A new hybrid photobioreactor design for microalgae culture

From oil refinery to microalgal biorefinery

Carbon dioxide capture and use in photobioreactors: The role of the carbon dioxide loads in the carbon footprint

Surface processes occur in various ecosystems and landscapes and at multiple spatial and temporal scales. Because of their small-scale, surface heterogeneities are often not represented or poorly parameterized in climate models. These local soil and vegetation heterogeneities are often important or even fundamental for energy and carbon balances. This is of particular interest in high-latitude ecosystems, because of the large amount of carbon stored in the soil of northern peatlands. Greenhouse gas fluxes, such as methane, carbon dioxide and water vapor, vary largely within the environment, also as an effect of the small-scale processes that characterize the landscape. Therefore, a characterization of the effects of such small-scale features on high-latitude environments is needed in order to consistently assess the water, carbon, and energy balance of these landscapes. As a first example, I considered permafrost dominated landscapes in the Arctic lowlands, such as the polygonal tundra. These landscapes display characteristic smallscale features generated by contraction and expansion of water by freezing and melting cycles. These small-scale surface heterogeneities may deeply affect the hydrology in this environment. In the first part of my thesis I present a stochastic model for the surface topography of low center polygonal tundra using Poisson-Voronoi diagrams and I compare the results with available recent field studies. I analyze seasonal dynamics of water table variations and the landscape response under different scenarios of precipitation income. Using an idealized model for methane emissions, I can upscale methane fluxes at the landscape level. Hydraulic interconnections and large-scale drainage may also be investigated through percolation thresholds of the model. The model is able to reproduce the statistical characteristics of the landscape, from the area distribution to the water balance. This novel approach statistically relates large-scale properties of the system to the main small-scale surface heterogeneities, which are generally neglected in large-scale models. In order to generalize the findings from the stochastic model, in the second part of my thesis I present a surface model for small-scale surface heterogeneities in boreal peatlands. Water table depth and dynamics are in turn regulated by the peatland micro-topography, i. e. the elevated and drier hummocks, and the lower and wetter hollows. A classical mean field approximation of a single bucket model may not be adequate to describe land-atmosphere interactions in northern peatlands. I can assess the potential effects of the representation of small-scale surface heterogeneities on greenhouse gas fluxes by coupling this fine scale model with a process based model for methane emissions. By partitioning of space in smaller subunits and then by analyz-

Global warming threatens the entire planet, and solutions such as direct air capture (DAC) can be used to meet net-zero goals and go beyond. This study investigates using DAC in a 5-step temperature vacuum swing adsorption (TVSA) cycle with adsorbents' Li-X and Na-X, readily available industrial zeolites, to capture and concentrate CO2 from air in cold climates. From this study, we report that Na-X in cold conditions has the highest known CO2 adsorption capacity in air of 2.54mmol/g. This combined with Na-X's low CO2 heat of adsorption, and fast uptake-rate in comparison to other benchmark materials, allowed for Na-X operating in cold conditions to have the lowest reported DAC operating energy of 1.1 MWh/tonCO2. These findings from this study show the promise of this process in cold climates of Canada, Alaska, Greenland, and Antarctica to be part of the solution to global warming.

Recurring dry-wet cycles of soils, such as in rice paddies and on floodplains, have a dramatic impact on biogeochemical processes. The rates and trajectories of microbial metabolic functions during transition periods from drained to flooded conditions affect the transformation rates and phase partitioning of carbon, nutrients, and contaminants. However, the regulating mechanisms responsible for diverging functional metabolisms during such transitions are poorly resolved. The chemistry of organic carbon within the microbially available pool likely holds key information regarding carbon cycling and redox transformation rates. In this study, we used mesocosms to examine the influence of different carbon sources (glucose, straw, manure, char) on microbial energetics, respiration rates, and carbon balances in rice paddy soils during the transition from drained to flooded conditions following inundation. We found that variability in carbon solubility (1.6-400 mg g-1) and chemical composition of the amendments led to non-uniform stimulation of carbon dioxide production per unit carbon added (0.4-32.9 mmol CO2 mol-1 added C). However, there was a clear linear correlation between energy release and net CO2 production rate (R2=0.85), between CO2 and initial soluble C (R2=0.91, excluding glucose treatment) and between heat output and Gibbs free energy of initial soluble C (R2=0.78 and 0.69, with/without glucose respectively). Our results further indicated that the chemical composition of the soluble C from amendments initiated divergent anaerobic respiration behavior, impacting methane production and the partitioning of elements between soil solid phase and solution. This study shows the benefit of monitoring energy and element mass balances for elucidating the contribution of various microbial metabolic functions in complex systems. Further, our results highlight the importance of organic carbon composition within the water soluble pool as a key driver of microbially mediated redox transformations with major impacts on greenhouse gas emissions, contaminant fate, and nutrient cycling in paddy soils and similar ecosystems.

Carbon emission and sequestration of urban turfgrass systems in Hong Kong

Limits to Paris compatibility of CO2 capture and utilization

Photosynthesis, respiration and growth: A carbon and energy balancing act for alternative oxidase

Temperaturabhängigkeit des CO2-Gaswechsels stammsukkulenter Asclepiadaceen mit Säurestoffwechsel

Carbon dioxide output in laparoscopic cholecystectomy

Aims Forest fire is a major disturbance factor for forest ecosystems and an important pathway of decreasing vegetation- and soil-carbon storage. Scientifically and effectively measuring carbonaceous gases emission from forest fire is important in understanding the significance of forest fire in carbon balance and climate change. However, carbon emissions from forest fire remain unclear. Our objective was to estimate carbon emissions from forest fires from 1965 to 2010 in Daxing’an Mountains of Heilongjiang Province, China. Methods We used a geographic information system (GIS) based modeling approach to generate emission estimates using a two-step procedure. First, we calculated total carbon released from forest fires in Daxing’an Mountains for selected years between 1965 and 2010 by merging and analyzing several measurement parameters. Second, we calculated amounts of four carbonaceous gases released during the burns, carbon dioxide (CO 2 ), carbon monoxide (CO), methane (CH 4 ), and nonmethane hydrocarbon (NMHC), using several different experimentally derived emission factors. The origin of each of the inputs used in our models is based on a combination of analysis of forest fire statistics, forest resources inventory, field research and laboratory experiments. Important findings Direct total carbon emissions from forest fires in Daxing’an Mountains during 1965–2010 are about 2.93 × 10 7 t, and mean annual carbon emissions are about 6.38 × 10 5 t per year, accounting for 5.64% of the direct total carbon emissions from forest fires in China. Carbon atmospheric emissions of CO 2 , CO, CH 4 and NMHC from forest fires were 1.02 × 10 8 t, 9.41 × 10 6 t, 5.41 × 10 5 t and 2.11 × 10 5 t, respectively, and mean an- nual emissions of CO 2 , CO, CH 4 , and NMHC from forest fires were 2.22 × 10 6 t, 2.05 × 10 5 t, 1.18 × 10 4 t and 4.59 × 10 3 t, respectively, accounting for 5.46%, 7.56%, 10.54% and 4.06% of the amounts of four carbonaceous gases released from forest fires in China, respectively. Our results indicate that combustion efficiency of coniferous broad-leaved mixed forests is lower than other forest types, and burned area of coniferous broad-leaved mixed forests accounts for 21.23% of total burned area, but carbon emissions accounts for 7.81% of total carbon emissions.

The actual biotrickling filtration technology addresses volatile organic compounds (VOCs) removal from air, by their conversion into less harmful gaseous compounds (e.g. carbon dioxide). The actual study extends this capability towards not only VOCs removal, but also removal of carbon dioxide issued from biodegradation, in the same biotrickling filter (BTF). This upgrade results in higher C-capture and the reduction of greenhouses gases associated with this process, thus increasing the environmental performance of such BTFs. The model pollutant used in this study is ethanol, while a co-immobilised microalgae and compost-derived microorganisms is used for the first time accomplishing the above mentioned desiderate (simultaneously removal of VOC and carbon dioxide in the same BTF), under continuous regime and illumination provided by an array of light-emitting diodes (LED)). Very promising performances are obtained, revealing new competitive alternatives with high potential for further development, in the light of atmospheric protection and climate change issues.

Investigation on removal of multi-component volatile organic compounds in a two-stage plasma catalytic oxidation system - Comparison of X (X=Cu, Fe, Ce and La) doped Mn2O3 catalysts

Municipal solid waste landfills are a source of major greenhouse gases such as methane (CH4) and carbon dioxide (CO2) and emit a trace amount of hydrogen sulfide (H2S). Recently, steel slag has extensively been used for mineral CO2 sequestration to minimize the CO2 releases to the atmosphere. This study explores the potential of basic oxygen furnace (BOF) steel slag to simultaneously remove CO2 and H2S from landfill gas (LFG). Various batch and column tests were conducted to evaluate the CO2 and H2S removal potential of the BOF slag under various conditions such as moisture content and particle size of the BOF slag. The three different particle sizes of BOF slag (coarse, as-is, and fine) were exposed to continuous flow of a synthetic LFG [50% CO2, 48.25% CH4, and 1.75% H2S by volume (v/v)] in a column reactor to evaluate the effect of particle size on CO2 and H2S removal capacity of the slag. Similarly, the BOF slag was exposed to synthetic LFG as well as 20% (v/v) of H2S alone in batch reactors at varying moisture contents (10%–30% by weight) to evaluate the effect of moisture content on the CO2 and H2S removal capacity of the slag. A significant H2S removal of 27 g H2S kg−1 BOF slag and CO2 removal of 76 g CO2 kg−1 BOF slag were obtained in the batch reactor. The fine BOF slag (<0.106 mm) showed the maximum CO2 removal (300 g CO2 kg−1 BOF slag) and H2S removal (38 g H2S kg−1 BOF slag) upon exposure to continuous synthetic LFG flow in the column reactor. The quantitative X-ray diffraction (QXRD) analysis showed the highest increase in carbon (77.5 g C kg−1 BOF slag) and sulfur (28 g S kg−1 BOF slag) contents in the fine BOF slag, which was consistent with the mass balance of carbon and sulfur from CO2 and H2S uptake in column tests. The major reaction product with H2S was elemental sulfur depicted by the significant increase in the sulfur content in the X-ray fluorescence analysis. The key minerals involved in carbonation reactions were lime, portlandite, and larnite, as these minerals showed significant reduction in weight percentage (100%, 82%, and 80%, respectively) in the QXRD analysis. Overall, BOF slag showed promising results in mitigating CO2 and H2S from LFG.

Methane hydrate exists in huge amounts in certain locations, in sea sediments and the geological structures below them, at low temperature and high pressure. Production methods are in development to produce the methane to a floating platform. There it can be reformed to produce hydrogen and carbon dioxide, in an endothermic process. Some of the methane can be burned to provide heat energy to develop all needed power on the platform and to support the reforming process. After separation, the hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform can be separated from other gases and then sequestered in the sea as carbon dioxide hydrate. In this way, hydrogen is made available without the release of carbon dioxide to the atmosphere, and the hydrogen could be an enabling step toward a world hydrogen economy.