Sustainable use of rice husk for the cleaner production of value-added products

This paper covers a comprehensive review of the thermochemical conversion of rice husk (RH) into value-added products. RH is an organic residue and is produced in large quantities in China, India, Indonesia, and Bangladesh and appears to be a viable source for value-added products from thermochemical processes. The RH properties and operating conditions affect the quality and yield of the bio-oil, gaseous, and biochar products. The conversion techniques such as gasification, slow and fast pyrolysis, and product distribution are systematically reviewed. The literature shows that the Ni-based catalysts demonstrated high activity towards cracking of tar compounds and hydrocarbons, upgraded gas quality, and yielded high hydrogen production. Zeolite-based systems are promising catalysts for the upgradation of bio-oils. Due to the structured porosity and higher acidity, the metal-loaded zeolites catalysts have shown high removal efficiency towards the oxygenated compounds. RH ash is also used as an alternative cementitious material in the construction sector. The optimum level of cement replacement with RH ash in concrete is 15–20%, and higher compressive strength is witnessed for RH ash used concrete than conventional cement concrete. RH ash utilization for soil remediation and blended cement production are also discussed. A sustainable framework has been proposed for the utilization of RH in the chemical and construction sectors.