Biochar metallurgy is increasingly regarded as a key pathway for deep decarbonization in the metallurgical industry beyond 2030. By replacing fossil-based coke with sustainable biochar, it can potentially serve two critical functions: as a reducing agent and as a heat source. However, this is not a technology that can be rapidly deployed at scale. The industry often focuses heavily on pyrolysis technology while overlooking several equally critical factors: feedstock supply, quality standards, practical application, and system integration. These gaps can become major barriers to project operation and long-term scalability. This article explores 4 key technical challenges facing biochar metallurgy.
Whether biochar can be used effectively and produced at scale depends first on the feedstock rather than biochar production equipment. If the feedstock is poorly selected or supply is unstable, even highly optimized process parameters cannot compensate for these limitations.
The physicochemical properties of biomass feedstocks directly determine the performance that biochar can ultimately achieve. Four factors are particularly important:
Therefore, it is difficult to consistently produce qualified metallurgical-grade biochar without strict feedstock control. This is why the availability and consistency of feedstock resources should be evaluated from the early stages of project development.
The feedstock requirements of metal smelting are far greater than those of conventional biochar applications. The availability of regional biomass resources, reliable collection systems, and long-term supply capacity are widely recognized as major bottlenecks to large-scale adoption. However, 2 approaches to scaling up feedstock supply have already been demonstrated in the industry:
Aperam BioEnergia operates approximately 124,000 hectares of eucalyptus plantations in Brazil and produces more than 400,000 tons of charcoal annually. The charcoal is supplied to Aperam’s steel plant in the same state. However, the replicability of this model depends on whether a project developer has the capacity to secure and manage large areas of land. Its potential ecological impacts also need to be carefully assessed.
Our strategic partner Exomad Green in Bolivia uses residual materials from local sawmills as feedstock. Its project is located between the feedstock supply area and the biochar application area. The company plans to increase annual biochar production capacity to more than 400,000 tons by 2027. However, this pathway is currently focused on biochar CDR applications and has not yet been extended to metallurgical applications.
For years, the industry has relied primarily on fixed carbon content as the benchmark for biochar qualification. However, testing has shown that biochar with qualified fixed carbon content can still exhibit uneven reactions inside the furnace and cause unstable operating conditions. The performance of biochar in metallurgical applications is also determined by five often-overlooked indicators:
Therefore, the quality evaluation system for metallurgical biochar needs to be comprehensively upgraded. Instead of relying solely on fixed carbon content, the evaluation should incorporate multiple dimensions, including high-temperature reactivity and dynamic reaction behavior inside the furnace.
Key metallurgical biochar properties are not inherent characteristics of the biomass. They are directly influenced by pyrolysis system parameters. Comparative tests under different operating conditions show that three variables play a particularly important role:
Crushing and densification modify the physical form of the feedstock before pyrolysis. This physical restructuring optimizes the resulting pore structure and enhances high-temperature reduction reactivity, allowing the biochar to better meet the demanding requirements of metallurgical furnace conditions.
Under normal operating ranges, increasing pressure and extending residence time significantly improve product yield and carbon conversion efficiency. Pushed to an extreme — high pressure combined with rapid heating — the same variables can fundamentally reshape the biochar’s microcrystalline structure.
The real challenge lies in standardizing the optimal combination of these parameters. Changes in feedstock batches or equipment configurations can significantly affect the process. The same parameter settings therefore cannot simply be transferred from one project to another. Targeted process testing and adjustment are required for each specific feedstock and equipment configuration.
Even with clear quality indicators and optimized pyrolysis parameters, biochar still isn’t fully ready for metallurgical use. Several practical challenges remain.
Compared with coke, conventional biochar has two inherent disadvantages:
Densification, water washing for ash removal, and elemental doping are three key processes for improving the mechanical strength of biochar, reducing impurity content, and optimizing its high-temperature reaction performance. However, each process also introduces additional limitations:
Most projects concentrate resources on production equipment. However, storage and logistics are equally critical for preserving the metallurgical properties of biochar.
The optimal industrial model for biochar metallurgy in the future may not be to build standalone biochar production plants. Instead, biochar pyrolysis equipment could be integrated directly into metallurgical facilities. By recovering waste heat from metallurgical processes to power biochar production, this model could achieve energy integration and resource circularity. However, integrating metallurgical waste heat presents several challenges.
A pyrolysis unit already involves two heat sources: waste heat from pyrolysis flue gas and heat generated by combustible gas combustion. Once integrated into a metallurgical plant, these two heat sources must also be coordinated with the plant’s waste heat system. This adds another layer of complexity to heat matching.
Both waste heat streams can be used to dry biomass feedstock. However, integrating them into the drying system requires dedicated piping infrastructure. Pipe routing, connection interfaces, and transmission distances all be reconfigured during engineering design.
Pyrolysis requires much tighter temperature control than feedstock drying. Determining how to proportion and regulate the two heat sources to maintain the precise temperature profile required for pyrolysis requires project-specific commissioning and optimization.
Combustible gas typically contains reducing and high-calorific-value components such as CH4, CO, and H2. Directly burning and discharging these gases without recovering their energy represents a waste of resources. Once external waste heat replaces part of the combustible gas combustion, the existing heating and recovery systems of the biochar production facility must be modified accordingly.
The conventional direct-combustion heating system used in is not readily compatible with external waste heat. The heating system may need to be modified to a hot-air heating configuration, with precise air-flow regulation used to control the pyrolysis temperature.
Recovering and utilizing combustible gas requires downstream facilities such as gas storage and power generation systems. The capacity specifications of these facilities must match the combustible gas output of the production facility to establish a complete energy recovery chain.
Biochar metallurgy is not an isolated technical improvement. It is a key pathway for the steel industry to achieve deep decarbonization beyond 2030. Whether this pathway can truly be scaled and replicated does not depend on a breakthrough in any single process parameter, but on whether the entire industry chain can mature in a coordinated way. For the industry, now is the window to act. If you’re interested in metallurgical biochar production solutions, feel free to contact us.