As the pressure mounts for climate-neutral horticulture and high-performance substrates, Klasmann-Deilmann has long been introducing renewable raw materials into their substrate formulations. TerraCoal®, a biochar-based material, represents a further addition to this portfolio.
"With TerraCoal®, we're not only adding a new material, we're introducing one with unique properties that improve plant performance while actively contributing to long-term carbon sequestration," Johanna Heim, Technical Manager for the Biochar Department at Klasmann-Deilmann, explains.
Technically speaking, TerraCoal® is characterized by its fine porous structure, which offers several key benefits when used in greenhouse substrates. Johanna shares that it helps with nutrient buffering, where the pores in the biochar act as adsorption sites, helping to retain nutrients during irrigation and fertilizer application and release them slowly over time.
"Improved water retention is another advantage. Its porosity also contributes to better water-holding capacity, reducing irrigation frequency and supporting plants during dry-down periods," she adds.
TerraCoal® is also extremely dimensionally stable, adding structural stability. "It does not degrade like organic fibers or shrink over time, therefore preserving air-filled porosity and root-zone aeration throughout the cropping cycle," she shares. "Another example of its benefits is carbon permanence. Unlike other organic materials, TerraCoal® locks carbon in a stable form for hundreds to thousands of years, helping growers meet CO₂-reduction targets through the substrate alone."
"It's the combination of horticultural functionality and climate performance that makes TerraCoal® stand out."
Integration into growing media: tried and tested
Greenhouse growers are rightly cautious about new raw materials, particularly in high-value crops like fruiting vegetables and soft fruits. But Johanna emphasizes that TerraCoal® has been rigorously tested and carefully integrated into substrate mixes without compromising crop performance.
"Every new material we use must meet our core criteria: compatibility, safety, and added value for plant cultivation," she says.
Substrates containing TerraCoal® are currently being tested and applied across a range of crops with promising results. Johanna shares that in the Netherlands, intensive greenhouse systems are trialing TerraCoal® Growbags in the cultivation of tomatoes and peppers, supporting the sector's ambitious goal of achieving climate neutrality by 2040. In soft fruit production, trials with strawberries are focusing on key aspects such as root development, moisture management, and substrate longevity while targeting pH.
Ornamental growers are also exploring TerraCoal® for its structural stability and buffering capacity, which contribute to consistent growth and high-quality results in long-cycle flowering crops. Additionally, TerraCoal® has already been commercially adopted in basil cultivation, proving particularly effective in retail pot herb production, where the product's sustainable value resonates with environmentally conscious consumers.
Carbon sink potential: A new responsibility for growers
According to Johanna, one of the most important messages for greenhouse growers is that using TerraCoal® means participating in a larger carbon sink ecosystem. This requires a new mindset around substrate disposal.
"Once the crop cycle ends, how you handle the used substrate determines whether TerraCoal® 's carbon remains locked or is released." Klasmann-Deilmann is promoting closed-loop systems, especially with their Growbags. These are retrieved post-harvest and sent for composting or agricultural reuse, ensuring the carbon remains in the soil rather than being incinerated or landfilled.
However, in more open systems where substrates reach the end consumer (e.g., potted herbs), education for proper end-of-life disposal along the value chain is necessary.
"From manufacturer to grower to retailer and even consumer, everyone has a role in ensuring TerraCoal® 's environmental benefit is preserved," she says.
The name TerraCoal® might raise eyebrows, especially given "coal's fossil fuel associations. "We're redefining 'coal'", Johanna simply states. "TerraCoal® is not fossil-based as it's derived from woody biomass, a renewable and organic resource. The name reflects our product family, like TerraActiv, and signals a new generation of carbon-rich, green materials."
For more information:
Klasmann-Deilmann GmbH
Johanne Heim, Technical Manager: Biochar Department
[email protected]
klasmann-deilmann.com