Agro-Waste Biochar to Reduce the Leaching of Heavy Metals from Coal Fly Ash Amended Soil

The soils added with coal fly ash may contain heavy metals potentially up to the levels of toxicity. Biochars have been successfully used in the past to reduce the bioavailability and leaching of heavy metals in contaminated soils. Therefore, the co-application of biochar together with coal fly ash could positively change the bioavailability and leaching characteristics of heavy metals in sandy soils through various fixing mechanisms. In the present study, the authors investigated the effect of agro-waste biochar in modifying the leaching loss of heavy metals from coal fly ash contaminated soils. Column leaching tests with simulated rainfall conditions were conducted for sandy Ultisol soils mixed with coal fly ash and avocado branch cut biomass biochar at 5 tons/ha rate. The results showed the presence of heavy metals in the leachate of fly ash added soil. Application of biochar significantly reduced the leachability of all the tested heavy metals in the study. The reduction rates were up to 55% compared to non-amended samples. Therefore, the agro-waste biochar can effective be used in stabilizing the heavy metals in coal fly ash contaminated soils, to minimize the risk of environmental contamination.