Researchers have published their findings in the journal 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 under the leadership of Soumen Mandal along with collaborators from Hanyang University and other institutions. Their work addresses the critical need for efficient energy storage to support renewable sources like solar and wind power, which are often inconsistent. The team explored the potential of using neem seeds, an abundant agricultural byproduct, to create carbon-rich biochar. This biochar acts as a stabilizing framework for phase change materials, which are substances that store and release large amounts of energy as they melt and solidify. By turning waste into a high-tech storage solution, the study promotes both energy efficiency and environmental sustainability.

The primary discovery of the research is that the temperature used to create the biochar significantly changes its effectiveness for energy storage. When neem seeds were processed at 500 degrees Celsius, the resulting material developed a vastly more complex network of microscopic pores compared to material processed at only 300 degrees Celsius. This increased porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More is vital because it provides more space to hold the energy-storing chemicals. Specifically, the higher-temperature biochar could accommodate double the mass of the storage liquid, leading to a much higher capacity for holding heat. This relationship between processing temperature and surface area proved to be the decisive factor in creating a more powerful storage composite.

In addition to capacity, the researchers focused on the stability and durability of these new materials. One of the common problems with thermal storage materials is that they can leak when they melt into a liquid state. However, the study found that the microscopic pores in the neem biochar acted like a sponge, trapping the storage material through physical forces and chemical bonds. Tests showed that the composites remained completely stable even when heated above their melting point, with no visible leakage. This shape stabilization ensures that the energy storage system can function reliably over a long period without losing its active components or causing maintenance issues.

The study also confirmed that these biochar-based materials are exceptionally durable over repeated use. To simulate real-world conditions, the researchers subjected the materials to 500 continuous cycles of heating and cooling. The results were impressive, showing that the storage capacity remained nearly identical from the first cycle to the last. This thermal resilience is essential for practical applications in building heating systems or electronic cooling, where the material must perform consistently every day. The chemical analysis further revealed that the biochar surface actually improved the thermal stability of the entire composite, allowing it to withstand higher temperatures before breaking down.

Finally, the research highlights the environmental benefits of this approach beyond just clean energy storage. Neem seeds are often discarded after their oil is extracted, sometimes leading to waste management problems. By converting this waste into high-performance biochar, the process effectively traps carbon that would otherwise be released into the atmosphere as greenhouse gases. This creates a carbon-negative cycle where waste is removed, carbon is sequestered, and renewable energy usage is made more efficient. The researchers conclude that these sustainable composites offer a cost-effective and eco-friendly alternative to traditional, often expensive, energy storage technologies.

Source: Mandal, S., Mendhe, A. C., Park, T., & Lee, H. S. (2026). Temperature-modulated surface features of neem seed biochar for sustainable thermal energy storage applications. Biochar, 8(9).