It is generally accepted by the scientific community that anthropogenic CO2 emissions are leading to global climate change, notably an increase in global temperatures commonly referred to as global ...warming. The primary source of anthropogenic CO2 emissions is the combustion of fossil fuels for energy. As society’s demand for energy increases and more CO2 is produced, it becomes imperative to decrease the amount emitted to the atmosphere. One promising approach to do this is to capture CO2 at the effluent of the combustion site, namely, power plants, in a process called postcombustion CO2 capture. Technologies to achieve this are heavily researched due in large part to the intuitive nature of removing CO2 from the stack gas and the ease in retrofitting existing CO2 sources with these technologies. As such, several reviews have been written on postcombustion CO2 capture. However, it is a fast-developing field, and the most recent review papers already do not include the state-of-the-art research. Notable among CO2 capture technologies are amine-based technologies. Amines are well-known for their reversible reactions with CO2, which make them ideal for the separation of CO2 from many CO2-containing gases, including flue gas. For this reason, this review will cover amine-based technology developed and published in and after the year 2013.
Photochemical grid models are addressing an increasing variety of air quality related issues, yet procedures and metrics used to evaluate their performance remain inconsistent. This impacts the ...ability to place results in quantitative context relative to other models and applications, and to inform the user and affected community of model uncertainties and weaknesses. More consistent evaluations can serve to drive improvements in the modeling process as major weaknesses are identified and addressed. The large number of North American photochemical modeling studies published in the peer-reviewed literature over the past decade affords a rich data set from which to update previously established quantitative performance "benchmarks" for ozone and particulate matter (PM) concentrations. Here we exploit this information to develop new ozone and PM benchmarks (goals and criteria) for three well-established statistical metrics over spatial scales ranging from urban to regional and over temporal scales ranging from episodic to seasonal. We also recommend additional evaluation procedures, statistical metrics, and graphical methods for good practice. While we primarily address modeling and regulatory settings in the United States, these recommendations are relevant to any such applications of state-of-the-science photochemical models. Our primary objective is to promote quantitatively consistent evaluations across different applications, scales, models, model inputs, and configurations. The purpose of benchmarks is to understand how good or poor the results are relative to historical model applications of similar nature and to guide model performance improvements prior to using results for policy assessments. To that end, it also remains critical to evaluate all aspects of the model via diagnostic and dynamic methods. A second objective is to establish a means to assess model performance changes in the future. Statistical metrics and benchmarks need to be revisited periodically as model performance and the characteristics of air quality change in the future.
Implications: We address inconsistent procedures and metrics used to evaluate photochemical model performance, recommend a specific set of statistical metrics, and develop updated quantitative performance benchmarks for those metrics. We promote quantitatively consistent evaluations across different applications, scales, models, inputs, and configurations, thereby (1) improving the user's ability to quantitatively place results in context and guide model improvements, and (2) better informing users, regulators, and stakeholders of model uncertainties and weaknesses prior to using results for policy assessments. While we primarily address U.S. modeling and regulatory settings, these recommendations are relevant to any such applications of state-of-the-science photochemical models.
Abstract
Recently, carbon dioxide capture and conversion, along with hydrogen from renewable resources, provide an alternative approach to synthesis of useful fuels and chemicals. People are ...increasingly interested in developing innovative carbon dioxide hydrogenation catalysts, and the pace of progress in this area is accelerating. Accordingly, this perspective presents current state of the art and outlook in synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols through two leading hydrogenation mechanisms: methanol reaction and Fischer-Tropsch based carbon dioxide hydrogenation. The future research directions for developing new heterogeneous catalysts with transformational technologies, including 3D printing and artificial intelligence, are provided.
In order to use an air quality modeling system with confidence, model performance must be evaluated against observations. While ozone modeling and evaluation is fairly developed, particulate matter ...(PM) modeling is still an evolving science. EPA has issued minimal guidance on PM and visibility model performance evaluation metrics, goals, and criteria. This paper addresses these issues by examining various bias and error metrics and proposes PM model performance goals (the level of accuracy that is considered to be close to the best a model can be expected to achieve) and criteria (the level of accuracy that is considered to be acceptable for modeling applications) that vary as a function of concentration and extinction. In this paper, it has been proposed that a model performance goal has been met when both the mean fractional error (MFE) and the mean fractional bias (MFB) are less than or equal to +50% and ±30%, respectively. Additionally, the model performance criteria has been met when both the MFE⩽+75% and MFB⩽±60%. Less abundant species would have less stringent performance goals and criteria. These recommendations are based upon an analysis of numerous PM and visibility modeling studies performed throughout the country.
Implementing Paris Climate Accord is inhibited by the high energy consumption of the state-of-the-art CO2 capture technologies due to the notoriously slow kinetics in CO2 desorption step of CO2 ...capture. To address the challenge, here we report that nanostructured TiO(OH)2 as a catalyst is capable of drastically increasing the rates of CO2 desorption from spent monoethanolamine (MEA) by over 4500%. This discovery makes CO2 capture successful at much lower temperatures, which not only dramatically reduces energy consumption but also amine losses and prevents emission of carcinogenic amine-decomposition byproducts. The catalytic effect of TiO(OH)2 is observed with Raman characterization. The stabilities of the catalyst and MEA are confirmed with 50 cyclic CO2 sorption and sorption. A possible mechanism is proposed for the TiO(OH)2-catalyzed CO2 capture. TiO(OH)2 could be a key to the future success of Paris Climat e Accord.
Acidity (pH) plays a key role in the physical and chemical behavior of PM2.5. However, understanding of how specific PM sources impact aerosol pH is rarely considered. Performing source apportionment ...of PM2.5 allows a unique link of sources pH of aerosol from the polluted city. Hourly water-soluble (WS) ions of PM2.5 were measured online from December 25th, 2014 to June 19th, 2015 in a northern city in China. Five sources were resolved including secondary nitrate (41%), secondary sulfate (26%), coal combustion (14%), mineral dust (11%), and vehicle exhaust (9%). The influence of source contributions to pH was estimated by ISORROPIA-II. The lowest aerosol pH levels were found at low WS-ion levels and then increased with increasing total ion levels, until high ion levels occur, at which point the aerosol becomes more acidic as both sulfate and nitrate increase. Ammonium levels increased nearly linearly with sulfate and nitrate until approximately 20 μg m–3, supporting that the ammonium in the aerosol was more limited by thermodynamics than source limitations, and aerosol pH responded more to the contributions of sources such as dust than levels of sulfate. Commonly used pH indicator ratios were not indicative of the pH estimated using the thermodynamic model.
Policy directives in several nations are focusing on the development of smart cities, linking innovations in the data sciences with the goal of advancing human well-being and sustainability on a ...highly urbanized planet. To achieve this goal, smart initiatives must move beyond city-level data to a higher-order understanding of cities as transboundary, multisectoral, multiscalar, social-ecological-infrastructural systems with diverse actors, priorities, and solutions. We identify five key dimensions of cities and present eight principles to focus attention on the systems-level decisions that society faces to transition toward a smart, sustainable, and healthy urban future.
Aerosol pH can affect gas-particle partitioning of semivolatile species, secondary aerosol formation, aerosol water uptake and growth, acid deposition, and, potentially, aerosol toxicity. Despite its ...importance, aerosol pH projected in the near future has not been addressed explicitly while investigating the response of aerosol concentrations to emission regulations. In this study, we apply CMAQ to simulate aerosol pH in 2011 and 2050 across the continental U.S. We also assess the influence of two major emission trends, declining SO2 emissions and rising NH3 emissions, with a set of sensitivity simulations. Our results show that the aerosols will remain acidic with average pH typically ranging from 0.5 to 3.5 in 2050. Further reducing domestic SO2 emissions does not significantly decrease aerosol acidity, even if SO2 emissions were reduced to preindustrial levels because of the nonlinear response of SO4 2– concentration to SO2 emissions, and the semivolatile NH3–NH4 + buffering effect. Aerosol pH response to NH3 emission increase will remain minor. Consequently, future fine particulate matter control efficiency will not be undercut by additional nitrate aerosol formation even if SO2 emissions from industry and electricity generation are aggressively controlled, although areas will see some substitution leading to nitrate increases if NO x emissions are not reduced.
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•Alcohols-amines-water significantly increase the CO2 desorption rates.•Ethanol increases the cyclic CO2 capture capacity by 6.8 times at 75 °C.•Addition of ethanol can change the ...reaction pathway.•Low temperature CO2 desorption can effectively prevent amines from degradation.•This technology can utilize low-temperature waste heat for CO2 capture.
The conventional regeneration processes for aqueous amine-based sorbents require high regeneration temperature and are very energy intensive. In this work, a low-temperature and energy-saving CO2 capture technology has been successfully developed by using alcohols-amines-water mixtures as sorbents. The addition of certain amounts of alcohols especially ethanol (EtOH) to amines can significantly increase the CO2 desorption rates and cyclic CO2 capture capacities in comparison with those of monoethanolamine-water, diethanolamine-water, and methyldiethanolamine-water systems. The sorbent containing 40 wt% EtOH, 20 wt% monoethanolamine (MEA), and 20 wt% H2O can increase cyclic CO2 capture capacity by 6.8 times and a maximum improvement of 236 times in CO2 desorption rate at 75 °C, which makes the use of the low-temperature waste heat in power plants for CO2 capture or self-supported CO2 capture in power plants possible. To the best of authors’ knowledge, this is the first time that Raman and Fourier transform infrared spectroscopy characterizations have been used to confirm that ethanol in EtOH-MEA-H2O can change the reaction pathway by forming C2H5OCO2− instead of HCO3−, which is difficult to decompose. In addition, the experimental results confirm that the new technology can significantly avoid amine degradation – a common challenge of the state-of-the-art CO2 capture technologies. Therefore, the new CO2 capture technology is promising from the perspectives of energy saving and environmental protection.
A Focus on Particulate Matter and Health Russell, Armistead G; Brunekreef, Bert
Environmental science & technology,
07/2009, Letnik:
43, Številka:
13
Journal Article
Recenzirano
Odprti dostop
Through analytical characterization, and toxicity end epidemiologic studies, the health implications of airborne particulate matter are slowly being elucidated.
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