Doctor of Philosophy (PhD)


The School of Plant, Environmental and Soil Sciences

Document Type



Multiple benefits of biochar conversion and utilization, including soil carbon sequestration and environmental remediation, have been proposed by researchers. Biochar may be produced from a wide array of feedstocks and pyrolytic process conditions. This influences the final biochar composition, which includes the presence of potential pollutants that could ultimately result in detrimental environmental impacts. The major purpose of this research was to improve our understanding of potential unintended effects of biochar addition to the environment either as a potential source of toxicity towards organisms or as a material influencing availabilities of other soil contaminants. Biochars were produced from ten different feedstocks at pyrolysis temperatures from 350 to 650 °C, and characterized for total and bioavailable elemental composition, PAHs as well as other intrinsic properties. Bioassays that included the bacterium Vibrio fischeri, the alga Pseudokirchneriella subcapitata, and the plants Lepidium sativum and Sorghum saccharatum were employed to evaluate biochar ecotoxicity. Despite many samples yielding an acceptable pollutant content based on the International Biochar Initiative standard, 28 % of biochar samples were considered toxic for organisms (≥ 50% inhibition), which emphasized the need to complement the traditional analytical characterization of ecotoxicological criteria. The inhibition effect found on biochars produced from cattle manure, poultry litter, and rice straw was attributed to salinity stress, mostly caused by high potassium concentrations. In addition, greater toxicity was detected in feedstocks pyrolyzed at 350 °C compared to higher temperatures, which was presumed to be associated with some VOCs. Regardless of the hazard classification obtained by cattle manure-based biochar, its addition into an acid soil at 20 g kg-1 was effective in alleviating the soil toxicity caused by exchangeable aluminum, which highlighted the importance of guiding biochar users in management recommendations of salt-rich biochar. Biochar added to soil affected the dissipation parameters and the ecotoxicological properties of herbicides, which resulted in an enhancement of metolachlor dissipation, an increase in the persistence of trifluralin, a greater inhibition of bacterial luminescence, and a toxicity reduction to plants with respect to non-amended soil. The present research provided valuable information about the importance of responsible and sustainable use of biochar.



Committee Chair

Wang, Jim J.



Available for download on Thursday, December 04, 2025

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