Through appropriate soil and crop residue management, soil can function as a sink for carbon (C) and nitrogen (N) for the mitigation of greenhouse gases (GHG). No research has yet investigated the potential of intercrop agroecosystems to reduce emissions of GHG to the atmosphere. This research evaluates whether maize-soybean intercrop agroecosystems sequester more C and N and emit fewer GHG than maize and soybean sole crop agroecosystems. An experiment was conducted at Balcarce, Argentina using four treatments: a maize sole crop, a soybean sole crop, and two intercrops with either 1:2 or 2:3 rows of maize to soybean. The objectives were to quantify soil organic carbon (SOC) and soil total nitrogen (TN) at 0-10, 10-20, 20-40, 40-80 and 80-120 cm depths, rates of decomposition of maize and soybean crop residue after 312 days, crop residue C- and N-input at harvest, and emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Significant decreases in SOC were observed with depth in all treatments after 40 cm, and significant decreases in TN were observed with depth in all treatments after 20 cm. Crop residue from maize had the greatest input of C and N to the soil, but the slowest rate of decomposition. Soybean biomass had the least input of C and N to the soil and the fastest rate of decomposition. The 1:2 and 2:3 intercrop agroecosystems had moderate crop residue inputs of C and N and intermediate rates of decomposition. No significant differences in GHG emissions were detected between treatments throughout the growing season. The major influences on GHG emissions were weather events, soil temperature and moisture, and crop residue input. Annual GHG emissions were determined; the CH4 sink in the 1:2 intercrop and the soybean sole crop was significantly greater (P < 0.05) than the 2:3 intercrop and the maize sole crop. Emissions of CO2 were inversely proportionate to N2O, with the greatest C sink in the 1:2 intercrop.

Reservoirs impound and store large volumes of water and flood land. The water is used for electricity generation, irrigation, industrial and municipal consumption, flood control and to improve navigation. The decomposition of flooded soil and vegetation creates greenhouse gases and thus reservoirs are a source of greenhouse gases. Reservoirs are not well studied for greenhouse gas flux from the water to the atmosphere. The FLooded Upland Dynamics EXperiment (FLUDEX) involves the creation of three experimental reservoirs in the upland boreal forest to study greenhouse gas and mercury dynamics. The balance of biological processes, decomposition, primary production, CH₄ oxidation and the nitrogen cycle in the reservoirs controls the greenhouse gas flux from the reservoir to the atmosphere. Understanding the importance and controlling factors of these processes is vital to understanding the sources and sinks of greenhouse gases within reservoirs. The carbon and oxygen dynamics near the sediment-water interface are very important to the entire reservoir because many processes occur in this area. Light and dark benthic chambers were deployed, side-by-side, to determine the benthic flux of DIC and CH₄ across the sediment-water interface and to determine the role of benthic photoautotrophs in benthic DIC, CH₄ and O₂ cycling. Benthic chambers have shown photoautotrophs use the decomposing soil, rocks and exposed bedrock as a physical substrate to colonize and the CO₂ produced by the decomposing soil as a carbon source since the delta¹³C-DIC value of the DIC added to light chambers is enriched relative to dark chambers and net photosynthesis rates are linked to community respiration. Benthic photoautotrophs consume 15-33% of the potential DIC flux into the water column. CH₄ produced by the decomposition of soils is partially oxidized by methanotrophs that use the photosynthetically produced oxygen. The delta¹³C-CH₄ values of the CH₄ added to light chambers is enriched relative to dark chambers and 15-88% of the potential CH₄ flux into the water column is oxidized. An isotope-mass budget for DIC and CH₄ is presented for each reservoir to identify the importance of processes on areservoir scale. Input of DIC to the reservoirs from overland flow can be important because concentration is greater and delta¹³C-DIC values are depleted relative to inflow from Roddy Lake. Estimates of total reservoir primary production indicate that 3-19% of the total DIC production from decomposition is removed by photoautotrophs. The carbon cycling in biofilm and the importance of periphytic primary production needs to be better understood. Dissolved delta¹³C-CH₄ values of CH₄ in reservoir outflow enriched 45-60permil, indicating that CH₄ oxidation was an important CH₄ sink within the reservoirs. Stable carbon isotope data indicates that the CH₄ in the bubbles is partially oxidized so the site of bubble formation is the upper portion of the flooded soil. The fraction of CH₄ converted to CO₂ in the FLUDEX reservoirs is similar to that of the wetland flooded for the Experimental Lakes Area Reservoir Project (ELARP). Approximately half of the dissolved CH₄ in the FLUDEX reservoirs was removedby CH₄ oxidation. The ebullitive flux of CH₄ from FLUDEX reservoirs is reduced 25-75% by CH₄ oxidation. The CH₄ flux to the atmosphere from peat surface of the ELARP reservoir became less oxidized after flooding: 91% to 85% oxidized. The floating peat islands of the ELARP reservoir were less oxidized than the peat surface. Similar to the CH₄ in the FLUDEX reservoirs, CH₄ in the ELARP peat islands was oxidized 56%. CH₄ oxidation is an important process because it reduces the global warming potential of the greenhouse gas flux since CO₂ is less radiatively active than CH₄.

Through appropriate soil and crop residue management, soil can function as a sink for carbon (C) and nitrogen (N) for the mitigation of greenhouse gases (GHG). No research has yet investigated the potential of intercrop agroecosystems to reduce emissions of GHG to the atmosphere. This research evaluates whether maize-soybean intercrop agroecosystems sequester more C and N and emit fewer GHG than maize and soybean sole crop agroecosystems. An experiment was conducted at Balcarce, Argentina using four treatments: a maize sole crop, a soybean sole crop, and two intercrops with either 1:2 or 2:3 rows of maize to soybean. The objectives were to quantify soil organic carbon (SOC) and soil total nitrogen (TN) at 0-10, 10-20, 20-40, 40-80 and 80-120 cm depths, rates of decomposition of maize and soybean crop residue after 312 days, crop residue C- and N-input at harvest, and emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Significant decreases in SOC were observed with depth in all treatments after 40 cm, and significant decreases in TN were observed with depth in all treatments after 20 cm. Crop residue from maize had the greatest input of C and N to the soil, but the slowest rate of decomposition. Soybean biomass had the least input of C and N to the soil and the fastest rate of decomposition. The 1:2 and 2:3 intercrop agroecosystems had moderate crop residue inputs of C and N and intermediate rates of decomposition. No significant differences in GHG emissions were detected between treatments throughout the growing season. The major influences on GHG emissions were weather events, soil temperature and moisture, and crop residue input. Annual GHG emissions were determined; the CH4 sink in the 1:2 intercrop and the soybean sole crop was significantly greater (P < 0.05) than the 2:3 intercrop and the maize sole crop. Emissions of CO2 were inversely proportionate to N2O, with the greatest C sink in the 1:2 intercrop.

With climate change arising as an important issue in the 21th century, many states have been working diligently to develop climate action plans with the hopes of reducing greenhouse gas emissions and stop climate change from occurring. According to scientists' theories, however, many places across the globe are already feeling the effects of a changing climate and must therefore switch their focus from mitigation to adaptation. In the United States, there has been a focus on how climate change will impact one of the most vulnerable parts of the country, the transportation infrastructure. Many countries have already begun adapting their transportation infrastructure to climate change including the United States. This thesis focuses on how states are adapting to climate change by analyzing strategies, frameworks, and reports released by these states in order to document where they stand in regards to adaptation of the transportation network. The states that are adapting their transportation infrastructure are Washington, Oregon, California, Hawaii, Alaska, Florida, North Carolina, Maryland, Delaware, Pennsylvania, Michigan, Connecticut, Massachusetts, Vermont, and Maine. There is also a brief summary of how Canada and the United Kingdom are preparing for climate change with an analysis of frameworks and strategies used to adapt their transportation infrastructure. The ultimate goal of this thesis is to provide engineers and policymakers with evidence that several states are implementing adaptation into transportation projects and provide a variety of strategies for them to use in their own state. Specifically, this report provides applications of adaptation for Georgia to use, so that they can begin the lengthy process of adapting their transportation infrastructure to climate change.

published_or_final_version / Applied Geosciences / Master / Master of Science

Climate change constitutes one of the greatest challenges facing the world today, as it will influence the way we live and work in future decades. Excessive greenhouse gas (GHG) emissions are recognized as the key contributor to climate change, and the construction sector has an indispensable role to play in emission reduction, as building facilities are energy- and emission-intensive to construct and operate. Previous research indicates that up to 30 percent of buildings’ lifecycle emissions can be minimized through the careful selection of low-carbon materials. Although building environmental assessment (BEA) tools have been widely used in identifying and mitigating the lifecycle environmental impacts of building facilities, the existing BEA tools provide no rigorous regime for assessing the embodied GHG emissions of building materials. Therefore the aim of this research is to bridge the research and practical gaps by developing an integrated BEA assessment model that comprehensively audits and benchmarks the embodied GHG emissions of building materials at product level. The research began by examining the limitations of current BEA tools, in particular their means of evaluating the embodied GHG emissions of buildings. Then, an embodied GHG emissions evaluation module model under an existing BEA scheme was proposed. The proposed model comprised (i) product category, (ii) product-based GHG auditing framework, and (iii) emissions benchmarking measure. After that, a thorough review of the relevant literature and international classification systems was carried out to establish a systematic product categorization regime for building materials. An auditing framework comprising system boundary, process map, emission sources, and a carbon auditing tool in Microsoft TM Excel has been developed by reviewing international standards on product carbon footprint assessments and eliciting knowledge from domain experts through a series of interviews. The emission benchmarks for each product category have been determined through the application of fuzzy set theory to facilitate easy comparison and decision-making. Finally, the developed product categorization regime, GHG auditing framework, and benchmarks were validated through a Delphi study, a discussion of which concluded the thesis. The research outcomes confirm that the GHG emissions embodied in a building facility can be meticulously analyzed and integrated into the BEA. The research also improves the understanding of how the materials’ embodied emissions can be accurately calculated at the product level. More importantly, it enhances existing BEA tools by incorporating embodied GHG emissions into the analysis, thus makes the lifecycle emission assessment of building facilities possible. The proposed integrated BEA model will enable clients and design teams to minimize the carbon footprints of buildings and assist users and the general public in identifying green building facilities. The originality of this research lies in the establishment of a set of emissions benchmarks for five most emission-intensive building materials using fuzzy set theory. These benchmarks provide a seamless platform allowing the assessment of materials’ embodied emissions to be integrated with the existing BEA model, thereby not only encouraging the adoption of low-carbon building materials but also fostering ongoing product carbon footprint reductions. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

The second generation bioenergy crops Miscanthus x giganteus and short rotation coppice (SRC) willow are the two main bioenergy crops in the UK and have become an integral part of legislation to provide an alternative to fossil fuels and to reduce national greenhouse gas (GHG) emissions. To reach emission targets, it is estimated that approximately 350,000 ha of land could be made available for bioenergy crops by 2020. Despite the promise of these crops, there have been very few field-studies regarding soil GHG (CO2, CH4 and N2O) emissions and many of the published studies are life cycle analyses or modelled fluxes from soils using default values from the IPCC. The first aim of this research was to quantify the in situ soil GHG budget and to establish the drivers of these GHG fluxes for Miscanthus and SRC willow. The second aim of this research was to provide a more in-depth understanding of C cycling under Miscanthus i.e. litter and roots through two field experiments. Overall, the results from this work confirm minimal emissions of CH4 and N2O from soil under Miscanthus and SRC willow. CO2 flux was found to be the major efflux from soils and it was found in Miscanthus, that the majority of this flux was derived from below ground respiration. Litter played an important part in providing nutrients to the soil, which is vital in systems that are not fertilised. Litter also contributed to SOM accumulation on the soil surface and may promote long-term C sequestration. The results from this work combined with other literature would suggest that these second generation crops offer advantages to first generation crops, but more field-based studies are required to say if they can offer the large-scale GHG savings needed to be a viable alternative to fossil fuels.

This Master thesis connects two interrelated environmental issues – climate change and waste management. Both have been under discussion for few decades and are currently two of the top priorities on EU’s environmental agenda. The goal of this thesis is to find out in what ways waste management in Lithuania and Sweden can contribute towards reducing global warming and how the release of greenhouse gases could be reduced. Four different material flows – food, metal, plastic, and paper and cardboard – are examined and greenhouse gas reduction potentials are calculated, using data found in various reports. The case studies of Lithuania and Sweden help to find out the strong and the weak points of waste management systems in the two countries by comparing their differences. The results show that in Lithuania significant greenhouse gas reductions can be achieved by improving waste sorting and decreasing disposal rates, whereas in Sweden waste management is well-developed, but still could be upgraded by switching to more efficient waste treatment practices. The thesis is concluded by indicating the pros and cons of waste management in Lithuania and Sweden.

Enhanced interest in biofuel production has renewed interest in bioenergy crop production within the United States. Agriculture’s role in biofuel production is critical because it has the potential to supply renewable energy while minimizing greenhouse gas (GHG) emissions. However, agronomic management practices influence direct and indirect GHG emissions, and both can have a significant impact on biofuel production efficiency. Our overall objective was to determine the carbon (C) footprint of bioenergy sorghum (Sorghum bicolor L.) production in central Texas. Specifically, we determined the impacts of crop rotation, nitrogen (N) fertilization, and residue return on direct and indirect GHG emissions, theoretical biofuel yield, C pools, and life cycle GHG emissions from bioenergy sorghum production in 2010 and 2011. An experiment established in 2008 near College Station, TX to quantify the impacts of crop management practices on bioenergy sorghum yield and soil properties was utilized, and included two crop rotations (sorghum-sorghum or corn-sorghum), two fertilization levels (0 or 280 kg N ha^(-1) annually), and two residue return rates (0 or 50% biomass residue returned) to assess management impacts on sorghum production, C cycling, and life cycle GHGs. Corn production was poor under moderate drought conditions, while bioenergy sorghum produced relatively large yields under both moderate and severe drought conditions. Nitrogen addition increased crop yields, and rotated sorghum had higher yield than monoculture sorghum. Fluxes of CO_(2) and N_(2)O were higher than those reported in literature and highest soil fluxes were frequently observed following precipitation events during the growing season. Residue return increased cumulative CO_(2) emissions and N fertilization increased N_(2)O emissions. Residue return also increased soil microbial biomass-C, an important indicator of soil quality. Continuous sorghum significantly increased soil organic C (SOC) concentrations near the soil surface and at two depths below 30 cm. Analysis of change in SOC across time to estimate net CO_(2) emissions to the atmosphere revealed bioenergy sorghum production accrued high amounts of SOC annually. Most treatments accrued more than 4 Mg C ha^(-1) yr^(-1) from 2008 to 2012, which indicated great potential for C sequestration and offsetting GHG emissions. Life cycle GHG emissions (as g CO_(2)-eq MJ^(-1)) were all negative due to high SOC increases each year and indicated all bioenergy sorghum production treatments sequestered atmospheric CO_(2) per unit of theoretical energy provided. Despite its relatively low production efficiency, rotated sorghum with N addition and residue return was selected as the ideal bioenergy sorghum production scenario due to a number of sustainability factors. Bioenergy sorghum may offer great benefit as a high-yielding biofuel feedstock with minimal impacts to net GHG emissions.

This study uses life cycle analysis to examine the net greenhouse gas (GHG) emissions from the activities of the peat industry in Canada for the period 1990 to 2000. GHG accounting is undertaken for (1) land use change, (2) peat extraction and processing, (3) the transport of peat to market by truck, train and ship, and (4) the in situ decomposition of extracted peat. The emission estimates were based on results from GHG accounting models using data derived from scientific literature, government and industry statistics, and the responses to a questionnaire sent to Canada's peat establishments. The questionnaire, designed to obtain information on peat extraction methods, land and fuel use, as well as the transportation of peat, had a response rate representing 69% of Canada's total peat production in the year 2000. Results indicate that 540 600 tonnes of greenhouse gases were emitted in 1990 and 893 300 tonnes were emitted in the year 2000 (emission figures are measured in CO2 equivalents using a 100-year time horizon). Peat decomposition was by far the largest source of GHG emissions, averaging 70.6% of total emissions during the eleven-year period from 1990 to 2000. Greenhouse gases from land use change averaged 14.7%. An average of 10.4% of total emissions resulted from the transport of peat to market, while GHGs from extraction and processing averaged 4.3%. Predictions of the annual GHG emissions from the peat industry, assuming a "business as usual" context, were produced for the years 2001 to 2012. These figures were compared with those resulting from various greenhouse gas reduction scenarios.