Adsorption of naphthenic acids on high surface area activated carbons.

In oil sands mining extraction, water is an essential component; however, the processed water becomes contaminated through contact with the bitumen at high temperature, and a portion of it cannot be recycled and ends up in tailing ponds. The removal of naphthenic acids (NAs) from tailing pond water is crucial, as they are corrosive and toxic and provide a substrate for microbial activity that can give rise to methane, which is a potent greenhouse gas. In this study, the conversion of sawdust into an activated carbon (AC) that could be used to remove NAs from tailings water was studied. After producing biochar from sawdust by a slow-pyrolysis process, the biochar was physically activated using carbon dioxide (CO2) over a range of temperatures or prior to producing biochar, and the sawdust was chemically activated using phosphoric acid (H3PO4). The physically activated carbon had a lower surface area per gram than the chemically activated carbon. The physically produced ACs had a lower surface area per gram than chemically produced AC. In the adsorption tests with NAs, up to 35 mg of NAs was removed from the water per gram of AC. The chemically treated ACs showed better uptake, which can be attributed to its higher surface area and increased mesopore size when compared with the physically treated AC. Both the chemically produced and physically produced AC provided better uptake than the commercially AC.

Early atmospheric detection of carbon dioxide from carbon capture and storage sites.

UNLABELLED: The early atmospheric detection of carbon dioxide (CO2) leaks from carbon capture and storage (CCS) sites is important both to inform remediation efforts and to build and maintain public support for CCS in mitigating greenhouse gas emissions. A gas analysis system was developed to assess the origin of plumes of air enriched in CO2, as to whether CO2 is from a CCS site or from the oxidation of carbon compounds. The system measured CO2 and O2 concentrations for different plume samples relative to background air and calculated the gas differential concentration ratio (GDCR = -ΔO2/ΔCO2). The experimental results were in good agreement with theoretical calculations that placed GDCR values for a CO2 leak at 0.21, compared with GDCR values of 1-1.8 for the combustion of carbon compounds. Although some combustion plume samples deviated in GDCR from theoretical, the very low GDCR values associated with plumes from CO2 leaks provided confidence that this technology holds promise in providing a tool for the early detection of CO2 leaks from CCS sites. IMPLICATIONS: This work contributes to the development of a cost-effective technology for the early detection of leaks from sites where CO2 has been injected into the subsurface to enhance oil recovery or to permanently store the gas as a strategy for mitigating climate change. Such technology will be important in building public confidence regarding the safety and security of carbon capture and storage sites.

Removal and biodegradation of naphthenic acids by biochar and attached environmental biofilms in the presence of co-contaminating metals.

This study evaluated the efficacy of using a combined biofilm-biochar approach to remove organic (naphthenic acids (NAs)) and inorganic (metals) contaminants from process water (OSPW) generated by Canada's oil sands mining operations. A microbial community sourced from an OSPW sample was cultured as biofilms on several carbonaceous materials. Two biochar samples, from softwood bark (SB) and Aspen wood (N3), facilitated the most microbial growth (measured by protein assays) and were used for NA removal studies performed with and without biofilms, and in the presence and absence of contaminating metals. Similar NA removal was seen in 6-day sterile N3 and SB assays (>30%), while biodegradation by SB-associated biofilms increased NA removal to 87% in the presence of metals. Metal sorption was also observed, with up to four times more immobilization of Fe, Al, and As on biofilm-associated biochar. These results suggest this combined approach may be a promising treatment for OSPW.

Pyrolysis of wood to biochar: increasing yield while maintaining microporosity.

The objective of this study was to determine if biochar yield could be increased by the deposition of volatile pyrolysis species within the bed during production, without negatively influencing the microporosity and adsorption properties. Aspen (Populus tremuloides) wood chips were loaded into three vertically stacked zones within a reactor and heated in nitrogen to temperatures between 420 and 650°C (i.e., pyrolyzed). The yield did increase from the zone at the reactor inlet to the subsequent zones as volatile species deposited and carbonized, and importantly, the carbonized deposits had a similar microporous structure and organic vapor uptake (1,1,1,2-tetrafluoroethane) to that of the primary biochar. Based on these results, bio-oil from previous runs at 600°C was recycled to the bed, which further increased the yield while maintaining the desirable adsorption properties of the biochar.

Enhancing biochar yield by co-pyrolysis of bio-oil with biomass: impacts of potassium hydroxide addition and air pretreatment prior to co-pyrolysis.

The influence of KOH addition and air pretreatment on co-pyrolysis (600 °C) of a mixture of bio-oil and biomass (aspen wood) was investigated with the goal of increasing biochar yield. The bio-oil was produced as a byproduct of the pyrolysis of biomass and recycled in subsequent runs. Co-pyrolysis of the biomass with the recycled bio-oil resulted in a 16% mass increase in produced biochar. The yields were further increased by either air pretreatment or KOH addition prior to co-pyrolysis. Air pretreatment at 220 °C for 3 h resulted in the highest mass increase (32%) compared to the base case of pyrolysis of biomass only. No synergistic benefit was observed by combining KOH addition with air pretreatment. In fact, KOH catalyzed reactions that increased the bed temperature resulting in carbon loss via formation of CO and CO2.

Feasibility study of a Great Lakes bioenergy system.

A bioenergy production and delivery system built around the Great Lakes St. Lawrence Seaway (GLSLS) transportation corridor was assessed for its ability to mitigate energy security and climate change risks. The land area within 100 km of the GLSLS and associated railway lines was estimated to be capable of producing at least 30 Mt(dry) yr(-1) of lignocellulosic biomass with minimal adverse impacts on food and fibre production. This was estimated to be sufficient to displace all of the coal-fired electricity in Ontario plus more than 620 million L of green diesel (equivalent to 5.3% of diesel consumption in GLSLS provinces). Lifecycle greenhouse gas emissions were 88% and 76% lower than coal-fired power and conventional diesel, respectively. Production costs of $120 MWh(-1) for power and up to $30 GJ(-1) ($1.1 L(-1)) for green diesel were higher than current market prices, but a value for low-carbon energy would narrow the price differential.

Production of bio-synthetic natural gas in Canada.

Large-scale production of renewable synthetic natural gas from biomass (bioSNG) in Canada was assessed for its ability to mitigate energy security and climate change risks. The land area within 100 km of Canada's network of natural gas pipelines was estimated to be capable of producing 67-210 Mt of dry lignocellulosic biomass per year with minimal adverse impacts on food and fiber production. Biomass gasification and subsequent methanation and upgrading were estimated to yield 16,000-61,000 Mm(3) of pipeline-quality gas (equivalent to 16-63% of Canada's current gas use). Life-cycle greenhouse gas emissions of bioSNG-based electricity were calculated to be only 8.2-10% of the emissions from coal-fired power. Although predicted production costs ($17-21 GJ(-1)) were much higher than current energy prices, a value for low-carbon energy would narrow the price differential. A bioSNG sector could infuse Canada's rural economy with $41-130 billion of investments and create 410,000-1,300,000 jobs while developing a nation-wide low-carbon energy system.

Isolation and characterization of hydrogen-oxidizing bacteria induced following exposure of soil to hydrogen gas and their impact on plant growth.

In many legumes, the nitrogen fixing root nodules produce H2 gas that diffuses into soil. It has been demonstrated that such exposure of soil to H2 can promote plant growth. To assess whether this may be due to H2-oxidizing microorganisms, bacteria were isolated from soil treated with H2 under laboratory conditions and from soils collected adjacent to H2 producing soybean nodules. Nineteen isolates of H2-oxidizing bacteria were obtained and all exhibited a half-saturation coefficient (Ks) for H2 of about 1 ml l(-1). The isolates were identified as Variovorax paradoxus, Flavobacterium johnsoniae and Burkholderia spp. using conventional microbiological tests and 16S rRNA gene sequence analysis. Seventeen of the isolates enhanced (57-254%) root elongation of spring wheat seedlings. Using an Arabidopsis thaliana bioassay, plant biomass was increased by 11-27% when inoculated by one of four isolates of V. paradoxus or one isolate of Burkholderia that were selected for evaluation. The isolates of V. paradoxus found in both H2-treated soil and in soil adjacent to soybean nodules had the greatest impact on plant growth. The results are consistent with the hypothesis that H2-oxidizing bacteria in soils have plant growth promoting properties.

Adenylate-coupled ion movement. A mechanism for the control of nodule permeability to O2 diffusion.

In response to changes in phloem supply, adenylate demand, and oxygen status, legume nodules are known to exercise rapid (seconds to hours) physiological control over their permeability to oxygen diffusion. Diffusion models have attributed this permeability control to the reversible flow of water into or out of intercellular spaces. To test hypotheses on the mechanism of diffusion barrier control, nodulated soybean (Glycine max L. Merr.) plants were exposed to a range of treatments known to alter nodule O2 permeability (i.e. 10% O2, 30% O2, Ar:O2 exposure, and stem girdling) before the nodules were rapidly frozen, freeze dried, and dissected into cortex and central zone (CZ) fractions that were assayed for K, Mg, and Ca ion concentrations. Treatments known to decrease nodule permeability (30% O2, Ar:O2 exposure, and stem girdling) were consistently associated with an increase in the ratio of [K+] in cortex to [K+] in the CZ tissue, whereas the 10% O2 treatment, known to increase nodule permeability, was associated with a decrease in the [K+]cortex:[K+](CZ). When these findings were considered in the light of previous results, a proposed mechanism was developed for the adenylate-coupled movement of ions and water into and out of infected cells as a possible mechanism for diffusion barrier control in legume nodules.

In vivo gas exchange measurement of the site and dynamics of nitrate reduction in soybean.

A gas analysis system was built to study the relationship between the reductant cost of NO(3)(-) assimilation and the measured rate of CO(2) and O(2) exchange in roots, leaves, and stems+ petioles of soybean (Glycine max L. Merr. cv Maple glen) plants. The measurements were used to calculate the diverted reductant utilization rate (DRUR = 4*[measured rate of CO(2) + measured rate of O(2)], in moles of high-energy electron [e(-)] per gram per hour) in plants in the presence (N+) and absence (N-) of NO(3)(-). The differences in DRUR between the N+ and N- treatments provided a measure of the NO(3)(-)-coupled DRUR of 25-d-old plants, whereas a (15)NO(3)(-)-enriched nutrient solution was used to obtain an independent measure of the rate of NO(3)(-) assimilation. The measured reductant cost for the whole plant was 9.6 e(-) per N assimilated, a value within the theoretical range of four to 10 e(-) per N assimilated. The results predicted that shoots accounted for about 55% of the whole-plant NO(3)(-) assimilation over the entire day, with shoots dominating in the light, and roots in the dark. The gas analysis approach described here holds promise as a powerful, noninvasive tool to study the regulation of NO(3)(-) assimilation in plant tissue.

Adenylate gradients and Ar:O(2) effects on legume nodules: I. Mathematical models.

Mathematical models were developed to test the likelihood that large cytosolic adenylate concentration gradients exist across the bacteria-infected cells of legume nodules. Previous studies hypothesized that this may be the case to account for the unusually low adenylate energy charge (AEC; 0.65) measured in the plant fraction of metabolically active nodules (M.M. Kuzma, H. Winter, P. Storer, I. Oresnik, C.A. Atkins, D.B. Layzell [1999] Plant Physiol 119: 399-407). Simulations coupled leghemoglobin-facilitated O(2) diffusion into the infected cell, through bacteroid nitrogenase activity, with the ATP demand for transport and ammonia assimilation in the plant fraction of ureide- and amide-producing nodules. Although large cytosolic adenylate gradients were predicted to exist in both nodule types, amide nodules were predicted to have steeper AEC gradients (0.82-0.52) than ureide nodules (0.82-0.61). The differences were attributed to an additional ATP demand for Asn synthesis in the amide nodule. Simulations for nodules transferred to an Ar:O(2) atmosphere predicted a major reduction in the magnitude of adenylate gradients and an increase in the AEC of the plant fraction. Results were consistent with a number of experimental studies and were used to propose an experimental test of the models.

Adenylate gradients and Ar:O2 effects on legume nodules. II. Changes in the subcellular adenylate pools.

Central infected zone tissue of soybean (Glycine max L. Merr.) nodules was fractionated into separate subcellular compartments using density gradient centrifugation in nonaqueous solvents to better understand how exposure to Ar:O(2) (80:20%, v/v) atmosphere affects C and N metabolism, and to explore a potential role for adenylates in regulating O(2) diffusion. When nodules were switched from air to Ar:O(2), adenylate energy charge (AEC) in the plant cytosol rose from 0.63 +/- 0.02 to 0.73 +/- 0.02 within 7 min and to 0.80 +/- 0.01 by 60 min. In contrast, AEC of the mitochondrial compartment of this central zone tissue remained high (0.80 +/- 0.02 to 0.81 +/- 0.02) following Ar treatment while that of the bacteroid compartment was unchanged, at 0.73 +/- 0.02, after 7 min, but declined to 0.57 +/- 0.03 after 60 min. These results were consistent with a simulation model that predicted Ar:O(2) exposure would first reduce ATP demand for ammonia assimilation and rapidly increase cytosolic AEC, before the Ar:O(2)-induced decline mediated by a decrease in nodule O(2) permeability reduces bacteroid AEC. The possibility that adenylates play a key, integrating role in regulating nodule permeability to oxygen diffusion is discussed.