The global iron and steelmaking sector remains a primary contributor to anthropogenically driven greenhouse gas emissions due to its historic, heavy reliance on fossil fuel combustion. Within typical integrated factory settings, the traditional carbothermic reduction of iron oxides via large blast furnaces consumes immense volumes of coal and generates massive amounts of carbon dioxide. To counteract this severe environmental strain, engineering teams are aggressively evaluating the incorporation of renewable biogenic carbon alternatives to act as direct coal replacements. Raw agricultural waste biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More, however, introduces major process limitations, including excessive moisture content, minimal fixed carbon, and low density. While heating the biogenic material via oxygen-free processing increases the baseline fuel value, it simultaneously degrades the structural strength of the carbon, preventing its straightforward addition into high-load steelmaking towers. To bypass this mechanical block, researchers are creating self-reducing composite briquettes that blend iron ore fine materials with precise portions of processed sugarcane bagasse waste.

The precise temperature chosen to process raw sugarcane waste alters the inner chemical alignment of the resulting biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, dictating how the composite briquettes behave during subsequent high-heat reduction. Processing the biogenic material at a low target of two hundred and fifty degrees leaves behind significant volatile matterVolatile matter refers to the organic compounds that are released as gases during the pyrolysis process. These compounds can include methane, hydrogen, and carbon monoxide, which can be captured and used as fuel or further processed into other valuable products.   More that vents away early in the steelmaking cycle, generating an exceptionally open and porous internal oxide network. Conversely, ramping the charcoalCharcoal is a black, brittle, and porous material produced by heating wood or other organic substances in a low-oxygen environment. It is primarily used as a fuel source for cooking and heating.   More processing threshold up to five hundred and fifty degrees maximizes the absolute availability of fixed carbon while concentrating alkaline ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More minerals. When these highly carbonaceous blocks undergo high-temperature reduction inside the iron bundle matrix, they promote exceptionally rapid carbon gasificationGasification is a high-temperature, thermochemical process that converts carbon-based materials into a gaseous fuel called syngas and solid by-products. It takes place in an oxygen-deficient environment at temperatures typically above 750°C. Unlike combustion, which fully burns material to produce heat and carbon dioxide (CO2​), gasification More through the classic Boudouard reaction mechanism. This intense gas generation causes a massive spike in internal gas pressure along the internal reaction boundaries, exposing the structural core of the composite blocks to severe, localized physical forces.

These distinct internal gas patterns and shifting chemical reaction rates directly govern whether the composite metal blocks maintain physical integrity or undergo catastrophic structural failure. Agglomerates constructed with high-temperature sugarcane waste display extreme volumetric swelling of up to seventy-five percent when exposed to moderate processing environments. This massive expansion stems from the immense internal pressure of the escaping reducing gases combined with a highly distinct microstructural alteration where metallic iron nucleates into fine, elongated whiskers. These expanding metallic filaments press forcefully against adjacent ore particles, generating internal mechanical stresses that trigger severe cracking and a near-total loss of crushed handling resistance. In stark comparison, the highly porous internal oxide framework created by lower-temperature volatile venting allows escaping gases to move freely through internal voids, completely suppressing filament creation and shielding the block from catastrophic expansion.

Exposing the composite metal agglomerates to extreme temperatures of twelve hundred and fifty degrees triggers a complete microstructural transformation characterized by widespread volumetric shrinkage and a substantial recovery of mechanical durability. This late-stage contraction happens because reduced metallic iron particles begin to coalesce and sinter together, while internal binder components, ore impurities, and biogenic ash fuse into a liquid slag phase. This molten matrix fills internal voids and pulls neighboring iron clusters into a highly densified network, causing the expanding whiskers to melt away into consolidated metallic blocks. Briquettes made with four hundred degree charcoal display a highly uniform internal reduction pattern across the entire cross-section, enabling them to shrink by sixty-nine percent and achieve the highest overall compressive strength. Ultimately, choosing a middle-range processing target for biogenic steelmaking additives balances initial reduction potential with long-term structural survivability, providing a clear pathway for factories to introduce green agricultural fuels without disrupting automated operations.

Source: Leão, P. M. G. C., de Oliveira, I. G., Isaac, A., & Bagatini, M. C. (2026). Structural behavior of self-reducing briquettes containing biochar pyrolyzed at different temperatures. Journal of Materials Research and Technology, 42, 8512-8527.