Turning Waste Biomass Into Biochar for Application In Remediation of Contaminated Waters and Soils.

Biochar is increasingly receiving attention as a promising functional material in environmental and agricultural application. Considering the C-rich and recalcitrant nature of biochar, its production on a large scale is a potential strategy for sequestering C from the atmosphere and helping to mitigate climate change. Application of biochar to soil can also help improve soil quality by retaining higher moisture, nutrients and microbial activity, therefore increasing crop production.

Our recent studies indicated that the biochar derived from dairy manure can effectively sorb both Pb and atrazine from wastewater and immobilize them in co-contaminated soils. Sorption of Pb by biochar followed a dual Langmuir-Langmuir model, with a capacity of up to 680 mmol Pb kg^-1. Chemical speciation, x-ray diffraction, and infrared spectroscopy showed that P originally contained in biochar reacted with soil Pb to form insoluble phosphate minerals, which was presumably responsible for Pb sorption. Atrazine sorption may result from its partitioning into the organic phase or adsorption onto surface of biochar. Incorporation of the biochar into two contaminated soils at the rate of 5.0% for 210d showed more than 57% and 66% reduction in Pb and atrazine concentrations in 0.01 M CaCl₂ extraction, respectively. Lead and atrazine concentrations in the toxicity characteristic leaching procedure solution were reduced by 70-89% and 53-77%, respectively. Uptake of Pb and atrazine by earthworms (Eisenia  fetida) were reduced by up to 79% and 73%. The results highlighted the potential of dairy-manure biochar as a unique sorbent for sorption of both heavy metal and organic contaminants in co-contaminated waters and as a unique amendment for immobilization of the contaminants in co-contaminated soils.

In short, biochar production from waste biomass may bring multiple benefits: reuse of solid waste and remediation of contaminated waters and soils in addition to increase of crop production and mitigation of global warming.