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Academic and political debates over long-run climate policy often invoke “stabilization” of atmospheric concentrations of greenhouse gases (GHGs), but only rarely are non-CO2 greenhouse gases addressed explicitly. Even though the majority of short-term climate policies propose trading between gases on a global warming potential (GWP) basis, discussions of whether CO2 concentrations should be 450, 550, 650, or perhaps as much as 750 ppm leave unstated whether there should be no additional forcing from other GHGs beyond current levels or whether separate concentration targets should be established for each GHG. Here we use an integrated modeling framework to examine multi-gas stabilization in terms of temperature, economic costs, carbon uptake, and other important consequences. We show that there are significant differences in both costs and climate impacts between different "GWP equivalent" policies and demonstrate the importance of non-CO2 GHG reduction on timescales of up to several centuries. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/). / Sarofim was supported in part by a Martin Sustainability Fellowship

Fossil fuels dominate the world energy supply today and the transport sector is no exception. Renewable alternatives must therefore be introduced to replace fossil fuels and their emissions, without sacrificing our standard of living. There is a good potential for biofuels but process improvements are essential, to ensure efficient use of a limited amount of biomass and better compete with fossil alternatives. The general aim of this research is therefore to investigate how to improve efficiency in biofuel production by process development and co-generation of heat and electricity. The work has been divided into three parts; power cycles in biofuel production, methane production via pyrolysis and biofuels from renewable electricity. The studies of bio-based methanol plants showed that steam power generation has a key role in the large-scale biofuel production process. However, a large portion of the steam from the recovered reaction heat is needed in the fuel production process. One measure to increase steam power generation, evaluated in this thesis, is to lower the steam demand by humidification of the gasification agent. Pinch analysis indicated synergies from gas turbine integration and our studies concluded that the electrical efficiency for natural gas fired gas turbines amounts to 56-58%, in the same range as for large combined cycle plants. The use of the off-gas from the biofuel production is also a potential integration option but difficult for modern high-efficient gas turbines. Furthermore, gasification with oxygen and extensive syngas cleaning might be too energy-consuming for efficient power generation. Methane production via pyrolysis showed improved efficiency compared with the competing route via gasification. The total biomass to methane efficiency, including additional biomass to fulfil the power demand, was calculated to 73-74%. The process benefits from lower thermal losses and less reaction heat when syngas is avoided as an intermediate step and can handle high-alkali fuels such as annual crops. Several synergies were discovered when integrating conventional biofuel production with addition of hydrogen. Introducing hydrogen would also greatly increase the biofuel production potential for regions with limited biomass resources. It was also concluded that methane produced from electrolysis of water could be economically feasible if the product was priced in parity with petrol. / <p>QC 20121127</p>

Methane-air, ethane-air, and n-heptane-air over-ventilated co-flow laminar diffusion flames were studied up to pressures of 2.03, 1.52, and 0.51 MPa, respectively, to determine the effect of pressure on flame shape, soot concentration, and temperature. A spectral soot emission optical diagnostic method was used to obtain the spatially resolved soot formation and temperature data. In all cases, soot formation was enhanced by pressure, but the pressure sensitivity decreased as pressure was increased. The maximum fuel carbon conversion to soot, ηmax, was approximated by a power law dependence with the pressure exponent of 0.92 between 0.51 and 1.01 MPa, and 0.68 between 1.01 and 2.03 MPa with ηmax=9.5% at 2.03 MPa for methane-air flames. For ethane-air flames, the pressure exponent was 1.57 between 0.20 and 0.51 MPa, 1.08 between 0.51 and 1.01 MPa, and 0.58 between 1.01 and 1.52 MPa where ηmax=23% at 1.52 MPa. For nitrogen-diluted n-heptane-air flames, ηmax=6.5% at 0.51 MPa.

Methane-air, ethane-air, and n-heptane-air over-ventilated co-flow laminar diffusion flames were studied up to pressures of 2.03, 1.52, and 0.51 MPa, respectively, to determine the effect of pressure on flame shape, soot concentration, and temperature. A spectral soot emission optical diagnostic method was used to obtain the spatially resolved soot formation and temperature data. In all cases, soot formation was enhanced by pressure, but the pressure sensitivity decreased as pressure was increased. The maximum fuel carbon conversion to soot, ηmax, was approximated by a power law dependence with the pressure exponent of 0.92 between 0.51 and 1.01 MPa, and 0.68 between 1.01 and 2.03 MPa with ηmax=9.5% at 2.03 MPa for methane-air flames. For ethane-air flames, the pressure exponent was 1.57 between 0.20 and 0.51 MPa, 1.08 between 0.51 and 1.01 MPa, and 0.58 between 1.01 and 1.52 MPa where ηmax=23% at 1.52 MPa. For nitrogen-diluted n-heptane-air flames, ηmax=6.5% at 0.51 MPa.

Despite the spatial significance of Canadas boreal forest, there is very little known about greenhouse gas emissions within it. The primary objective of this project was to study the atmosphere-soil exchange of CH4 and N2O in the boreal forest of central Saskatchewan. In the summers of 2006 and 2007, greenhouse gas emissions were measured along transects in three different mature forest stands (trembling aspen, black spruce and jack pine) using a sealed chamber method. In addition, the gross rates of mineralization and nitrification, and the relative contribution of nitrification and denitrification to N2O emissions, were measured at the trembling aspen site using a stable isotope technique in which 15N-enriched nitrate and ammonium were injected into intact soil cores. The amount of 14N found in the labeled pools was used to measure the gross rates, and the amount of 15N found in the emitted N2O was used to determine the relative contribution of the different N pathways to total N2O emissions. Results indicated that the jack pine and black spruce sites were slight sinks of CH4 (-1.23 kg CH4-C ha-1 yr-1and -0.17 kg CH4-C ha-1 yr-1 respectively in 2006 and -0.95 kg CH4-C ha-1 yr-1and 0.45 kg CH4-C ha-1 yr-1 respectively in 2007), whereas the trembling aspen site was a net source (46.7 kg CH4-C ha-1 yr-1 in 2006 and 196.0 kg CH4-C ha-1 yr-1 in 2007). All three sites had very low cumulative N2O emissions, ranging from -0.02 to 0.14 kg N2O-N ha-1 yr-1 in both years. Of the environmental controls examined for CH4, consumption at the jack pine site was correlated positively with organic carbon and negatively with water-filled pore space. Black spruce CH4 emissions were correlated negatively with both organic carbon and clay content, and emissions at the trembling aspen site were positively correlated with soil temperature and organic carbon, while also related to the presence of standing water (2006 and 2007 had very high precipitation, causing a high water table and ponding in depressions). The N2O emissions were not correlated with any of the environmental parameters measured at the jack pine or black spruce sites, but clay content was positively related to emissions at the trembling aspen site. The 15N results indicated that N cycling at the trembling aspen site was very rapid, allowing little N to escape the system as N2O; the majority of emissions that did occur were due to a nitrification-related process.

Sol-gel (solution-gelation) method was used to prepare Ni-Ti and Ni-Ti-Al catalysts for reforming of methane with carbon dioxide. This method, after optimizing the parameters such as hydrolysis and acid/alkoxide ratio, is able to make a Ni-Ti catalyst with a surface area as high as 426m2/g when calcined at 473K; but calcination at higher temperature lead to dramatic decrease in surface area. XRD, XPS, TEM and SEM were used to understand this change. Using a packed bed reactor, the catalysts were evaluated with the reforming reaction. It was found that the activity of the Ni-Ti catalyst increases with the Ni loading in the range of 1-10wt%. The reduction temperature has strong effect on activity of the reduced catalyst. Up to 973K, the activity increases with the reduction temperature; but after 973K, the activity decreases and become 0 when the temperature is over 1023K. The Ni-Ti catalyst also deactivated as 15% after 4h of time on stream. The XRD analysis shows that Ti3O5 formed in the catalyst after higher-temperature reduction as well as after the reaction for a period of time. The formation of Ti3O5 may render the catalyst to loss its activity. However, further study is expected to understand the mechanism. TG/DTA analysis shows that both Ni-Ti and Ni-Ti-Al catalysts had carbon deposition; but the latter maintained higher activity in a longer period of time.

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.

The project is a research on liquid methane. It is stored in a standing and static pressure vessel specially calculated for cryogenic purposes. All the simulations have been done using the finite element method.  The  finite  element  method  (FEM)  or  finite  element  analysis  (FEA)  is  a  numerical technique to find approximate solutions for partial differential equations and it is used to simulate the strength of materials. FEM allows the user to visualize the distribution of stresses and displacements. There is a wide range of software to do FEM simulations, the software chosen for the project is Pro/Engineer Wildfire 4.0.  Pro-Engineer  is  a  CAD/CAM/CAE  software  developed  by  Parametric  Technology Corporation (PTC).  It provides solid modeling, assembly modeling and finite element analysis.  The  results  obtained  in  the  mechanical  analysis  executed  with  the  application  Pro-mechanica show that the designed container holds the loads applied and stands stable.  The thermal analysis of the insulation verifies that the amount of heat exchanged with the environment is on acceptable levels. Finally, to protect the integrity of the structure the proper paints have been selected.

Biogas is a source of renewable energy and is produced at anaerobic conditions. The gas consists mainly of methane (55-70 %) and carbon dioxide (30-45 %). Biogas can be used as vehicle fuel after the gas has been upgraded to a methane content of approximately 97 %. There are several companies in Sweden producing biogas. Svensk biogas AB in Linköping is one of the largest. The company has two biogas production plants; one in Linköping and one in Norrköping. To meet the surge demand for biogas it is not only important to increase the volumetric capacity of the digesters, but also to optimize the process at the existing production plants in different ways. Zeolites, a clay mineral, have earlier been shown to have a positive effect on anaerobic digestion of certain substrates. The aim of this master’s thesis was to investigate if the organic loading rate could be increased and/or if the hydraulic retention time could be reduced by addition of zeolites to a reactor treating slaughterhouse waste as a substrate. The aim was further to investigate which substance/substances that zeolites possibly could affect. Addition of the zeolite clinoptilolite in a continuously stirred lab tank reactor showed a significantly lower accumulation of volatile fatty acids compared to that in a control reactor without zeolites added, when the hydraulic retention time was kept low (30 days) and the organic loading rate was high (4.8 kg VS/ (m3 × day)). The same results were observed upon zeolite addition in a batch experiment, which also showed a decreased lag phase. Neither the specific gas production nor the methane concentration was significantly affected by addition of zeolites. Furthermore, addition of a possible inhibitor, long-chain fatty acids (LCFA), increased the lag phase further when slaughterhouse waste was used as a substrate. The conclusion from the observed results is that a metabolite or metabolites produced during the anaerobic degradation is/are the reason to inhibition and an increased lag phase.