In a recent study published in the journal ACS Omega, authors Kowsalya Sathyabama and Saiyyeda Firdous provide a comprehensive analysis of how 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 temperature affects 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 derived from agricultural waste. The article, titled “Effect of Pyrolysis Temperature on the Physicochemical Properties and Structural Characteristics of Agricultural Wastes-Derived Biochar,” examines biochar produced from rice husk, sugarcane bagasse, and groundnut shells at three distinct pyrolysis temperatures: 250, 300, and 350∘C. The findings offer new insights into producing biochar with desirable properties for improving soil health and addressing environmental issues. This research is particularly relevant for India, a country that generates around 500 million tonnes of crop residues annually, with a significant portion often burned in open fields.

The study reveals a strong correlation between the pyrolysis temperature and the resulting biochar properties. A key finding is the inverse relationship between temperature and biochar yield. As the temperature increased from 250 to 350∘C, the biochar yield dropped by more than 50% across all feedstocks. For example, rice husk yield fell from 44.63% at 250∘C to 22.69% at 350∘C. This decrease is attributed to the intense thermal degradation and release of 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 at higher temperatures.

In contrast, other important properties showed a positive trend with rising temperatures. The electrical conductivity (EC) and pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More of the biochar increased significantly. The pH increased from 4.0 to 7.7 in rice husk biochar, while the EC rose from 0.56 to 2.290 dS/m within the temperature range of 250 to 350∘C. Sugarcane bagasse biochar exhibited the highest EC at 350∘C, reaching 4.567 dS/m. This is due to the breakdown of organic acids and the enhancement of minerals like calcium, magnesium, sodium, and potassium, which are present as oxides, hydroxides, and carbonates. The 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 content also increased with temperature, with rice husk biochar having the highest ash content at 350∘C (39.12%).

Elemental analysis confirmed that an elevated pyrolysis temperature positively correlated with increased carbon content. The highest carbon content (75.56%) was found in groundnut shell biochar produced at 350∘C. Conversely, elements such as nitrogen, hydrogen, and sulfur decreased at higher temperatures. The reduction in the H/C and O/C ratios as temperature increased indicates enhanced aromatization and structural stability. This improved stability makes the biochar more effective for long-term carbon sequestration and for applications that require resistance to microbial decomposition.

The study also included a zeta potential analysis, which measures the electrical charge on the biochar particles. As the temperature increased, the zeta potential values became more negative. At 350∘C, the values ranged from -36.4 to -59.3 mV, indicating a high electrostatic interaction with positively charged ions, heavy metals, and pollutants. This negative surface charge is crucial for its use in soil remediation and wastewater treatment. Morphological analysis using scanning electron microscopy (SEM) showed that biochar produced at 300 and 350∘C had a well-defined porous structure, which is vital for adsorption capacity.

In conclusion, the research by Sathyabama and Firdous demonstrates that biochar produced at moderate to high temperatures, specifically 350∘C, exhibits significantly improved physicochemical properties and structural characteristics. The optimal temperature enhances carbon content and structural integrity, making the biochar a more sustainable and effective resource for environmental management and soil improvement. The findings highlight the importance of pyrolysis temperature in tailoring biochar properties for specific applications and provide a scientific foundation for the efficient valorization of agricultural waste.

Source: Sathyabama, K., & Firdous, S. (2025). Effect of Pyrolysis Temperature on the Physicochemical Properties and Structural Characteristics of Agricultural Wastes-Derived Biochar. ACS Omega.