Biochar is produced through pyrolysis, a thermal process in which biomass is heated with little or no oxygen. Under these conditions, the feedstock separates into three principal products: a solid carbon-rich material, liquid bio-oil, and combustible gases. The process is already attracting global interest because biochar can lock carbon into a relatively stable form for long periods while improving soil structure, retaining nutrients, removing contaminants, and supporting chemical reactions. Yet most laboratory and industrial studies have traditionally used nitrogen, a relatively unreactive gas, to create what researchers assumed was a controlled environment.

The review, led by Professor Ondřej Mašek of the University of Edinburgh, shows that this assumption may be limiting the technology’s potential. The authors examined how nitrogen, argon, carbon dioxide, steam, oxygen, methane, ammonia, flue gas, and recycled pyrolysis gases influence the chemistry and physical structure of biochar. Each atmosphere can alter heat transfer, reaction pathways, carbon conversion, pore formation, surface chemistry, and the balance between solid, liquid, and gaseous products. The result is that two biochars made from the same biomass at the same nominal temperature may perform very differently if they are produced under different gases.

Inert atmospheres such as nitrogen and argon generally preserve more of the original biomass carbon in the solid fraction. This makes them attractive when the central objective is to maximize biochar yield and retain carbon for storage. However, their chemical neutrality can also limit the development of specialized surface properties. By contrast, reactive gases can interact directly with the evolving char. Carbon dioxide and steam, for example, may trigger gasification reactions in which carbon atoms are removed from the solid matrix, creating additional pores and increasing surface area.

That transformation could make biochar more effective as an environmental material. A larger internal surface area provides more locations where nutrients, heavy metals, and organic pollutants can attach through adsorption. Steam can also introduce oxygen-containing functional groups onto the biochar surface, changing its polarity and chemical reactivity. These groups may improve interactions with dissolved contaminants or soil nutrients. In some processing conditions, steam may increase bio-oil production or alter its composition, although the benefits can come at a cost: stronger reactions with steam may consume more solid carbon and lower the final biochar yield.

Carbon dioxide offers a different set of possibilities. As it reacts with hot carbon, it can enlarge pores and encourage the breakdown of tar compounds that might otherwise condense in the reactor or contaminate downstream products. The process can shift more carbon into carbon monoxide-rich gas, which may be recovered and burned to provide heat or generate energy. This creates the possibility of a more integrated system in which carbon dioxide is not merely emitted but is circulated through the reactor to influence the product while supporting energy recovery.

Oxygen is even more powerful—and more difficult to control. Small, carefully managed amounts can generate heat directly inside the reactor through partial oxidation, potentially reducing the external energy required to maintain pyrolysis temperatures. Controlled oxidative conditions may also increase porosity and create acidic surface groups that improve ion exchange, a property important for nutrient retention and some catalytic applications. But excessive oxygen can rapidly oxidize the char itself, burning away valuable carbon and sharply reducing the solid product. The boundary between useful process intensification and destructive combustion may therefore be narrow.

Ammonia could enable another form of customization by adding nitrogen to the material during production. At comparatively low temperatures, ammonia can react with the developing biochar and introduce nitrogen-containing functional groups. These groups may increase cation exchange capacity, improve adsorption, or enhance catalytic performance. In conventional manufacturing, similar properties might require post-production treatment with additional chemicals. Ammonia-assisted pyrolysis could combine production and modification in a single step, potentially simplifying the process, although safety, emissions, cost, and life-cycle impacts would need careful evaluation before large-scale adoption.

The review also points toward an industrial future in which biochar reactors use gases that facilities already produce. Flue gas, recycled pyrolysis gas, and other industrial streams could replace some purified nitrogen, reducing gas costs and lowering the energy associated with gas separation and compression. Such integration could also recover waste heat and connect biochar production with existing biomass, waste-management, or energy infrastructure. The authors emphasize that no atmosphere is universally superior: the best choice depends on whether a facility prioritizes carbon retention, contaminant capture, nutrient management, fuel generation, or overall process efficiency.

The researchers are calling for systematic experiments that vary gas composition alongside temperature, feedstock type, residence time, and reactor design. Pilot-scale trials will be essential because gas behavior in a small laboratory reactor may not translate directly to an industrial system. Real-time monitoring of gases, vapors, temperature, and char chemistry could help operators control the process as it unfolds rather than relying only on fixed settings. Environmental assessments must also account for emissions, energy use, chemical inputs, and the long-term fate of the resulting biochar. If these challenges are addressed, changing the atmosphere around biomass could transform pyrolysis from a one-size-fits-all heating process into a precision manufacturing platform for climate, agricultural, and environmental technologies.

Subject of Research: Biochar production and pyrolysis under different gas atmospheres

Article Title: Biochar production under different atmospheres: an overview

News Publication Date: 29-Jul-2026

Web References: https://doi.org/10.1007/s42773-026-00626-8; https://link.springer.com/journal/42773

References: Mašek, O., Buss, W., Wang, L. et al. “Biochar production under different atmospheres: an overview.” Biochar 8, 129 (2026). DOI: 10.1007/s42773-026-00626-8

Image Credits: Ondřej Mašek, Wolfram Buss, Liang Wang, Jiacheng Sun, Xutong Wang, Yue Wang and Øyvind Skreiberg

Keywords: Biochar, biomass pyrolysis, carbon storage, carbon dioxide, steam, ammonia, oxygen, gasification, soil improvement, pollutant removal, bio-oil, renewable energy

Composting, a natural method of recycling organic waste, has long faced challenges due to its slow pace and inefficiency in tropical climates, where rapid decomposition risks nutrient loss. The team at Hainan University has addressed these issues by developing a biochar infused with calcium derived from oyster shells, integrated with the carbonaceous matrix of coconut shells. This synergy not only mobilizes beneficial microbial communities but also introduces critical functional groups that facilitate organic matter stabilization, fostering a more efficient humification pathway.

The process begins by pyrolyzing a blend of oyster and coconut shells at a controlled temperature of 600 °C. During this thermal treatment, calcium ions from the oyster shells chemically bind to the carbon structures originating from the coconut shells, forming a composite abundant in carboxyl and carbonyl functionalities. These chemical groups are crucial as they enhance the structural integrity of the compost and improve the interaction between microbial enzymes and organic substrates, thus catalyzing the breakdown of complex molecules.

Humification—a critical step in compost maturity—refers to the transformation of labile organic compounds into stable humic substances, which are essential for soil health. The biochar developed in this study acts as a scaffold and microhabitat for specialized microbial consortia, predominantly Proteobacteria and Bacteroidetes, whose populations nearly doubled with its addition. These bacteria possess enzymatic capabilities to decompose recalcitrant biopolymers such as lignin, facilitating the conversion into humic acids and fulvic acids that enrich the soil with long-lasting organic carbon.

The introduction of oyster shell-functionalized biochar into the composting system not only speeds up microbial colonization but also elevates the Seed Germination Index by approximately 19%, indicating a substantial reduction in phytotoxic compounds. This improvement is critical for agricultural productivity as it ensures that seedlings are exposed to a safer and more nurturing growing medium, directly translating into enhanced crop yields and healthier plants in downstream applications.

Advanced spectroscopic analyses reveal that the chemical milieu of the compost undergoes significant modification when biochar is present. Protein-like substances, which are typically transient and prone to rapid decomposition, are progressively transformed into more stable humic acid-like molecules. This shift enhances the overall stability and nutrient-retention capacity of compost, effectively reducing nitrogen volatilization and leaching losses, a common environmental concern in tropical farming systems.

This research represents a major stride towards sustainable agricultural practices, particularly in tropical regions where dealing with abundant agricultural residues is both a necessity and a challenge. By converting locally sourced oyster and coconut shells—considered waste products—into a high-value compost additive, the study pioneers a circular economy model that minimizes environmental footprints, maximizes resource efficiency, and fosters climate resilience in farming communities.

The scalability of this technology holds promising prospects for industrial composting operations. The ability to accelerate compost maturation while stabilizing organic matter could reduce the temporal and spatial requirements of composting facilities. This efficiency gain could facilitate broader adoption of organic fertilizers, diminish dependence on chemical inputs, and ultimately support global endeavors to maintain soil health and biodiversity amidst increasing agricultural demands.

Furthermore, the interdisciplinary collaboration between the College of Tropical Agriculture and Forestry and the School of Breeding and Multiplication at Hainan University exemplifies the integration of ecological knowledge and biotechnological innovation. Their shared vision unites the fields of soil science, environmental chemistry, and agricultural engineering to tackle pressing ecological challenges through tailored material science interventions.

The implications of this study extend beyond composting practices; they underscore the vital role that biochar modifications can play in enhancing microbial ecology and biogeochemical cycles in soil environments. By engineering biochar with specific elements like calcium, researchers can design multifunctional soil amendments that not only aid waste decomposition but also support plant nutrition and carbon sequestration, which are pivotal for mitigating climate change.

In essence, this pioneering work harnesses the combined strengths of natural materials from the land and sea, transforming them into a powerful catalyst for environmental sustainability. As the agricultural sector seeks innovative solutions to balance productivity with ecological stewardship, oyster shell-functionalized biochar stands out as a beacon of hope for resilient and regenerative farming systems worldwide.

Subject of Research: Not applicable

Article Title: Oyster shell-functionalized biochar enhanced compost humification during the co-composting of pig manure with rice straw

News Publication Date: 20-Jan-2026

Web References: http://dx.doi.org/10.1007/s44246-025-00249-x

References: He, J., Li, L., Shi, Y. et al. Oyster shell-functionalized biochar enhanced compost humification during the co-composting of pig manure with rice straw. Carbon Res. 5, 7 (2026).

Image Credits: Jinfeng He, Li Li, Yulin Shi, Keke Wang, Jiaxu He, Yunze Ruan, Huanyu Bao, Muhammad Usman Khan, De-qiang Li, Shanshuai Chen & Pingshan Fan

Keywords: Biomineralization, Bioremediation, Environmental engineering, Biotechnology, Food science, Soil science, Environmental chemistry, Environmental sciences