New method accurately predicts carbon dioxide equilibrium adsorption isotherms

Among the methods that are being developed to date for CO₂ capture and separation, carbon dioxide adsorption is of great interest due to its low energy consumption, low equipment cost and easiness for application. In this work, a simple method which is easier than existing approaches requiring more complicated and longer computations is presented to accurately predict the carbon dioxide adsorption isotherms for a microporous material as a function of temperature and partial pressure of carbon dioxide. The method appears promising and can be extended for CO₂ capture as well as for separation of wide range of adsorbents and microporous materials including several molecular sieves merely by the quick readjustment of tuned coefficients. The proposed method showed consistently accurate results across the proposed pressure and temperature ranges. Predictions showed an average absolute deviation of 1.4% compared to existing Sips and Langmuir equations which show an average absolute deviations of 2.3% and 4%, respectively. The proposed method is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly for various cases. This simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on adsorption capacities of a given adsorbent at various temperatures and pressures without the necessity of any experimental measurements. In particular, personnel dealing with regulatory bodies of greenhouse gas control and process industries would find the proposed approach to be user friendly involving transparent calculations with no complex expressions.     

Comparison and application of different component municipal solid wastes based carbon on adsorption of carbon dioxide

The prepared different components municipal solid wastes based carbons were used to investigate the adsorption of CO₂. The optimum conditions for CO₂ adsorption were investigated firstly. And then, the CO₂ adsorption performance of different components based carbon adsorbents were compared with each other under the optimum parameters. The results illustrated that the triple components (pinewood, acrylic textile, and tire) based carbon exhibited the best adsorption performance, which is 1.522 mmol/g and its physical prosperity was also conducted to interpret the adsorption mechanism. Besides, to further approach to the actual gas, the influence of additional O₂ and SO₂ on CO₂ adsorption properties of ternary-component-based carbon was investigated. The results illustrate that O₂ concentration exerts little effect on adsorption capacity. SO₂ plays the dominated role in the competitive adsorption effect.     

The influence of different surface-modification treatments on biomass-based carbons and their effects on adsorption of carbon dioxide

Surface modification of biomass-based carbon with nitrogen-containing functional groups is performed by the different modification method, including the thermal and chemical methods. We also investigate the effect of the different reaction parameters on their pore structure using the Brunauer–Emmett–Teller surface area and adsorption performance based on methylene blue value. Fourier transforms infrared spectroscopy methods are performed to confirm the presence of N-containing groups. Based on above results, the comparison effect of different modification methods on physico-chemical propriety and adsorption properties of biomass-based carbon materials are carried out. In conclusion, all modification methods could enhance CO₂ adsorption capability. However, the carbon materials treated with ammonia using thermal method show the best performance.     

A statistical analysis of the carbon dioxide capture process

Post combustion carbon dioxide (CO₂) capture is one of the most commonly adopted technologies for reducing industrial CO₂ emissions, which is now an important goal given the widespread concern over global warming. Research on amine-based CO₂ capture has mainly focused on improving effectiveness and efficiency of the CO₂ capture process. Our research work focuses on studying the relationships among the significant parameters influencing CO₂ production because an enhanced understanding of the intricate relationships among the parameters involved in the process is critical for improving efficiency of the CO₂ capture process. This paper presents a statistical study that explores the relationships among parameters involved in the amine-based post combustion CO₂ capture process at the International Centre for CO₂ Capture (ITC) located in Regina, Saskatchewan of Canada. A multiple regression technique has been applied for analysis of data collected at the CO₂ capture pilot plant at ITC. The parameters have been carefully selected to avoid issues of multicollinearity, and four mathematical models among the key parameters identified have been developed. The models have been tested, and accuracy of the models is found to be satisfactory. The models developed in this study describe part of the CO₂ capture process and can help to predict performance of the CO₂ capture process at ITC under different conditions. Some results from a preliminary validation process will also be presented.     

Energy and carbon dioxide intensity of Thailand's steel industry and greenhouse gas emission projection toward the year 2050

The purpose of this article is to study the energy and carbon dioxide intensities of Thailand's steel industry and to propose greenhouse gas emission trends from the year 2011 to 2050 under plausible scenarios. The amount of CO₂ emission from iron and steel production was calculated using the 2006 Intergovernmental Panel on Climate Change (IPCC) guidelines in the boundary of production process (gate to gate). The results showed that energy intensity of semi-finished steel product was 2.84 GJ/t semi-finished steel and CO₂ intensity was 0.37 tCO_2eq/t semi-finished steel. Energy intensity of steel finishing process was 1.86 GJ/t finished steel and CO₂ intensity was 0.16 tCO_2eq/t finished steel. Using three plausible scenarios from Thailand's steel industry, S1: without integrated steel plant (baseline scenario), S2: with a traditional integrated BF–BOF route and S3: with an alternative integrated DR-EAF route; the Greenhouse Gas emissions from the year 2011 to 2050 were projected. In 2050, the CO₂ emission from S1 (baseline scenario) was 4.84 million tonnes, S2 was 21.96 million tonnes increasing 4.54 times from baseline scenario. The CO₂ emission from S3 was 7.12 million tonnes increasing 1.47 times from baseline scenario.     

Adsorption of carbon dioxide on alkali-modified zeolite 13X adsorbents

Shaped zeolite 13X adsorbent with kaolin as binder was hydrothermally modified in sodium hydroxide solution to improve its adsorption performance. The characterization of the product by XRD, N₂ adsorption–desorption and water vapour adsorption displayed that kaolin component in zeolite adsorbent can be converted into zeolite during the alkali treatment, resulting in the modified adsorbent consisting entirely of effectual adsorption composition. Compared with the unmodified adsorbent, the modified adsorbent exhibited higher adsorption capacity and uptake rate for carbon dioxide, because of the increase of effective adsorption surface and the decrease of diffusion resistance owing to conversion of kaolin binder into zeolite. The model parameters of isotherms and the isosteric heats calculated by the Clausius–Clapeyron equation for CO₂ adsorption showed the stronger interaction of adsorbate–adsorbent and the higher degree of heterogeneity of adsorption centers in modified than unmodified adsorbents.     

Public risk perspectives on the geologic storage of carbon dioxide

Carbon Dioxide Capture and Storage (CCS) technology has the potential to enable large reductions in global greenhouse gas emissions, but one of the unanswered questions about CCS is to what extent it will be accepted by the public. To provide insight regarding risk perception as an important component that will influence the public acceptance of CCS, this study discusses different notions of risk and their varying uses by the public, who generally use a social constructivist risk perspective, and risk experts, who generally use a realist perspective. Previous studies discussing the public acceptance of CCS have relied on survey response data and/or focus groups. This study instead uses the psychometric theory of public risk perception to postulate how the public is likely to respond to efforts to use geologic storage of CO₂, a component of the CCS architecture. Additionally this paper proposes further actions that could favorably impact the public's perception of risk from geologic storage projects. Through the psychometric analysis this study concludes that the risks of geologic storage are likely to eventually be considered no worse than existing fossil fuel energy technologies. However, since geologic storage of CO₂ is a new technology with little operational experience, additional field tests and a demonstrated ability to mitigate problems should they arise will be necessary to improve the public's perception of risk from CCS technologies.     

Adsorption of carbon dioxide using impregnated activated carbon promoted by Zinc

The effect of impregnation of activated carbon with Cr₂O and Fe₂O₃ and promotion by Zn²⁺ on its adsorptive properties of carbon dioxide was studied using a volumetric adsorption apparatus at ambient temperature and low pressures. Slurry and solution impregnation methods were used to compare CO₂ capture capacity of the impregnated activated carbon promoted by Zinc. The obtained adsorption isotherms showed that amount of CO₂ adsorbed on the samples impregnated by Cr₂O was increased about 20% in compare to raw activated carbon. The results also showed that Fe₂O₃ was not an effective impregnating species for activated carbon modification. Moreover slurry impregnation method showed higher CO₂ adsorption capacity in comparison with solution impregnation method. Samples prepared by co-impregnation of two metal species showed more adsorption capacity than samples impregnated by just one metal species individually. Washing the impregnated samples by metal oxide resulted in 15% increase in CO₂ adsorption capacities of activated carbons which can be attributed to the metal oxides removal covering the adsorption surface. Decreasing impregnation temperature from 95 to 25 °C in solution method showed a significant increase in CO₂ adsorption capacity. Sips equation was found a suitable model fitting to the adsorption data in the range studied.     

Identifying the major players behind increasing global carbon dioxide emissions: a decomposition analysis

The paper using data on 114 countries during 1992–2004 identifies the major perpetrators of escalating global emissions. Using the LMDI decomposition technique, we examine the contribution of the major factors in changing the level of emissions. The effect of GDP on emission is found to be substantially more than that of population. However, the income effect shows high fluctuation over time, while the population effect has been roughly constant. The upper middle-income countries, particularly of Europe and Central Asia, despite high economic growth have reduced their emissions substantially, while in the countries of North America, East Asia Pacific and South Asia increase in income have been significantly accompanied by increase in emission. Apart from few low emitting countries, almost all others have been successful in increasing emission efficiency, but their energy efficiencies have not been remarkable. Although emission efficiency has been more instrumental in curtailing emission, in some cases the path of change in emission follows that of change in energy intensity. Thus, both energy and emission intensity have crucial roles in determining the level of emissions. It may be suggested that emphasis should be given on policies oriented towards sufficient counteractive energy and emission efficiencies before embarking on a path towards economic growth.     

Environmental impacts of asphalt mixes with electric arc furnace steel slag

Electric arc furnace (EAF) steel slag can be used as an alternative high-quality material in road construction. Although asphalts with slag aggregates have been recognized as environmentally acceptable, there is a lack of data concerning the potential leaching of toxic Cr(VI) due to the highly alkaline media of EAF slag. Leaching of selected water extractable metals from slag indicated elevated concentrations of total chromium and Cr(VI). To estimate the environmental impacts of asphalt mixes with slag, leachability tests based on diffusion were performed using pure water and salt water as leaching agents. Compact and ground asphalt composites with natural aggregates, and asphalt composites in which the natural aggregates were completely replaced by slag were prepared. The concentrations of total chromium and Cr(VI) were determined in leachates over a time period of 6 mo. After 1 and 6 mo, the concentrations of some other metals were also determined in the leachates. The results indicated that chromium in leachates from asphalt composites with the addition of slag was present almost solely in its hexavalent form. However, the concentrations were very low (below 25 μg L) and did not represent an environmental burden. The leaching of other metals from asphalt composites with the addition of slag was negligible. Therefore, the investigated EAF slag can be considered as environmentally safe substitute for natural aggregates in asphalt mixes.     

Grey relation analysis of carbon dioxide emissions from industrial production and energy uses in Taiwan

This study aims to identify key factors affecting energy-induced CO₂emission changes from 34 industries in Taiwan, in order to have an integrated understanding of the industrial environmental-economic-energy performance and to provide insights for relevant policy making in Taiwan. Grey relation analysis was used in this paper to analyse how energy-induced CO₂emissions from 34 industries in Taiwan are affected by the factors: production, total energy consumption, coal, oil, gas and electricity uses. The methodology was modified by taking account of the evolutionary direction among relevant factors. Furthermore, tests of sensitivity and stability, which are seldom discussed in most grey relation analyses, were conducted to ensure the reliability of outcomes. We found that values ranging from 0·3 to 0·5 are appropriate, and the analytical results with value of 0·5 offer moderate distinguishing effects and good stability. Results indicate that industrial production has the closest relationship with aggregate CO₂emission changes; electricity consumption the second in importance. It reveals that the economy in Taiwan relied heavily on CO₂intensive industries, and that electricity consumption had become more important for economic growth. The relational order of fuels is electricity, coal, oil then gas, accordant with their CO₂emission coefficients in Taiwan. The positive relational grade of aggregate production implies that the aggregate industrial CO₂intensity tended to decline. The total energy consumption had a smaller and negative relational grade with CO₂emissions, and implies an improvement on aggregate energy intensity, while the CO₂emission coefficient increased. For industries with significant influence on CO₂emissions, the total energy consumption had the largest relational grades. It is important to reduce the energy intensity of these industries. Nevertheless, it is also critical to decouple energy consumption and production to reduce the impacts of CO₂mitigation on economic growth.     

Organic carbon diminution and estimates of carbon dioxide release from plantation soil

Summary This paper evaluates the rates of organic carbon diminution in the soil under monospecific tree plantations of teak, gmelina, rubber, oil palm, cashew and coffee. The differences between the organic carbon status of their soils and soil under nearby natural rain forest vegetation are compared. Annual rates of organic carbon decrease for the 0–10 cm soil layer, varied from 82.1 kg ha^–1 for cashew to 316.7 kg ha^–1 for oil palm. The tree plantations appear to release more carbon dioxide from the soil into the atmosphere than the natural forest. They therefore, appear to have the potential of contributing towards global warming — a threat they are supposed to mitigate.     

Degradation of aqueous piperazine in carbon dioxide capture

Concentrated, aqueous piperazine (PZ) is a novel solvent for carbon dioxide (CO₂) capture by absorption/stripping. One of the major advantages of PZ is its resistance to thermal degradation and oxidation.At 135 and 150 °C, 8 m PZ is up to two orders of magnitude more resistant to thermal degradation than 7 m monoethanolamine (MEA). After 18 weeks at 150 °C, only 6.3% of the initial PZ was degraded, yielding an apparent first order rate constant for amine loss of 6.1 × 10^?9 s^?1. PZ was the most resistant amine tested, with the other screened amines shown in order of decreasing resistance: 7 m 2-amino-2-methyl-1-propanol, 7 m Diglycolamine^®, 7 m N-(2-hydroxyethyl)piperazine, 7 m MEA, 8 m ethylenediamine, and 7 m diethylenetriamine. Thermal resistance allows the use of higher temperatures and pressures in the stripper, potentially leading to overall energy savings.Concentrated PZ solutions demonstrate resistance to oxidation compared to 7 m MEA solutions. Experiments investigating metal-catalyzed oxidation found that PZ solutions were 3–5 times more resistant to oxidation than MEA. Catalysts tested were 1.0 mM iron (II), 4.0–5.0 mM copper (II), and a combination of stainless steel metals (iron (II), nickel (II), and chromium (III)). Inhibitor A reduced PZ degradation catalyzed by iron (II) and copper (II).     

Tillage and crop residue effects on soil carbon and carbon dioxide emission in corn-soybean rotations

Soil C change and CO2 emission due to different tillage systems need to be evaluated to encourage the adoption of conservation practices to sustain soil productivity and protect the environment. We hypothesize that soil C storage and CO2 emission respond to conservation tillage differently from conventional tillage because of their differential effects on soil properties. This study was conducted from 1998 through 2001 to evaluate tillage effects on soil C storage and CO2 emission in Clarion-Nicollet-Webster soil association in a corn [Zea mays L.]-soybean [Glycine max (L.) Merr.] rotation in Iowa. Treatments included no-tillage with and without residue, strip-tillage, deep rip, chisel plow, and moldboard plow. No-tillage with residue and strip-tillage significantly increased total soil organic C (TC) and mineral fraction C (MFC) at the 0- to 5- and 5- to 10-cm soil depths compared with chisel plow after 3 yr of tillage practices. Soil CO2 emission was lower for less intensive tillage treatments compared with moldboard plow, with the greatest differences occurring immediately after tillage operations. Cumulative soil CO2 emission was 19 to 41% lower for less intensive tillage treatments than moldboard plow, and it was 24% less for no-tillage with residue than without residue during the 480-h measurement period. Estimated soil mineralizable C pool was reduced by 22 to 66% with less intensive tillage treatments compared with moldboard plow. Adopting less intensive tillage systems such as no-tillage, strip-tillage, deep rip, and chisel plow and better crop residue cover are effective in reducing CO2 emission and thus improving soil C sequestration in a corn-soybean rotation.     

Value of information analysis for adequate monitoring of carbon dioxide storage in geological reservoirs under uncertainty

As monitoring is essential for the proper management of geological storage of carbon dioxide (CO₂), the ability to value information from monitoring is indispensable to adequately design a monitoring program. It is necessary to judge whether the expected improvement in management is worth the cost of monitoring. The value of information (VOI) is closely related to the possible increase in expected utility gained by gathering the information, the concept of which can be applied to such judgement. Although VOI analysis has been extensively studied in the context of decision analysis, its application to the management of carbon dioxide capture and storage (CCS) operations is rare. This paper introduces and discusses the methodology of VOI analyses in the context of monitoring CO₂ storage. A motivating problem with discrete probabilities is used to illustrate the concept of VOI. It is demonstrated that information is not always of value; for information to be worthwhile, monitoring under uncertainty must satisfy certain conditions. This concept is then extended to continuous probability distributions. The effects of prior uncertainty and information reliability on the VOI are examined. It is shown that an excessive improvement in information accuracy yields little value and that the optimal level of reliability can be inferred. VOI analyses provide quantitative insights into the value of information-gathering activities and therefore can be an objective means to adequately design and impartially justify a monitoring program.     

Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution

A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide–tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time decreases with the increase of the initial carbon dioxide pressure up to 2.96 MPa. Beyond this pressure, the induction time is becoming relatively constant with the increase of initial carbon dioxide pressure indicating that the liquid phase is completely supersaturated with carbon dioxide. Experimental results show that the inclusion of tetrahydrofuran reduces the induction time required for hydrate formation. These observations indicate hydrate nucleation process and onset growth are more readily to occur in the presence of tetrahydrofuran. In contrast, the presence of sodium chloride prolongs the induction time due to clustering of water molecules with the ions and the salting-out effects. It is also shown that the degree of subcooling required for hydrate formation is affected by the presence of tetrahydrofuran and sodium chloride in the hydrate forming system. The presence of tetrahydrofuran in the hydrate system significantly reduces the amount of carbon dioxide uptake. The apparent rate constant, k, for those systems are reported.     

Synthesis and characterization of zwitterionic carbon dioxide fixing reagents

The synthesis of three amine-based carbon dioxide fixing reagents is presented. The reagents were designed so that they would be able to bind CO₂ reversibly through the formation of the well known carbamates that was stabilized through forming a zwitterion. CO₂ fixing experiments were performed with ¹³CO₂ labeling and medium pressure NMR. The experiments showed that two of the three reagents were able to form carbamates and thus bind CO₂. In addition we investigated this particular class of molecules for the possible formation of neutrally charged spiro compounds and we show that these did not form under the conditions studied.     

Effects of elevated atmospheric carbon dioxide on biomass and carbon accumulation in a model regenerating longleaf pine community

Plant species vary in response to atmospheric CO2 concentration due to differences in physiology, morphology, phenology, and symbiotic relationships. These differences make it very difficult to predict how plant communities will respond to elevated CO2. Such information is critical to furthering our understanding of community and ecosystem responses to global climate change. To determine how a simple plant community might respond to elevated CO2, a model regenerating longleaf pine community composed of five species was exposed to two CO2 regimes (ambient, 365 micromol mol(-1) and elevated, 720 micromol mol(-1)) for 3 yr. Total above- and belowground biomass was 70 and 49% greater, respectively, in CO2-enriched plots. Carbon (C) content followed a response pattern similar to biomass, resulting in a significant increase of 13.8 Mg C ha(-1) under elevated CO2. Responses of individual species, however, varied. Longleaf pine (Pinus palustris Mill.) was primarily responsible for the positive response to CO2 enrichment. Wiregrass (Aristida stricta Michx.), rattlebox (Crotalaria rotundifolia Walt. Ex Gmel.), and butterfly weed (Asclepias tuberosa L.) exhibited negative above- and belowground biomass responses to elevated CO2, while sand post oak (Quercus margaretta Ashe) did not differ significantly between CO2 treatments. As with pine, C content followed patterns similar to biomass. Elevated CO2 resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO2-enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO2 plots, but only 8% under high CO2. Therefore, while longleaf pine may perform well in a high CO2 world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO2 on plant communities are complex, dynamic, and difficult to predict, clearly demonstrating the need for more research in this important area of global change science.     

Biochar and earthworm effects on soil nitrous oxide and carbon dioxide emissions

Biochar is the product of pyrolysis produced from feedstock of biological origin. Due to its aromatic structure and long residence time, biochar may enable long-term carbon sequestration. At the same time, biochar has the potential to improve soil fertility and reduce greenhouse gas (GHG) emissions from soils. However, the effect of biochar application on GHG fluxes from soil must be investigated before recommendations for field-scale biochar application can be made. A laboratory experiment was designed to measure carbon dioxide (CO) and nitrous oxide (NO) emissions from two Irish soils with the addition of two different biochars, along with endogeic (soil-feeding) earthworms and ammonium sulfate, to assist in the overall evaluation of biochar as a GHG-mitigation tool. A significant reduction in NO emissions was observed from both low and high organic matter soils when biochars were applied at rates of 4% (w/w). Earthworms significantly increased NO fluxes in low and high organic matter soils more than 12.6-fold and 7.8-fold, respectively. The large increase in soil NO emissions in the presence of earthworms was significantly reduced by the addition of both biochars. biochar reduced the large earthworm emissions by 91 and 95% in the low organic matter soil and by 56 and 61% in the high organic matter soil (with and without N fertilization), respectively. With peanut hull biochar, the earthworm emissions reduction was 80 and 70% in the low organic matter soil, and only 20 and 10% in the high organic matter soil (with and without N fertilization), respectively. In high organic matter soil, both biochars reduced CO efflux in the absence of earthworms. However, soil CO efflux increased when peanut hull biochar was applied in the presence of earthworms. This study demonstrated that biochar can potentially reduce earthworm-enhanced soil NO and CO emissions. Hence, biochar application combined with endogeic earthworm activity did not reveal unknown risks for GHG emissions at the pot scale, but field-scale experiments are required to confirm this.