Application of a full‐scale wood gasification biochar as a soil improver to reduce organic pollutant leaching risks

Abstract

AbstractBACKGROUNDThe application of biochar to sandy loam soil to reduce leaching of three representative pollutants (a persistent hydrocarbon (phenanthrene; logKOW 4.46), a herbicide (isoproturon; logKOW 2.50), and an antibiotic (sulfamethazine; logKOW 0.28)) were investigated. The wood‐derived biochar evaluated in our laboratory study was the solid co‐product of a full‐scale gasifier feeding a combined heat and power plant. The research aimed to demonstrate multiple environmental benefits with the innovative use of this biochar as a soil improver.RESULTSBatch sorption experiments indicated that 5% biochar added to soil enhanced the partitioning coefficient (Kd) by factors of 2 for phenanthrene and 20 for both sulfamethazine and isoproturon. Column leaching experiments indicated a reduced porewater flow rate, up to 80% slower in the column amended with 5% biochar, and reduced pollutant leaching risks. Numerical models interlinked batch and column study observations.CONCLUSION(i) Biochar enhanced sorption for the hydrophobic pollutant phenanthrene, and also the less hydrophobic pollutants sulfamethazine and isoproturon; (ii) reduced porewater flow rates following biochar amendment gave rise to greater opportunity for pollutant–solid interaction; (iii) mixing with soil resulted in biochar fouling affecting pollutant partition; and (iv) irreversible retention of pollutants by the soil was an important mechanism affecting pollutant transport. © 2017 Society of Chemical Industry