The global shift toward low-carbon construction models is driving the conversion of high-volume agricultural residues into functional building materials. Rice husk represents an ideal renewable precursor because it naturally combines organic components like cellulose, hemicellulose, and lignin with a high mineral content of biogenic amorphous silica. Hydrothermal carbonization uses subcritical water at moderate temperatures and autogenous pressure to transform wet 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 into functional hydrochar without requiring energy-intensive pre-drying steps. Process parameters can be tuned to direct chemical reactions, allowing hemicellulose to decompose below 200 degrees Celsius while cellulose and lignin decompose between 200 and 260 degrees Celsius. Subsequent physical or chemical activation using agents like potassium hydroxide, potassium carbonate, or phosphoric acid generates hierarchical porous architectures featuring specific surface areas exceeding 2000 square meters per gram. These nanoporous carbon networks possess high densities of oxygen-containing functional groups that facilitate chemical interactions in composite materials.

Integrating rice husk hydrochar and activated carbonActivated carbon is a form of carbon that has been processed to create a vast network of tiny pores, increasing its surface area significantly. This extensive surface area makes activated carbon exceptionally effective at trapping and holding impurities, like a molecular sponge. It is commonly More into cementitious matrices provides major mechanical and environmental benefits. When combined with accelerated carbonation curing, incorporating corn stover or rice husk 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 into cement mortar significantly increases carbon sequestration, achieving a 31.6 percent improvement in carbon dioxide uptake compared to untreated mixes. These improvements stem primarily from the physical pore network of the hydrochar rather than surface chemisorption alone. Furthermore, combining rice husk ash with carbon nanotube additives yields concrete composites that reduce mass loss under acid attack by up to 61.7 percent and decrease chloride diffusion coefficients by 62.8 percent. Life-cycle assessments indicate that these nano-engineered cementitious composites lower manufacturing costs by up to 27.8 percent while reducing carbon dioxide emissions by up to 22.2 percent. Alkali-activated geopolymer systems containing rice husk ash can achieve compressive strengths of 16 megapascals without using Portland cement, providing viable zero-clinker options for non-structural paving applications.

Source: Kuzbayeva, L., Alimkhan, B., Serikbayev, M., Ainabekova, S., Gushchin, A., Sultan, Y., Yespenbetova, S., Balykbayeva, G., Roza, N., & Appazov, N. (2026). Hydrothermal carbonization of rice husk for the production of nanoporous carbon materials: Recent advances and prospects for construction applications. Chemical Review and Letters, 9, 1342–1364.