Biochar: The next generation of sustainable soil additives

Biochar could replace what expanded clay, perlite or pumice have offered until now – while not only supporting plant growth and water retention but also helping to protect the climate. In urban construction and horticulture, this is becoming increasingly important.

Whether in urban greening projects or professional horticulture, planners, landscape architects and substrate producers all face the same challenge: plants need to grow reliably and remain resilient, even in compacted, nutrient-poor or heavily used soils. To achieve this, powerful soil additives that improve structure, moisture balance and nutrient availability are required. Until now, the industry has largely relied on expanded clay, vermiculite, perlite or pumice. But their ecological footprint is far from green.

The established additives are widely used in, for instance, growing potting mixes for seedlings, green roofs, tree planting, urban planting systems, and rainwater management substrates because they are affordable and technically reliable. Yet their functional benefits come at a high environmental cost.

Expanded clay, for example, is produced by firing clay at temperatures above 1,200°C, making it lightweight, stable and durable, but also energy-intensive. The production of perlite and vermiculite is has similar impact. Both minerals are extracted through open-pit mining and then expanded in high-temperature processes. While this creates airy, water-retaining materials that can improve substrates, the processes also generate considerable CO₂ emissions. In addition, the mining of these minerals carries ecological risks for the landscape.

Pumice is often seen as the more “natural” option since it does not require artificial expansion. However, extracting it still means disturbing the landscape.

In short: conventional soil additives may solve the immediate problems of compacted and nutrient-poor soils, but they do nothing to support climate protection, and in some cases may even intensify the ecological issues we actually need to address.

The way biochar is produced differs fundamentally from that of conventional soil conditioners. Instead of extracting new raw materials, it uses what is already available: residual wood, green waste, fruit pits and other organic by-products. These residues are heated without oxygen in a process called pyrolysis. What remains is a highly porous, carbon-rich material.

This process is climate-relevant in several ways. First, biochar stores carbon long-term: plants absorb CO₂ from the atmosphere, and pyrolysis locks this carbon into a stable structure – for centuries. Second, biochar replaces resource-intensive materials, reducing emissions from production. Third, it enables a circular economy approach by making use of residual biomass.

Functionally, biochar matches conventional additives. Thanks to its enormous porosity, it can store two to three times its own weight in water. At the same time, it acts as a nutrient buffer: minerals and organic compounds accumulate in the pores and are released to plants as needed.

Expanded clay is valued for its porous structure and high water-retention capacity in substrates, green roofs or hydroponic systems. Similarly, vermiculite is commonly used in seedling and horticultural substrates for its ability to buffer water and aerate the soil. Biochar fulfills these same functions: it stores water and nutrients, improves aeration and provides an excellent habitat for microorganisms. The same comparison applies to perlite and pumice. In essence, biochar can replace traditional additives while offering a significantly smaller ecological footprint.

Novocarbo has already translated these potentials into market-ready products. The company has been developing biochar solutions for substrate manufacturers – particularly in Scandinavia – for many years. Two specially developed types of biochar are available:

Made from biogas digestate, NutriChar Pellets are designed for easy handling. In addition to loosening substrates, they provide valuable nutrients such as phosphorus and potassium.

For substrates requiring high water retention and structural stability, WoodChar Classic, produced from residual wood, is ideal. Its high porosity allows it to store more than twice its own weight in water, ensuring that substrates remain functional during prolonged dry periods or heavy rainfall and helping to efficiently filter unwanted substances.

All Novocarbo biochar products are fully certified under the European Biochar Certification (EBC) scheme, one of Europe’s leading quality standards for the sustainable production and use of biochar. This certification confirms that the biochar is produced in an environmentally friendly, safe and scientifically verified process.

For landscape architecture, urban planning, engineering and horticulture, biochar opens the door to embedding sustainability from the very beginning. Whether designing green roofs, planning tree plantings or raising seedlings, biochar can help solve multiple challenges at once: improved water retention, better soil aeration, increased resilience to weather extremes and a contribution to climate protection.

It pays to look beyond initial costs and consider a project’s full life cycle. More stable and less maintenance-intensive substrates reduce long-term irrigation needs and follow-up work. In this way, biochar not only makes urban projects more environmentally valuable but also more economically robust.

To unlock its full potential, biochar must be properly applied. When adding pure biochar to soil, it must be pre-loaded with nutrients. Depending on the application, it can be blended with compost, slurry or manure to biologically “charge” it. In substrate mixes, the proportion of pure biochar typically ranges from 3 to 10 percent.

Application is straightforward and comparable to other additives:

• NutriChar Pellets are ready to use. Their compact shape and particle size (6–8 mm diameter and 5–15 mm length) make them free-flowing, dust-free and easy to integrate into industrial mixing processes.
• WoodChar Classic has a particle size of under 40 mm and should be mixed with nutrients or substrate before use. To reduce dust during mixing, the biochar can be lightly moistened beforehand.

Biochar not only replaces traditional, non-sustainable soil additives but also combines functionality with climate protection, resource efficiency with resilience. As such, biochar becomes a symbol of the paradigm shift needed among cities, municipalities and horticultural businesses: away from short-term functionality and towards long-term sustainability.

📩 If you’re currently testing new blends, developing product lines, or planning green infrastructure: Send us a message to receive a free sample or a tailored price overview. We’re happy to support your next project!