Rice Husk Biomass Valorization in the Circular Bioeconomy: Energy, Soil, and Industrial Applications

Rice husk is a high-volume lignocellulosic residue that remains underutilized despite its silica-rich composition, leading to environmental pollution and inefficient resource use. This review evaluates integrated valorization pathways within a circular bioeconomy, focusing on energy conversion, soil improvement, and industrial material applications. A systematic review of peer-reviewed studies published from 2000 to 2025 was conducted to synthesize evidence on rice husk utilization across sectors. Studies were screened for relevance and rigor, then grouped into three domains: thermochemical energy processes, agricultural and environmental applications, and industrial material development. Data were extracted and analyzed using thematic synthesis to identify trends, performance outcomes, and research gaps. Results show that one ton of rice husk can generate about 800 kWh of energy and reduce up to 1 ton of carbon emissions through gasification and combustion systems. In agriculture, biochar application increases soil cation exchange capacity by 20 to 30% in sandy soils and improves water retention, nutrient availability, and microbial activity. In industrial applications, rice husk ash contains 85 to 95% amorphous silica, which enhances strength and durability in cement and composite materials and supports pollutant adsorption in water and soil systems. Additional findings highlight its role in water purification, soil stabilization, and development of composites and nanosilica-based materials. Rice husk valorization improves resource efficiency and supports sustainable production across energy, agriculture, and industry. However, variability in processing methods, scalability constraints, and limited long-term validation restrict wider adoption. Integrated, standardized, and field-based approaches are required to enable practical and large-scale implementation.