Volker Sick

Anthropogenic disruption of Earth’s carbon cycle necessitates urgent action to stabilize atmospheric CO₂ while preserving economic prosperity. Carbon Capture and Storage (CCS) and Carbon Capture and Utilization (CCU), though often conflated, play distinct, complementary roles in a net-zero future. This perspective contrasts CCS’s critical function in permanent emissions mitigation with CCU’s capacity to deliver essential carbon-based products, advocating for integrated deployment and supportive policies to address the carbon management imperative’s technical, economic, and societal challenges.

<div>Alcohol-to-jet (ATJ) upcycling of ethanol to sustainable aviation fuel (SAF) is an attractive emerging pathway for SAF production, especially in the US Midwest with large-scale corn ethanol production. Only 39% of the corn carbon is converted to ethanol, 20% is emitted as CO<sub>2</sub>. Capturing the CO<sub>2</sub> to produce additional ethanol or SAF directly can increase the carbon yield. To guide technology selection, this work used life cycle assessment for several CO<sub>2</sub>-to-SAF production pathways. Additionally, improvements for corn ethanol production were explored by replacing natural gas burners with heat pumps for corn drying, which reduced the carbon intensity of corn ethanol by nearly 16%. But subsequent upgrading of the ethanol to SAF is only 4.5–20% better than conventional aviation fuel. By contrast, CO<sub>2</sub>-based alternative routes to SAF fared better, reducing carbon intensities between 83% and 90%. Gas fermentation of CO<sub>2</sub> to ethanol with subsequent ATJ upcycling to SAF was contrasted to Fischer–Tropsch conversion of CO<sub>2</sub> to SAF. Both streams require CO<sub>2</sub> conversion to CO, which can be produced using reverse water–gas shift or solid oxide electrolyzer cells. The Fischer–Tropsch synthesis shows a higher reduction in carbon intensity (up to 90%) compared to ATJ (up to 84.4%). For other impact categories, such as ozone depletion, ecotoxicity, and the like, the differences are of similar magnitude. Capturing CO<sub>2</sub> locally at the bioethanol factory and converting that CO<sub>2</sub> to ethanol might overall be preferable with a fermentation process that is quite like bioethanol production compared to Fischer–Tropsch synthesis for which products require a new transportation infrastructure. The aviation fuel yield from ATJ can reach 90%, higher than the 50–70% yield from Fischer–Tropsch synthesis, with gasoline and diesel fuel as major by-products for which markets will shrink in the future. Overall, ATJ appears to be the best choice for CO<sub>2</sub>-to-SAF using the synergy with corn ethanol factories for quick launch.</div>

Carbon dioxide removal plays an important role in any strategy to limit global warming to well below 2 °C. Keeping abreast with the scientific evidence using rigorous evidence synthesis methods is an important prerequisite for sustainably scaling these methods. Here, we use artificial intelligence to provide a comprehensive systematic map of carbon dioxide removal research. We find a total of 28,976 studies on carbon dioxide removal-3-4 times more than previously suggested. Growth in research is faster than for the field of climate change research as a whole, but very concentrated in specific areas-such as biochar, certain research methods like lab and field experiments, and particular regions like China. Patterns of carbon dioxide removal research contrast with trends in patenting and deployment, highlighting the differing development stages of these technologies. As carbon dioxide removal gains importance for the Paris climate goals, our systematic map can support rigorous evidence synthesis for the IPCC and other assessments.

The Global CO2 Initiative at the University of Michigan hosted a dialogue to accelerate commercial deployment of carbon capture and utilization (CCU) technologies that commoditize CO2 and transform it from a waste product into a valuable feedstock. The goal was to identify barriers to scaling-up CCU production and ways to overcome these barriers. Participants included representatives from across the value chain (startups, established companies, policy entities, NGOs, and investors). Case studies examined CCU operations producing precipitated calcium carbonate, cement, methanol, and aviation fuel. Key impediments to scaling the industry are the lack of knowledge of CCU products, insufficient demand, insufficient supply, inadequate relevant experience and expertise, inconsistent and cumbersome regulations, lack of supportive certifications and standards, treatment that is disadvantaged compared to carbon capture and storage (CCS), and inadequate availability of cost competitive renewable energy and green hydrogen. Discussions covered, in varying degrees, what would be needed to rectify each of these barriers. The clear conclusion is that, despite these challenges, CCU products represent a significant opportunity for which the United States is well positioned to lead. Potential benefits include improvements in the following areas: energy independence, competitiveness, manufacturing, industrial resilience, domestic supply chains, jobs for skilled workers, and use of existing infrastructure. Benefits could also include aggregate revenues exceeding a trillion dollars.

This study details a life cycle analysis (LCA) of a hybrid direct air capture (HDAC) system which integrates moisture swing adsorption (MSA) and atmospheric water extraction (AWE) technologies for the simultaneous capture of CO 2 and water from ambient air. A HDAC plant with an annual capture capacity of 3000 tonne CO 2 per year is modeled and life cycle impacts assessed for two locations (California and Louisiana) considered as potential deployment sites. The system is powered solely by electricity and is heat integrated across major sources and sinks in order to increase efficiency. A range of deployment scenarios are considered, varying both electricity source and the operational performance of the plant. Five electricity sources are considered based on the maturity of the electricity production processes and the practicality of their use at the chosen sites. The aim of this study is the evaluation of the viability of these potential deployment scenarios based on assessed life cycle impacts. In the majority of the deployment cases, electricity production dominates the global warming impacts related to capture, compression and sequestration of CO 2 . The impacts related to non-electricity contributions are also explored, where it is found that the construction materials of the plant can have a notable impact in sufficiently decarbonized electricity scenarios. Sorbents are shown to have a minimal impact (carbon burden about 1 %) in agreement with previous studies. Significant net removals of CO 2 from the atmosphere are found for all scenarios considered with the carbon burden for full plant operation (capture to sequestration) ranging from 3.5 % to 64.0 % dependent mainly on the carbon intensity of the power source. A broader environmental impact assessment suggests no immediate concerns when selecting between nuclear, wind or solar power for plant operation.

This paper presents a pilot-scale study on carbonation curing of ductile Engineered Cementitious Composites (ECC), also known as bendable concrete. We aim to advance the technology maturity for broader deployment by validating its performance in a real fabrication and service environment, marking the first demonstration beyond the laboratory scale. To achieve this goal, we examined the mechanical properties and net climate impact of ECC cured in large volumes and then fabricated a set of non-reinforced slabs with the carbonated ECC. These slabs were installed for a sidewalk renovation project located in Southeast Michigan for long-term tests. Based on typical M45-ECC, we revealed a prominent size effect on the carbonation efficiency, with the total CO 2 uptake decreasing from 26.6% to 4.3% (by cement mass) as the specimen thickness increased from ½ to 4 inch. The carbonated slabs manifested a “sandwich” structure comprised of a heavily carbonated surface and nearly non-carbonated core. This structure, despite its limited capacity for CO 2 storage, was found to improve the slab's flexural strength by 31.7% while maintaining a high intensity of fine cracks. The durability improvement was also evident, and the carbonated ECC showed a marginal compromise in strength and ductility for 3 years and remained intact after 34 months in service. Compared to the emissions offset by direct CO 2 uptake, carbonation curing demonstrates a greater potential of emission mitigation by improving the load-carrying capacity (thus leveraging smaller structural dimensions and lower cement usage). These findings indicate that carbonation curing can be implemented for ECC's low-carbon design and fabrication beyond laboratory scales and offers a feasible path towards sustainable and resilient infrastructure developments through CO 2 utilization.

Purpose: To quantitatively investigate the chemical origins of near-UV excited fluorescence in the crystalline lens, and demonstrate the potential usefulness of a rapid and noninvasive diagnostic approach for screening and monitoring of lens damage. Methods: Anterior segment UV fluorescence imaging was applied to a population of 30 healthy adults, ages 18 to 64 years. Absolute fluorescence intensities and intensity ratios were compared across the population as a function of age. Fluorescence quantum yield (FQY) was calculated from imaging results based on a previous radiometric characterization. Results: Typical FQYs at 365 nm excitation are approximately 0.2% for healthy adults. Intensity and FQY were observed to increase significantly with age, consistent with ex vivo and confocal microscopy studies. The ratio of blue to green fluorescence is strongly correlated with FQY and age, suggesting that both increases in fluorophore concentration and changes in composition occur with age. Fluorescence data is quantitatively and qualitatively consistent with pyridine nucleotides in young adults, and changes with age are consistent with formation of β-carbolines or advanced glycation end products. Intralens variation is consistent with increased oxidation or glycation in the lens nucleus relative to the cortex. Conclusions: Lenticular fluorescence can be measured rapidly, accurately, and quantitatively in vivo which provides a spatially resolved, quantitative measure of lens chemistry, including damage from oxidation and glycation. Careful interpretation of fluorescence intensities and intensity ratios can provide chemical insight into lens health. Anterior segment UV fluorescence imaging can thus serve as a useful tool for screening, monitoring, and research of lens damage and cataract formation.

This study, sponsored by the Department of Energy (DOE), examines markets; infrastructure; and research, development, and demonstration (RD&D) needs for CO2 and coal waste utilization in a net-zero emissions future, as requested by Congress in the Energy Act of 2020. The committee focused on regional and national market opportunities, infrastructure needs, and RD&D needs for technologies that transform CO2 or coal waste3 into products that will contribute to a net-zero emission future. It analyzed challenges in expanding infrastructure, mitigating environmental impacts, accessing capital, overcoming technical hurdles, and addressing geographic, community, and equity issues for carbon utilization. In a first report, the committee assessed the state of and opportunities to improve and expand on infrastructure for CO2 utilization. The first report highlighted priority products that could be made from CO2; discussed needs for enabling infrastructure; and overviewed policy, regulatory, and environmental justice considerations for utilization infrastructure. For this second and final report from the study, the committee was tasked to identify potential market opportunities for CO2 utilization; identify opportunities for federal support of small businesses; examine infrastructure for CO2 utilization and the economic, climate, and environmental impacts of any well-integrated national CO2 pipeline system applied for CO2 utilization; assess current and emerging technologies and approaches for CO2 utilization, identify their research needs, and develop a comprehensive research agenda to advance CO2 utilization; and determine the feasibility of and opportunities for commercializing coal waste–derived products.

Radiative transfer, or the propagation of radiation (light) through a system, is an important problem in imaging and optical diagnostics in complex media including turbulent gas flows, biological tissues, and particle suspensions. Monte Carlo (MC) methods are the de facto standard for radiative transfer simulation in complex media. While many sophisticated tools exist within this domain, few are well-suited to investigating laser- and fluorescence-imaging in turbid media. Here, a fast MC code for investigating light propagation in turbid media is presented. This tool is intended to enable detailed, physics-based analysis of laser and imaging techniques of simple model systems for use in experimental design and interpretation.

This study presents a whole building life cycle assessment for a 265 m 2 end-terrace home built in Michigan, United States. The study scrutinized the embodied carbon footprint of conventional construction materials, focusing on high-impact materials like concrete, steel, gypsum, paint, and insulation. Stages from raw material extraction to transportation and processing of the raw materials into finished products and transportation of finished products to the site are considered. The baseline materials contributed to approximately 28,450 kg CO 2 e, equivalent to 107.35 kg CO 2 e/m 2 . A notable reduction in the embodied carbon footprint, ranging from 19% to 39%, was observed by substituting with ‘like-for-like’ alternatives. However, the study highlighted challenges in shifting to low-embodied carbon materials, primarily due to limited market readiness and scalability of some eco-friendly options. The study also assessed the feasibility of these alternatives using the United States Department of Energy’s “Technology Readiness Level” framework, examining their current production capacity, estimating potential future demand, and identifying key development areas to meet net-zero carbon goals effectively. This comprehensive approach underscores the complexity of transitioning to low embodied-carbon building practices while balancing feasibility and environmental impact.

Today, the built environment, including infrastructure for tunnels, bridges, highways, subways, railroads, harbors, buildings and airports, is responsible for a significant portion of the energy consumption, natural resource utilization, waste generation as well as CO 2 and other environmentally harmful emissions in the United States and around the world. There is no silver bullet solution to achieve the ambitious goal of zero carbon buildings and a city infrastructure with significantly reduced CO 2 emissions. Thus, multifaceted solutions should be developed. Another challenge associated with the built environment is aging and a large economic burden to upgrade and maintain the outdated infrastructure. The current status of the U.S. built environment is far below sustainable condition. Rapidly deteriorating infrastructure that must be replaced provides us with the unique opportunity to rethink where and how we should live in the future. In addition, current challenges related to economic and societal inequality in the United States and other global communities also force us to re-evaluate how humanity is connected and how we share resources for a sustainable and healthy future while keeping the Earth safe. The engineering solutions for our future built environment include, but are not limited to, the design and synthesis of new infrastructure materials with low carbon intensity, the development of new manufacturing options and technologies, and the integration of innovative functionalities into building envelopes.

Diagnostic technologies for the anterior segment of the eye, especially for hard-to-diagnose diseases such as microbial keratitis, are still lacking. Although in vivo confocal microscopy and optical coherence tomography are becoming more widely applicable to a variety of conditions, they are often prohibitively expensive, require specialized training and equipment, and are intrinsically insensitive to chemical changes. Here, ultraviolet-fluorescence imaging is proposed as a new technique to aid in investigation of the anterior segment. In this work, a novel two-color line-of-sight fluorescence imaging technique is described for imaging of the anterior segment. The technique is applied to seven ex vivo porcine eyes to illustrate the utility of the technique. The image data was used to estimate an effective fluorescence quantum yield of each eye at 370 nm. The eyes were then inoculated with bacteria to simulate microbial keratitis, a common sight-threatening infection, and the measurement was repeated. A simplified fluorescence-extinction model was developed to describe and analyze the relative intensities of the eye and biofilm fluorescence. Overall, the technique appears to have utility in clinical practice and with proper development may be suitable for detecting chemical changes in the eye, or the presence of foreign matter; however, further investigation is needed to develop the technique and analysis procedures into a quantitative diagnostic tool.

Carbon dioxide capture, utilization, and sequestration (CCUS) is a collection of approaches needed to supplement other efforts to achieve net zero carbon emissions. The specific combination of CO 2 sources and sinks (a “usage pathway”) determines the environmental impact, economic viability, overall role in climate change mitigation and continued availability of carbon-based products. Optimal deployment requires a clear understanding of the nature of carbon sources and the durability and economic value of downstream processes and materials. Rigorous life cycle and techno-economic assessments (LCA and TEA) are critical. This paper presents a CO 2 sources and sinks matrix as the high-level basis for assessing a usage pathway's climate relevance and economics.

Author(s): Renforth, Phil; Bellamy, Rob; Beerling, David; Boettcher, Miranda; Bonalumi, Davide; Brandão, Miguel; Fridahl, Mathias; Fuss, Sabine; Hansson, Anders; Heyward, Clare; Kolosz, Ben; Lamers, Patrick; McLaren, Duncan; Pomi, Raffaella; Sanchez, Daniel L; Shayegh, Soheil; Sick, Volker; Van der Spek, Mijndert; Vishal, Vikram; Wilcox, Jennifer

The Global CO2 Initiative hosted the 2023 TEA/LCA Workshop on Harmonizing CCU Assessments on May 16-18. This fifth workshop in the series was planned and conducted by the International CCU Assessment Harmonization Group with members from the USA (GCI at U-M, NETL, NREL, ANL), Canada (NRC), Germany (RIFS, formerly known as IASS), Switzerland (ETH Zürich), and Japan (NIAIST). This team works to advance transparent and uniform assessments of CCU technologies and products. These workshops have traditionally engaged a broad audience in breakout sessions to debate, resolve, and define key issues with assessments in CCU. Note that occasionally, it makes sense to include border aspects and include assessments of CO2 sequestration into the discussions. Hence, in some sections, the mention of CCUS is included. The focus topics for 2023 had been selected to address social aspects and standardization. 51 on-site and up to 265 remote attendees spent one-and a-half days in lively discussions. This report presents a summary of the breakout session discussions, key status descriptions, and open issues. We will take this as a starting point for a year of continued collaboration to advance LCA & TEA for CCU and for planning our next annual gathering on May 22 & 23, 2024 in Ann Arbor. We welcome suggestions and questions that can be submitted to info@globalco2initiative.org

Droplets residing on textured oil-impregnated surfaces form a wetting ridge due to the imbalance of interfacial forces at the contact line, leading to a wealth of phenomena not seen on traditional lotus-leaf-inspired non-wetting surfaces. Here, we show that the wetting ridge leads to long-range attraction between millimeter-sized droplets, which coalesce in three distinct stages: droplet attraction, lubricant draining, and droplet merging. Our experiments and model show that the magnitude of the velocity and acceleration at which droplets approach each other horizontally is the same as the vertical oil rise velocity and acceleration in the wetting ridge. Moreover, the droplet coalescence mechanism can be modeled using the classical mass-spring system. The insights gained from this work will inform future fundamental studies on remote droplet interaction on textured oil-impregnated surfaces for optimizing water harvesting and condensation heat transfer.

Abstract Fluorescence imaging of certain biochemicals, including flavins and pyridine nucleotides, has utility in characterizing the metabolic state of tissue and in discriminating between microbial species. There is significant clinical utility in this class of imaging techniques but most measurements reported to date require specialized training and equipment rendering most implementations unsuitable for routine medical imaging. Here, a low-cost and robust imaging technique is designed using ultraviolet-induced fluorescence of pyridine nucleotides (primarily NADH) and flavins (primarily FAD) in microbial samples. The diagnostic is optimized to distinguish between different microbial species based on previously reported spectral data using a ratiometric imaging approach. A detailed performance analysis is provided that relates the measured fluorescence intensity ratio (FIR) to the relative concentration ratio of NADH to FAD using a simplified spectroscopic model. Analysis suggests the technique is sensitive to changes in the NADH/FAD concentration ratio over several orders of magnitude, with better than 10% FIR precision on a per-pixel basis for microbial smears as thin as 10 s of microns at a resolution of 30 mm −1 and exposures of 20 ms. Representative microbe samples from eight species were imaged to demonstrate the proposed technique. Results show that the FIR varies by an order of magnitude across different species but the intra-species variation is only ∼5% for the conditions used here. An additional imaging band may be necessary to classify species that contain red pigments or bacteriochlorophyll. Radiative trapping was discussed as a possible limitation of the technique, but no clear evidence for radiative trapping was observed here. Overall, the results suggest that the proposed approach is feasible for rapid, low-cost, and robust characterization of microbial samples.

Stabilizing the climate will require significant efforts to curb greenhouse gas emissions, manage emissions that cannot be avoided, and remove as many legacy emissions as possible [i.e., carbon dioxide (International Energy Agency, 2020; Author Collective, 2022)]. In that context, negative emissions technologies will take CO₂ from the air (Direct Air Capture) or the water (Direct Ocean Capture) and permanently remove it (Roger et al., 2021) either by sequestering the CO₂ underground or converting it to so-called Track 1 materials (Sick et al., 2021) that have lifetimes of >100 years. Shorter-lived products that decompose back into CO₂ in <100 years are categorized as Track 2 materials and will at best be carbon neutral. A carbon neutral status can also be achieved if captured CO₂ from fossil-based point sources is sequestered or used to create Track 1 materials. Conversion of CO₂ from fossil-based sources to any Track 2 material and subsequent decomposition would add new fossil-based carbon to the atmosphere, constituting an ultimately undesirable process. The overall carbon footprint of a process or product will depend on many factors associated with the carbon production, use, and disposal phases.

Novel methods are needed for diagnosis of microbial keratitis. Two-color fluorescence imaging is proposed and tested on ex vivo porcine eyes. Results show the technique may be feasible but further quantitative characterization is needed.

Rapid, low-cost diagnosis of infections is challenging and requires innovation. Two-color fluorescence imaging is proposed to distinguish between microbial species. Microbial smear images show the technique is promising for classifying species in vitro .

This data set contains corrected two-color fluorescence intensity image data from 44 bacterial smears presented in the associated journal article, along with summary statistics, fluorescence spectra, and fluorescence intensity ratio histograms. <br> <strong>Article: </strong>Herzog et al 2023 <em>Meas. Sci. Technol.</em> https://doi.org/10.1088/1361-6501/acd711 <br> The individual files are as files: <br> <strong>Corrected two-color fluorescence image data</strong> B.cereus.tif B.subtilis.tif E.coli.tif M.luteus.tif Mold.tif P.fluorescens.tif R.rubrum.tif S.marcescens.tif <br> Each file contains three-channel, 16-bit per sample image stacks. The Red and Blue image channels contain the corrected Red- and Blue-band fluorescence intensity data, respectively. Images were registered and corrected for LED intensity profile variation before storing. Each image corresponds to a different microbial smear. Image data is stored as 16-bit integers, although the raw data range is only 10-bit; typical intensity values are on the order of 1000. <br> It is recommended that ImageJ or a similar viewer be used to view the red and blue color channels independently with an appropriate scale. <br> <strong>Summary data</strong> Summary.xlsx <br> This file contains a table of summary statistics from each of the 44 analyzed microbial smears. The columns are as follows: <br> Species: Name of the microbial species Exposure: Exposure duration (UV LED and camera) in ms Ratio: Most common ratio value (i.e., the mode of the ratio histogram) Red: Median corrected red-band fluorescence intensity in counts Blue: Median corrected blue-band fluorescence intensity in counts R_fwhm: Full-width at half maximum of the ratio PDF sR: Standard deviation of the corrected red-band fluorescence intensity in counts sB: Standard deviation of the corrected blue-band fluorescence intensity in counts R0: Median raw red-band fluorescence intensity in counts B0: Median raw blue-band fluorescence intensity in counts sR0: Standard deviation of the raw red-band fluorescence intensity in counts sB0: Standard deviation of the raw blue-band fluorescence intensity in counts <br> <strong>Histogram data</strong> Histogram.csv <br> Comma-separated histogram data, smoothed using a 7-bin wide 2nd order Savitzky-Golay filter. Each histogram is stored as a separate block with the format: <br> [Name] [Comma-separated ratio bin values] [Comma-separated smoothed count values] <br> <strong>Spectroscopy data</strong> Spectra.csv <br> Comma-separated fluorescence spectra data, smoothed using a 10.5 nm wide 1st order Savitzky-Golay filter. Data was corrected for background and relative spectral response, then normalized by its integral and scaled by a factor of 100. Each histogram is stored as a separate block with the format: <br> [Species name] [Comma-separated wavelength values] [Comma-separated normalized corrected intensity values x 100]