Hazard Assessment of Rice Husk Ash Generated from Rice Mills in Bangladesh and Way Forward to Overcome or Adopt the Hazards

Abstract Rice husk (RH), an agricultural waste, is abundantly available in Bangladesh, where the major agricultural crop is paddy consisting of 73.94 percent of all crops. Bangladesh produced 37.61 million metric tonnes of paddy in 2020-21, among which the volume of rice husk was 7.52 million metric tonnes. These are mainly used for low-value applications such as fuel in the parboiling of the rice mills, where the burning of rice husk produces more than 5 million metric tonnes of rice husk ash (RHA). The disposal in landfills or open fields causes serious environmental and human health hazards due to the low bulk density of RHA. As silicon dioxide (SiO2) has the highest amount of presence in the rice husk ash, long-term exposure can lead to lung cancer, silicosis, chronic obstructive pulmonary disease, or tuberculosis. This research primarily focuses on the feasible and cost-effective technology to convert the rice husk ash into environment-friendly valuable products namely amorphous silica, crystalline silica, and porous silica, apart from ash’s usage as construction material, pesticide, or soil improvement material.