NORDIC CARBON
A grower’s briefing
Biochar is a stable, carbon-rich material made by heating residual plant biomass to around 650 °C in a low-oxygen kiln — a process called pyrolysis. What survives is a porous skeleton of almost-pure carbon that, once worked into the soil, behaves very differently from raw organic matter or compost.
Unlike compost, it does not rot away — its carbon resists microbial breakdown, so one application keeps working for a decade or more.
For growers, that permanence is the point. Biochar improves the soil physically, chemically and biologically at the same time: it holds more water, buffers acidity, retains nutrients and shelters soil life — with the biggest gains on the sandy, acidic and degraded soils where crops struggle most.
Nordic Carbon produces biochar from underutilised biomass, turning a residue stream into a durable soil amendment.
01
Residual biomass
Agricultural & forestry residues
02
Pyrolysis at 650 °C
Heated with little oxygen
03
Stable biochar
Porous, carbon-rich solid
One material changes the soil’s water, chemistry and structure at once.
Water and soil structure
Biochar’s honeycomb of pores gives a single gram hundreds of square metres of internal surface, so it acts like a sponge in the soil. Across a meta-analysis of 74 studies it raised water-holding capacity by ~15%, total porosity by 8% and water infiltration by 25%. The effect is largest on light, sandy soils, where the plant-available water reservoir rose by up to 51% and the wilting point by 47% — so crops endure dry spells far longer.
pH, nutrients and retention
Most biochar is alkaline, giving a natural liming effect that raises soil pH by up to ~0.9 units and eases the acidity that limits weathered and tropical soils — still measurable ten years on. Its negatively-charged surfaces lift cation-exchange capacity, gripping potassium, calcium, magnesium and micronutrients (iron, zinc, copper, manganese, boron) so they resist leaching. The result is steadier nutrient supply, better phosphorus availability and improved nitrogen-use efficiency.
Biology and chemistry combine where it matters — in the harvest.
Average crop-yield response
+2%
+14%
+25%
Temperate regions
Global average
Tropical regions
Yield response tracks the starting soil — weak, acidic soils gain most.
The living soil
Biochar reshapes the community of organisms that actually cycle nutrients. It increases microbial biomass and activity, strengthens the plant–mycorrhizal fungi symbiosis that extends roots’ reach for water and phosphorus, and raises the activity of enzymes that free nutrients from organic matter. Its pores act as habitat, sheltering microbes from predators, drought and pH swings.
What it means for yields
These effects show up at harvest. A meta-analysis found biochar lifts crop yields by about 14% on average, with water- and nitrogen-use efficiency each up roughly 14%. On weathered, acidic tropical soils yields climb around 25%, while already-fertile temperate soils show little change.
Results depend on the soil, the biochar and how it is applied.
Proven in the field
Long-term trials confirm the benefits last. In Ghana, a single application improved yields across three consecutive cropping cycles on a sandy-loam soil. In Kenya, maize–soybean rotations kept gaining fertility and yield for ten years after application. On salt-affected soils, where few amendments help, higher biochar rates improved crop productivity.
Soil situation
t/ha
Notes
Healthy — maintenance
5–10
Cost-effective top-ups
General improvement
10–20
Common optimal range
Degraded / eroded
~30
Rebuilds structure
Saline / sodic
40–50
Higher rates needed
Getting it into the soil
Incorporate into the topsoil (10–20 cm), not left on the surface.
Charge it first — pre-mix with compost, manure or fertiliser.
Slurry or irrigation — fine, charged biochar can be applied through water.
A few cautions: quality varies with feedstock and pyrolysis temperature, so use characterised biochar; fresh high-carbon char can briefly tie up nitrogen (charge it or add N); and very high rates can raise salinity — test before scaling up.
Summary
1
Applied once, biochar improves soil water, chemistry and biology together — and lasts a decade or more.
2
It holds more water (+15%, up to +51% on sandy soils), raises pH ~0.9 units and retains nutrients.
3
Yields rise most on poor, acidic tropical soils — around +25% — with ~14% better water and nitrogen use.
4
Ghana and Kenya field trials show gains persisting for years after a single application.
5
Match the rate to the soil, use characterised biochar, and charge it before applying.
Sources & further reading
Razzaghi, Obour & Arthur (2020). Soil water retention meta-analysis. Geoderma 361.
Edeh, Mašek & Buss (2020). Biochar & soil water properties. Sci. Total Environ. 714.
Discover Soil (2025). Biochar, soil health & CEC. 10.1007/s44378-025-00041-8.
Jeffery et al. (2017). Tropical vs temperate yields. Environ. Res. Lett. 12(5).
Ye et al. (2023). Yield, water & N-use efficiency meta-analysis. J. Cleaner Prod. 420.
Ghana cropping-cycle trial (2021). PMC7902543.
Kätterer et al. (2019). 10-year fertility & yield, Kenya. Field Crops Res. 235.
Salt-affected soils meta-analysis (2024). Carbon Research.