Carbon Removal Research Articles

The maintenance of carbonscapes: Enacting Net Zero in Stavanger, Norway

As a stable, democratic petrostate, Janus-faced Norway balances fossil fuel incumbency (profitable oil and gas exports) with leadership in green transitions (domestic hydropower supply and transport electrification) and just transitions (major donor to global green initiatives). These roles imbue domestic politics with reverence for fossil fuels as enablers of generous welfare state support, alongside a push to show progress on low-carbon energy transitions. This political dynamic has embraced the global rise to prominence of Net Zero target-setting, highly reliant on speculative, yet-to-emerge carbon mitigation technologies. Such a hubristic response to this target has served to direct massive financing to innovation activities of fossil incumbents. Nowhere is this push felt keener than in Stavanger, the oil capital rebranded to Norway’s ‘energy capital’, and the site of the country’s largest industrial hub Forus and great performative spectacles such as the Offshore Northern Seas conferences and numerous other oil and gas events. Yet it is also here that critique is often focused, pointing out the folly of continued investment that assumes oil and gas persistence in tempered form over rapid renewable energy rollout. We investigate the forms this enactment of Net Zero takes at the urban scale in Stavanger through which the promise of carbon removal is used to uphold carbonscapes. Empirical material includes place-based observation, participatory ethnography at events, and media reports. We engage with conceptual scholarship on the positionality of researchers, role of actionable knowledge, and the specific function of the knowledge economy to enable Stavanger’s juggling act as the site of fossil success since 1969, and champion of carbon removal innovation and development as one of Europe’s 112 climate-neutral 2030 Mission Cities. We argue that unpacking urban spectacle offers evidence of the interwoven nature of domestic politics and performative carbon mitigation approaches, constituting an entry point to critique mitigation deterrence.

Next stop carbon dioxide removal? German climate policies and the risky road to negative emission technologies

Both the global and the German climate targets are ambitious given recent emission reduction rates. In addition to emission reduction measures, carbon dioxide removal has been increasingly discussed recently and initial measures have been developed to potentially scale-up carbon removals in order to meet net zero targets. In this article, we undertake a political economy-based analysis of the historical development and structural conditions of German climate policy measures and their enabling role for the emergence and strengthening of carbon dioxide removal policy options. We refer to regulation theory and the Modell Deutschland approach and argue that within this model the concept of ecological modernization has been established as the dominant approach to regulate society-nature relations. In light of the ambitious climate policy goals, such as net zero by 2045, ecological modernization reaches its current limits and must be recalibrated. Against this background, we conclude by discussing the risk of mitigation deterrence associated with carbon dioxide removals and considering alternative pathways, such as degrowth, to social ecological transformation.

Synergistic Integration of Anammox and Endogenous Denitrification Processes for the Simultaneous Carbon, Nitrogen, and Phosphorus Removal.

The feasibility of a synergistic endogenous partial denitrification-phosphorus removal coupled anammox (SEPD-PR/A) system was investigated in a modified anaerobic baffled reactor (mABR) for synchronous carbon, nitrogen, and phosphorus removal. The mABR comprising four identical compartments (i.e., C1-C4) was inoculated with precultured denitrifying glycogen-accumulating organisms (DGAOs), denitrifying polyphosphate-accumulating organisms, and anammox bacteria. After 136 days of operation, the chemical oxygen demand (COD), total nitrogen, and phosphorus removal efficiencies reached 88.6 ± 1.0, 97.2 ± 1.5, and 89.1 ± 4.2%, respectively. Network-based analysis revealed that the biofilmed community demonstrated stable nutrient removal performance under oligotrophic conditions in C4. The metagenome-assembled genomes (MAGs) such as MAG106, MAG127, MAG52, and MAG37 annotated as denitrifying phosphorus-accumulating organisms (DPAOs) and MAG146 as a DGAO were dominated in C1 and C2 and contributed to 89.2% of COD consumption. MAG54 and MAG16 annotated as Candidatus_Brocadia (total relative abundance of 16.5% in C3 and 4.3% in C4) were responsible for 74.4% of the total nitrogen removal through the anammox-mediated pathway. Functional gene analysis based on metagenomic sequencing confirmed that different compartments of the mABR were capable of performing distinct functions with specific advantageous microbial groups, facilitating targeted nutrient removal. Additionally, under oligotrophic conditions, the activity of the anammox bacteria-related genes of hzs was higher compared to that of hdh. Thus, an innovative method for the treatment of low-strength municipal and nitrate-containing wastewaters without aeration was presented, mediated by an anammox process with less land area and excellent quality effluent.

Promoting the ecological restoration of black and odorous water by Fe/C internal electrolysis

Three ecological restoration systems vegetated with Vallisneria natans, containing ceramisite (VC), bio-carrier and ceramisite (BVC) or Fe/C filler, bio-carrier and ceramisite (FBVC) as functional substrates were constructed for black and odorous water restoration. The average ammonia nitrogen (NH4+-N) conversion rate of FBVC (90.51 %) was similar to that of BVC (88.49 %) and significantly higher than that of VC (53.35 %). However, the average total nitrogen (TN) removal rate of FBVC (84.93 %) was much higher than that of BVC (73.02 %) and VC (52.06 %). Additionally, the average COD removal efficiencies for VC, BVC and FBVC were 52.54 %, 71.84 % and 80.59 %, respectively; while they were 69.72 %, 74.79 % and 97.38 % for total phosphorus (TP). High-throughput sequencing revealed that the richness and diversity of autotrophic denitrifying bacteria, such as Pseudomonas, Pseudoxanthomonas, Arenimonas and Hydrogenophaga increased significantly in FBVC, while the plant growth-promoting bacterium Rhodobacter was dominant. Overall, this study demonstrated that a Vallisneria natans based ecological restoration system coupled with Fe/C internal electrolysis (Fe/C-IE) effectively improved the quality of black and odorous water. In addition, the mechanism of nitrogen, phosphorus and carbon removal was proposed.

CNT/Nafion functionalized Ti/SnO2-Sb/β-PbO2-CNT/Nafion composite electrode toward highly active and robust degradation of octadecylamine and 4-dodecylmorpholine in real high-salinity system

The efficient removal of recalcitrant organics in high-salinity systems, specifically brine, poses a significant challenge for electrochemically advanced oxidation processes in terms of both activity and stability. Herein, a composite electrode comprising of CNT/Nafion functionalized Ti/SnO2-Sb/β-PbO2-CNT/Nafion was developed for efficient and stable removal of octadecylamine (ODA) and 4-dodecylmorpholine (DMP) in a real high-salinity environment. The degradation efficiencies of ODA and DMP on the composite electrode can reach 100 % within 60 min, respectively. The total organic carbon (TOC) removal efficiency of ODA and DMP was significantly improved to 78 % and 66 % with remarkably low energy consumption (0.414 and 1.402 kWh/g TOC), respectively. The electrochemical characterizations demonstrate that the composite electrode exhibits improved electrochemical activity (oxygen evolution potentials = 1.791 V) and electrode surface area (ECSA = 20 cm2), while maintaining reduced charge transfer resistance (Rct = 18.21 Ω/cm2) and enhanced corrosion-resistant capacity (corrosion potential = 1.115 V). Based on recycling and accelerated lifespan testing, the composite electrode demonstrates exceptional stability and recyclability. Additionally revealed was the linked stability mechanism. The electrocatalytic degradation of ODA and DMP begins with the removal of amino and morpholine rings, and then the decomposition of the carbon chains. Gas chromatography-mass spectrometry (GC–MS) and theoretical calculations were used to identify intermediate products generated during the degradation of ODA and DMP, and possible degradation pathways were provided in high-salinity systems, respectively. This work offered a fresh perspective on electrocatalytic oxidation for a real high-salinity system that is more efficient and stable.

Additive effects of basalt enhanced weathering and biochar co-application on carbon sequestration, soil nutrient status and plant performance in a mesocosm experiment

Co-deployment of a portfolio of carbon removal technologies is anticipated in order to remove several gigatons of carbon dioxide from the atmosphere and meet climate targets. However, co-application effects between carbon removal technologies have rarely been examined, despite multiple recent perspectives suggesting potential synergies between basalt enhanced weathering and biochar application. To study the co-application effects of basalt for enhanced weathering and biochar on carbon sequestration, along with related co-benefits and risks, we conducted a fully replicated factorial mesocosm experiment with wheat. Basalt applied alone (74 t ha−1) resulted in an estimated carbon sequestration potential of 1.13 t of equivalent CO2 ha−1 over the course of approximately 6 months. Co-application with biochar (12 t ha−1) did not significantly increase estimated carbon sequestration potential. Total alkalinity fluxes and isotopic evidence indicated nearly exactly additive effects of basalt and biochar co-applied, with no significant interaction effect. Biochar carbon sequestration, approximately 32 t of equivalent CO2 ha−1 in our experiment, was unaffected by basalt addition during our experiment. Co-benefits of basalt and biochar on plant biomass as well as nutrient uptake and availability similarly mostly showed additive tendencies when co-applied. Nonetheless, a few synergistic tendencies were observed when co-applied for plant potassium and magnesium uptake as well as soil calcium availability. Soil calcium availability increased by 126% compared to expected effects based on separate application. Finally, we did not observe a reduction in the increased uptake of potentially harmful trace elements released from basalt when co-applied with biochar. Overall, our results support the co-application of basalt for enhanced weathering and biochar, with additive effects on carbon sequestration and additive, if not synergistic, effects on associated co-benefits.

Renewable Energy Technical Potential Performance for Zero Carbon Emissions.

Global 2021 energy flows indicate sectors with the greatest opportunities for efficiency improvements and emissions reduction. Analysis of the International Energy Agency's 2050 Net Zero Emissions (NZE) Scenario with respect to the 2021 energy profile as a reference point provides a model for changes in energy efficiency, emissions reduction, cost, and land use resulting from substitutions of fossil fuels with renewable options at the levels required for net zero emissions by 2050. Even with optimized outcomes, the probability of such widespread changes occurring over the next 30 years is reduced by the need for large investments, infrastructure changes, and the successful deployment of technologies still under development. Achievement of the technical potential outcomes for alternative solar energy to fuels conversion technologies, including cultivated microalgae biomass and biofuels and photocatalytic and photobiological hydrogen, would reduce reliance on mature renewable technologies and provide increase in net energy ("power to wheels") to help meet the demands of a growing population while reducing cost and CO2 emissions compared to the baseline 2050 NZE scenario. Such technical potential performance along with those for solar and wind represents 4 billion tons of CO2 removal (a 28% increase) over the baseline 2050 NZE Scenario but still requires another 9.5 billion tons of carbon capture and removal (CCR) to achieve NZE.

A hydrodynamic cavitation prototype reactor evaluation for decreasing cephalexin concentration in aqueous solution

A prototype of a hydrodynamic cavitation reactor was evaluated to determine the effectiveness of this system on the percentage decrease of cephalexin concentration present in an aqueous solution prepared with ultrapure water. The process variables or factors were pH [5 and 9], number of holes in the cavitation plate [5 and 7] and reaction time (30 min and 60 min). The results indicate that the percentage removal of Cephalexin (CFX) and total organic carbon (TOC) depends on the variables studied and the interaction between them. The highest yields were achieved at pH 5, 5 holes in the cavitation plate and 60 min of reaction reaching values of 24.16 % for CFX and 16.8 % for TOC. It was determined that, for the lowest number of holes in the cavitation plate and acid pH, the phenomenon that guides the process is the hydrodynamic cavitation, when increasing the number of holes and therefore decreasing the intensity of cavitation, the pH becomes more relevant and has incidence on the performance of the analyzed process. On the other hand, it was determined that, also in reaction times of 30 min, removal values very close to the maximum values obtained are achieved. The process can be intensified by the simultaneous application of other advanced oxidation processes to increase the effectiveness.

Effects of micro- and nano-bubbles on the flotation separation of unburned carbon from coal fly ash

ABSTRACT Nanobubble technology has found extensive use in enhancing the flotation efficiency of various minerals. The utilization of nanobubbles in flotation encompasses bulk nanobubbles, surface nanobubbles, and microbubbles; however, a comprehensive comparison of their respective roles is lacking. Furthermore, there is a dearth of studies on employing nanobubble systems in the flotation of coal fly ash. The coal fly ash characters were initially studied to reveal its ultrafine size (d50: 24.80 μm) and porous structure that includes a multitude of hydrophilic functional groups. These attributes contribute to the inadequate hydrophobicity of unburned carbon within the ash. Subsequently, the effects of different collector types, frother types, and air flow rates on the efficiency of carbon removal using conventional flotation methods were examined. Comparative analysis showed that conventional flotation using diesel oil outperformed that which employed kerosene as the collector. Additionally, higher carbon removal efficiency was achieved using MIBC, with a longer carbon chain length, as the frother, as opposed to sec-Octyl alcohol. Furthermore, a direct relationship between air flow rate and coal fly ash flotation performance was observed – higher air flow rates corresponded to improved flotation outcomes. Finally, a comparison between conventional flotation and nanobubble-assisted flotation (utilizing bulk nanobubbles, surface nanobubbles, and micro-nanobubbles) was conducted. Remarkably, micro-nanobubble flotation yielded the most promising results, with the lowest loss-on-ignition in flotation tailings (3.15%) and the highest removal efficiency of unburned carbon (85.01%). These findings satisfied the loss-on-ignition requirements of Grade I fly ash standards.

Aerobic granulation and resource production under continuous and intermittent saline stress

Three sequential batch reactors (SBR) were operated to evaluate salt addition's impact on granulation, performance, and biopolymer production in aerobic granular sludge (AGS) systems. System R1 was fed without adding salt (control); system R2 operated with saline pulses, i.e., one cycle with salt (2.5 g NaCl/L) addition followed by another without salt; and R3 received continuous supplementation of 2.5 g NaCl/L. The results indicated that the reactors supplemented with salt presented higher concentrations of mixed liquor volatile suspended solids (MLVSS) and better settleability than R1, showing that osmotic pressure contributed to biomass growth, accelerated granulation, and improved physical characteristics. The faster granulation occurred in R2, thus proving the beneficial effects of intermittent salt addition through alternating pulses. Salt addition did not impair the simultaneous removal of carbon, nitrogen, and phosphorus. In fact, R2 showed better carbon removals. In conclusion, continuous or intermittent (pulsed) supplementation of 2.5 g NaCl/L did not lead to increased production of extracellular polymeric substances (EPS) and alginate-like exopolymers (ALE). This outcome could be attributed to the low saline concentration employed, a higher food-to-microorganism (F/M) ratio observed in R1, and possibly greater endogenous consumption of biopolymers in the famine period in R2 and R3 due to the greater solids retention time (SRT). Therefore, this study brings important results that contribute to a better understanding of the effect of salt in continuous dosing or in pulses as a selection pressure strategy to accelerate granulation, as well as the behavior of the AGS systems for saline effluents.

Carbon footprint reduction by coupling intermittent aeration with submerged MBR: A pilot plant study

To find a possible trade-off between effluent quality, sludge production, energy consumption and GHG emissions, this study monitored the carbon and nutrient removal and greenhouse gas (GHG) emissions in a membrane bioreactor (MBR) pilot plant with intermittent aeration (IA). The pilot plant was operated by alternating aerobic and anoxic conditions inside the biological reactor. Up to 98.2 % of carbon and 76.4 % of nitrogen were respectively remove through this MBR pilot plant with IA. The carbon footprint was equal to 2.4 kgCO2eq m−3. Indirect emissions contributed the most to the carbon footprint (55.3 %), mainly due to energy consumption, despite the alterations in aeration during the pilot plant operation. The result of this study provides theoretical guidance for building the wastewater treatment plant in a sustainable way.

Electro-Fenton degradation of pefloxacin using MOFs derived Cu, N co-doped carbon as a nanocomposite catalyst

Electro-Fenton (EF) can in-situ produce H2O2 and effectively activate H2O2 to generate powerful reactive species for the destruction of contaminants under acidic conditions, however, the production of iron-containing sludge and requirement of low working pH significantly hinder its practical application. Herein, a novel Cu, N co-doped carbon (Cu–N@C) with metal organic framework (MOF) as a precursor was constructed and adopted for the elimination of pefloxacin (PEF) in the heterogeneous electro-Fenton (HEF) process. PEF could be almost completely removed within 1 h and total organic carbon (TOC) removal efficiency was 48.57% within 6 h. Meanwhile, Cu–N@C had good repeatability and environmental adaptability, it can still maintain excellent catalytic performance after 10 cycles, and it exhibited satisfactory remediation performance in simulated water matrix. In addition, the HEF process catalyzed by Cu–N@C also showed satisfactory degradation effect on other organic pollutants including atrazine, methylene blue, and chlorotetracycline. Under the action of impressed current, the HEF system could generate H2O2 in-situ, and the active species could be generated in the redox cycle of Cu0/Cu1+/Cu2+. Electron paramagnetic resonance and quenching experiments confirmed that •OH was the dominant active species in the degradation of organic compounds. The degradation process of PEF was studied by mass spectrometry analysis of intermediate products. This study provided a simple method to prepare MOF-based electrocatalyst, which exhibits promising application potential for treatment wastewater.

Scaling carbon removal systems: deploying direct air capture amidst Canada’s low-carbon transition

Carbon dioxide removal (CDR) technologies, such as direct air carbon capture and storage (DACCS), will be critical in limiting the rise of the average global temperature over the next century. Scaling up DACCS technologies requires the support of a complex array of policies and infrastructure across multiple overlapping policy areas, such as climate, energy, technology innovation and resource management. While the literature on DACCS and other CDR technologies acknowledges the path-dependent nature of policy development, it has tended to focus on abstract policy prescriptions that are not rooted in the specific political, social and physical (infrastructural) context of the implementing state. To address this gap, this paper provides a country-level study of the emerging DACCS policy regime in Canada. Drawing on the existing literature that identifies idealized (acontextual) policy objectives that support DACCS development and effective regulation, we identify the actionable policy objectives across six issue domains: general climate mitigation strategies; energy and resource constraints; carbon storage and transport regulation and infrastructure; financing scale-up and supporting innovation; removal and capture technology availability and regulation; and addressing social acceptability and public interest. Using a database of Canadian climate policies (n = 457), we identify policies within the Canadian (federal and provincial) policy environment that map to the idealized policy objectives within each of these domains. This exercise allows us to analyze how key policy objectives for DACCS development are represented within the Canadian system, and enables us to identify potential niches, and landscape influences within the system, as well as gaps and potential barriers to the system transition process. This paper contributes to our understanding of national DACCS policy development by providing a framework for identifying components of the DAC system and linking those components to desired policy outcomes and may provide a basis for future cross-country comparisons of national-level DACCS policy.

Integrated anoxic/oxic biofilm reactor and photocatalytic treatment for enhanced antibiotic removal from real wastewater matrices

The widespread occurrence of sulfamethoxazole (SMZ), one of the widely used antibiotics, in aqueous environments, poses a significant threat to ecosystem health. In this study, the combination of a biofilm-based treatment system and photocatalysis was explored for the effective removal of SMZ. Initially, sulfur-doped g-C3N4 (S-C3N4) was synthesized and then combined with Bi2O3 to improve the overall photocatalytic performance. Characterization of as-prepared photocatalysts was performed to understand the chemical structures, morphologies, and optical properties. Batch studies have shown that, at neutral pH, using 1 g/L of S-C3N4/Bi2O3 (CNBI) composite results in the removal of 87.2 % of SMZ with an initial concentration of 10 mg/L. In accordance with the scavenging study, O2–• was identified as the dominant reactive species for the degradation of SMZ. After that, the identification of SMZ degradation products was carried out, and possible degradation pathways were proposed. After obtaining the optimal dosage, continuous experimentation was conducted using a photocatalytic reactor coated with CNBI composite combined with anoxic/oxic moving bed biofilm reactor. The investigation of real municipal and hospital liquid wastes containing SMZ showed an overall total organic carbon removal of 87 % and 81 %, respectively. Economic assessment, including capital and operational expenditures and synthesis costs involved in photocatalyst material, was performed to check the feasibility of photocatalysis integrated with biological systems at large-scale treatment.

Co-occurrence of simultaneous carbon and nitrogen removal and in-situ sludge separation in a novel single unit combined airlift bioreactor (CALBR) for milk processing wastewater treatment

Combined anaerobic-aerobic bioreactors offer considerable potential for treating different industrial wastewaters. However, difficulty in maintaining a stable coexistence of anaerobic, anoxic, and aerobic microbial communities and the necessity of space-consuming external settlers remain as crucial drawbacks associated with these systems. In this study, an innovative single stage combined airlift bioreactor (CALBR) comprising multiple bioreactors (anaerobic/anoxic/aerobic) and an internal settler (a rotating spiral separator for in-situ separation of biomass) was exploited to achieve simultaneous carbon and nitrogen removal from milk processing wastewater (MPW). Results demonstrated that the anaerobic pre-treatment zone made a substantial contribution towards COD and TN removal. Successful biomass separation and high effluent quality revealed that the rotating spiral separator can be used as a coupled clarifier to sustain higher biomass concentration through boosting the sludge compressibility and settleability which further upgrades the overall treatment bioprocess. sCOD removal, TN removal, SVI, and effluent turbidity of ˃96%, ˃75%, ˂90 mL/g, and ˂10 NTU were reached, respectively under optimum condition. The outcomes suggested that the novel CALBR is a promising technology which has a great potential to be transferred into practical implementation for high-rate combined biological wastewater treatment and sludge separation.

Aerobic Polishing of Liquid Digestate for Preparation of Hydroponic Fertiliser

Nutrient pollution—mainly nitrogen and phosphorus—caused by organic waste continues to impact the environment. The implementation of a circular economy is integral to alleviating these effects. Liquid digestate, which is a byproduct of anaerobic digestion (a waste-valorising process), is a nutrient-dense organic fertiliser with vast applications in agriculture. Using an aerobic polishing unit, this study developed a viable method for the preparation of a hydroponic fertiliser by investigating the effect of pH on the nutrient recycling capabilities of said system. The heterotrophic bacteria present in the biofilm, identified by 16S gene sequencing, are responsible for 90% of organic carbon (as TOC) removal with minimal ammonium loss. This is ideal for promoting optimal nitrification in hydroponic systems in the absence of organic carbon to ensure plant growth is not affected. Although pH 8 was found to be ideal for batch operation, this pH condition resulted in decreased microbial longevity and, therefore, increased ammonification due to microbial decay. Therefore, continuous operation at pH 7 proved to be a better option owing to the ammonium-rich effluent (>220 mg/L) which was produced, which is on par with the nitrogen concentration of a Hoagland solution. The continuous carbon polishing of liquid digestate provides an efficient way of utilising organic fertilisers in hydroponic systems.

Unveiling the interaction regimes between atomic oxygen and amorphous carbon surface depending on incident energy

The chemical reactions between atomic oxygen (AO) and solid surface are particularly crucial for numerous fundamental fields. However, it is lack of clearly understanding the reaction mechanisms between AO and the solid surface because the complex interaction dynamics are extremely difficult to be measured experimentally and to be modelled theoretically. In this work, the reactive molecular dynamics simulations are conducted to fully reveal the interactive mechanisms of AO irradiation on the amorphous carbon surface. As the incident energy (E) increases, our simulations demonstrate three distinct interaction regimes: (I) surface oxidation without carbon removal, (II) surface oxidation accompanied by minor material removals, and (III) continuous material removal. The first critical energy (E1) of ∼3.5 eV as the boundary between regime I and II is related to the dissociative energy of C–C bonds. The second critical energy (E2) of ∼6.5 eV as the boundary between regime II and III corresponds to the largest repulsion energy that the oxidized surface could provide. We further establish a phenomenological model to quantitatively describe how the rebound ratio varies with incident energy and surfacial oxygen density, which not only fit all simulation data perfectly but also give a very precise prediction of E2 value.

Redox-neutral electrochemical decontamination of hypersaline wastewater with high technology readiness level.

Industrial hypersaline wastewaters contain diverse pollutants that harm the environment. Recovering clean water, alkali and acid from these wastewaters can promote circular economy and environmental protection. However, current electrochemical and advanced oxidation processes, which rely on hydroxyl radicals to degrade organic compounds, are inefficient and energy intensive. Here we report a flow-through redox-neutral electrochemical reactor (FRER) that effectively removes organic contaminants from hypersaline wastewaters via the chlorination-dehalogenation-hydroxylation route involving radical-radical cross-coupling. Bench-scale experiments demonstrate that the FRER achieves over 75% removal of total organic carbon across various compounds, and it maintains decontamination performance for over 360 h and continuously treats real hypersaline wastewaters for two months without corrosion. Integrating the FRER with electrodialysis reduces operating costs by 63.3% and CO2 emissions by 82.6% when compared with traditional multi-effect evaporation-crystallization techniques, placing our system at technology readiness levels of 7-8. The desalinated water, high-purity NaOH (>95%) and acid produced offset industrial production activities and thus support global sustainable development objectives.

Carbon capture and utilization under EU law: impermanent storage of CO2 in products and pre-combustion carbon capture

Abstract The evolving regulatory landscape within the European Union demonstrates a transition from prioritizing carbon capture and storage over carbon capture and utilization towards a more equitable treatment of both approaches in relevant legislation and policy frameworks. Nevertheless, the ‘permanence’ criterion of carbon dioxide in the products remains an ongoing challenge. Within the current European legal framework, harnessing the regulatory incentives depends on how long carbon dioxide remains in carbon capture and utilization products. The study elucidates the evolving regulatory landscape surrounding carbon capture and utilization by examining recent legislative initiatives and amendments to key directives such as the Emissions Trading System Directive and the Renewable Energy Directive. Furthermore, it explores the implications of the European Union Net-zero Industry Act and the Carbon Removal Certification Framework. In addition, this article examines and explains the need for expanding the scope of carbon capture and utilization and storage by incorporating pre-combustion carbon capture through methane splitting into the definition.

Bubble-less photocatalytic ozonation with ceramic membranes and static mixers enhances the total organic carbon removal and degradation of iodinated X-ray contrast agents

Conventional bubble-based ozonation of wastewater creates several issues, e.g., the low degradation of certain micropollutants like X-ray contrast agents, mass transfer limitations due to inhomogeneous mixing, and the waste of undissolved ozone. In contrast, this work uses tubular ceramic membranes for bubble-free and bubble-less ozonation. Static mixers are placed around the membrane to enhance the radial mixing of ozone, creating homogeneous reaction conditions throughout the membrane contactor. Additionally, the ozone mass transfer significantly increases with static mixers. Furthermore, the membrane is made of a photocatalyst (TiO2) on the shell-side to improve the micropollutant degradation by photocatalytic ozonation. An ozone-stable hydrophobic treatment method is developed to use ceramic membranes as a membrane contactor for the ozonation of water. After hydrophobic treatment, the ozone mass transfer coefficient is in the order of 1.3 ⋅ 10−6 ms−1 using bubble-less operation resulting in an ozone concentration up to 4.0 mg L−1. Overall, bubble-less operation significantly increases the ozone mass transfer compared to bubble-free operation. Photocatalytic ozonation in a membrane contactor with static mixers increases the degradation of diatrizoate by 37% compared to sole ozonation in the same membrane contactor. Furthermore, this process increases the removal of total organic carbon in experiments with a water matrix consisting of four different micropollutants by 115% compared to sole ozonation.