Date of Award
Doctor of Philosophy
Soil Science; Environmental Science
David A. Laird
Hans van Leeuwen
Biochar is the solid residue of organic materials heated under low-oxygen conditions and is a co-product of pyrolysis based bioenergy production (PBBP) in which biorenewable materials are utilized to produce energy. Biochar exhibits long residence times in soil, thus soil application can sequester atmospheric carbon. Biochar can also improve soil properties. Biochar can contribute to the success of PBBP by high economic value, however, variable properties and performance in soil preclude agronomic recommendations, limiting application and hence, demand and value. Biochar with significant anion exchange capacity (AEC) has potential to become a co-product of PBBP with implications for sustainable agriculture and environmental remediation, however knowledge of the persistence of biochar AEC and the mechanisms by which biochar surface chemistry changes as it ages and weathers in soil environments was lacking. This research intended to investigate biochar ageing, ageing impacts on AEC, increase AEC for alkaline pHs, and produce biochar for the remediation of chlorinated hydrocarbon contaminants (CHCs). Biochars were oxidized under alkaline conditions to understand ageing in relevant conditions and enhanced with metal oxyhydroxides to increase AEC. Pyrolysis temperature influences aromatization of biochar carbon which oxidizes by pathways related to degree of aromatization and exhibits ageing recalcitrant AEC due to position stabilized oxonium heterocycles. Metals can form organometallic bonding structures in pyrolysis that can increase biochar AEC by the high points of zero net charge (PZNC) of metal oxyhydroxides. Pyrolysis can be used to reduce iron to yield biochar-zerovalent iron (BC-ZVI) which can reductively dechlorinate CHCs. Feedstocks low in silicon and phosphorus yield BC-ZVI suitable for this purpose. High AEC biochar and BC-ZVI add value to biochar, increasing the economic competitiveness of PBBP, and proffer green advances to existing production technologies.
Lawrinenko, Michael, "Biochar for sustainable advances in agriculture and environmental remediation" (2016). Graduate Theses and Dissertations. 15951.