Reusable substrate becomes reality with new steam-based treatment system

A new study from Proefcentrum Hoogstraten reveals that used substrate, when treated with the SoilSteam SubstrateSaver, delivers strawberry growth, yield, and shelf life on par with new substrate.

Every year, the world consumes over 80 million cubic meters of substrate in greenhouse production. As climate change accelerates the shift toward indoor farming of vegetables, fruits, and berries, demand for high-quality growth media is projected to rise to 280 million cubic meters within 20 years.

Yet, growers often discard their substrate after just one crop cycle—sometimes replacing it 3–4 times per year. This practice not only increases costs but also generates massive amounts of waste. Until now, reusing substrate without sacrificing crop performance has remained an unsolved challenge.

© SoilSteam

A landmark collaboration
In the first half of 2025, SoilSteam and Proefcentrum Hoogstraten conducted an extensive joint research project to test the effect of steam-treated reused substrate compared to fresh, virgin substrate. The study also included mixed combinations of treated and new substrate.

Researchers grew strawberries in each substrate type and measured plant growth, root development, fruit yield, and storage longevity.

The results were eye-opening, showing that steam-treated substrate performed just as well as fresh substrate.

© SoilSteam

Peter Melis, leading researcher at Proefcentrum Hoogstraten, expressed his surprise: "We've tested many ways to reuse substrate over the years, but none have matched the results of new material—until now. To see equal, and in some cases even better, plant development in steam-treated substrate was truly unexpected."

Proven technology meets a new market
Hans Kristian Westrum, founder and Head of Sales at SoilSteam, wasn't surprised by the results: "We've seen this many times before. Steam treatment eliminates harmful organisms, giving growers a cleaner and safer starting point than even freshly manufactured substrate. In many ways, treated substrate is actually more reliable."

Westrum emphasizes that this breakthrough could transform the industry: "Whether growers reuse 100% or blend with just 50% new material, this innovation will dramatically reduce the need for fresh substrate. It's clear that single-use substrate isn't sustainable. Reuse must become the norm if we want greenhouse farming to be future-proof."

© SoilSteam

Towards a circular future
The potential environmental impact is significant. Substrate production is one of the largest environmental contributors in indoor farming due to raw material extraction, water usage, and long-distance transport. Steam treatment now offers a scalable and cost-effective solution to close the loop.

"The era of single-use substrate is over," Westrum says. "We now have the tools to make indoor farming truly circular."

© SoilSteamHans Kristian Westrum

When will SubstrateSaver hit the market?
Ken Roar Riis, CEO of SoilSteam, confirms: "Our first full-scale SubstrateSaver machine is ready and scheduled for delivery in April 2026. It will handle 5–10 cubic meters per hour. We're also developing a smaller version that processes 1–2 cubic meters per hour for growers with lower volumes."

© SoilSteam

"Growers can expect to treat substrate for around €10 per cubic meter," Riis explains. "At this price point, there's no reason the entire industry shouldn't adopt reuse."

© SoilSteamKen Roar Riis