15.2 billion and an operating result (adjusted EBITDA) of €2.1 billion in 2024. The common motivation of its approximately 32,000 employees: to offer customers a decisive competitive advantage with tailor-made products and solutions as a superpower for industry – and thus improve people's lives. In all markets. Every day. With nine production units and nearly 1,000 employees, Evonik Antwerp is one of the group's largest sites.