Short Rotation Forestry (SRF) for bioenergy could be used to meet biomass requirements and contribute to achieving renewable energy targets. As an important source of biomass it is important to gain an understanding of the implications of large-scale application of SRF on the soil-atmosphere greenhouse gas (GHG) exchange. This study examined the effects of land use change (LUC) from grassland to SRF on soil fluxes of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2), and the important drivers in action. Examining soils from a range of sites across the UK, CO2 emission potentials were reduced under SRF with differences between coniferous and broadleaved transitions; these changes were found to be related to changes in soil pH and microbial biomass. However, there were limited effects of SRF tree species type on CH4 and N2O fluxes. A detailed study at an experimental SRF site over 16 months demonstrated a reduction in CH4 and net CO2 emissions from soils under SRF and revealed intriguing temporal dynamics of N2O under Sitka spruce and common alder. A significant proportion of the variation in soil N2O fluxes was attributed to differences between tree species, water table depth, spatial effects, and their interactions. The effects of microtopography (ridges, troughs, flats), and its interactions with water table depth on soil GHG fluxes under different tree species was tested using mesocosm cores collected in the field. Microtopography did not significantly affect soil GHG fluxes but trends suggested that considering this spatial factor in sampling regimes could be important. N2O fluxes from Sitka spruce soils did not respond to water table depth manipulation in the laboratory suggesting that they may also be determined by tree-driven nitrogen (N) availability, with other research showing N deposition to be higher in coniferous plantations. An N addition experiment lead to increased N2O emissions with greatest relative response in the Sitka spruce soils. Overall, LUC from rough grassland to SRF resulted in a reduction in soil CH4 emissions, increased N2O emissions and a reduction or no change in net CO2 emissions. These changes in emissions were influenced both directly and indirectly by tree species type with Sitka spruce having the greatest effect on N2O in particular, thus highlighting the importance of considering soil N2O emissions in any life cycle analysis or GHG budgets of LUC to SRF for bioenergy. This research can help inform decisions around SRF tree species selection in future large-scale bioenergy planting.

The quality of electricity infrastructure and supply to a nation is seen as vital for the development of the local and regional economy. In recent times, electricity generation industries worldwide have undergone significant changes pertaining to the kind of technologies used. These changes were made in order to address concerns related to energy security and sustainability. South Africa has been identified as a carbon-intensive economy, with the electricity sector being at the high end of the carbon intensity spectrum. The need to analyse the socio-environmental impacts of existing electricity generation techniques becomes vital when taking into account the transitions in the South Africa electricity industry. Socio-environmental impacts are categorised into public, environmental and occupational impacts, based on the point of impact. The methodology used to quantify these impacts is based on the Impact Pathway Approach used in the Externalities of Energy study. The Externalities of Energy study was devised in Europe and has gained prominence particularly in developing countries because of its ability to adapt to local conditions. Since South Africa is a developing country, the methodology is suitable for the quantification of externalities when analysing scenarios that have a dearth of local data. iii South Africa historically focused on non-renewable electricity generation mechanisms. This was done primarily because of the abundant supplies of coal and secondly because of the need to provide electricity at affordable prices to the masses. The focus of the analysis is set on impacts caused by coal and nuclear electricity in South Africa, since these two technologies together contribute to more the 95% of the electricity generated. The impacts in each category are identified, prioritised, analysed and quantified. Once impacts are quantified, monetary costs are attributed to the impacts. The aggregation of the costs caused by the impacts results in determining the damages associated with the quantified impacts. Monetary damages individually are not of much use, and therefore the significance of such damages are underlined once calculated. Determined monetary damages are interpreted in average and total terms relative to the total electricity generated with the intention of highlighting the significance of the costs. The average damage costs are compared to existing electricity prices, which enables policy- and decision-makers to segregate the damages relative to electricity prices. The results of this analysis should enable policy-makers to prudently make decisions about the significance of the social and environmental impacts associated with the dominant non-renewable electricity generation technologies in the country while prioritising the sustainability of the society and environment. / Thesis (PhD)--University of Pretoria, 2013. / cp2013 / Graduate School of Technology Management / PhD / Unrestricted

We present joint analyses of satellite-observed combustion products to examine bulk characteristics of combustion in megacities and fire regions. We use retrievals of CO, NO2 and CO2 from NASA/Terra Measurement of Pollution In The Troposphere, NASA/Aura Ozone Monitoring Instrument, and JAXA Greenhouse Gases Observing Satellite to estimate atmospheric enhancements of these co-emitted species based on their spatiotemporal variability (spread, sigma) within 14 regions dominated by combustion emissions. We find that patterns in sigma(XCO)/sigma(XCO2) and sigma(XCO)/sigma(XNO2) are able to distinguish between combustion types across the globe. These patterns show distinct groupings for biomass burning and the developing/developed status of a region that are not well represented in global emissions inventories. We show here that such multi-species analyses can provide constraints on emission inventories, and be useful in monitoring trends and understanding regional-scale combustion.

Methane is the second most important long-lived greenhouse gas. However, it is typically emitted to the atmosphere by spatially and temporally heterogeneous sources, meaning that local measurements cannot easily be extrapolated to represent global scales. As a consequence, its global sources and sinks are generally poorly quantified. This thesis focuses on the use of airborne observations to improve flux estimates of methane at regional scales. A commercially available cavity-enhanced absorption spectrometer has been modified here for airborne measurements of methane and carbon dioxide. An algorithm employing the system's simultaneous water vapour measurement has been derived, using laboratory experiments, to determine dry air mole fractions without the need for sample drying. The system was found to be relatively independent of the aircraft's motion and its measurements were found to be accurate to within 1.28 ppb (1 standard deviation repeatability at 1Hz of 2.48 ppb) for methane and 0.17 ppm (1 standard deviation repeatability at 1Hz of 0.66 ppm) for carbon dioxide. This new measurement capability has been deployed during three international field campaigns, data from which is used in this thesis. The composition of boreal biomass burning was measured in eastern Canada. Methane emission factors showed a high degree of variability (range 1.8 $\pm$\ 0.2 to 8.5 $\pm$\ 0.9 g (kg dry matter)$^{-1}$), accentuating the challenges with using a purely bottom-up approach to determine total methane emissions and that top-down constraints are needed. Two case studies have shown that an aircraft mass balance approach can be a valuable tool for deriving regional scale top-down flux estimates, when a suitable sampling strategy can be employed under appropriate atmospheric conditions. First, this technique was applied to the European Arctic wetlands; and second, its suitability to derive emissions from a megacity was investigated using London, UK as a test case. On both occasions, the derived fluxes were found to be in good agreement with coincident surface observations within the aircraft's sampling domain. In the case of the Arctic wetlands the excellent agreement with seasonally averaged surface observations allowed this information to be used for the evaluation of land surface models. Two commonly used models, the Joint UK Land Environment Simulator and Hybrid8 were found to underestimate the methane emission flux for this region by an order of magnitude, highlighting the large uncertainties present in future methane emission scenarios at regional scales under a changing climate.

Given the rapid rise in global mean temperature as a direct consequence of increasing levels of greenhouse gases (GHGs) emissions, various climate geoengineering techniques, for example, solar radiation management (SRM), have been suggested. Often criticized as a distraction from global efforts of removing and reducing GHGs, most notably carbon dioxide (CO2), SRM involves both marine cloud brightening (MCB) and stratospheric aerosol injection (SAI), both of which are based on increasing the Earth’s albedo by seeding aerosols in the marine boundary layer and in the lower stratosphere, respectively. SAI has been explored more extensively in various modeling studies following observations of major volcanic eruptions. A significant loading of sulfate particles, a byproduct of the eruptions, were monitored to cool the Earth’s surface temperature temporarily, albeit with some significant consequences including increasing stratospheric ozone (O₃) depletion and reducing precipitation. For our studies, we solely focused on the application of SAI by studying relevant heterogeneous chemistry of alternative aerosols to sulfate, specifically, calcite (CaCO₃) aerosols, to better understand the aerosols’ unintended impact on stratospheric O3 level. CaCO₃ aerosols, often serve as an idealized proxy for calcium-rich mineral dust, have been modeled to have minimal negative impact on both stratospheric O₃ level, through heterogeneous chemistry, and stratospheric temperature. However, only a few laboratory studies have been done on the heterogeneous chemistry of CaCO₃ aerosols with relevant stratospheric trace gases, such as HNO3 and HCl. These gases play a significant role in O₃ catalytic loss cycles in the stratosphere. Since HNO₃ is a common oxidation product of nitrogen oxides which contribute significantly to urban air pollution, a handful of ambient laboratory studies of CaCO₃ heterogeneous reaction with HNO₃ have been conducted. However, very little is known about CaCO₃ heterogeneous chemistry with HCl. Thus, the modeled impact of CaCO₃ aerosols on stratospheric O₃ so far may not be reliable given the lack of experimentally measured kinetics data. Here we report the results of an experimental study of the uptake of HNO₃ and HCl onto submicron CaCO₃ particles in two different flow reactors. Products and reaction kinetics were observed by impacting aerosolized CaCO₃ onto ZnSe windows, exposing them to the reagent gases at a wide range of concentrations, at 296 K and under dry conditions, and analyzing the particles before and after trace gas exposure using Fourier transform infrared spectroscopy (FTIR). A Ca(OH)(HCO₃ termination layer was detected in the form of a HCO₃¯ peak in the FTIR spectra, indicating a hydrated surface even under dry conditions. The results demonstrate the reaction of HNO₃ with Ca(OH)(HCO₃) to produce Ca(NO₃)2, water, and CO₂. HCl reacted with Ca(OH)(HCO₃) to produce CaCl₂ and also water and CO₂. The depletion of the Ca(OH)(HCO₃)/Ca(CO₃) signal due to reaction with HNO3₃ or HCl followed pseudo-first order kinetics. From the FTIR analysis, the reactive uptake coefficient for HNO₃ was determined to be in the range of 0.013 ≤γ_(HNO₃) ≤0.14, and that for HCl was 0.0011 ≤γ_HCl ≤0.012 within the reported uncertainty. The reaction of HCl with airborne CaCO₃ aerosols was also studied in an aerosol flow tube (AFT) coupled with a quadrupole chemical ionization mass spectrometer (CIMS) under similar conditions to the FTIR study, and γ_HCl was determined to be 0.013  0.001. However, the heterogeneous chemistry of CaCO₃ aerosols at stratospheric conditions is still underexamined. We studied the kinetics of HCl uptake on airborne CaCO₃ aerosols at stratospheric temperature, 207 ± 3 K, by performing experiments under dry conditions. Using the same aerosol generation and characterization method, we coupled a low-temperature flow tube with the CIMS for HCl detection. The reactive uptake coefficient for HCl was measured to be 0.076 ± 0.009. This exceeds the reactive uptake coefficient of 0.013 ± 0.001 that we previously reported for this system at 296 K, consistent with the expected negative temperature dependence of gas uptake on solid surfaces. This finding suggests an initial strong reactive uptake of HCl gas on CaCO₃ aerosol surfaces in the stratosphere. Following the most recent modeling studies, our initial kinetic results suggest that the reactions of HCl and HNO₃ with CaCO₃ in the stratosphere could lead to a O₃ column change between -5% and +25%. This wide range of O₃ impact highlights the high uncertainties in estimating the true atmospheric impact of CaCO₃ aerosols, the most well-studied proposed SAI aerosols after sulfate, upon its release into the stratosphere. Nevertheless, our kinetic study establishes a good experimental standard for studying airborne aerosol heterogeneous chemistry under stratospheric conditions as a necessary step to evaluate SAI as a realistic method to battle global warming.

The global climate is changing and much of this is attributed to the greenhouse effect, which has been exacerbated by increased anthropogenic releases of greenhouse gases (GHGs). However, important GHGs, carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), are produced naturally in the soil during the metabolism of many soil microbial and plant communities. The generation rate of GHGs depends on many factors, including soil community composition, nutrient availability, temperature, and soil moisture. Predicted climate variability is expected to alter temperature and rainfall patterns, which can impact the factors regulating natural generation of GHGs. With changing fluxes of GHGs, the natural feedback loops between GHG generation and climate may change. Increased emissions from natural sources would exacerbate climate change, whereas decreased emissions may mitigate its impacts. Floodplains may be particularly susceptible to climate change, as their biogeochemical processing is driven by hydrology. For this study, ten mesocosms were installed on the floodplain of Stroubles Creek in southwest Virginia. A flood event was simulated in half of these mesocosms in both early spring and mid-summer, which represent extremes in soil moisture and primary productivity on the floodplain. Headspace gases were monitored for CO, N2O, and CH4. Efflux of CO2 and N2O was higher in summer than spring, and also increased following wetting events. Methane production was greater in the spring, with no detectable change with wetting. Increases in summer rainfall events could increase the release of important GHGs to the atmosphere, potentially at levels significant to climate change. / Master of Science

Master thesis "Effort sharing as a legal measure of climate protection" strives to give a comprehensive account of the key characteristics of the effort sharing system, which is one of the two principal EU mitigation tools of the EU. In order to provide a better insight, the thesis first discusses the topic in context of economic theory and international law on climate. The thesis itself is divided into four chapters. First chapter defines the object of climate regulation i.e. greenhouse gases their production and the legal framework of their measuring and accounting.Second chapter focuses on the economic background of climate regulation and it compares different theoretical approaches with existing regulation in force on international and European level. Third chapter gives basic account of the international framework of climate law and specifically on the international mitigation obligations of the EU, which are relevant for the EU law. Fourth and final chapter describes the main aspects of the effort sharing system in contrast to the EU ETS. It draws mainly from the Decision no. 406/2009/ES, which is currently in force and the Regulation no. 2018/842, which will shape the effort sharing system for the 2021 - 2030 period. In four sub- chapters it focuses on the definition of regulated emission...

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