The world currently faces severe environmental crises that threaten ecosystems and human health, with global warming and climate change taking center stage as the most critical challenges. These disruptions originate primarily from the accumulation of greenhouse gases in the atmosphere, which are released by human activities such as fossil fuel combustion. Because population growth, industrialization, and rising living standards make it virtually impossible to eliminate these activities entirely, scientists are focused on transitioning to products based on renewable resources. Utilizing 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 resources helps achieve net zero carbon emissions because the carbon dioxide released during processing is balanced by the carbon absorbed during biomass growth. Among these innovative bio-products, biochar stands out as a stable, carbon-rich substance. Published in the journal Results in Engineering, a review article by Maryam Afshar and Saeed Mofatteh explores the technical and environmental performance of biochar as a powerful alternative to traditional waste management and energy routes.

The expanding global industry for this bio-product reflects its growing significance as a cornerstone of the circular bioeconomy. Valued at approximately 541.8 million dollars in 2023, the global biochar market is projected to expand at an impressive annual growth rate of 13.9 percent from 2024 to 2030. This remarkable economic trajectory is supported by the massive availability of lignocellulosic agro-food biomass, which yields about 200 billion metric tons of material per year globally. Utilizing abundant agricultural residues like rice husk, wheat straw, coffee husk, and sugarcane bagasse allows manufacturers to scale up operations without supply worries. Converting these materials into stable products diverts agricultural waste from landfills and open burning, directly supporting the United Nations Sustainable Development Goals. For example, global rice production generates about 800 million tons of straw annually, which causes severe air pollution when burned. Transforming this straw into a soil modifier instead reduces harmful particle emissions while significantly increasing agricultural yields.

Thermochemical conversion processes dictate the structural characteristics and final performance of the material, with slow pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More emerging as the most practical approach for maximizing yields. Slow pyrolysis operates at low heating rates and relatively low temperatures, typically between 300 and 700 degrees Celsius, to optimize solid production over liquid and gaseous byproducts. The process generates a substance characterized by a well-developed pore structure and high internal surface area, which are essential for environmental and agricultural applications. When biomass undergoes thermal decomposition, the dehydration process drives off water and volatile components, creating a network of micropores, mesopores, and macropores. This internal architecture directly enhances the ability of the material to retain water, trap pollutants, and store nutrients when integrated into natural systems. The specific physical and chemical properties remain highly dependent on process parameters like the maximum temperature, the overall residence timeResidence time refers to the duration that the biomass is heated during the pyrolysis process. The residence time can influence the properties of the biochar produced.   More, the heating rate, and the composition of the initial feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More.

From an environmental perspective, the deployment of this material delivers massive carbon abatement benefits across its life cycle by shifting system boundaries toward negative emissions. A century of processing residues can avoid up to 130 billion metric tons of carbon dioxide equivalent emissions, with about 50 percent of the reduction coming from long-term carbon sequestration in soils. Another 30 percent of the emissions reduction comes from substituting fossil fuels with the renewable syngasSyngas, or synthesis gas, is a fuel gas mixture consisting primarily of hydrogen and carbon monoxide. It is produced during gasification and can be used as a fuel source or as a feedstock for producing other chemicals and fuels.   More and bio-oil generated during pyrolysis, while the remaining 20 percent occurs by preventing methane and nitrous oxide emissions from decomposing waste. When applied to agricultural land, the material enhances soil organic carbon, boosts cation exchange capacity, and decreases the leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More of soluble macronutrients. This reduces the need for chemical fertilizers, which otherwise contribute to groundwater contamination and soil acidification. Furthermore, its high surface area makes it an ideal platform for supporting catalysts, filtering contaminated water, and formulating sustainable construction materials like carbon-negative concrete.

Source: Afshar, M., & Mofatteh, S. (2024). Biochar for a sustainable future: Environmentally friendly production and diverse applications. Results in Engineering, 23, 102433.