Dissertations / Theses on the topic 'Methane emissions'

Methane is the second most influential anthropogenic greenhouse gas. There are large uncertainties in the magnitudes and trends of methane emissions from different source types and source regions. Satellite observations of methane offer dense spatial coverage unachievable by suborbital observations. This thesis evaluates the capabilities of using satellite observations of atmospheric methane to provide high-resolution constraints on continental scale methane emissions. In doing so, I seek to evaluate the supporting role of suborbital observations, to inform the emission inventories on which policy decisions are based, and to enable inverse modeling of the next generation of satellite observations.
Earth and Planetary Sciences

Atmospheric CH4 is derived from both natural and anthropogenic sources, and the rapid increase in atmospheric CH4 levels over the past two centuries has predominantly been a result of increased anthropogenic emissions. Nonetheless, natural sources have also changed as a result of global change, and quantifying the fluxes of CH4 from these sources, and their associated climatic feedbacks, is of paramount importance. In this thesis I have developed a method to upscale the global CH4 emissions from UV irradiation of foliar pectin (chapter 2). I have quantified the magnitude and distribution of CH4 emissions from wetlands on a global scale and determined the sensitivity of wetlands to temporal changes in water volume and temperature (chapters 3 and 4). Finally I determine that tropical wetland organic matter decomposition on a global scale behaves non-linearly over seasonal timescales. This implies a substantially different seasonality in CH4 emissions from wetlands (chapter 5). I show that (i) satellites such as MODIS and GRACE can be used to improve the understanding of individual CH4 sources and sinks, and (ii) the newly available satellite observations of CH4 can be effectively used for more than constraining atmospheric chemistry and transport model inversions. Moreover, the work shown in this thesis has contributed new biogenic CH4 source estimates, but has also posed new questions which will ultimately help guide new projects in the atmospheric CH4 research area.

A variety of approaches, spanning a range of spatial and temporal scales, were applied to the investigation of the effects of low dose SO₄^2- deposition, at rates comparable to those experienced in acid rain impacted areas, on methane (CH₄) emissions from natural wetlands. Over two years of experimental manipulation of SO₄^2- deposition to a peatland in northeast Scotland, CH₄ emissions were suppressed by around 40%. There was no significant difference in suppression of CH₄ flux within the sol- deposition range of 25-100 kg-S ha^-1yr^-1. In a similar short-term controlled environment SO₄^2- manipulation experiment, the suppressive effect of SO₄^2- was found to be independent of the simulated SO₄^2- deposition rate within a range of 15-100 kg-S ha^-1yr^-1. The possibility that suppression of CH₄ fluxes may have been the result of a 'salt effect' was ruled out. Both temperature and water table controlled the extent of CH₄ flux suppression in acid rain impacted wetlands. Sulfate reduction potential in SO₄^2- treatments were found to be 10 times larger than in control plots, suggesting that long-term suppression of CH₄ fluxes is the result of the formation of an enlarged population of competitively superior sulfate reducing bacteria. SO₄^2- concentrations were smaller in peat pore water from SO₄^2- treatments than from controls. This is possibly the result of a stimulated SO₄^2- reducing community scavenging available SO₄^2-, thereby decreasing concentrations to below ambient levels. In northern peatlands (>50°) the effect of SO₄^2- deposition at 1990 rates may have been sufficient to reduce emissions from these systems by around 15% annually. Globally, the effect of acid rain SO₄^2- deposition may be sufficient to reduce CH₄ emissions by as much as 22-28 Tg by 2030, which places this interaction within the same size category as many other components of the global CH₄ budget that have received far greater attention.

This work investigated the variability of CH4 emissions from a Welsh raised bog Cors Fochno and evaluated the role of ebullition as a mechanism of CH4 flux to the atmosphere. Between 31st March 2008 and 20th March 2009, CH4 fluxes were measured weekly/biweekly from four microform-types - mud-bottomed hollow, hummock, sedge lawn and Sphagnum lawn. CH4 fluxes (measured using flux-chambers) ranged from -8.9 190.1 mg m-2 d-1 (n = 505). The abundance of two key species Rhynchospora alba and Sphagnum moss - was most relevant for describing spatial variation in annual CH4 emissions (best fit model r2 = 0.68, p < 0.001). A combination of air temperature, rainfall, barometric pressure and solar radiation variables produced the best fit model of temporal variation of CH4 flux (r2 = 0.29, p < 0.001). Winter emissions represented 9.4% of the annual CH4 budget of the peat dome. CH4 ebullition fluxes to 28 funnel-traps were measured weekly between 28th May and 12th September 2009. Daily averaged rates of CH4 ebullition ranged from -1.0 784.5 mg CH4 m-2 d-1 (n = 414). Based on assumed rates of methanotrophic processing, CH4 ebullition flux to the water table was entirely consumed before reaching the atmosphere in only one week of the season. In the remaining 15 weeks it was estimated that between 5% and 81% of CH4 ebullition would have escaped to the atmosphere. Ebullition was shown to be an important transport mechanism of CH4 flux from Cors Fochno during the season, accounting for an estimated 7 - 36% of CH4 emissions. Large changes in barometric pressure appeared to be important drivers of ebullition in some microforms. However, air temperature was the most widely-important predictor of temporal variation of ebullition fluxes during the season and during two low pressure events.

Methane (CH_4) and nitrous oxide (N_2O) are the second- and third-most important long-lived greenhouse gas species after carbon dioxide (CO_2) in terms of radiative forcing. This thesis describes the magnitude, spatial distribution, and seasonality of N_2O and CH_4 sources over North America using atmospheric data. We also investigate the environmental drivers and/or anthropogenic source sectors that can explain these emissions patterns. Overall, this thesis provides information on the magnitude, distribution, and likely drivers of greenhouse gas emissions to aid existing or future climate change mitigation policies in the US and Canada. We estimate anthropogenic N_2O and CH_4 emissions that greatly exceed most existing inventory estimates. Our US budgets for N_2O and CH_4 are approximately 2.8 and 1.5 times higher, respectively, than inventory estimates from the US EPA. Much of the discrepancy in methane appears to stem from oil and natural gas industry and agricultural emissions. In contrast, we estimate natural CH_4 sources that are smaller than most existing process-based biogeochemical models. These estimated fluxes have a spatial distribution centered around the Hudson Bay Lowlands. Most existing models estimate fluxes that are far more spatially distributed across the Canadian shield. These estimates provide negative information on the spatial distribution of fluxes relative to a spatially-constant model. We find that a simple model using only three environmental variables can describe flux patterns (as seen by the atmospheric observations) as well as any process-based estimate.
Earth and Planetary Sciences

With population growing every year, more and more people are looking for places to live. This can lead to construction of houses near and around landfills. As homes get closer to landfills, the odors these landfills produce become more of a problem, and lead to an increase in odor complaints. Modeling these odors and recommending odor buffer distances will help determine limits on how close to landfills new homes should be allowed. This should help reduce future odor complaints. To solve this problem one must accurately estimate odorous gas emissions from the landfill. Often odors can be indicated by methane emissions. A new technique using hundreds of ambient VOC concentrations, which are taken from landfills on a quarterly basis, was used to invert and solve the Gaussian dispersion equation for methane emissions. In this technique, Voronoi diagram theory was used to automatically locate numerous point sources for optimal positioning relative to receptors. The newly solved methane emission rates can now be input into a dispersion model, and the resulting methane concentrations used as surrogates for odors around the landfill. One of the most important steps in the analysis is to determine which model is best to use for odor modeling. There are many considerations that go into this decision, such as how much time it takes to run the model, how accurate the model is, and how easy the model is to use. Two current models CALPUFF and AERMOD were compared. In the modeling, methane was used as a surrogate for the odors. Since landfills handle many different combinations of waste, the type of odor may vary from landfill to landfill. In this test case, H2S was assumed to be the main contributor to the odor emitted from the landfill, and the H2S-to-methane ratio was used to estimate downwind H2S concentrations from the modeled methane concentrations. Once an air dispersion model is selected, it can be used to model odors and to develop a graphical screening method to show where these odors are most likely to occur and how strong they will be. This can be used to determine how close to a landfill homes can be built without having significant odor impacts bothering these new residents. Also, this tool can be used for improving landfill gas management. Several example scenarios include the possibility of not enough soil cover placed on the waste, leaks from an aging collection system, or cracks in the collection piping created by the settling of waste.
M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environment Engr Sciences MS

The effect of global warming on methane (CH₄) and nitrous oxide (N₂O) emissions from agriculture was investigated and simulated from a soil warming experiment. Experiments were designed and installed in a temperature controlled greenhouse. The relationships between elevated temperatures and CH₄ and N₂O emissions were determined and calculated as the Q₁₀s of production, emission and oxidation. A study of the populations of methanogens and methanotrophs at a range of soil temperatures was performed based on soil molecular DNA analysis. This study showed that global warming would increase CH₄ emissions from rice agriculture and that the resultant emissions will be potentially large enough to cause changes in the present atmospheric concentrations. This research also showed that this increase was most evident for soil temperatures below 30⁰C, above which emissions decreased with increasing temperature. The seasonal average Q₁₀s of CH₄ emission, production, oxidation, methanogen and methanotroph populations were found to be 1.7, 2.6 and 2.2, 2.6 and 3.8, respectively, over a temperature of 20-32⁰C. Considering that the processes of CH₄ production and emission are similar to those in natural wetlands, which is the largest source of atmospheric CH₄, the contribution of this feedback is likely to cause a significant increase to the present CH₄ atmospheric budget if the current global warming trend persists over the next century. The Q₁₀s of N₂O emissions and production were 0.5-3.3 and 0.4-2.9, respectively. The low Q₁₀ values found for N₂O suggest that although global warming will have a direct impact on the production and emission rates. Nevertheless, the magnitude of the impact of global on both CH₄ and N₂O emissions from agriculture is likely to vary from one region to another due to the spatial variations in agricultural soil temperatures and the likely changes in the global regional distribution of water resources (water tables, rainfall patterns), water management practices and the responses of terrestrial CH₄ and N₂O sources such as natural wetlands and plants.

Comprehensive and systematic aerial and field investigations were conducted at representative California landfills to quantify emissions of methane and nitrous oxide. Landfills are highly engineered; however, they are one of the largest anthropogenic sources of greenhouse gases, causing human health and safety concerns. Methane (CH4) and nitrous oxide (N2O) are significant greenhouse gases with high global warming potentials that are generated in a landfill environment. For site selection, sites were evaluated based on waste in place, climate zone, faults and oil and gas operations, population density, cover conditions and percentage of cover types, age of waste, waste profile, landfill style and configuration, and disposal of waste tires. Fifteen representative sites were chosen for the aerial portion of testing, and of those fifteen, five sites were selected for extensive ground testing using the static flux chamber method, conducted over a year-long time period. At the five sites for ground testing, between five and seven cover systems were tested at each site during the wet and dry season. Daily, intermediate, and final covers were tested to obtain representative and comparative measurements during the wet and dry season to account for seasonal variation. In addition to the flux chamber testing, geotechnical characterization of cover materials was conducted. CH4 flux values exhibited higher variability in the dry season (102 g/m2/d to -101 g/m2/d) than the wet season (102 g/m2/d to 10-1 g/m2/d). N2O flux values exhibited slightly higher variability in the wet season (10-1 g/m2/d to -10-3 g/m2/d) than the dry season (10-1 g/m2/d to -10-3 g/m2/d). The measured flux value for CH4 was generally greater than the measured flux value for N2O across both seasons. N2O flux values (10-1 g/m2/d to -10-3 g/m2/d) exhibited less variability than CH4 flux values (102 g/m2/d to -10-1 g/m2/d). Relationships were developed between aerial emissions and areal coverage, throughput, waste column height, and waste in place. All correlations were positive. Relationships were also developed between flux values and geotechnical properties of covers, including density and cover thickness. Most geotechnical parameters yielded limited correlation. The surface flux values from the field investigation were scaled up to estimate facility-wide surface emission values. The methane surface emissions ranged from 10-1 to 103 and from 100 to 102 tonnes/year in the wet season and dry season. The nitrous oxide surface emissions ranged -10-2 to 100 and from 10-2 to 10-1 tonnes/year in the wet season and dry season, respectively. Emissions were converted to CO2 equivalent (CO2 E) to allow for comparison between methane and nitrous oxide. The methane surface emissions in CO2 E terms ranged from 101 to 104 tonnes/year in both the wet season and dry season, respectively. The nitrous oxide surface emissions in CO2 E terms ranged from -100 to 102 and from 101 to 102 tonnes/year in the wet season and dry season, respectively. Aerial and ground emissions were compared, with aerial results being higher at all five ground sites. This study provides systematic and comprehensive field emissions testing comparing climate and waste in place, among other parameters, that demonstrate the complicated nature of the landfill environment.

Wetland carbon sequestration is offset by carbon dioxide (CO₂) and methane (CH₄) emissions for which the magnitudes remain coarsely constrained. To better understand the spatial and temporal variations of gaseous carbon fluxes from marsh soils in a Mediterranean climate, I collected air and soil samples over the course of 10 months at Carpinteria Salt Marsh Reserve (CSMR) located in the County of Santa Barbara, California. The CSMR consists of four zones characterized by differences in elevation, tidal regime, soil properties, and vegetation. Twelve static chambers were deployed among two lower marsh zones, a mudflat, and a marsh-upland transition zone for fortnightly flux measurements from September 2015 to May 2016. In August 2015 and June 2016, soil cores up to 50 cm deep were extracted near the chambers, segmented by depth, and analyzed for soil moisture, bulk density, particle size distribution, electrical conductivity, pH, organic/inorganic carbon, and total nitrogen content. Averaged over the 9-month study period, the marsh-upland transition zone had the highest CO₂ fluxes at 5.3 ± 0.7 g CO₂ m^–2 d^–1 , followed closely by the lower marsh zones (3.8 ± 0.6 g CO ₂ m^–2 d^–1 and 2.8 ± 0.7 g CO₂ m^–2 d^–1), which were one order of magnitude higher than the CO₂ fluxes from the mudflat (0.4 ± 0.1 g CO₂ m^–2 d ^–1). The CO₂ fluxes varied significantly on a seasonal scale but were not consistently correlated with environmental variables measured. The CH₄ fluxes had no clear seasonal patterns, but overall CH ₄ flux rates from the lower marsh zones (2.2 ± 1.5 mg CH ₄ m^–2 d^–1 and 1.9 ± 0.2 mg CH₄ m^–2 d^–1) surpassed those from the mudflat (0.2 ± 0.06 mg CH₄ m^–2 d^–1) by an order of magnitude, and the marsh-upland transition zone was a net methane sink (-0.07 ± 0.1 mg CH₄ m^–2 d^–1). The CH₄ fluxes correlated well with most soil properties by zone. Our results show that soil gaseous carbon fluxes from a coastal salt marsh vary by salt marsh zone.

This thesis links papers reporting field measurements, modelling studies and reviews of greenhouse gas (GHG) emissions and their abatement from agriculture, in particular from livestock production. The aims of the work were to: quantify GHG emissions from litter-based farmyard manures; evaluate means by which GHG emissions from agricultural production may be abated; assess synergies and conflicts between the abatement of other N pollutants on emissions of nitrous oxide (N2O); analyse two records of soil temperature from 1976-2010 from Wolverhampton (UK) and Vienna (Austria). Agricultural emissions of GHGs are not readily abated by ‘end of pipe’ technologies. Large decreases in agricultural GHG emissions may require changes in the production and consumption of food that could have unwelcome impacts on both consumers and producers. However, identifying and prioritizing both modes and locations of production, together with utilizing inputs, such as N fertilizer and livestock feeds, more efficiently can reduce GHG emissions while maintaining outputs. For example, GHG emissions from livestock production may be lessened by increasing the longevity of dairy cows, thereby decreasing the proportion of unproductive replacement animals in the dairy herd. Sourcing a larger proportion of calves from the dairy herd would decrease emissions of GHGs from beef production. The distance between the region of food production to that of consumption has relatively little impact on total GHG emissions per tonne of food product. Due to greater productivity or lesser energy inputs, importing some foods produced in other parts of the world may decrease GHG emissions per tonne compared with UK production, despite the additional emissions arising from long-distance transport. Manure application techniques to abate ammonia (NH3) emissions do not axiomatically increase emissions of N2O and may decrease them. Soil temperature measurements from 1976 to 2010 were consistent with the warming trends reported over the last 40 years.

Treating elevated nutrients, suspended solids, oxygen demanding materials, heavy metals and chemical fertilizers and pesticides in agricultural wastewaters is necessary to protect surface and ground waters. Constructed wetlands (CWs) are an increasingly important technology to remediate wastewaters and reduce negative impacts on water quality in agricultural settings. Treatment of high strength effluents typical of agricultural operations results in the production of methane (CH4), a potent greenhouse trace gas. The objective of this study was to evaluate CH4 emissions from two subsurface flow (SSF) CWs (223 m2 each) treating dairy wastewater. The CWs were implemented at the University of Vermont Paul Miller Dairy Farm in 2003 as an alternative nutrient management approach for treating mixed dairy farm effluent (barnyard runoff and milk parlor waste) in a cold, northern climate. In 2006, static collars were installed throughout the inlet, mid and outlet zones of two CWs (aerated (CW1) and a non-aerated (CW2)) connected in-series, and gas samples were collected via non-steady state chambers (19.75 L) over a nine-month period (Feb-Oct 2007). Methane flux densities were variable throughout the nine-month study period, ranging from 0.026 to 339 and 0.008 to 165 mg m-2 h-1 in CW1 and CW2, respectively. The average daily CH4 flux of CW1 and CW2 were 1475 and 552 mg m-2 d-1, respectively. Average CH4 flux of CW1 was nearly threefold greater than that of CW2 (p = .0387) across all three seasons. The in-series design may have confounded differences in CH4 flux between CWs by limiting differences in dissolved oxygen and by accentuating differences in carbon loading. Methane flux densities revealed strong spatial and seasonal variation within CWs. Emissions generally decreased from inlet to outlet in both CWs. Average CW1 CH4 flux of the inlet zone was nearly threefold greater than mid zone and over tenfold greater than flux at the outlet, while fluxes for CW2 zones were not statistically different. Methane flux of CW1 was nearly fifteen fold greater than CW2 during the fall, representing the only season during which flux was statistically different (p = .0082) between CWs. Fluxes differed significantly between seasons for both CW1 (p = .0034) and CW2 (p = .0002). CH4 emissions were greatest during the spring season in both CWs, attributed to a consistently high water table observed during this season. Vegetation was excluded from chambers during GHG monitoring, and considering that the presence of vascular plants is an important factor influencing CH4 flux, the potential CH4 emissions reported in our study could be greatly underestimated. However, our reported average CH4 fluxes are comparable to published data from SSF dairy treatment CWs. We estimate average and maximum daily emissions from the entire CW system (892 m2) at approximately 1.11 and 6.33 kg CH4 d-1, respectively, yielding an annual average and maximum flux of 8.51 and 48.5 MtCO2-e y-1, respectively.

Globally agriculture and livestock producers have come under increasing pressure over the environmental impact of production systems. The objectives of this study were to re-calculate the direct methane (CH4) and nitrous oxide (N2O) emissions of livestock production systems in South Africa, taking into consideration the uniqueness of the South African scenario and to identify and evaluate possible greenhouse gas mitigation strategies for extensive production systems. It is important to generate accurate greenhouse gas (GHG) baseline figures to develop South Africa’s capacity to understand and reduce GHG emissions emitted from the livestock sector. Livestock produce GHG’s in the form of methane from enteric fermentation and nitrous oxide and methane from manure management and manure deposited on pastures and rangeland by grazing animals. Agriculture, forestry and land use (corrected for carbon sink values) emitted an estimated 4.9% of South African GHG gases in 2004, which makes it the third largest GHG contributor in South Africa after the energy industry and industrial processes. Livestock produced approximately 27% of the national methane emissions and 98% of the agricultural sector’s methane emissions in 2004. Methane is a potent GHG that remains in the atmosphere for approximately 9 to 15 years and is 28 times more effective in trapping heat in the atmosphere than carbon dioxide (CO2) over a 100-year period. Nitrous oxide has an atmospheric lifetime of 150 years and a global warming potential of 265 times that of CO2 over a 100-year period. South African livestock production is based on a unique combination of commercial (intensive and extensive) and emerging and communal (subsistence) production systems. The levels of productivity and efficiency in these production systems vary greatly in certain areas and it is important to distinguish between them when calculating GHG emissions. Previous inventories were conducted on a national scale utilizing IPCC default values (Tier 1 approach) for some or all of the emission calculations. These emission factors do not distinguish effectively between classes of animals, production efficiencies, and production systems. They are often based on assumptions of animals utilizing diets which are not representative of South African production systems. The IPCC Tier 2 methodology seeks to define animals, animal productivity, diet quality and management circumstances to support a more accurate estimate of feed intake for use in estimating methane production from enteric fermentation. It was also considered important to do separate calculations for each province as provinces differ in vegetation or biomes and production systems which may require different approaches to mitigation recommendations. Due to the heterogeneity of available feed types within South Africa it was considered important to use methodologies that could reflect such differences and was developed under similar conditions. The methodology utilized is based on the Australian national greenhouse account’s National Inventory Report, which contains Australian country-specific and IPCC default methodologies and emission factors. Emission factors specific to South African conditions and management systems were calculated where possible. A Tier 2 approach was adopted for all major livestock categories including privately owned game in accordance with the IPCC Good Practice requirements. Recently game farming has become a recognized commercial enterprise in the agricultural sector which needs to be included as an anthropogenic emissions source. Methane emissions from South African livestock were estimated at 1328 Giga gram (Gg) during 2010. Dairy and beef cattle contributed an estimated 964 Gg or 72.6% of the total livestock methane emissions in South Africa during 2010. Beef cattle in extensive systems were the largest contributor (83.3%), followed by dairy cattle (13.5%), and feedlot cattle (3.2%). The estimated direct enteric methane emission factors for dairy and beef cattle were higher than the IPCC default factors for Africa. The Eastern Cape recorded the highest dairy and beef cattle methane emissions, whereas Gauteng showed the highest feedlot methane emissions primarily due to cattle numbers. Small stock was responsible for 15.6% of the total livestock emissions contributing an estimated 207.7 Gg, with sheep producing 167 Gg and goats producing 40.7 Gg. Calculated enteric methane emission factors for both commercial and communal sheep were higher than the IPCC default values for developing countries. A similar tendency was found with goat emission factors. The highest sheep and goat methane emissions were reported for the Eastern Cape province. The pig and ostrich industry both contributed approximately 8 Gg CH4 during 2010. The North- West province produced the highest commercial pig GHG emissions with the highest communal pig emissions originating from the Eastern Cape. The poultry industry was the largest direct N2O producer of the non-ruminant livestock industries, contributing 2.3 Gg or 92.8% of the total nonruminant N2O emissions. The privately owned game industry contributed an estimated 131.9 Gg of methane emissions with the provinces of Limpopo, Eastern Cape and Northern Cape being the three largest contributors with 43.4, 37.3 and 21 Gg methane, respectively. The total privately owned game population was estimated at 2 991 370 animals, utilizing 20.5 million hectares. Beef cattle are the major contributors to livestock GHG emissions in South Africa followed by sheep, privately owned game, dairy cattle, goats, pigs, ostriches, equine, and poultry. The IPCC default values for Africa underestimate emission factors across all livestock categories. The methane emission factors calculated for commercial livestock production systems are more comparable to emission factors from developed countries and the emerging/communal production systems to those of developing countries. This emphasizes the need to develop country-specific emission factors through quantitative research for livestock in all provinces and on all types of production systems to produce accurate baseline figures, which is critical to future mitigation protocols. As part of this study fourteen tropical grass species typical of transitional rangeland regions of South Africa were characterised in terms of chemical composition, in vitro total gas and in vitro methane production. The results of the study demonstrated that in vitro methane production varied between tropical grass species typical of transitional rangeland in South Africa. The variation between species allows for the potential to identify and select species with a lower enteric methane production potential. Panicum maximum, Eragrostis curvula and Elionurus miticus were the three species which produced the lowest in vitro methane production but which also had a crude protein (CP) concentration of more than 3.5% of dry matter (DM) and with an in vitro organic matter digestibility (IVOMD) above the group average for the study. Furthermore, the results of the study revealed that in vitro methane production was higher in Decreaser species compared to Increaser species. Improving the quality of available forages through the use of cultivated pastures and fertilization is known to improve ruminant production efficiency. The effect of level of nitrogen (N) fertilization on certain qualitative parameters and in vitro total gas and methane production of improved grass species commonly utilised in South Africa was evaluated. Treatments included seven grass species divided into two photosynthetic pathways (C3 and C4) with three levels of N fertilization (0, 50 and 100 kg N/ha). No effect was found for N fertilization on in vitro total gas or methane production. The CP concentration increased (P < 0.05) and the NDF concentration tended to decrease (P < 0.1) as the level of N fertilization increased for both C3 and C4 species. Increasing the level of N fertiliser increased (P < 0.05) the methanogenic potential of Dactylis glomorata, Festuca arundinacea and Cenchrus ciliaris after the 24 hour incubation period but no effects (P>0.05) were found after the 48 hour incubation period. Results suggests that the stage of physiological development of forages might have a greater influence on the methanogenic potential of forages compared to the effect of N fertiliser application.
Thesis (PhD)--University of Pretoria, 2017.
Animal and Wildlife Sciences
PhD
Unrestricted

A comprehensive field investigation was conducted at Potrero Hills Landfill (PHL) located in Suisun City, California to quantify emissions of twelve (hydro)chlorofluorocarbons (i.e. F-gases). The specific target constituents for this study included CFC-11, CFC-12, CFC-113, CFC-114, HCFC-21, HCFC-22, HCFC-141b, HCFC-142b, HCFC-151a, HFC-134a, HFC-152a, and HFC-245fa. The majority of the F-gas emission studies have been conducted outside of the United States and very limited field landfill emission data are available in the United States. Because of historical usage of blowing agents in insulation foams including CFC-11, HCFC-142b, HFC-134a, and HFC-245fa, models reported in literature predicted high F-gas emissions from a landfill environment, but very limited field data are available to verify such predictions. In this investigation, the surface flux of the twelve F-gases, methane, and carbon dioxide was quantified from various landfill cover systems and in areas with different waste ages, waste heights, and cover thicknesses at Potrero Hills Landfill. In addition, destruction efficiencies for the twelve F-gases were determined based on inlet and outlet concentrations of the onsite flare system. Lastly, the surface flux values were scaled up to a facility-wide emission value to estimate the total fugitive emissions from the landfill. The F-gas flux values for the daily covers were in the 10 -8 to 10-1 g m-2 day -1 range and 10-7 to 10-2 g m-2 day-1 range for the wet and dry season, respectively. The F-gas flux values for the intermediate covers in the -10-6 to 10-4 g m-2 day-1 range and -10-6 to 10-4 g m-2 day-1 range for the wet and dry season, respectively. The F-gas flux values for the final covers were in the 10-7 to 10-5 g m-2 day-1 range and -10-7 to 10-6 g m-2 day-1 range for the wet and dry season, respectively. F-gas fluxes for the final covers had the highest number of below detection limit cases as well as lower than R2 threshold cases. Thest F-gas fluxes were measured from daily cover system constructed with auto shredder residue (i.e. auto fluff) for the both the wet and dry seasons. The highest fluxes were measured for CFC-11, HCFC-21, and HCFC-141b in the wet season and for CFC-11, HCFC-141b, and HFC-134a in the dry season across the seven cover locations. Lower level of variation was observed for methane and carbon dioxide with flux values ranging over five orders of magnitude for the seven tested locations. The methane flux values for the daily covers were in the 10-2 to 10+1 g m-2 d-1 range and 1 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. The carbon dioxide flux values for the daily covers were in the -10+1 to 10+2 g m-2 day-1 range and -10+1 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. The methane flux values for the intermediate covers were in the -10-2 to 10+1 g m-2 d-1 range and -10-3 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. The carbon dioxide flux values for the intermediate covers were in the 1 to 10+2 g m-2 day-1 range for both seasons. The methane fluxes for the final cover were -10 -3 g m-2 day-1 and 10-4 g m-2 day-1 for the wet and dry season, respectively. The carbon dioxide flux values for the final cover were in the 10+1 g m-2 d-1 range and 1 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. Negative flux values were typically observed during the wet season and at the intermediate and final covers. The destruction efficiencies for the twelve F-gases were above 99.5% for the onsite flare. Highest F-gas raw gas concentrations were measured for HFC-134a while the lowest F-gas concentration was measured for CFC-113. The F-gas concentrations in the raw gas ranged from 103 to 106 pptv. Similar to what has been reported in the literature, the landfill gas flare system was an efficient abatement device in controlling F-gas emissions. The surface emission measurement values from the field investigation were scaled up to estimate facility-wide fugitive emission values using the relative surface areas of the daily, intermediate, and final cover distributions in the landfill. The total fugitive emissions from the landfill including twelve F-gases, methane, and carbon dioxide ranged from 6,900 to 94,000 CO2E tonnes per year during the wet season, from 21,000 to 47,000 CO2E tonnes per year during the dry season, and from 13,000 to 75,000 CO2E tonnes per year during the year, prorated by the season (representing weighted average of 58% wet season emission rate and 42% dry season emission rate in a 12-month calendar year). The total fugitive F-gas emissions ranged from 1,600 to 4,800 CO2E tonnes per year during the wet season, from 140 to 600 CO2E tonnes per year during the dry season, and from 1,000 to 3,000 CO2E tonnes per year, prorated by the season. The total fugitive methane emissions ranged from 530 to 75,000 CO2E tonnes per year during the wet season, 17,000 to 35,000 CO2E tonnes per year during the dry season, and from 7,500 to 58,000 CO2E tonnes per year, prorated by the season. The total fugitive carbon dioxide emissions ranged from 5,000 to 14,000 CO2E tonnes per year during the wet season, 4,200 to 12,000 CO2E tonnes per year during the dry season, and from 4,500 to 13,000 CO2E tonnes per year, prorated by the season. In comparison to the total fugitive emission value derived from the first-order decay (FOD) model reported by USEPA and the total fugitive emission values calculated using waste-in-place (WIP) – landfill gas correlation equation presented in Spokas et al. (2015), the field-derived methane emission values were one to three orders of magnitude lower.

Master of Science
Department of Biological and Agricultural Engineering
Zifei Liu
This study reviewed state-of-the-art cattle enteric methane (CH4) emissions with three reported measuring units: g/head/d, g/kg DMI (dry matter intake), and %GEI (gross energy intake). Cattle emissions studies included in this meta-analysis were reported from 1995 to 2013. Fifty-five published studies were analyzed with specific objectives: (1) to gain basic information regarding magnitudes and distributions of enteric CH4 emission rates with various units, regions, cattle types and feed situations; (2) to identify and evaluate effects of influence factors or diet mitigation techniques on enteric CH4 emissions; and (3) to evaluate Intergovernmental Panel on Climate Change (IPCC) approaches to estimate enteric CH4 emissions. Emissions data (n=165) with the unit of g/head/d had large variances and non-normal distribution, and were not homogeneous across the studies. Emissions data (n=134) with the unit of g/kg DMI were not homogeneous across the studies, while emissions data (n=76) with the unit of %GEI had small variances and normal distribution, and were homogeneous across the studies. Therefore, data with the unit of %GEI may be better for meta-analysis compared to data with the units of g/head/d and g/kg DMI; however, the number of data with the unit of %GEI was small relative to the number of data with the units of g/head/d and g/kg DMI. Enteric CH4 emissions with the unit of g/head/d are significantly influenced by geographic region, cattle classification, sub-classification, humidity, temperature, body weight, and feed intake. Emissions and feed intake had a strong positive linear relationship with R2 of 0.75 (n=148). Emissions with the unit of g/kg DMI are significantly affected by humidity, body weight, and feed intake. The relationship between emissions and feed intake is positive. Emissions with the unit of %GEI are significantly associated with humidity, production stage, and body weight. IPCC Tier 1 and Tier 2 estimated emissions were approximate to most of the measured enteric CH4 emissions; however, the residuals were not normally distributed. Based on results from PRD method and paired t-tests, IPCC Tier 1 overestimated emissions in Asian studies, underestimated emissions in European studies for beef cattle, and underestimated emissions in Oceanian studies for dairy cattle. IPCC Tier 2 underestimated emissions in Asian studies for beef cattle. The underestimated emissions of IPCC Tier 2 in Asian studies might result from no consideration of effects from production stage and body weight.

Net ecosystem exchange of CO$ sb2$ (NEE) and CH$ sb4$ flux were measured at five sites within a boreal peatland near Thompson, Manitoba, from June through September, 1994. Sites were chosen to represent the different plant communities present along a productivity gradient where the water table was at or near the peat surface. Methane emissions, water table depth, and peat temperature were measured on weekly basis, while the relationship between photosynthetically active radiation (PAR) and net ecosystem exchange of CO$ sb2$ was determined three times during the field season, and then used to develop net ecosystem production (NEP) models at each site. Porewater methane was sampled for $ rm delta sp{13}C/ sp{12}C$ isotopic analysis once a month.
Among the sites, after PAR, light CO$ sb2$ flux was primarily controlled by sedge biomass and water table position, while dark CO$ sb2$ flux was controlled by peat temperature. From early June to late August, the five sites consumed approximately 1 to 2 g $ rm CO sb2$-C m$ rm sp{-2}d sp{-1}$. Seasonal CH$ sb4$ fluxes ranged between 16 and 456 mg $ rm CH sb4 m sp{-2}d sp{-1}$, and were higher than fluxes measured at other boreal sites in the same latitude. Seasonal average NEP was a good predictor of seasonal CH$ sb4$ fluxes from the sites (r$ sp2$ = 0.50), providing a model which estimates CH$ sb4$ flux based on site productivity alone. Stable carbon isotope analysis indicates root exudates that stimulate methanogenesis are an important control on this relationship, as is a high water table, particularly in its influence on the depth of the CH$ sb4$ oxidizing layer in the peat. These results suggest NEP measurements have the potential to be used in remote sensing applications to estimate CH$ sb4$ flux from wetlands, but that their use may be restricted to inundated sites.

Methane is the second most important anthropogenic greenhouse gas, with a radiative warming of 0.97 [0.74-1.20] W m-2 (Stocker et al., 2013a) and a global warming potential of 21 times that of CO2 over a 100 year timescale (Reay et al., 2010). Its significance to climate change is significant whereas our current understanding and quantification of its sources and sinks lack completeness. This thesis explains the development of novel technique to estimate methane emissions at high spatial resolution. There is a growing need for comparisons between emission estimates produced using bottom-up and top-down techniques. In response to this, an inversion approach, InTEM, was adapted to estimate methane emissions for the East of England at high spatial resolution. InTEM incorporates in situ atmospheric methane measurements and computer dispersion modelling into a statistical technique. Methane emission estimates are inferred using cost function analysis within a simulated annealing method. This thesis presents results covering a two year period (July 2012 - June 2014) in which atmospheric methane concentrations were recorded at 1 - 2 minute time steps at four locations within East Anglia. Precise measurements are obtained using gas chromatographs with flame ionisation detectors (GC-FID) for all sites except one, which uses a Picarro cavity ring down spectroscopy (CRDS) instrument. The UK Met Office's NAME dispersion model is used within InTEM to represent the physical atmospheric processes which occur throughout this period. Methane concentrations are shown to vary over different time frames and are dependent on various meteorological variables, particularly boundary layer height and wind speed. A case study into methane concentration at the Haddenham site shows influence from local landfill sources. Isotopic analysis from whole air samples give a δ13C isotopic signal of -58.3 ±2 ⁄ at the Haddenham site and -59.2 ±2 ⁄ at the nearby landfill. Emission estimates for the East of England are calculated at varying spatial resolutions, on annual and seasonal time frames. County scale methane emission estimates are produced and directly compared with the UK National Atmospheric Emissions Inventory (NAEI). Estimates between the InTEM inventory and the NAEI are shown to be similar in counties close to the observation sites. The Norfolk, Suffolk and Cambridge countries are estimated to produce 80.4 ±3.3 kt yr-1 of methane between June 2013 - May 2014 (NAEI equivalent of 89.6 kt yr-1). Multiple site sensitivity analysis shows that all four sites are necessary for the county methane estimates but coarser estimates can be observed using a sub-selection of sites. Individual site biases were shown to have an impact on 1 -2 site inversions but the four site results minimised these biases.

Hydroelectricity is an energy resource which for a long time has been consideredenvironmentally neutral regarding greenhouse gas emission. During the last years this viewhas changed. Studies have shown that reservoirs connected to hydroelectric power plants emitmethane (CH4) and other greenhouse gases to the atmosphere, especially in the tropicalregions where the emission level of CH4 is the highest. The purpose of this thesis was toinvestigate the variations of CH4 emissions in Funil reservoir, Santo Antônio reservoir andTrês Marias reservoir and to identify variables that increase the CH4 emissions.The CH4 emissions were measured by floating static chambers positioned on the surface atseveral locations within each reservoir. A gas sample was collected after 10, 20 and 30minutes from each chamber. The samples were analyzed through gas chromatography toobtain the concentration of CH4 in each sample. Calculations of the change in CH4concentration over time were used to establish the flux of CH4 at each location.The obtained result from Funil reservoir showed CH4 fluxes in the range of -0.04 to 13.16mmol/m2/day with significantly different fluxes between sites (p < 0.05). The CH4 fluxes inSanto Antonio reservoir were within the range of -0.33 to 72.21 mmol/m2/day. In thisreservoir fluxes were not significantly different between sites (p <0.05). The results obtainedfrom Três Marias showed CH4 fluxes in the range of -0.31 to 0.56 mmol/m2/day withsignificantly different fluxes between sites (p < 0.05). The highest fluxes were found in SantoAntônio which were significantly different from the CH4 fluxes in Três Marias (p <0.05).The CH4 flux was positively correlated with CO2 and dissolved organic carbon (DOC) andnegatively correlated with O2 and depth in Santo Antônio. The same correlations were evidentfor the whole data set. In total the measured fluxes from the three reservoirs ranged from -0.33 to 72. 21 mmol/m2/day and the mean flux was 2.31 mmol/m2/day. These fluxes are lowcompared to earlier results. The variation in CH4 flux within and between the reservoirs wassignificantly different in a major part of the comparisons. Even though the majority of thefluxes were different, variables that increase the CH4 emission rate were illuminated. A lowdepth and low O2 concentration increase the CH4 emission rate. A high concentration of DOCand CO2 indicates that a high amount of organic carbon was available for the production ofCH4, leading to an increased CH4 emission rate.
BALCAR (Balanço de Carbono)

Agriculture has been reported to contribute a significant amount of greenhouse gases to the atmosphere among other anthropogenic activities. With still more than 870 million people in the world suffering from under-nutrition and a growing global food demand, it is relevant to study ways for mitigating the environmental impact of food production. The objective of this work was to identify gaps in the knowledge regarding the main factors affecting greenhouse gas (GHG) emissions from beef farming systems, to reduce the uncertainty on carbon footprint predictions, and to study the relative importance of mitigation options at the system level. A lack of information in the literature was identified regarding the quantification of the relevant animal characteristics of extensive beef systems that can impact on methane (CH4) outputs. In a meta-analysis study, it was observed that the combination of physiological stage and type of diet improved the accuracy of CH4 emission rate predictions. Furthermore, when applied to a system analysis, improved equations to predict CH4 from ruminants under different physiological stages and diet types reduced the uncertainty of whole-farm enteric CH4 predictions by up to 7% over a year. In a modelling study, it was demonstrated that variations in grazing behaviour and grazing choice have a potentially large impact upon CH4 emissions, which are not normally mentioned within carbon budget calculations at either local or national scale. Methane estimations were highly sensitive to changes in quality of the diet, highlighting the importance of considering animal selectivity on carbon budgets of heterogeneous grasslands. Part of the difficulties on collecting reliable information from grazing cattle is due to some limitations of available techniques to perform CH4 emission measurements. Thus, the potential use of a Laser Methane Detector (LMD) for remote sensing of CH4 emissions from ruminants was evaluated. A data analysis method was developed for the LMD outputs. The use of a novel technique to assess CH4 production from ruminants showed very good correlations with independent measurements in respiration chambers. Moreover, the use of this highly sensitive technique demonstrates that there is more variability associated with the pattern of CH4 emissions which cannot be explained by the feed nutritional value. Lastly, previous findings were included in a deterministic model to simulate alternative management options applied to upland beef farming systems. The success of the suggested management technologies to mitigate GHG emissions depends on the characteristics of the farms and management previously adopted. Systems with high proportion of their land unsuitable for cropping but with an efficient use of land had low and more certain GHG emissions, high human-edible returns, and small opportunities to further reduce their carbon footprint per unit of product without affecting food production, potential biodiversity conservation and the livelihood of the region. Altogether, this work helps to reduce the uncertainty of GHG predictions from beef farming systems and highlights the essential role of studies with a holistic approach to issues related to climate change that encompass the analysis of a large range of situations and management alternatives.

Methane (CH4) is included in the direct greenhouse gases listed in the Kyoto protocol. The composting of anaerobic digestion (henceforth AD) material is a source of CH4. CH4 is the major contributor to overall CO2 emissions. Therefore, it is important to know the formation of this gas from different stages and substrates of the composting process. This study investigated CH4, CO2 and O2 profiles in two open-windrows in composting plants treating AD material. One composting windrow was turned one a week; whereas another was turned twice a week using a special windrow turner. To assess the gaseous formation in the composting windrows, CH4, CO2 and O2 volume concentrations were measured at different depths. Active aeration has been considered as a method to reduce CH4 generation during composting. However, our results showed that frequent turned windrow generated more CH4 than less turned windrow. The highest CH4 concentrations were found at a depth of 1 m, and were 45% and 37% for 2 times a week turned windrow and 1 time a week turned windrow respectively. Gas concentrations of CH4, O2 and CO2 in both windrows differed. Concentrations of CO2 and CH4 increased with depth, whereas concentration of O2 decreased from the surface to the lowest point. The O2 and CO2 are important factors in determining whether the windrows are anaerobic or aerobic
Khí mê tan (CH4) là một trong những khí nhà kính được liệt kê trong nghị định thư Kyoto. Quá trình ủ phân compost từ các chất thải của hầm ủ biogas là nguồn phát sinh loại khí này. Khí mê tan đóng góp chủ yếu trong tổng lượng khí nhà kính phát thải vào khí quyển. Do đó, những hiểu biết về quá trình hình thành loại khí này trong các giai đoạn khác nhau của quá trình ủ phân compost từ chất thải hầm ủ biogas là rất quan trọng. Nghiên cứu này tìm hiểu sự phát thải khí CH4, CO2 và O2 trong 2 luống ủ ngoài trời tại các nhà máy xử lý rác thải hữu cơ bằng phương pháp kỵ khí. Luống ủ 1 được đảo trộn một lần một tuần trong khi luống ủ số 2 được đảo trộn 2 lần 1 tuần. Để đo đạc lượng khí phát thải từ các luống ủ phân compost, nồng độ các khí CH4, CO2 và O2 được đo ở các độ sâu khác nhau. Việc cung cấp khí oxy được coi như là một biện pháp để làm giảm sự hình thành khí mê tan. Tuy nhiên, kết quả đo đạc của chúng tôi chứng minh rằng việc đảo trộn thường xuyên phát thải nhiều khí mê tan hơn ít đảo trộn. Nồng độ khí mê tan cao nhất 45% và 37% đo được ở khoảng cách 1m từ bề mặt đối với luống ủ đảo trộn hai lần và một lần. Nồng độ các khí CH4, CO2 và O2 khác nhau ở hai luống trong thí nghiệm. Nồng độ khí CH4 và CO2 tăng theo độ sâu, trong khi O2 giảm theo độ sâu. Nồng độ khí CO2 và O2 đóng vai trò quyết định luống ủ được cung cấp đủ oxy cho quá trình phân hủy hiếu khí hay không

The aim of this study was to investigate the effects of biochar amendment on soil greenhouse gas (GHG) emissions and to elucidate the mechanisms behind these effects. I investigated the suppression of soil carbon dioxide (CO2) and nitrous oxide (N2O) emissions in a bioenergy and arable crop soil, at a range of temperatures and with or without wetting/drying cycles. More detailed investigation on the underlying mechanisms focused on soil N2O emissions. I tested how biochar altered soil physico-chemical properties and the subsequent effects on soil N2O emissions. In addition, 15N pool dilution techniques were used to investigate the effect of biochar on soil N transformations. Biochar amendment significantly suppressed soil GHG emissions for two years within a bioenergy soil in the field and for several months in an arable soil. I hypothesised that soil CO2 emissions were suppressed under field conditions by a combination of mechanisms: biochar induced immobilisation of soil inorganic-N (BII), increased C-use efficiency, reduced C-mineralising enzyme activity and adsorption of CO2 to the biochar surface. Soil CO2 emissions were increased for two days following wetting soil due to the remobilisation of biochar-derived labile C within the soil. Soil N2O emissions were suppressed in laboratory incubations within several months of biochar addition due to increased soil aeration, BII or increased soil pH that reduced the soil N2O: N2 ratio; effects that varied depending on soil inorganic-N concentration and moisture content. These results are significant as they consistently demonstrate that fresh hardwood biochar has the potential to reduce soil GHG emissions over a period of up to two years in bioenergy crop soil, while simultaneously sequestering C within the soil. They also contribute greatly to understanding of the mechanisms underlying the effect of biochar addition on soil N transformations and N2O emissions within bioenergy and arable soils. This study supports the hypothesis that if scaled up, biochar amendment to soil may contribute to significant reductions in global GHG emissions, contributing to climate change mitigation. Further studies are needed to ensure that these conclusions can be extrapolated over the longer term to other field sites, using other types of biochar.

Mestrado em Engenharia do Ambiente - Instituto Superior de Agronomia
The primary aim of this study was to quantify garden waste potential for GHG emissions (with focus on CH4 and N2O); and to identify relationships between these GHG emissions and meteorological variables in different climates. The study was carried out in two countries with contrasting climates and soil structures: Portugal with a Mediterranean climate and Scotland with a hyperoceanic climate. A closed static chamber methodology was used for measure N2O and CH4 gaseous flux in three types of treatments installed in containers kept outdoors: S with soil; S+GW with soil and garden waste layered on top; and GW with only garden waste. The range of N2O fluxes varied on a log-normal scale, ranging from slightly negative values to very high values (3 orders of magnitude). With the exception of the “control” S treatments (maximum flux of 0.54 N2O nmolm-2s-1 at both sites). The percentage of the emitted CO2 equivalent (CO2eq) from the original C content applied to the treatments as garden waste indicates the overall impact on emissions of the composting process. Based on CO2eq global warming potential (GWP) multipliers stated by the IPCC (2014) (25 for CH4 and 298 for N2O), Portugal emitted 28.47% from the treatment S+GW and 11.26% from GW, while the majority of the C remained on soils (>70%). Scotland’s treatment S+GW had a lower CO2eq emission of 11.99%, with 58.47% emitted from the GW treatment. These results show that the overall impact on GWP of composting varies dramatically depending on management, and that CO2 is being converted into considerably high quantities of longer lived GHGs like CH4 and N2O. Cumulative CH4 flux measurements showed sequestration in Portugal and emissions in Scotland, the effects were more pronounced in treatment S for both sites (-210.85 and 209.0519 mgCH4m-2d-1, respectively). The garden waste diminished the emissions for Scotland and hindered the sequestration for Portugal. The contribution of weather conditions from each site was significant and very different relatively to the behaviour of each GHG. Portugal had constant moderate/high temperatures with peaks of rain which stimulated the GHG; Scotland on the other hand had constant rain with low temperatures with occasional rises which was the controlling factor stimulating the GHG
N/A

Thesis (Ph. D.)--Sverges lantbruksuniversitet, 2001.
Thesis statement in Swedish and English abstract inserted. Based on 5 previously prepared or published papers reprinted here. Includes bibliographical references.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references.
Methane is the second most important greenhouse gas after carbon dioxide, and it can significantly impact global climate change. Considerable amounts of methane can be released to the atmosphere from freshwater lakes, particularly through bubbling. However, spatial and temporal heterogeneity in ebullition has complicated efforts to accurately measure such methane emissions. This thesis presents the results from a two-year study of methane biogeochemistry conducted at the eutrophic, stratified, Upper Mystic Lake located in eastern Massachusetts, US. Field sampling was done between June and November 2007, and between April and November 2008. In both years, ebullition at the lake was strongly episodic, and the amount and composition of bubbled gas varied considerably between sites. In 2008, under-water bubble traps were equipped with pressure sensors that measured the gas collected every 5 minutes for 4-6 months. The high-temporal resolution data showed that synchronized lake-wide bubbling episodes were triggered when hydrostatic pressures fell below a site-dependent threshold. Twice as much bubbling was observed in 2007 than in 2008. In both years, approximately 70% of the total methane export from the lake occurred through ebullition, and 30% through diffusion across the air-water interface at the lake surface. About 6-11 kg CH4/d was emitted to the atmosphere from the Upper Mystic Lake during the sampling periods of 2007 and 2008.
(cont.) The results from this research indicate that freshwater lakes should be considered as important natural sources in the global methane budget. Other contributions include the development a low-cost, low-power bubble trap for automated measurement of ebullition. The electronics in this device can also be used to measure other phenomena where a pressure differential is of interest, such as lake water level. To our knowledge, there has been no previous study that has measured bubbling fluxes over a comparable period of time with such high temporal resolution. Finally, the wavelet transform is presented as a new tool for identification of bubbling events from sensor data at multiple time scales.
by Charuleka Varadharajan.
Ph.D.

The objectives of this study are to measure the non-methane volatile organic carbon (NMVOC'
s) emissions from passenger cars in Turkey having gasoline engines, to determine emission factors of these vehicles for BTEX compounds and comparison of emission factors obtained in this study with the emission factors of the other countries. This study was conducted in two parts: The first part was to determine the categories of passenger cars widely used in Turkey, and also to determine the average carbon monoxide (CO) and hydrocarbon (HC) emissions at idle condition for these car types based on the exhaust emission measurements of Ankara Ç
evre Koruma Vakfi (ANÇ
EVA). The second part of the study was to analyze the gas composition of exhaust gasses at different road conditions for BTEX components by using gas chromatography. The results of the study have shown that the cars named under &lsquo
&lsquo
Tofas&rsquo
&rsquo
constitute 31.5% and &lsquo
&lsquo
Fiat&rsquo
&rsquo
13.1% of the total cars in Turkey and they are manufactured by the same company. Therefore, studies have been performed with &lsquo
&lsquo
Tofas/Fiat&rsquo
&rsquo
cars. The highest emission factors among hydrocarbons investigated in this study were found for toluene and m-xylene. Generally, as driving speed increases the emissions of HC&rsquo
s are found to decrease in concentration. It was interesting to note that the highest emissions occur at 30 km/hr speed which is the mostly used speed in crowded streets and busy intersections. Therefore, it was concluded that it is very important to take measures for emissions in the city traffic. Cold start emissions were also found to be higher than the hot start emissions.

[EN] Climate change, a resultant effect of greenhouse gas emissions, is a worldwide concern because its continuation is having significant impacts on people, natural resources and economic conditions around the world. The root cause of this recent past and projected climate change is now recognised to be the warming potential of a number of greenhouse gases that, by absorbing terrestrial infrared radiation, raise the temperature of the troposphere and with it, global surface temperatures. The major greenhouse gases are water vapour, carbon dioxide, methane, nitrous oxide and fluorinated gases. While carbon dioxide receives the most attention as a factor which causes global warming, methane also cause significant radiative forcing. Methane is only second to carbon dioxide in its contribution to global warming and its emissions are caused by both natural and anthropogenic actions. Human activities such as intensive livestock farming are the primary cause of the increased methane concentrations in the atmosphere, being ruminants the animals which create large amounts of methane via fermentation of feeds in the rumen. During this physiological digestive process, hydrogen is released by some microbes during fermentation of forage and is used by methanogenic Archaea (methanogens) to convert carbon dioxide to methane, which is released through eructation, normal respiration and small quantities as flatus. Rumen fermentation of cattle contributes the most towards the greenhouse effect through methane emission followed by sheep, goats and buffalos, respectively. Several techniques have been developed to quantify methane emissions from ruminants - indirect calorimetry, sulphur hexafluoride tracer technique and in vitro gas production technique - and some strategies for reduction of methane emissions from the rumen have been described - defaunation treatment, vaccine and dietary composition -. The initial topics of this research were: design the experiments with goats because there are not many reports about methane emissions in these animals; investigate the influence of dietary composition (carbohydrates) as a strategy for reduction methane emissions from the rumen; and use the indirect calorimetry as method to quantify methane production. Consequently, three experiments were performed. Murciano-Granadina goats during mid or late lactation were used. Diets were mixed rations that differed in the inclusion of cereal or fibrous by-products. The effect of diet was studied on milk yield, digestibility, rumen parameters, energy partitioning, carbon and nitrogen balance, substrate oxidation and methane productions. In the first experiment, gas exchange was measured using a face mask which was fixed to the head of the goat by a rubber band; a sample of exhaled gas was stored in a gas collection bag which was connected to an analyzer, and it measured the concentration of O2, CO2 and CH4 from the air. This first experiment replaces corn grain with beet pulp and the amount of methane recovered was 19.6 and 29.7 g/day, respectively. In the other two experiments, gas exchange was measured by a head box designed for small ruminants where the goat introduced the whole head and a specific software automatically recorded concentrations of O2, CO2 and CH4 from the exhaled air continuously throughout the day. The second experiment involved two diets with high and low level of starch and no differences were found on methane emission (28.5 g/day). The experiment number three replaces ingredient by ingredient like in the experiment number one. Here, barley grain was replaced with orange pulp or soybean hulls and no differences were found, with an average methane production value of 41 g/day. The metabolizable energy intake during the three experiments was 1279 kJ/kg of BW0.75 and day on average, and the efficiency use of metabolizable energy intake for milk production was 0.6.
[ES] El cambio climático es una preocupación de ámbito mundial debido a que su perpetuación en el tiempo está teniendo un impacto significativo sobre las personas, los recursos naturales y las condiciones económicas de todo el mundo. La causa fundamental de este fenómeno es el potencial de calentamiento de una serie de gases de efecto invernadero que, mediante la absorción de la radiación infrarroja terrestre, elevan la temperatura de la troposfera y, con ella, las temperaturas superficiales de la Tierra. Los principales gases de efecto invernadero son el vapor de agua, el dióxido de carbono, el metano, el óxido nitroso y los gases fluorados. El metano, después del dióxido de carbono, es el gas que más repercusión tiene sobre el calentamiento global y sus emisiones son causadas tanto por acciones naturales como humanas. Actividades antropogénicas tales como la ganadería intensiva son la principal causa de aumento de las concentraciones de metano en la atmósfera, siendo los rumiantes los animales que mayores cantidades de metano generan a través de la fermentación de alimentos que se produce en el rumen. Las emisiones de metano del ganado vacuno son las que principalmente contribuyen al efecto invernadero seguido de las ovejas, las cabras y los búfalos, respectivamente. Se han descrito diferentes técnicas para medir las emisiones de metano de los rumiantes - la calorimetría indirecta, la técnica del marcador con hexafluoruro de azufre y la técnica de producción de gas in vitro - y, además, se han mencionado algunas estrategias para reducir las emisiones de metano - la defaunación, las vacunas y la composición de la dieta -. Los puntos clave de esta Tesis fueron: diseñar los experimentos con cabras, debido a que no hay muchas investigaciones sobre emisiones de metano en estos animales; estudiar la influencia de la composición de la dieta (hidratos de carbono) como una posible estrategia para la reducción de las emisiones de metano del rumen; y utilizar la calorimetría indirecta como método para cuantificar la producción de metano. Se realizaron tres experimentos. Se utilizaron cabras de la raza Murciano-Granadina en mitad o final de la lactación. Las dietas eran raciones mixtas que diferían en la inclusión de cereal o subproductos fibrosos. El efecto de la dieta se estudió en la producción de leche, la digestibilidad, los parámetros del rumen, la partición de energía, el balance de carbono y nitrógeno, la oxidación de nutrientes y las producciones de metano. En el primer experimento, el intercambio de gases se midió utilizando una mascarilla que se fijó a la cabeza de la cabra con una goma; se almacenó una muestra de gas exhalado en una bolsa de recogida de gas que estaba conectada a un analizador, y se midió la concentración de O2, CO2 y CH4 del aire. En este primer experimento se reemplazó el grano de maíz con pulpa de remolacha y la cantidad de metano recuperado fue del 19,6 y 29,7 g/día, respectivamente. En los otros dos experimentos, el intercambio de gases se midió mediante una urna o cajón diseñado para pequeños rumiantes, donde la cabra introducía toda la cabeza y un programa informático grababa automáticamente las concentraciones de O2, CO2 y CH4 del aire exhalado de forma continua a lo largo del día. El segundo experimento consistió en dos dietas con alto y bajo nivel de almidón y no se encontraron diferencias en la emisión de metano (28,5 g/día). En el tercer experimento se sustituyó ingrediente por ingrediente como en el experimento número uno. El grano de cebada se sustituyó por pulpa de naranja o cascarilla de soja y tampoco se encontraron diferencias, con un valor promedio de la producción de metano de 41 g/día. La energía metabolizable ingerida durante los tres experimentos fue de 1279 kJ/kg de peso metabólico (PV0.75) y día de promedio, y la eficiencia de utilización de la energía metabolizable ingerida para la producción de leche fue de
[CAT] El canvi climàtic és una preocupació d'àmbit mundial ja que la seua perpetuació en el temps està tenint un impacte significatiu sobre les persones, els recursos naturals i les condicions econòmiques de tot el món. La causa fonamental d'aquest fenòmen és el potencial d'escalfament d'una sèrie de gasos d'efecte hivernacle que, mitjançant l'absorció de la radiació infraroja terrestre, eleven la temperatura de la troposfera i, amb ella, les temperatures superficials de la Terra. Els principals gasos d'efecte hivernacle són el vapor d'aigua, el diòxid de carboni, el metà, l'òxid nitrós i els gasos fluorats. El metà, després del diòxid de carboni, és el gas que més repercussió té sobre l'escalfament global i les seues emissions són causades tant per accions naturals com humanes. Activitats antropogèniques com ara la ramaderia intensiva són la principal causa d'augment de les concentracions de metà a l'atmosfera, sent els remugants els animals que més quantitats de metà generen a través de la fermentació d'aliments que es produeix al rumen. Les emissions de metà dels bovins són les que principalment contribueixen a l'efecte hivernacle seguit de les ovelles, les cabres i els búfals, respectivament. S'han descrit diferents tècniques per mesurar les emissions de metà dels remugants - la calorimetria indirecta, la tècnica del marcador amb hexafluorur de sofre i la tècnica de producció de gas in vitro - i, a més, s'han esmentat algunes estratègies per reduir les emissions de metà - la defaunació, les vacunes i la composició de la dieta -. Els punts clau d'aquesta Tesi van ser: dissenyar els experiments amb cabres, pel fet que no hi ha moltes investigacions sobre emissions de metà en aquests animals; estudiar la influència de la composició de la dieta (hidrats de carboni) com una possible estratègia per a la reducció de les emissions de metà del rumen; i utilitzar la calorimetria indirecta com a mètode per quantificar la producció de metà. Es van realitzar tres experiments. S'utilitzaren cabres de la raça Murciano-Granadina a la meitat o final de la lactació. Les dietes eren racions mixtes que diferien en la inclusió de cereal o subproductes fibrosos. L'efecte de la dieta es va estudiar en la producció de llet, la digestibilitat, els paràmetres del rumen, la partició d'energia, el balanç de carboni i nitrogen, l'oxidació de nutrients i les produccions de metà. En el primer experiment, l'intercanvi de gasos es va mesurar utilitzant una màscara que es va fixar al cap de la cabra amb una goma; es va emmagatzemar una mostra de gas exhalat en una bossa de recollida de gas que estava connectada a un analitzador, i es va mesurar la concentració d'O2, CO2 i CH4 de l'aire. En aquest primer experiment es va reemplaçar el gra de blat de moro amb polpa de remolatxa i la quantitat de metà recuperat va ser del 19,6 i 29,7 g/dia, respectivament. En els altres dos experiments, l'intercanvi de gasos es va mesurar mitjançant una urna o calaix dissenyat per a petits remugants, on la cabra introduïa tot el cap i un programa informàtic gravava automàticament les concentracions d'O2, CO2 i CH4 de l'aire exhalat de forma contínua al llarg del dia. El segon experiment va consistir en dues dietes amb alt i baix nivell de midó i no es van trobar diferències en l'emissió de metà (28,5 g/dia). En el tercer experiment es va substituir ingredient per ingredient com en l'experiment número u. El gra d'ordi es va substituir per polpa de taronja o pellofa de soja i tampoc es van trobar diferències, amb un valor mitjà de la producció de metà de 41 g/dia. L'energia metabolitzable ingerida durant els tres experiments va ser de 1279 kJ/kg de pes metabòlic (PV0.75) i dia de mitjana, i l'eficiència d'utilització de l'energia metabolitzable ingerida per a la producció de llet va ser de 0,6.
Ibáñez Sanchis, C. (2015). INFLUENCE OF NUTRITION ON METHANE GAS PRODUCTION IN MURCIANO-GRANADINA GOATS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59389
TESIS

The aim of this study was to investigate the importance of winter season for the production of carbon dioxide (CO2) and methane (CH4) in humic and clear-water boreal aquatic systems. The study was conducted in 16 experimental ponds in northern Sweden during the winter of 2013. Half of the ponds had a higher concentration of dissolved organic carbon (DOC). CO2, CH4, DOC and dissolved inorganic carbon (DIC) were measured repeatedly under the ice from January to April. The results show that CO2 was accumulated continually during winter. No difference in winter accumulation were found between humic and clear ponds. CH4 was rarely accumulated in neither humic nor clear ponds, and was not an important part of the gas flux at spring ice melt. At ice melt, the flux from humic ponds accounted for 1.6 g C m-2 and 1.7 g C m-2 from clear ponds, which was equivalent for 15.6% respective 100% of the annual gas emissions. On a whole-year basis humic ponds acted as a source of 10.3 g C m-2, while clear ponds acted as a sink of 14.7 g C m-2. 76 mg m-2 d-1 DOC was consumed in humic and 59 mg m-2 d-1 DOC in clear ponds while the DIC accumulation was 125 mg m-2 d-1 in humic and 118 mg m-2 d-1 in clear ponds. This study stresses the importance of ice-covered boreal aquatic systems as a significant parts of the global carbon cycling.

Emissions of methane were measured by a static chamber technique at 9 sites on 5 wetlands in the Eastern Temperate Wetland Region, north of Montreal. Mean daily methane fluxes measured from May to October ranged from 0.18 to 1071 mg/m$ sp2$/d, and estimated annual flux ranged from 0.02 to 186 g/m$ sp2$/y. Laboratory incubations of peat samples showed potential anaerobic methane production rates which ranged from 0.00 to 9.12 $ mu$g/g/d, and potential aerobic consumption rates from 0.55 to 3.75 $ mu$g/g/d. Seasonal methane emission patterns are related to water table level and CH$ sb4$ production and consumption potentials in the peat profile. Episodic fluxes were found to be important at several sites, contributing a significant portion of the total emissions.
Analysis of spectral reflectance data from 20 sites on 2 subarctic fens was carried out to address the issue of scaling up CH$ sb4$ emissions using satellite imagery. Hummocks, lawns and pools were found to be spectrally distinct enough to be differentiated by band 5 of Landsat MSS and band 3 of Landsat TM sensors. The averaging of spectral information in mixed pixels proved unlikely to be able to distinguish between wet lawn and string and pool communities. Such weaknesses can be overcome with the use of higher resolution data.

This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.

Ice core records show that the atmospheric concentration of methane (CH₄) during the Last Glacial Maximum (LGM) was 40-50% lower than during the preindustrial Holocene. To understand this natural variation it is important to know how the sources and sinks of CH₄ change over time. Natural wetlands were the single largest contributor of CH₄ to the atmosphere in glacial times, yet models used to estimate their behaviour and CH₄ flux are largely based around relationships derived under modem day conditions. This thesis responds to this issue by exposing wetland mesocosms with contrasting nutrient availability, to the atmospheric concentration of carbon dioxide (CO₂) present at the LGM for 2 years. At the end of this experiment, total CH₄ flux was suppressed by an average of 29% in the nutrient rich fen (P < 0.05). In contrast, the nutrient poor bog showed no response to the treatment (P > 0.05). Further exploring the effects of CO₂ starvation showed that the fen ecosystem exhibited notable reductions in dissolved organic carbon, dissolved CH₄ and a change in the response of CH₄ flux to changing temperature, variables and relationships which all remained unchanged in the bog. The contrasting response of the two ecosystems to CO₂ starvation could be largely explained by differences in nutrient status, species composition and dominant CH₄ production pathways. In particular, it is hypothesised that bog plants under LGM CO₂ concentrations supplemented photosynthesis through the use of subsurface derived CO₂, thus counteracting the treatment effect. The results from this thesis suggest that the CH₄ source strength of late-glacial and early Holocene wetlands may currently be over-estimated because fen ecosystems are a far smaller CH₄ source under low atmospheric [CO₂] than they are today. Furthermore, the results provide new insights into the role of glacial atmospheric CO₂ concentrations in influencing CH₄ emissions from terrestrial ecosystems and provide empirical evidence for a connection between glacial-interglacial changes in atmospheric CH₄ and CO₂ concentrations observed in ice cores.

Methane is a radiatively active, naturally occurring atmospheric trace gas which is thought to account for as much as 19% of the enhanced greenhouse effect. Ice core studies have shown that the atmospheric concentration has more than doubled since pre-industrial times. Wetlands are the largest natural source of atmospheric methane, contributing around 21 % of the annual global flux. The magnitude of various sources of methane is still poorly defined. Stable isotope measurements are increasingly being used to constrain global budgets of atmospheric trace gases because isotopic analysis provides a much clearer picture of global atmospheric chemistry than C~ concentration measurements alone. Conventional analytical techniques for studying dual stable isotopic composition of methane (813e and 8D) require prohibitively large quantities of CH4 for analysis. At the Planetary Sciences Research Institute of the Open University, a highly sensitive static mass spectrometer has been developed which uniquely uses CH4 as the analyte. The method requires only 8 ng ofCH4 for analysis «10 ml ambient air), making replicated measurements of the isotopic composition of CH4 emissions from wetlands feasible for the first time. Methane emissions from an ombrotrophic mire in Snowdonia have been measured over 2 years, (1995-1997) and analysed for 817M. Parallel laboratory studies have also been conducted, to constrain the effects of environmental variables such as peat temperature and water table depth. The presence of vascular plants enhanced methane flux. In the field, methane flux showed seasonal variation. Peat temperature and water table depth could account for 68% of this variation. The isotopic composition of methane flux from the ombrotrophic mire also exhibited seasonal variation, with 817M ranging from -34 to -17%0. The lowest values were observed in summer and the highest in winter. Variations in the isotopic composition of peat water are unlikely to account for more than a 2%0 shift in 817M. Although there was a strong correlation between peat temperature and methane isotopic composition in the field, peat temperature is thought to be an indirect effect, because in laboratory studies this relationship was absent. There was no relationship between water table depth and 817M. It was concluded that the seasonal variation in the isotopic composition of methane emission is linked to the plant growth cycle. Comparison of 817M values determined for methane emissions in Snowdonia with published 813C and 8D data leads to the conclusion that methane is produced mainly by C02 reduction. Contrasting terrains in a paisa mire in the Arctic region of Finland exhibited methane _ emissions with distinct 817M values: lakes, +4.8 ±1.2%0; pools, -3.9 ±O.IO/oo and hummocks, -28.6 ±5.8%0 . From these isotope data it was concluded that in pool and lake sediments the methanogenic pathway is acetate fermentation, while in hummocks methane is produced by CO2 reduction. This study is the first investigation of the stable isotopic composition of methane emissions from wetlands in the UK. The data collected in Snowdonia, and in Finland, show the need for systematic, year round isotopic analysis of methane emissions, if isotope data are to be used in constraining the global methane budget.

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Rumen bacterial, archaeal and anaerobic fungal communities of Holstein dairy heifers and cows, in a tropical system of production, were characterized through sequencing the 16s rRNA and the ITS genes. In addition, we investigated the relationship between these communities and enteric methane (CH4) emissions and productive traits, such as digestible dry matter intake (dDMI), digestible organic matter intake (dOMI), average body weight (BW), rumen pH, volatile fatty acids (VFA) and its main components, acetate, propionate and butyrate. Prepubertal heifers (PP), pubertal heifers (PB), and pregnant heifers (PG) were used in Chapter 1. Pregnant heifers emitted more CH4 than others, followed by PB and PP. Regarding CH4 emissions, the animals were split in high and low CH4 emitters. Heifers were fed a diet composed by corn silage and concentrate (corn, soybean meal and minerals). Prevotella, Ruminococcus, Coprococcus, Butyrivibrio, Clostridium, Shuttleworthia, SHD- 231, CF231, p-75-a5, Methanobrevibacter, Methanosphaera and Caecomyces communis were detected to be the core microbiome of the evaluated heifers. Families Bifidobacteriaceae and RF16 and genera Acetobacter and Coprococcus were strongly correlated with CH4 emissions. Genera Eubacterium, p-75-a5 and SHD-231 showed inverse correlations with CH4 emissions, dDMI, dOMI, BW and rumen pH. Methanobrevibacter, in archaeal community, and Orpinomyces, in anaerobic fungal, showed positive and weak correlations with CH4 emissions. On the other hand, strong and negative correlations were observed among Methanosphaera and this variable. Prepubertal and PG heifers were the most divergent groups in relation to CH4 emissions. Surprisingly, they did not differ in relative abundances of Firmicutes and Bacteroidetes, but PG had greater abundance of Methanobrevibacter and Vadin CA11 and lower abundance of Methanosphaera. None of the bacterial, archaea and anaerobic fungi which correlate with CH4 emissions showed significant correlations (P>0.10) with VFA and the individual concentrations of acetate, propionate and butyrate. Lastly, this work showed that bacterial, archaeal and anaerobic fungal communities did not covaried and the microbial communities did not covaried with volatile fatty acids concentration either. In Chapter 2, high-producing (HP), medium- producing (MP), low-producing (LP) and dry (DC) were evaluated. The forage:concentrate ratios they were fed were 50:50 for HP, 70:30 for MP, 80:20 for LP, and 90:10 for DC. Considering the intake of digestible fraction of feed, DC emitted more CH4, followed by MP, HP and LP, but the HP and LP emissions were similar. The core microbiome of the evaluated Holstein cows in tropical environment was composed by Prevotella, Ruminococcus, Butyrivibrio, Clostridium, Coprococcus, Shuttleworthia, CF231, SHD-231, Methanobrevibacter, and Methanosphaera. None of the anaerobic fungal operational taxonomic units (OTU) were found in all samples. Firmicutes and Bacteroidetes were the most abundant phyla found in the rumen of Holstein cows. For the archaeal community, Methanobrevibacter genera was the most abundant and in anaerobic fungi, most of the sequences were unclassified. The strongest negative correlations with CH4 emissions detected were with the relative abundance of family Coriobacteriaceae and S24-7 and of genera Butyrivibrio, Clostridium and Schwartzia. Positive correlations were found between CH4 emissions and families RF16 and Succinivibrionaceae. In the archaeal community, genera Methanosphaera relative abundance showed a strong negative correlation with CH4. Surprisingly, no significant correlation between CH4 emissions and Methanobrevibacter relative abundance was found. Relative abundance of genera Vadin CA11 (in archaea) and Caecomyces (in anaerobic fungi) were detected to be positively correlated with CH4 in g/day. Many families and genera from Firmicutes phylum showed positive correlations with dDMI and dOMI. None of the bacterial, archaea and anaerobic fungi which correlate with CH4 emissions showed significant correlations (P>0.1) with VFA and the individual concentrations of acetate, propionate and butyrate. The most opposite results observed in the present study were among DC and HP. Dry cows showed greater CH4 emissions in g/kg dDMI and g/kg of dOMI and, besides no differences were observed in relative abundances of Firmicutes, Bacteroidetes and Firmicutes:Bacteroidetes ratio, DC had lower relative abundance of Coriobacteriaceae, which was negatively correlated with CH4, and greater relative abundance of Succinivibrionaceae, that was positively correlated with CH4. In addition, DC had greater relative abundance of Methanobrevibacter and lower of Methanosphaera. Lastly, bacterial, archaeal and anaerobic fungal communities did no covary and VFA and microbial communities did not vary in a similar way either. Chapter 3 was composed by two trials. In trial 1, CH4 emissions were estimated from the seven previously described Holstein dairy cattle categories based on the SF6 tracer gas technique and on IPCC (2006) equations. Enteric CH4 emission was higher for the PP heifers when estimated by the equations proposed by the IPCC Tier 2. However, higher CH4 emissions were estimated by the SF6 technique for MP, HP and DC. Pubertal heifers, PG, and LP had equal CH4 emissions as estimated by both methods. In trial 2, two dairy farms were monitored for one year to identify all activities that contributed in any way to GHG emissions. The total emission from Farm 1 was 3.21 t CO2e/animal/yr, of which 1.63 t corresponded to enteric CH4. Farm 2 emitted 3.18 t CO2e/animal/yr, with 1.70 t of enteric CH4. For the carbon balance calculations, when the carbon stock in pasture and other crops was considered, the carbon balance suggested that both farms are sustainable for GHG, by both estimation methods. On the other hand, carbon balance without carbon stock, by both estimation methods, suggests that farms emit more carbon than the system is capable of stock. It was concluded that IPCC estimations can underestimate CH4 emissions from some categories while overestimate others. However, considering the whole property, these discrepancies were offset and we would submit that the equations suggested by the IPCC properly estimate the total CH4 emission and carbon balance of the properties. Thus, the IPCC equations should be utilized with caution, and the herd composition should be analyzed at the property level.
As comunidades de bactérias, archaeas e fungos anaeróbios do rúmen de novilhas e vacas Holandesas, em um sistema de produção de leite em clima tropical foram caracterizadas. Além disso, a relação entre estas comunidades com a emissão de metano entérico (CH4) e com características produtivas, como consumo de matéria seca digestível (CMSd), consumo de matéria orgânica digestível (CMOd), peso corporal médio (PC), pH ruminal, ácidos graxos voláteis (AGV) e seus principais constituintes, acetato, propionato e butirato. Novilhas pré- púberes (PP), púberes (PB) e em gestação (PG) foram utilizadas no trabalho do Capítulo 1. O grupo PG emitiu mais CH4 que os demais, seguido por PB e PP. Em relação à emissão de CH4, os animais foram divididos em alto em baixo emissores. As novilhas foram alimentadas com uma dieta composta por silagem de milho e concentrado (milho, farelo de soja e minerais). Prevotella, Ruminococcus, Coprococcus, Butyrivibrio, Clostridium, Shuttleworthia, SHD-231, CF231 e p-75-a5, Methanobrevibacter, Methanosphaera e Caecomyces communis foram detectadas como o microbioma core das novilhas avaliadas. As famílias Bifidobacteriaceae e RF16 e gêneros Acetobacter e Coprococcus foram fortemente correlacionadas com as emissões de CH4. Os gêneros Eubacterium, p-75-a5 e SHD-231 mostraram correlações inversas com emissão de CH4, CMSd, CMOd, PC e pH ruminal. Methanobrevibacter, na comunidade de archaeas e Orpinomyces, dentre os fungos anaeróbios, mostraram correlações positivas e fracas com as emissões de CH4. Por outro lado, correlações fortes e negativas foram observadas entre Methanosphaera e esta variável. Novilhas PP e PG foram os grupos mais divergentes em relação às emissões de CH4. Inesperadamente, a abundância relativa de Firmicutes e Bacteroidetes não diferiram entre estes grupos, mas PG apresentou maior abundância relativa de Methanobrevibacter e Vadin CA11 e menor abundância de Methanosphaera. Nenhuma das bactérias, archaeas e fungos anaeróbios que foram correlacionados com as emissões de CH4 mostraram correlações significativas com AGV e com as concentrações individuais de acetato, propionato e butirato (P>0.10). Por fim, este trabalho mostrou que as comunidades ruminais de bactérias, archaeas e fungos anaeróbios não covariaram entre si e que estas comunidades também não covariaram com a concentração de AGV. No Capítulo 2, vacas de alta (HP), média (MP) e baixa (LP) produção de leite e vacas secas (DC) foram avaliadas. As relações volumoso:concentrado utilizadas foram 50:50 para HP, 70:30 para MP, 80:20 para LP e 90:10 para DC. Considerando o consume da fração digestível do alimento, DC emitiu mais CH4, seguida por MP, HP e LP, sendo que as emissões de HP e LP foram similares. O microbioma core das vacas Holandesas avaliadas em ambiente tropical, foi composto por Prevotella, Ruminococcus, Butyrivibrio, Clostridium, Coprococcus, Shuttleworthia, CF231, SHD-231, Methanobrevibacter e Methanosphaera. Nenhuma unidade taxonômica operacional (OTU) da comunidade de fungos anaeróbios foi encontrada em 100% das amostras. Firmicutes e Bacteroidetes foram os filos bacterianos mais abundantes encontrados no rúmen de vacas Holandesas. Na comunidade de archaeas, o gênero Methonobrevibacter foi o mais abundante e na comunidade de fungos anaeróbios a maioria das sequências foram de classificação indefinida. A correlação negativa mais forte com emissão de CH4 foi com a abundância relativa das famílias Coriobacteriaceae e S24-7 e dos gêneros Butyrivibrio, Clostridium e Schwartzia. Correlações positivas foram encontradas entre as emissões de CH4 e as famílias RF16 e Succinivibrionaceae. Na comunidade de archaeas, a abundância relative do gênero Methanosphaera apresentou uma forte correlação negativa com CH4. Surpreendentemente, não foram observadas correlações significativas entre emissões de CH4 e Methanobrevibacter. As abundâncias relativas dos gêneros Vadin CA11 (dentre as archaeas) e Caecomyces (dentre os fungos anaeróbios) foram correlacionadas positivamente com CH4 in g/day. Várias famílias e gêneros do filo Firmicutes apresentaram correlações positivas com CMSd e CMOd. Nenhuma das bactérias, archaeas e fungos anaeróbios que foram correlacionados com as emissões de CH4 mostraram correlações significativas com AGV e com as concentrações individuais de acetato, propionato e butirato (P>0.10). Os resultados mais opostos observados neste trabalho foram entre HP e DC. Vacas secas apresentaram maior emissão de CH4 em g/kg de CMSd e g/kg de CMOd e, apesar de não terem sido observadas diferenças nas abundâncias relativas de Firmicutes, Bacteroidetes e na relação Firmicutes:Bacteroidetes, DC apresentou menor abundância de Coriobacteriaceae, que foi negativamente correlationada com CH4 e maior abundância de Succinivibrionaceae, que foi positivamente correlacionada com CH4. Além disso, DC teve maior abundância relativa de Methanobrevibacter e menor de Methanosphaera. Por fim, este trabalho mostrou que as comunidades ruminais de bactérias, archaeas e fungos anaeróbios não covariaram entre si e que estas comunidades também não covariaram com a concentração de AGV. O Capítulo 3 foi composto de dois ensaios. No ensaio 1, emissões de CH4 das sete categorias de animais Holandeses previamente descritas utilizando a técnica do gás traçador hexafluoreto de enxofre (SF6) e as equações propostas pelo Tier 2 do IPCC (2006). A emissão de CH4 foi maior para PP quando estimada pelas equações do IPCC (2006). Entretanto, maiores emissões de CH4 foram observadas para MP, HP e DC, quando estimadas pela técnica do SF6. Os grupos PB, PG e LP tiveram emissões equivalentes quando estimadas pelos dois métodos. No ensaio 2, duas fazendas de gado de leite foram monitoradas por um ano para identificar todas as atividades que contribuíram, de alguma forma, para a emissão de gases de efeito estufa (GHG). A emissão total da Fazenda 1 foi 3,21 t CO2e/animal/ano, dos quais 1,63 t corresponderam à emissão de CH4 entérico. A Fazenda 2 emitiu 3,18 t CO2e/animal/ano, dos quais 1,70 t foram CH4 entérico. Para os cálculos de balanço de carbono, quando o estoque de carbono no pasto e em outras culturas foi considerado, o balanço de carbono sugeriu que ambas fazendas foram sustentáveis para a emissão de GHG, por ambos métodos de estimação. Por outro lado, o balanço de carbono sem o carbono estocado mostrou que as fazendas emitiram mais carbono que o sistema era capaz de estocar, por ambos métodos. Conclui-se que as equações do IPCC (2006) podem subestimar a emissão de CH4 de algumas categorias e superestimar de outras. Entretanto, considerando a propriedade como um todo, as discrepâncias foram anuladas e pode-se dizer que as equações sugeridas pelo IPCC (2006) podem estimar apropriadamente a emissão total de CH4 e o balanço de carbono de fazendas. Assim, as equações do IPCC (2006) devem ser utilizadas com cuidado, e a composição do rebanho deve ser levada em consideração.