Cellulose-Supported Ionic Liquids for Low-Cost Pressure Swing CO2 Capture

Reducing the cost of capturing CO2 from point source emitters is a major challenge facing carbon capture, utilization, and storage. While solid ionic liquids (SoILs) have been shown to allow selective and rapid CO2 capture by pressure swing separation of flue gases, expectations of their high cost hinders their potential application. Cellulose is found to be a reliable, cheap, and sustainable support for a range of SoILs, reducing the total sorbent cost by improving the efficiency of the ionic liquid (IL) through increased ionic surface area that results from coating. It was also found that cellulose support imparts surface characteristics, which increased total sorbent uptake. Combined, these effects allowed a fourfold to eightfold improvement in uptake per gram of IL for SoILs that have previously shown high uptake and a 9- to 39-fold improvement for those with previously poor uptake. This offers the potential to drastically reduce the amount of IL required to separate a given gas volume. Furthermore, the fast kinetics are retained, with adsorb–desorb cycles taking place over a matter of seconds. This means that rapid cycling can be achieved, which results in high cumulative separation capacity relative to a conventional temperature swing process. The supported materials show an optimum at 75% cellulose:25% IL as a result of even coating of the cellulose surface. The projected reduction in plant size and operational costs represents a potentially ground-breaking step forward in carbon dioxide capture technologies

Integrated CO2 capture and utilization using non-thermal plasmolysis

In this work, two simple processes for carbon dioxide (CO2) such as capture and utilization have been combined to form a whole systems approach to carbon capture and utilization (CCU). The first stage utilizes a pressure swing adsorption (PSA) system, which offers many benefits over current amine technologies. It was found that high selectivity can be achieved with rapid adsorption/desorption times while employing a cheap, durable sorbent that exhibits no sorbent losses and is easily regenerated by simple pressure drops. The PSA system is capable of capturing and upgrading the CO2 concentration of a waste gas stream from 12.5% to a range of higher purities. As many CCU end processes have some tolerance toward impurities in the feed, in the form of nitrogen (N2), for example, this is highly advantageous for this PSA system since CO2 purities in excess of 80% can be achieved with only a few steps and minimal energy input. Non-thermal plasma is one such technology that can tolerate, and even benefit from, small N2 impurities in the feed, therefore a 100% pure CO2 stream is not required. The second stage of this process deploys a nanosecond pulsed corona discharge reactor to split the captured CO2 into carbon monoxide (CO), which can then be used as a chemical feedstock for other syntheses. Corona discharge has proven industrial applications for gas cleaning and the benefit of pulsed power reduces the energy consumption of the system. The wire-in-cylinder geometry concentrates the volume of gas treated into the area of high electric field. Previous work has suggested that moderate conversions can be achieved (9%), compared to other non-thermal plasma methods, but with higher energy efficiencies (>60%)

New olefin production routes—A review of defossilised supply chain technologies with regards to surfactant production

With “defossilisation” at the core of many sustainability goals within industry, the exploration of new synthesis routes to chemicals has never been more vital. As part of their Clean Futures initiative, Unilever Home Care has published the Carbon Rainbow, a scheme which categorizes chemical sources into different “colors,” depending on their derivation. One of the sustainability goals of the Carbon Rainbow is to phase out non-renewable “black” carbon from supply chains by 2030. This complements the goals of the Clean Futures initiative, which looks toward a Net-Zero impact from all products from a cradle-to-shelf scope by 2039. Given the substantial contributions to atmospheric CO2 emissions from the production and use of conventional surfactants, this paper reviews methods to form Linear Alkylbenzene Sulfonate (LAS) through means which look to utilize Carbon Rainbow-categorized carbon sources outside of traditional fossil sources. The focus when reviewing each method is the overall defossilization of the LAS production process. The inventories of new defossilised methods collated within this research will ultimately provide the backbone for a future study on sustainability assessment screening. Through a literature search and technological overview, the construction of a tree diagram showing many new routes to LAS-appropriate olefins has been accomplished, illustrating the breadth of technologies available that share the common goal of defossilization. The expanse of technologies works well as to provide options to the necessary companies, though also resulting in a vast array of options to consider and assess before pursuing the optimum route. In total, 19 technologies were reviewed, forming a map containing 27 different supply chain routes from feedstock to LAS-appropriate olefins. This research therefore also shows the need for a short-form sustainability screening in order to green-light technologies which are suitable for a long-form sustainability assessment before any new process is adopted

Counterfactual sustainability screening - the definition and undertaking of a sustainability screening method for the assessment of defossilised supply chains

With the monumental shift in industrial interest towards sustainable, defossilised supply chains in response to the climate crisis, the understanding of alternative supply chain viability has never been more vital. As part of their Clean Future initiative, Unilever Home Care has committed to the phasing out of fossil carbon sources from their supply chains. To better assess the viability of these prospective supply chains within a quick timeframe, a counterfactual screening method has been developed which pits the performance of eleven selected sustainability indicators against a success baseline, returning a results array on the sustainability performance of these routes. This paper briefly introduces the initiatives laid out by Unilever Home Care, before undertaking a concise review on existing sustainability screening methods from the literature, with the key limitations of these methods outlined. In response to these limitations, a new methodology is then defined, with a case study of defossilised Linear Alkylbenzene Sulfonate (LAS)-appropriate olefins being applied. This study both illustrates the functionality of the methodology, as well as provides an insight into the viability of the assessed supply chains. Within the study, 18 technologies forming 18 routes were assessed, spanning green (“from plants”), grey (“from plastic waste”) and purple (“from CO2”) feedstocks (according to the Carbon Rainbow). General results trends suggest that green and grey routes hold much greater viability than the purple routes, given their relatively lower capital and operating costs, as well as their superior likelihood of being commercially viable by 2030. Plans for further research are also provided, with plans for results validation included

Perspectives for the circular chemical economy post COP26

More global action towards climate change in the UK is needed now. Carbon dioxide levels need to be decreased globally and more sustainable practices implemented throughout all sectors in the UK. Whilst many steps have been taken in the UK to reduce its overall carbon footprint, the UK chemical sector must become more sustainable. Whilst carbon dioxide emissions must be reduced, a holistic systematic approach is needed to reduce emissions and improve sustainable manufacture. The circular economy in conjunction with reducing carbon dioxide levels can therefore be used to tackle this issue. Carbon dioxide mitigation technologies, such as carbon capture utilisation and storage amongst others, must help complement a circular economy as well as push towards a more circular carbon-based UK chemical sector. This perspective will discuss policies pledged towards tackling climate change via carbon dioxide reduction methods, pre and post COP26, and critically discuss the good and bad aspects of the conference, especially in terms of creating a circular chemical economy in the UK

Environmental sustainability of cellulose-supported solid ionic liquids for CO2 capture

Solid ionic liquids (SoILs) with cellulose as a support have been demonstrated recently to be effective and low-cost sorbents for CO2 capture. However, at present it is not clear whether they remove more CO2 than is released in the rest of the life cycle, including their manufacture, regeneration and disposal. It is also unknown what other impacts they may have over the whole life cycle while attempting to mitigate climate change. Therefore, this study evaluates for the first time the life cycle environmental sustainability of cellulose-supported SoILs in comparison with unsupported SoILs and some other sorbents. Four SoILs are assessed for 11 life cycle impacts, including global warming potential (GWP), with and without the cellulose support: methyltrioctyl ammonium acetate ([N1888][Ac]), tetraethyl ammonium acetate ([N4444][Ac]), tetra-octylammonium bromide ([N8888]Br) and 1-butyl-4-methylimidazolium bromide ([Bmim]Br). They are compared with one of the ILs in the liquid state (trihexyltetradecylphosphonium 1,2,4-triazolide ([P66614][124Triz])) and with three conventional sorbents: monoethanolamine (MEA), zeolite powder and activated carbon. The results show that SoILs with cellulose loading in the range of 70%–80 wt% have better environmental performance per unit mass of CO2 captured than the unsupported SoILs. The net removal of CO2 eq. over the life cycle ranges from 20% for pure [Bmim]Br to 83% for [N1888][Ac] with 75% cellulose and for [N4444][Ac] with both 75% and 80% loadings. However, pure [N8888]Br generates three times more CO2 eq. over the life cycle than it removes. Among the SoILs, [N4444][Ac] with 80% cellulose has the lowest life cycle impacts for eight out of 11 categories. When compared to the conventional sorbents, it has significantly higher impacts, including GWP. However, it is more sustainable than [P66614][124Triz]. The results of this study can be used to target the hotspots and improve the environmental performance of cellulose-supported SoILs through sustainable design

Fast and Selective Separation of Carbon Dioxide from Dilute Streams by Pressure Swing Adsorption using Solid Ionic Liquids

The need to create a new approach to carbon capture processes that are economically viable has led to the design and synthesis of sorbents that selectively capture carbon dioxide by physisorption. Solid Ionic Liquids (SoILs) were targeted because of their tunable properties and solid form under operational conditions. Molecular modelling was used to identify candidate SoILs and a number of materials based on the low cost, environmentally friendly acetate anion were selected. The materials showed excellent selectivity for carbon dioxide over nitrogen and oxygen and moderate sorption capacity. However, the rate of capture was extremely fast, in the order of a few seconds for a complete adsorb-desorb cycle, under pressure swing conditions from 1 to 10 bar. This showed the importance of rate of sorption cycling over capacity and demonstrates that smaller inventories of sorbents and smaller process equipment are required to capture low concentration CO2 streams. Concentrated CO2 was isolated by releasing the pressure back to atmospheric. The low volatility and thermal stability of SoILs mean that both plant costs and materials costs can be reduced and plant size considerably reduced

Cereal grain, rachis and pulse seed amino acid δ15N values as indicators of plant nitrogen metabolism

AbstractNatural abundance δ15N values of plant tissue amino acids (AAs) reflect the cycling of N into and within plants, providing an opportunity to better understand environmental and anthropogenic effects on plant metabolism. In this study, the AA δ15N values of barley (Hordeum vulgare) and bread wheat (Triticum aestivum) grains and rachis and broad bean (Vicia faba) and pea (Pisum sativum) seeds, grown at the experimental farm stations of Rothamsted, UK and Bad Lauchstädt, Germany, were determined by GC–C–IRMS. It was found that the δ15N values of cereal grain and rachis AAs could be largely attributed to metabolic pathways involved in their biosynthesis and catabolism. The relative 15N-enrichment of phenylalanine can be attributed to its involvement in the phenylpropanoid pathway and glutamate has a δ15N value which is an average of the other AAs due to its central role in AA–N cycling. The relative AA δ15N values of broad bean and pea seeds were very different from one another, providing evidence for differences in the metabolic routing of AAs to the developing seeds in these leguminous plants. This study has shown that AA δ15N values relate to known AA biosynthetic pathways in plants and thus have the potential to aid understanding of how various external factors, such as source of assimilated N, influence metabolic cycling of N within plants

Solving the woolly mammoth conundrum: amino acid 15N-enrichment suggests a distinct forage or habitat

Understanding woolly mammoth ecology is key to understanding Pleistocene community dynamics and evaluating the roles of human hunting and climate change in late Quaternary megafaunal extinctions. Previous isotopic studies of mammoths’ diet and physiology have been hampered by the ‘mammoth conundrum’: woolly mammoths have anomalously high collagen δ15N values, which are more similar to coeval carnivores than herbivores and which could imply a distinct diet and (or) habitat, or a physiological adaptation. We analyzed individual amino acids from collagen of adult woolly mammoths and coeval species and discovered greater  15N enrichment in source amino acids of woolly mammoths than in most other herbivores or carnivores. Woolly mammoths consumed an isotopically distinct food source, reflective of extreme aridity, dung fertilization and (or) plant selection. This dietary signal suggests that woolly mammoths occupied a distinct habitat or forage niche relative to other Pleistocene herbivores