The biochar kilns

Biochar at MVC Farm is produced using double-retort kilns that were fully designed and fabricated by our own team. 

We begin by loading woody biomass—such as eucalyptus, pruning residues or forestry waste—into heavy-duty internal cages inside each chamber. Once the biomass is stacked evenly, the chamber doors are sealed to maintain a low-oxygen environment. External heat is applied in the firebox beneath the retorts, gradually raising the internal temperature until the wood begins to release pyrolysis gases. These gases ignite in the external combustion zone, creating a clean, efficient secondary burn that drives the process with very little additional fuel.

As the biomass carbonises, moisture and volatile compounds are removed, leaving behind stable, high-quality biochar. After several hours of controlled heating, the kilns are allowed to cool naturally to prevent the newly formed carbon from igniting when oxygen enters. Once fully cooled, the doors are opened, the cages are removed, and the finished biochar is unloaded—visibly transformed from raw wood into a lightweight, porous and agronomically powerful form of stable carbon. This process, carried out using equipment we engineered ourselves, allows us to convert local biomass into a long-lasting soil amendment while permanently storing carbon in the ground.

The biochar quality

Biochar quality testing ensures that every batch we produce meets the scientific, agronomic, and environmental standards required under the Isometric Biochar Production and Storage Protocol. These tests focus on verifying the chemical composition of the biochar—specifically its carbon content, moisture level, the ratios of hydrogen and oxygen, and the presence of inorganic carbon. These measurements determine how much organic carbon is actually stored in the biochar and how durable that carbon will be once placed in the soil. 

Parameters such as H/Corg and O/Corg ratios are particularly important, as they indicate the degree of aromaticity and structural stability, which directly determine the long-term permanence of the carbon. Alongside this, we measure ash content, bulk density, volatile matter, and key nutrients such as phosphorus, potassium, calcium, magnesium, and iron, all of which help characterize the agronomic value and behaviour of the biochar when applied to soil.

In addition to performance-related metrics, comprehensive safety tests ensure that the biochar is free of substances that could pose risks to soil health, crops or ecosystems. These include measurements of heavy metals, polycyclic aromatic hydrocarbons (PAHs), dioxins (PCDD/F), and PCBs, all of which must remain below strict international thresholds. 

Most core properties—carbon content, inorganic carbon, hydrogen, nitrogen, oxygen, ash, pH, salts, and nutrient content—are required measurements, typically conducted at validation and for every production batch depending on the parameter. 

Collectively, this testing framework guarantees that the biochar is both effective as a long-term carbon sink and safe for agricultural use, offering farmers a product that meets the highest scientific standards.

The biochar activation

Biochar activation in silage involves combining fresh biochar with nutrient-rich plant material—such as the grass and forage seen in this pile—so that the biochar adsorbs soluble organic compounds, moisture, and microbial communities during the ensiling process. As the biomass ferments under anaerobic conditions, organic acids and microbial metabolites bind to the biochar's highly porous structure, increasing its cation-exchange capacity and transforming it into a biologically active soil amendment. This co-storage phase enhances the biochar's agronomic value by improving nutrient retention, stabilising pH, and promoting beneficial microbial colonisation. When later applied to agricultural soils, activated biochar improves soil structure, water-holding capacity, and long-term carbon sequestration efficiency—making silage-based activation a practical, low-cost method particularly well suited to mixed livestock–crop systems.

Activated biochar must be stored under controlled agronomic conditions to preserve its functional properties between activation and field application. After activation—whether via nutrient charging, microbial inoculation, or moisture-driven adsorption—the material should be kept in a dry, aerated environment to prevent leaching of soluble nutrients, anaerobic microbial shifts, or structural degradation of its pore network. Maintaining moisture below ~15% is critical, as excess humidity can trigger unwanted microbial respiration or partial nutrient loss, while complete desiccation can reduce microbial viability if inoculated. The storage system must also minimise UV exposure and prevent contact with soil or organic contaminants that could alter the charged profile. Ideally, activated biochar is stockpiled on a well-drained surface, protected from direct rainfall but with sufficient ventilation to stabilise temperature and avoid condensation. Under these conditions, nutrient-enriched and microbially active biochar remains chemically stable and agronomically effective until incorporation into the soil during the next cropping season, ensuring consistent improvements in cation exchange capacity, nutrient-use efficiency, and long-term carbon retention.