Enzyme-induced Calcite Precipitation: A Biochemical Approach to Mitigate Dust Nuisance and Strength Enhancement of Fly Ash Deposits

Rapid urbanization coupled with industrial growth escalated energy demands, leading to large-scale generation of fly ash as a byproduct of coal-fired thermal power plants. The annual production of fly ash has reached around 592 million tonnes in 2022 and is forecasted to reach around 1090 million tonnes by 2032. Approximately 50 % of this generated ash is used in construction, and the rest is stored in the ash disposal facilities. The finer particles in the disposed ash, ranging from 10 μm to 100 μm, are highly susceptible to wind erosion, causing severe dust nuisance in the surrounding environment. Conventional dust suppression techniques, such as water spraying and chemical suppressants, are resource-intensive and, in certain conditions, are found to be ineffective. Enzyme-induced calcite precipitation (EICP) is an emerging biochemical process that has great potential in mitigating dust nuisance and soil erosion. The calcium carbonate crystals precipitated during this biochemical process result in the enhancement of surface strength, thus mitigating wind erosion. Enhancement of the surface strength of fly ash was studied using EICP treatment under varying conditions of dry density, moisture content, and substrate composition. EICP-treated samples were found to exhibit a substantial increase in penetration resistance of about 13.6 times that of pristine samples after 7 days of treatment. The strength enhancement leading to dust suppression was also validated using a wind tunnel experiment and particulate matter sampling. The results highlight the combined effect of moisture availability, density, and substrate composition in optimizing EICP performance. These findings demonstrate the potential of EICP as a sustainable and efficient solution to enhance the surface strength of fly ash deposits, thereby mitigating dust emissions from various industrial disposal facilities.