A prospective life cycle assessment was performed for global ammonia production across 26 regions from 2020 to 2050. The analysis was based on the IEA Ammonia Roadmap and IMAGE electricity scenarios model for three climate scenarios related to a mean surface temperature increase of 3.5 °C, 2.0 °C, and 1.5 °C by 2100. Combining these models with a global perspective and new life cycle inventories improves ammonia's robustness, quality, and applicability in prospective life cycle assessments. It reveals that complete decarbonisation of the ammonia industry by 2050 is unlikely from a life cycle perspective because of residual emissions in the supply chain, even in the most ambitious scenario. However, strong policies in the 1.5 °C scenario could significantly reduce climate impacts by up to 70% per kilogram of ammonia. The cumulative greenhouse gas emissions from the ammonia supply chain between 2020 and 2050 are estimated at 24, 21, and 15 gigatonnes CO₂-equivalent for the 3.5 °C, 2.0 °C, and 1.5 °C scenarios, respectively. The paper examines challenges in achieving these scenarios, noting that electrolysis-based (yellow) ammonia, contingent on electricity decarbonisation, offers a cleaner production pathway. However, achieving significant GHG reductions is complex, requiring advancements in technologies with lower readiness, like carbon capture and storage and methane pyrolysis. The study also discusses limitations such as the need to reduce urea demand, potential growth in ammonia as a fuel, reliance on CO₂ transport and storage, expansion of renewable energy, raw material scarcity, and the longevity of existing plants. It highlights potential shifts in environmental impacts, such as increased land, metal, and mineral use in scenarios with growing renewable electricity and bioenergy with carbon capture and storage.

Electrochemical CO₂ reduction in non-aqueous solvents is promising due to the increased CO₂ solubility of organic-based electrolytes compared to aqueous electrolytes. Here the effect of nine different salts in propylene carbonate (PC) on the CO₂ reduction product distribution of polycrystalline Cu is investigated. Three different cations (tetraethylammonium (TEA), tetrabutylammonium (TBA), and tetrahexylammonium (THA)) and three different anions (chloride (Cl), tetrafluoroborate (BF₄), and hexafluorophosphate (PF₆)) were used. Chronoamperometry and in-situ FTIR measurements show that the size of the cation has a crucial role in the selectivity. A more hydrophobic surface is obtained when employing a larger cation with a weaker hydration shell. This stabilizes the CO₂⁻ radical and promotes the formation of ethylene. CO₂ reduction in 0.7 M THACl/PC shows the highest hydrocarbon formation. Lastly, we hypothesize that the hydrocarbon formation pathway is not through C−C coupling, as the CO solubility in PC is very high, but through the dimerization of the COH intermediate.

Electrolytic bicarbonate conversion holds the promise to integrate carbon capture directly with electrochemical conversion. Most research has focused on improving the faradaic efficiencies of the system, however, the stability of the system has not been thoroughly addressed. Here, we find that the bulk electrolyte pH has a large effect on the selectivity, where a higher pH results in a lower selectivity. However, the bulk electrolyte pH has no effect on the stability of the system. A decrease in CO selectivity of 30 % was observed within the first three hours of operation in an optimized system with 3 M KHCO₃ and gap between the membrane and electrode. Single-pass electrolyte experiments at various constant pH values (8.5, 9.0, 9.5, and 10.0), show that only at a pH of 10 the CO selectivity was stable during three hours, reaching a faradaic efficiency toward CO of only 18 % as compared to an initial 55 % at pH 8.5. Trace metal impurities present in the electrolyte were found to be the cause of the decrease in stability as these deposit on the electrode surface. By complexing the trace metal ions with ethylenediaminetetraacetic acid (EDTA), the metal deposition was avoided and a stable CO selectivity was obtained.

In this study, the effect of halide anions on the selectivity of the CO₂ reduction reaction to CO was investigated in choline-based ethylene glycol solutions containing different halides (ChCl : EG, ChBr : EG, ChI : EG). The CO₂RR was studied using silver (Ag) and gold (Au) electrodes in a compact H-cell. Our findings reveal that chloride effectively suppresses the hydrogen evolution reaction and enhances the selectivity of carbon monoxide production on both Ag and Au electrodes, with relatively high selectivity values of 84 % and 62 %, respectively. Additionally, the effect of varying ethylene glycol content in the choline chloride-containing electrolyte (ChCl : EG 1 : X, X=2, 3, 4) was investigated to improve the current density during CO₂RR on the Ag electrode. We observed that a mole ratio of 1 : 4 exhibited the highest current density with a comparable faradaic efficiency toward CO. Notably, an evident surface reconstruction process took place on the Ag surface in the presence of Cl⁻ ions, whereas on Au, this phenomenon was less pronounced. Overall, this study provides new insights into anion-induced surface restructuring of Ag and Au electrodes during CO₂RR, and its consequences on the reduction performance on such surfaces in non-aqueous electrolytes.

Carbon capture and utilization (CCU) plays a key role in reducing greenhouse gas emissions and reaching carbon neutrality goals. This study assesses the environmental impacts of producing carbon nanotubes (CNTs) via molten salt CO2 capture and electrochemical transformation (MSCC-ET) and Catalytic Chemical Vapor Deposition (CCVD), both using CO2 as feedstock. We screened and selected technologies using a parameter-based method and conducted process modeling and an ex-ante Life Cycle Assessment (LCA) to move beyond lab-scale evaluations and included the purification steps. The MSCC-ET approach showed advantages in reducing impacts related to climate change, energy, and ozone depletion impacts, specifically suggesting lower CO2 emissions. However, traditional CCVD outperformed MSCC-ET in several other impact categories. Key contributors to the environmental impacts of MSCC-ET were found in high material use in electrolysis, purification, and electricity consumption, modeled using the Belgium grid. Moreover, including the carbon capture unit in the assessment could provide a complete view of the environmental impacts regarding CCU. For every 100 tons of MWCNTs produced, a monoethanolamine (MEA)-based carbon capture unit integrated into the MSCC-ET system could roughly reduce 716.5 tons CO2-eq. Additionally, electricity consumption was found to constitute a significant portion of the environmental impacts. Therefore, a sensitivity analysis was conducted, revealing that changes in the electricity source, catalyst used, and CO2 source significantly influenced the environmental performance of both technologies. Furthermore, we summarize practical insights from this study to guide the effective application of ex-ante LCA for carbon nanomaterials. The paper concludes with actionable recommendations for early-stage technology developers on optimizing energy use, improving material efficiency, and integrating recycling to enhance sustainability. In addition, we provide recommendations for LCA practitioners on incorporating dynamic systems to transition from lab-scale to industrial contexts, thereby bridging the gap between research and practical implementation.

Aqueous electrolytes are most commonly used for the CO₂ reduction reaction (CO₂RR), but suffer from a low CO₂ solubility that limits the reaction. Electrochemical CO₂ reduction in nonaqueous electrolytes can provide a solution, due to the higher CO₂ solubility of organic solvent-based electrolytes. Herein, the product distribution of the electrochemical CO₂ reduction on polycrystalline Cu in 0.7 m tetraethylammonium chloride in propylene carbonate with different water additions (0, 10, and 90 v%), and for different operating conditions (10, 25, 40, and 60 °C), is investigated. It is found that CO₂ reduction on Cu in a propylene carbonate solution results in H₂, CO, and formic acid formation only, even though Cu is known to produce C₂₊ products such as ethylene and ethanol in aqueous electrolytes. Increasing the operating temperature increases the CO₂RR kinetics and shows an improvement in CO formation and decrease in H₂ formation. However, increasing the operating temperature also increases water transport through the membrane, resulting in an increase of H₂ formation over time when operating at 60 °C.

We performed H-cell and flow cell experiments to study the electrochemical reduction of CO2 to oxalic acid (OA) on a lead (Pb) cathode in various nonaqueous solvents. The effects of anolyte, catholyte, supporting electrolyte, temperature, water content, and cathode potential on the Faraday efficiency (FE), current density (CD), and product concentration were investigated. We show that a high FE for OA can be achieved (up to 90%) at a cathode potential of -2.5 V vs Ag/AgCl but at relatively low CDs (10-20 mA/cm2). The FE of OA decreases significantly with increasing water content of the catholyte, which causes byproduct formation (e.g., formate, glycolic acid, and glyoxylic acid). A process design and techno-economic evaluation of the electrochemical conversion of CO2 to OA is presented. The results show that the electrochemical route for OA production can compete with the fossil-fuel based route for the base case scenario (CD of 100 mA/cm2, OA FE of 80%, cell voltage of 4 V, electrolyzer CAPEX of $20000/m2, electricity price of $30/MWh, and OA price of $1000/ton). A sensitivity analysis shows that the market price of OA has a huge influence on the economics. A market price of at least $700/ton is required to have a positive net present value and a payback time of less than 10 years. The performance and economics of the process can be further improved by increasing the CD and FE of OA by using gas diffusion electrodes and eliminating water from the cathode, lowering the cell voltage by increasing the conductivity of the electrolyte solutions, and developing better OA separation methods.

Logistics of hydrogen is one of the bottlenecks of a hydrogen economy. In this study, a pressure swing adsorption (PSA) system is proposed for the separation of hydrogen from natural gas, co-transported in the natural gas grid. The economic feasibility of hydrogen supplied by a PSA system at a refuelling station is assessed and compared with other alternatives. The adsorbent material is key to the design of a PSA system, which determines the operation performance and cost. It is concluded that a refuelling station with hydrogen supplied by a PSA system is economically feasible. The final hydrogen price including hydrogen supply, compression, storage, and dispensing is compared with two other hydrogen supply methods: on-site electrolysis and tube-trailer transported hydrogen. Currently, PSA supplied hydrogen is a more economical option. On-site electrolysis can become a more economical option in the future with improved cell efficiencies and reduced electricity prices. Tube-trailer transported hydrogen is highly influenced by the distance travelled. The findings of this study will help with more efficient distribution of hydrogen.

Carbon dioxide (CO2) is currently considered as a waste material due to its negative impact on the environment. However, it is possible to create value from CO2 by capturing and utilizing it as a building block for commodity chemicals. Electrochemical conversion of CO2 has excellent potential for reducing greenhouse gas emissions and reaching the Paris agreement goal of zero net emissions by 2050. To date, carbon capture and utilization technologies (i.e., capture and conversion) have been studied mostly independently. In this communication, we report a methodology based on the integration of CO2 capture and conversion by the direct utilization of a CO2 capture media as the electrolyte for electrochemical conversion of CO2. This has a high potential for reducing capital and operational cost when compared to traditional methodologies (i.e., capture, desorption, and then utilization). A mixture of chemical and physical absorption solvents allowed for the captured CO2 to be converted to formate with faradaic efficiencies of up to 50% and with carbon conversion of ca. 30%. By increasing the temperature in the electrochemical reactor from 20 to 75 °C, the reaction rate toward formate increased by a factor of 10, reaching up to 0.7 mmol/m2·s. The direct conversion of captured CO2 was also demonstrated for carbon monoxide formation with faradaic efficiencies of up to 45%.

Carbon utilisation is gaining attention on a scientific and public level, as part of a strategy to close the carbon cycle. Existing CO2 utilisation strategies, based on the use of pure CO2, lead to relatively high cost for e-fuels and commodity chemicals. This paper proposes an integration of CO2 capture with CO2 utilisation, directly in the CO2 capture solvent, to improve the cost performance. In this concept, ammonium bicarbonate is produced by CO2 capture and subsequently hydrogenated to ammonium formate. With the use of a thermal split, the ammonium formate can be split into a formic acid product solution and ammonia. Techno-economics show the potential of this route supported by proof-of-concept experiments for the innovative steps in the process. Assessment of a 100 ktonne/y CO2 capture and utilization leads to a formic acid production price of 365-456 €/t, using a varying hydrogen price of 2-4 €/kg, which is in the price range of industrial formic acid.

Electrochemical processes are a promising technology for industrial production of chemicals. One of the major drawbacks of electrochemical systems is the low mass transfer of reactants toward the active surface area of the electrode. In this paper, an approach is presented to enhance the mass transfer and increase the overall performance of the reactions. The strategy comprises introduction of a pulsed electrolyte flow in the electrochemical flow cell. This pulsating behavior results in an improved mass transfer of electroactive species due to a higher instantaneous velocity driven by the pulsations. Though the net residence time of the reactants will not be altered due to the pulsation, the resulting enhancement of mass transfer leads to an increase of the conversion. The oxidation of 1,2-propanediol to lactic acid and pyruvic acid mediated by 4-Acetamido-(2,2,6,6-Tetramethylpiperidin-1-yl) oxidanyl (ACT-TEMPO) was chosen to study the influence of the pulsed flow. Under the pulsating regime, a yield increase of lactic acid of a factor of two and a 15-20% gain in selectivity to a total of 95% toward lactic acid can be achieved by tuning the process parameters.

Herein, we describe a study of the electrochemical reduction of oxalic and glyoxylic acids toward a feasible green and sustainable production of tartaric acid in aqueous and/or acetonitrile solvent using silver and lead electrodes. Our results show that on the silver electrode, for both oxalic acid and glyoxylic acid, the reduction reaction is more favorable toward the dimerization step, leading to tartaric acid, due to the increase in the local pH, while on the lead electrode, the step involving the protonation of the intermediate is more favorable, leading to the formation of glycolate. Techno-economic analysis shows that tartaric acid production from glyoxylic acid and from oxalic acid via electrochemical synthesis can be a potential process at the industrial scale. In the present case, the oxygen evolution reaction was chosen as the reaction at the other electrode for practical reasons, but oxygen is a low-value product. Another anodic reaction with a more valuable oxidation product can be selected to increase the profitability of the overall electrochemical process and thereby decrease the total production costs of tartaric acid.

The electrochemical production of valeric acid from the renewable bio-based feedstock levulinic acid has the potential to replace the oxo-process, which uses fossil-based feedstock 1-butylene. The electrochemical reduction of the ketone functionality in levulinic acid using lead or mercury cathodes has already been known for over 100 years. However, large-scale electrochemical production of valeric acid might be limited, owing to the toxicity of these materials. In this study, we identified three additional cathode materials, cadmium, indium, and zinc, which selectively and efficiently produce valeric acid. Of these materials, indium and zinc are considered more benign. More specifically, at indium there is no formation of the side product γ-valerolactone, thus resulting in the highest selectivity towards valeric acid. For the electrochemical reduction, a reaction mechanism involving the formation of an organometallic compound is proposed. Furthermore, a possible processing strategy is outlined to enable the continuous electrochemical production of valeric acid on a large scale.

In industrial electrochemical processes it is of paramount importance to achieve efficient, selective processes to produce valuable chemicals while minimizing the energy input. Although the electrochemical reduction of CO ₂ has received a lot of attention in the past decades, an economically feasible process has not yet been developed. Typically, the electrochemical reduction of CO ₂ is paired to water oxidation, forming oxygen, but an alternative strategy would be coupling the CO ₂ reduction reaction to an oxidation in which a higher-value product is co-produced, significantly improving the economic feasibility for CO ₂ reduction as a whole. Importantly, both reactions need to be chosen wisely to ensure their compatibility and to minimize the voltage requirements for the redox system. In this study, as an example of this approach, we demonstrate such a match: the electroreduction of CO ₂ to CO, paired with the electrooxidation of 1,2-propanediol to lactic acid. Combining these reactions decreases energy consumption by 35%, increases product value of the system, and results in combined faradaic efficiencies of up to 160% when compared to the CO ₂ reduction reaction in which oxygen is formed in the anode.

The amine-based post combustion carbon capture process is one of the most advanced and preferred technologies to reduce CO2 emissions from point sources like power plants. The emissions of amine from capture plants is one of the biggest challenges faced by this technology. These emissions typically occur by means of aerosol/mist formation. To develop effective countermeasures, it is crucial to understand the dynamic behavior of aerosols within the column, which is currently not well understood. This manuscript presents the results from a study aiming to understand the mechanism of aerosol growth and its behavior along the absorber column in terms of particles number concentration, particle size distribution, and amine emissions. For that, a series of experiments were performed in TNO’s bench scale CO2 capture plant using 30 wt% monoethnolamine (MEA) as solvent. For a SO3 and CO2 concentrations of 5.25 ppm and 12.5 vol.% in the flue gas, MEA emissions at the top exit of the column were recorded as 1051 mg/Nm3 (with vapour emissions of 381 mg/Nm3). In the absence of SO3 in the flue gas, inlet particle concentration was 2.71 × 107/cm3 and resulting MEA emissions reduced by 63.5%–383 mg/Nm3.

From the bottom of the column until the point of maximum temperature, the MEA content in the vapour phase was consistent with the volatility of the solvent. After this point it drastically increases to 1051 mg/Nm3. Both the number of particles and the total particle mass has lowered from the bottom to the top of the column. For the benchmark test, inlet and outlet total particle concentration were found to be 6.24 × 107/cm3 and 2.3 × 107/cm3 respectively, while total particle mass is 2.22 mg/m3 at inlet and 1.32 mg/m3 at outlet. Particles with a dimeter below 0.006 μm contribute the most to total particle concentration both at the inlet (50%) and outlet (32%), while particles with diameter of 0.087 μm contributes the most to the total particle mass at inlet (47%) and outlet (55%). The measured total mass of particles was in the order of magnitude of 1 mg/m3. This is much lower than the expected aerosol mass emissions, in the order of magnitude of 1 g/Nm3 based on FTIR emissions.

No particles larger than 0.147 μm were recorded, which might explain the low total mass recorded. The cause for this is still under investigation, but it suggests that the sampling procedure may induce systematic errors to the measurements. Nonetheless, the observations from this study have given further insight into the aerosol dynamics in the absorber column and corresponding emissions.

Most fermentation products have a feedback inhibiting effect on the host organism. In situ product recovery (ISPR) can be a means to overcome this product inhibition in fermentations. Particles such as solvent impregnated resins or capsules can be valuable tools for product recovery based on extraction. To evaluate, which kind of particle will be feasible for a certain kind of fermentation product an evaluation is presented here. Furthermore, an assessment is made what the impact is of ISPR for enhancing productivities in relatively non-inhibiting (lactic acid), fairly inhibiting (phenol) and severely inhibiting (erythromycin) fermentation products. A process containing solvent impregnated resins or capsules is evaluated based on enhanced productivities and cost-effectiveness. It is shown that applying these particles inside a fermentor can result in a decrease in ±30% of total manufacturing costs for pharma-intermediate production.

The application of extractants in whole-cell biocatalysis can have a positive impact on industrial fermentations, in terms of productivity, total amount of product produced, and cell growth. When a product is continuously removed from the microorganism surroundings, product inhibition will be diminished. The strategy is exemplified using phenol as the product and the extractant is selected for solvent-impregnated resins, which can prevent emulsification problems that are commonly encountered in in situ extractive recovery of fermentation products. A systematic approach for selection of superior extractants in whole-cell biocatalysis is discussed in this paper. Three criteria are taken into account, namely, extractant toxicity (log P o/w values), product selectivity, and extractant regeneration.