Biochar, a form of black carbon produced from pyrolyzed biomass, has been touted as a product that may suppress agricultural soil emissions while also sequestering carbon. BC Biocarbon LTD, a recently established company in McBride, BC, has developed a method of producing a new product called biocoal. This biocoal is produced from a combination of crushed biochar and an organic-based binder also made from the original biomass feedstock. As their biocoal contains similar properties to fossil coal or petroleum coke, its use to reduce emissions as an energy fuel or sequestration method may be favourable to biochar’s use as a soil additive. Additionally, this biocoal may present a method of long-term carbon sequestration if buried. This dissertation assessed the greenhouse gas emissions from the production of biocoal from BC Biocarbon’s system and compared the results to wood pellet production and delivery (Project 1), coal and petroleum coke displacement (Project 2), landfilling for carbon sequestration, while also assessing biochar’s potential soil greenhouse gas reductions with added carbon sequestration (Project 3), and a regional and province-wide assessment for reducing emissions in BC using available sawmill and roadside slash residues (Project 4). Project 1 showed that when comparing biocoal made from sawmill residues to locally produced wood pellets, transportation emissions may be decreased 64% due to biocoal’s higher heating value. When comparing emissions produced for biocoal or wood pellets at gate, biocoal may show a 42% reduction in emissions or up to a 51% increase in emissions, however this is largely dependent on the data-sourced scenarios and their underlying assumptions of emissions allocation. Project 2 showed that displacing petroleum coke in cement kilns offered the largest reduction potential compared to coal applications such as electricity generation, or lead smelting. Project 3 showed that under 3 average conditions, sequestering biocoal offered greater emission reduction potential than soil applied biochar. Finally, Project 4 showed that an estimated GHG emission reduction or carbon sequestration of 28,000,00 Mg CO2e/year from current available residues, and 20,006,000 Mg CO2e/year in 10 years’ time, BC has the potential to reduce its current emissions by around 46%, and 33% in 10 years.
A saturated up-flow column experiment was conducted to compare the ability of locally-available organic amendments (hay and sawdust) to foster reducing conditions and attenuate permit-exceeding concentrations of sulfate, nitrate, and selenium in effluent from a British Columbia coal mine. Mine effluent was continuously passed through columns containing one or both amendments mixed with mine-sourced rock, and indicators of organic decomposition and redox conditions were quantified in influent and effluents. Over the 180-day trial, effluent from hay-amended columns exhibited the highest removal of target parameters (up to 99.9%, 98.6%, and 77.5% removal of nitrate, selenium, and sulfate, respectively), although performance decreased over time, suggesting possible long-term performance concerns. In contrast, sawdust-amended columns fostered only partial denitrification and no sulfate removal, which could be linked to the more recalcitrant nature of the organic matrix. Effluents from all columns amended with organics would require further treatment before discharge to a receiving environment.
Extensive industrial activities have led to Cr contamination in the environment, which poses threats to ecosystems and human health. Currently, very little is known regarding the Cr accumulation in soils during aging. The purpose of this dissertation was (i) to enhance our understanding of Cr transformations occurring over a long period of time; (ii) to investigate the reduction of toxic Cr(VI) to non-toxic Cr(III) by soil microorganisms for developing bioremediation strategies for Cr-contaminated sites. Soil samples were collected from a longterm (> 30 years) tannery waste contaminated area in Shuitou (China) for this research. Chemical extraction methods showed the Cr(III) form was dominant (> 96.7% of total Cr) in these aged Cr-contaminated soils, with toxic Cr(VI) up to 144 mg kg-1. Of the total Cr(VI) present, immobile Cr(VI) represented > 90%. Synchrotron-based X-ray near edge structure spectroscopy demonstrated Cr species present were CrFeO3, CrOOH, and CaCrO4. The occurrence of immobile Cr(VI) species in long-term contaminated soils was further verified by a spiking experiment over 240-day aerobic incubation. Available Cr(VI) in soils continually decreased during aging, with immobile Cr(VI) increasing by 4.5 – 31% and immobile Cr(III) increasing by 68 – 95% of total spiked Cr(VI). These findings reveal that Cr(VI) reduction and immobilization were occurring concurrently in soils. Cr(VI) reduction occurs in soils with low pH and high organic carbon content via both chemical and biological processes, while Cr(VI) immobilization occurs in soils with cations (such as Ca2+) and Fe oxides. Shotgun metagenomic sequencing was used to analyze the microbial community composition in the soils and a batch solution experiment was employed to determine the Cr(VI) reduction capacity by soil microbial consortia. The results demonstrated the accumulation of high levels of Cr in a soil (e.g., 3141 mg kg-1 in S3-2) led to the increased abundance of Cr resistant and reducing microorganisms: Proteobacteria (69.9%) at phylum level, Betaproteobacteria (39.1%) at class level, and Massilia (12.6%) and Bacilli (0.57%) at genus level. Batch experiment results showed the addition of 1.0 g Cr-contaminated soils reduced 10 – 20 mg L-1 Cr(VI) in 20 mL of K2Cr2O7 solution at the condition of 30 oC at pH 7.8 – 8.0 within 7 days anaerobically and aerobically, when supplied with 0.2 g L-1 of Na-acetate as carbon and electron sources. The amount of Cr(VI) removed was highest (29.0 mg L-1) at 40 mg Cr(VI) L-1 in the presence of soil S3-2. Therefore, prospective application of mixed microbial consortia from high Cr-contaminated soils for bioremediation of Cr(VI)-polluted environments could be expected.
