Energy consumption estimation for greenhouse gas separation processes by clathrate hydrate formation

Energy consumption estimation for greenhouse gas separation processes by clathrate hydrate formation

Separation Process of Hydrofluorocarbons (HFCs) by Clathrate Hydrate Formation

Reducing red meat consumption is an effective tactic for decreasing environmental impact of diets while maintaining nutritional adequacy, healthiness, and overall consumer acceptability. Still, dietary change in favor of plant foods is a controversial climate mitigation measure, especially in the Nordic region where agri-food heritage is linked to ruminant husbandry. In this study we aimed to explore sustainable diets for the Norwegian context by (1) investigating the environmental impacts of nutritionally optimized diets following the Nordic Nutrition Recommendations 2023 (NNR2023), (2) estimating potential for environmental impact reduction across scenarios of meat and legume consumption, and (3) identifying nutritional challenges. Quadratic optimization was employed to minimize departure from the average observed Norwegian diet while meeting nutrient, health, and carbon footprint constraints. The diet of Norwegian adults was estimated based on results from the national dietary survey Norkost 3. Global warming potential (GWP), freshwater and marine eutrophication, terrestrial acidification, water use, and transformation and use of land were calculated using data from the Norwegian Life Cycle Assessment Food Database version 01. Diets were optimized to meet NNR2023 nutrition and health recommendations for nutrients and food groups. Optimizations were first run without constraints on GWP, for three diet scenarios: (1) nutrients and health-based targets for food amounts (NNR2023), (2) nutrients and health-based targets for food amounts with ruminant meat ≥ observed intake (62 g/day) (Ruminant), and (3) nutrients and health-based targets for food amounts with legumes content ≥40 g/day (Legumes). Then, GWP constraints were applied in 5% increments until no solution was found. The optimal diet for each scenario was defined as the diet with the largest feasible reduction in GWP (NNR2023+/Ruminant+/Legumes+). Optimizing the diet to meet nutrient and health constraints alone resulted in a modest decrease in GWP (NNR2023); retaining ruminant meat consumption (Ruminant) impeded the reduction (-9% vs. 0%). Diets following NNR2023 nutrient and health constraints alone were feasible up until a 30% reduction in GWP (NNR2023+). A 35% reduction in GWP was achieved when legumes were added to the diet (Legumes+), while diets retaining 62 g of ruminant meat were not identified beyond a 15% reduction in GWP (Ruminant+). Sodium and selenium were the strongest limiting constraints in all scenarios. Diets with a 40% reduction in GWP were identified when nutrient constraints were lowered from the Recommended Intake to the Average Requirement (NNR2023+/Legumes+). Reductions in GWP coincided with reductions in all measured environmental indicators except marine eutrophication. The NNR2023 guidelines outline diets that have generally lower environmental impacts than the average Norwegian diet, though outcomes depend on distribution of meat and legume consumption in the diet. Regardless of degree of environmental impact reduction, diets following NNR2023 guidelines will require significant dietary changes compared to observed intake, including an increase in consumption of fruits, vegetables, and grains, and a strong decrease in consumption of red meat, total meat, and discretionary foods. Preventing the model from removing any ruminant meat from the diet limited GWP reduction to 15% and induced considerable changes in intake of other food groups, especially a decrease in other types of meat.

Clathrate hydrates are crystalline materials made of water molecules forming host cages within which guest molecules are located. The hydrogen bond network ensuring the stability of the host substructure includes ionic defects, having an impact on the physicochemical properties of the systems. In this paper, a new way of introducing these ionic defects is proposed. Type II clathrate hydrates mixing tetrahydrofuran (THF) and perchloric acid guest molecules are synthesized and investigated by means of calorimetric, X-ray diffraction, and Raman scattering measurements together with a computational structure relaxation in the density functional theory approximation. The formation of the mixed clathrate hydrate with perchlorate anion included in the large cage of the cationic host-substructure of the THF type II clathrate hydrate requires the cooling of a (1-α) THF·αHClO4·17H2O solution with α less than 0.125. Above this inherent limitation, a multiphasic regime is observed in the formation of clathrate hydrate (mixture of type I and type II). The substitution of a THF molecule per perchlorate anion allows the modification of the melting of the type II clathrate hydrate, by preserving the clathrate structure. Shrinkage of the type II unit cell is measured together with a softening of the host lattice mode. In the harmonic approximation, the observation of both phenomena is counterintuitive and outline existing competition between anharmonicity of the cage energy landscape and ionic host–guest interaction. This study reveals the key role played by acidic defects existing in the host substructure on the physicochemical properties of clathrate hydrate.

Methane and carbon dioxide are formed in landfills as wastes degrade. Molecule-for-molecule, methane is about 20 times more potent than carbon dioxide at trapping heat in the earth's atmosphere, and thus, it is the methane emissions from landfills that are scrutinized. For example, if emissions composed of 60% methane and 40% carbon dioxide were changed to a mix that was 40% methane and 60% carbon dioxide, a 30% reduction in the landfill's global warming potential would result. A 10% methane, 90% carbon dioxide ratio will result in a 75% reduction in global warming potential compared to the baseline. Gas collection from a closed landfill can reduce emissions, and it is sometimes combined with a biocover, an engineered system where methane oxidizing bacteria living in a medium such as compost, convert landfill methane to carbon dioxide and water. Although methane oxidizing bacteria merely convert one greenhouse gas (methane) to another (carbon dioxide), this conversion can offer significant reductions in the overall greenhouse gas contribution, or global warming potential, associated with the landfill. What has not been addressed to date is the fact that methane can also escape from a landfill when the active cell is being filled with waste. Federal regulationsmore » require that newly deposited solid waste to be covered daily with a 6 in layer of soil or an alternative daily cover (ADC), such as a canvas tarp. The aim of this study was to assess the feasibility of immobilizing methane oxidizing bacteria into a tarp-like matrix that could be used for alternative daily cover at open landfill cells to prevent methane emissions. A unique method of isolating methanotrophs from landfill cover soil was used to create a liquid culture of mixed methanotrophs. A variety of prospective immobilization techniques were used to affix the bacteria in a tarp-like matrix. Both gel encapsulation of methanotrophs and gels with liquid cores containing methanotrophs were readily made but prone to rapid desiccation. Bacterial adsorption onto foam padding, natural sponge, and geotextile was successful. The most important factor for success appeared to be water holding capacity. Prototype biotarps made with geotextiles plus adsorbed methane oxidizing bacteria were tested for their responses to temperature, intermittent starvation, and washing (to simulate rainfall). The prototypes were mesophilic, and methane oxidation activity remained strong after one cycle of starvation but then declined with repeated cycles. Many of the cells detached with vigorous washing, but at least 30% appeared resistant to sloughing. While laboratory landfill simulations showed that four-layer composite biotarps made with two different types of geotextile could remove up to 50% of influent methane introduced at a flux rate of 22 g m{sup -2} d{sup -1}, field experiments did not yield high activity levels. Tests revealed that there were high hour-to-hour flux variations in the field, which, together with frequent rainfall events, confounded the field testing. Overall, the findings suggest that a methanotroph embedded biotarp appears to be a feasible strategy to mitigate methane emission from landfill cells, although the performance of field-tested biotarps was not robust here. Tarps will likely be best suited for spring and summer use, although the methane oxidizer population may be able to shift and adapt to lower temperatures. The starvation cycling of the tarp may require the capacity for intermittent reinoculation of the cells, although it is also possible that a subpopulation will adapt to the cycling and become dominant. Rainfall is not expected to be a major factor, because a baseline biofilm will be present to repopulate the tarp. If strong performance can be achieved and documented, the biotarp concept could be extended to include interception of other compounds beyond methane, such as volatile aromatic hydrocarbons and chlorinated solvents.« less

<div class="htmlview paragraph">This paper explores the impact of U.S. emission controls and fuel economy improvements on the global warming potential (GWP) of new light-duty vehicles. Fuel economy improvements have reduced the GWP of both passenger cars and light-duty trucks by lowering the per mile emissions of carbon dioxide (CO<sub>2</sub>). Further GWP reductions have been achieved by emission standards for criteria pollutants: carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO<sub>x</sub>).</div> <div class="htmlview paragraph">The GWP of a criteria pollutant was calculated by multiplying the emission rate by a relative global warming factor to obtain a CO2 equivalent emission rate. Both CO2 and criteria pollutant emission rates per vehicle have decreased substantially for new light-duty vehicles over the period from 1968 to 1991. Over that period, the GWP from CO2 was reduced by almost 50% in new vehicles by improving fuel economy. In that same time period, the GWP from criteria pollutants from new vehicles was reduced with emission controls by from 80% to 90%, depending on the global warming time frame of interest. Consequently, total reductions in the GWP of new passenger cars and light-duty trucks have been on the order of 55 to 75 percent compared to precontrol (before 1968) new vehicles.</div> <div class="htmlview paragraph">However, the reduction in GWP caused by emission control of criteria pollutants has been larger than the reduction caused by improved fuel economy (i.e., reduced C02). The contribution of criteria pollutants to the GWP of precontrol new vehicles was substantial, but their contribution has been reduced significantly due to U.S. emission controls. As a result, the contribution of criteria pollutants to global warming is now much less than the contribution of CO2 from fuel consumption.</div>

Carbon dioxide (CO2) gas enrichment and separation process have been researched for decades and various methods are being applied in industries to reduce and resist CO2 gas due to its corrosive characteristics and negative effects on environment. Greenhouse gases such as methane (CH4) and CO2 are the most abundant in natural gas wells. They contribute significant negative effects to global warming. In this research, Pressure swing adsorption method was utilized as a mechanism to capture and recover binary gas via gas separation process by adsorbents. The adsorbents used in this study were Zeolite SA, Zirconium-benzene dicarboxylate (UiO-66) and activated carbons made from Kenaf and palm kernel shell (PKS) within the pressure differences of up to 3 bars. The adsorbents were prepared and characterized using Brunauer-Emmett-Teller (BET) analysis and particle size distribution analysis. Adsorbents selection and their capability were tested using binary mixture gas of 70% CO2 and 30% CH4 via breakthrough studies using volumetric method. The experimental data were collected by manipulating the adsorption and desorption time ranging up to 4 minutes. The results show that CO2 gas had higher affinity than CH4 for these adsorbents. Adsorbent saturation period declined towards increasing pressure and vice versa. Experimental data showed that activated carbon made from palm kernel shell yielded the optimum purity and recovery of CH4 and CO2 gases. Purity of CO2 of 94% was successfully achieved at recovery of CH4 and CO2 of 94% and 89% respectively. The other adsorbents were saturated quickly and less effective for high carbon dioxide content separation.Carbon dioxide (CO2) gas enrichment and separation process have been researched for decades and various methods are being applied in industries to reduce and resist CO2 gas due to its corrosive characteristics and negative effects on environment. Greenhouse gases such as methane (CH4) and CO2 are the most abundant in natural gas wells. They contribute significant negative effects to global warming. In this research, Pressure swing adsorption method was utilized as a mechanism to capture and recover binary gas via gas separation process by adsorbents. The adsorbents used in this study were Zeolite SA, Zirconium-benzene dicarboxylate (UiO-66) and activated carbons made from Kenaf and palm kernel shell (PKS) within the pressure differences of up to 3 bars. The adsorbents were prepared and characterized using Brunauer-Emmett-Teller (BET) analysis and particle size distribution analysis. Adsorbents selection and their capability were tested using binary mixture gas of 70% CO2 and 30% CH4 via breakthrough studi...

Using life-cycle inventory production data, the net global warming potential (GWP) of a typical inland Northwest softwood lumber mill was evaluated for a variety of fuel types used as boiler inputs and for electricity generation. Results focused on reductions in carbon emissions in terms of GWP relative to natural gas as the fossil alternative. Woody feedstocks included mill residues, forest residuals, and wood pellets. In all fuel-substitution scenarios, increasing the use of biomass for heat generation decreased GWP. Using woody biofuels for electricity production is somewhat less effective in lowering carbon emissions than when used for heat energy. Heat generation at the mill under the current practice of using about half self-generated mill residues and half natural gas resulted in a 35 percent reduction in GWP over 100 percent natural gas. The greatest reduction in GWP (66%) was from increased use of forest residuals for heat energy, eliminating the use of fossil fuels as a direct heating fuel at the mill. We summarize the results by documenting that greater use of woody biomass for heat energy will reduce carbon emissions over fossil-based fuels.

The objective of this research is to compare the greenhouse gas emissions between recycling of MSW recyclable value wastes and landfilling in Thailand. Methane emissions from the organic fraction of waste in landfills contribute to global warming whereas for recycling, the global warming potential comes from the energy consumption of the recycling process. The whole life cycle of the two scenarios is considered, including transportation. The recycling option reduces the methane emissions from landfill due to diversion of waste. The study shows that this reduction more than offsets the increase due to energy consumption in the recycling process. Apart from the reduction in global warming potential, recycling also contributes to resource conservation. Thailand has a high potential for recycling since a large proportion of the waste currently going to the landfills is actually recyclable. Two case studies of ecodesign are also considered to highlight the increase in recyclability and the benefits thereof.

The objective of this research is to compare the greenhouse gas emissions between recycling of MSW recyclable value wastes and landfilling in Thailand. Methane emissions from the organic fraction of waste in landfills contribute to global warming whereas for recycling, the global warming potential comes from the energy consumption of the recycling process. The whole life cycle of the two scenarios is considered, including transportation. The recycling option reduces the methane emissions from landfill due to diversion of waste. The study shows that this reduction more than offsets the increase due to energy consumption in the recycling process. Apart from the reduction in global warming potential, recycling also contributes to resource conservation. Thailand has a high potential for recycling since a large proportion of the waste currently going to the landfills is actually recyclable. Two case studies of ecodesign are also considered to highlight the increase in recyclability and the benefits thereof.

Carbon Capture and Sequestration (0r Storage)—known as CCS needs to be implemented in various development activities in Indonesia including downstream oil and gas industry because the government of Indonesia has adopted the Paris Agreement on Greenhouse Gas Emissions Reduction . Various capture techniques have been developed for capturing CO2 from post combustion emission. One of the new approaches considered for capturing CO2 and hence reducing to atmospheric emissions is based on gas hydrate (crystallization) technology. The basis of the technology is the selective partition of the target component between the hydrate phase and the gaseous phase. It is expected that CO2 is preferentially trapped and encaged into the hydrate crystal phase compared to the other components. Previous study found that the gas/hydrate equilibrium pressure and temperature for the fl ue gas mixture in the range of 7.6 MPa and 11.0 MPa at 274 K and 277 K respectively, are inappropriate to the downstream oil and gas industrial reality because the operating cost will be expensive to compress the gas to the hydrate formation pressure. Suitable hydrate promoters including Tetrahydrofuran (THF) and Sodium Dodecyl Sulfate (SDS) can be used to achieve moderate hydrate formation pressure and energy consumption appropriate to the industrial reality. In the presence of THF and SDS about 62.3 Nm3/m3 CO2 hydrate can be formed at 30 bar pressure and 274 to 277 K temperature within around 15 minutes reaction time.Many experiments result indicates that continuous hydrates formation will be feasible for scale-up to industrial settings including downstream oil and gas industry emission reduction if the technology assures an optimal contact between gas and liquid phases plus the proper hydrate promoter. However, compared to current international carbon credit, the feasibility of onshore CO2 abatement cost in downstream oil and gas industry sensitively depends on the distance of CO2 hydrate pipeline transportation.

The modern technology for the recovery of helium from heliumcontaining natural gas is based on the lowtemperature separation (fractional distillation) method, in which helium is separated from other gases in the course of their liquefaction. This method requires considerable energy and resource inputs. An energysaving route to separate gas mixtures can be enrichment of natural gas with helium upon clathrate hydrate formation (1). Gas (clathrate) hydrates are inclusion compounds consisting of water molecules, which form the host crystal lattice, and guest molecules occupying lattice cavities (2). Current interest in gas hydrates stems from their possible use as fuel, as well as from their possible effect on global climate changes (3) and the use of gas hydrate technologies for natural gas storage and transportation (4). The helium content in natural gas is usually low as compared with the major component methane, although there are some natural gas deposits contain� ing up to 8 vol % helium. Methane accounts for more than 70-80 vol % of such gas deposits. Commercially interesting for helium recovery are natural gas deposits containing more than 0.3 vol % helium (5). The exist� ence of clathrate helium hydrates is still debatable since no reliable experimental data supporting or refuting this fact have been available so far. However, experimental evidence for the possibility of helium hydrate formation has been reported in (6). It has been theoretically predicted that structure II helium hydrates can form at high pressures (beginning with 800 atm) and low temperatures (250 K) (7). It has been shown that, at the same temperatures, mixed structure I and II methane-helium clathrate hydrates form at lower pressures than pure helium hydrates even at small concentrations of methane in the gas phase (8). The present work is aimed to find a correlation between the composition of mixed methane-helium hydrates of cubic structures I and II and the composi� tion of the gas phase being at equilibrium with the hydrate, as well as to determine conditions of forma� tion of mixed methane-helium hydrates at low helium concentrations in the gas phase for developing meth� ods of deep purification of helium from methane via hydrate formation.

Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathrate hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery ofmore » the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate hydrate systems are pivotal in the fundamental understanding of crystalline clathrate hydrates and the discovery of new clathrate hydrate properties and novel materials for a broad spectrum of energy applications, including: energy storage (hydrogen, natural gas); carbon dioxide sequestration; controlling hydrate formation in oil/gas transportation in subsea pipelines. The Project has also enabled the training of undergraduate, graduate and postdoctoral students in computational methods, molecular spectroscopy and diffraction, and measurement methods at extreme conditions of high pressure and low temperature.« less

A chemical absorption process is the most commercially used process for CO2 separation in flue gases. However, the process needs a huge amount of energy to strip CO2 in a stripper. To overcome this problem, a new gas separation process using chemical absorption method based on self-heat recuperation technology is proposed in this study for energy saving. In this process, the regeneration energy of absorbent is provided from the exhausted heat of absorber and stripper by using a compressor and heat exchangers. The process is divided into two modules (absorber and stripper), in which the internal heat circulation is maximized. Then, the process is reconstructed by combining these modules. We evaluated the amount of energy consumption of the process as compared with the conventional gas separation process for CO2 by using a commercial process simulator (PRO/II). From the simulation results, energy consumption of the proposed process decreased to one-third at that of conventional heat recovery process. Thus, the proposed process based on self-heat recuperation technology is a very promising process for energy saving of gas separation.

Energy efficiency simulation of the process of gas hydrate exploitation from flue gas in an electric power plant