In a recent study published in 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 X, researchers Yuanling Li, Tao Wang, Jinyu Zhu, Siyu Duan, and Lina Liu explored a sustainable solution to mitigate greenhouse gas emissions by converting problematic marine macroalgal blooms into a high-performance carbon capture material. Harmful blooms of brown seaweed frequently wash ashore in massive quantities, creating coastal pollution and economic burdens. While converting agricultural residues into biochar is a standard practice, terrestrial 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 often competes directly with food crops and biofuel industries for land. Marine algae provide an abundant, fast-growing alternative that does not compete with arable farmland. The researchers set out to overcome the typical limitations of seaweed chars, which usually suffer from low surface area and poor surface chemistry, by testing how chemical activation timing and heating temperatures govern gas capture.

The experimental results revealed that applying potassium hydroxide to raw seaweed prior to thermal treatment at four hundred degrees Celsius yielded a porous biochar with an exceptional carbon dioxide capture capacity of 120.5 milligrams per gram. This performance represents a dramatic improvement over untreated seaweed biochar, which managed only 10.9 to 24.1 milligrams per gram across various heating levels. In fact, the optimized material achieved an adsorption capacity more than ten times higher than seaweed biochar prepared at six hundred degrees Celsius without chemical treatment. Treating the biochar after heating also proved far less successful, achieving only 40.0 milligrams per gram. The pre-treatment method produced an expansive internal surface area of nearly 570 square meters per gram, compared to just over one square meter per gram for the untreated four-hundred-degree material.

The material demonstrated rapid adsorption rates alongside its high capacity. Kinetic analyses showed that the optimized biochar reached adsorption equilibrium within approximately 11 minutes, whereas untreated biochars required 26 to 28 minutes to complete the process. This rapid uptake stems from an optimal internal architecture dominated by ultra-micropores measuring less than 0.7 nanometers in diameter. These tiny internal pockets create a confined physical space that pulls carbon dioxide molecules tightly into the matrix. At the same time, the moderate heating temperature avoids destroying delicate surface hydroxyl groups. These oxygen-containing basic sites engage in weak chemical interactions and hydrogen bonding with carbon dioxide, working hand-in-hand with the physical pore network to maximize uptake.

Long-term durability and recyclability represent critical benchmarks for real-world carbon capture deployment. Across nine consecutive adsorption and regeneration cycles under alternating gas flows, the optimized biochar maintained outstanding stability, losing only 1.1 percent of its initial capture performance. In contrast, biochar produced without chemical activation suffered capacity losses as high as 17 percent over the same operational span. The durable network established during simultaneous chemical activation and carbonization withstands repetitive heating and gas purging cycles without significant structural degradation, ensuring consistent operation over extended usage periods.

A preliminary lifecycle assessment evaluated the environmental footprint of the system from harvesting through eighteen capture and regeneration cycles. Accounting for biomass transport, energy needed for thermal activation, and regeneration heating, the total energy demand stood at roughly 6.24 megajoules per kilogram of captured carbon dioxide. When offset against standard grid electrical emissions, the process yielded an indirect greenhouse gas release of 0.71 kilograms of carbon dioxide equivalent for every kilogram captured. This balance produces a net removal of 0.29 kilograms of carbon dioxide equivalent per kilogram trapped, confirming that the algae-derived adsorbent delivers genuine net-negative carbon emissions while simultaneously repurposing troublesome marine coastal waste.

Source: Li, Y., Wang, T., Zhu, J., Duan, S., & Liu, L. (2026). Tailoring the 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 and surface chemistry of Sargassum biochar for enhanced CO2 capture. Biochar X, 2, e021.