Tejas Bhatelia

While CO2 reduction reaction (CO2RR) coupled with chlorine evolution reaction (CER) can enhance the energy efficiency and economic viability of CO2 electrolysis, its implementation in zero-gap membrane-electrode-assembly (MEA) electrolysers remains challenging as CER-compatible systems require acidic chloride-rich anolytes and chlorine-tolerant cation exchange membranes that induce detrimental cation crossover. The resulting disruption of the cathodic microenvironment causes (bi)carbonate precipitation, hydrogen evolution, and operational instability. Here we report an asymmetric ion-regulation strategy using chloride-bearing, water-miscible poly(diallyldimethylammonium chloride) in the anolyte to maintain high chloride availability for CER while reducing K+ crossover and modifying proton transport through the membrane. Optimised MEA electrolysers achieve about 90% Faradaic efficiencies for both CO and Cl2 and more than 200 h of cumulative operation under replenishment/maintenance protocols, advancing CO2RR-CER beyond laboratory flow-cell demonstrations toward zero-gap MEA operation. Techno-economic and life-cycle analyses indicate that Cl2 co-production can improve process economics under the stated assumptions and reduce the greenhouse-gas intensity of CO production by 75% relative to conventional CO2RR coupled with oxygen evolution benchmarks.

This study adopts a biochemical approach to sequester CO₂ while producing biomass rich in protein and lipids, using an adapted strain of Chlorella vulgaris (ALE-Cv), which had previously evolved to tolerate a gas mixture containing 10% CO₂ and 90% air. The research studied the operating parameters of the batch photobioreactor for ALE-Cv to evaluate the effects of inoculum size, photoperiod, light intensity, pH of culture, and CO₂ supply rate on biomass productivity and CO₂ bio-fixation rate. The optimal conditions were identified as 16:8 h light–dark cycles, 5000 lux, pH 7, 20 mL of 10 g/L inoculum, and 0.6 VVM; the system achieved a maximum total biomass production of 7.03 ± 0.21 g/L with a specific growth rate of 0.712 day⁻¹, corresponding to a CO₂ bio-fixation of 13.4 ± 0.45 g/L in batch cultivation. While the pre-adapted strain of Chlorella vulgaris under the same operating conditions, except for the gas supply, which was air, achieved a maximum total biomass production of 0.52 ± 0.008 g/L, and the total CO₂ bio-fixation was 1.036 ± 0.021 g/L during 7-day cultivation. A novel semi-continuous harvesting process, with and without nutrient addition, was also investigated to maximise biomass yield and enable water recycling for culture media. The maximum biomass production in semi-continuous harvesting process with and without nutrition added was 5.29 ± 0.09 and 9.91 ± 0.11 g/L, while the total corresponding CO₂ bio-fixation was 9.70 ± 0.13 and 18.16 ± 0.11 g/L, respectively, during 15-day cultivation. The findings provide critical insights into enhancing CO₂ bio-fixation through adaptive evolution of ALE-Cv and offer optimal operational parameters for future large-scale microalgae cultivation. This research also links microalgae-based CO₂ sequestration to green technologies and the bioeconomy, highlighting its potential contribution to climate change mitigation while supporting environmental sustainability, food security, and ecosystem resilience.

Methanol synthesis is carried out in a catalytic, packed bed reactor, where the shape and size of catalyst play a critical role in dictating overall reactor performance. In the current study, the effect of five different catalyst shapes including cylindrical, ring, trilobe, wagon wheel, and spherical on the reactor performance was investigated by conducting particle‐scale computational fluid dynamics (CFD) simulations. The predictions of pressure drop, velocity, temperature, reactant distribution and product yield were analyzed. When the performance of the simulated shapes was compared at the same tube Reynolds number of 50,000, internally contoured shapes (wagon wheel and ring) resulted in 40% higher pressure drops due to the tortuous flow path. However, the shape with internal void provided access for the reactant to reach the internal part of catalyst, resulting in higher yield produced per volume of catalyst. The wagon wheel shape produced 15% and 5% more yield per volume against the cylindrical shape and trilobe, respectively. The performance of the wagon wheel can be attributed to the lower diffusion limitation due to higher surface area available for reactant to penetrate the internal part of the catalyst.

The heterogenous mineralogy of ultramafic deposits hosting mining operations makes it challenging to accurately determine the waste rock’s mineral carbonation potential (MCP). Additionally, the significantly higher carbonation capabilities of olivine than serpentine add to the difficulty. To address this issue, in this work, a new and unique tool called the MCP calculator was developed as a Microsoft ExcelTM spreadsheet to accurately determine the amount of anthropogenic CO₂ that a given rock mass can sequester through mineral carbonation. The program estimates the modal mineral abundance of ultramafic rocks to aid in MCP estimation. This tool is designed to be cost-effective and tailored for use by the mining industry, utilising abundant lithogeochemical data to evaluate their deposit as a potential substrate for industrial mineral carbonation operations. The paper introduces the MCP calculator, outlines a framework for developing the MCP parameter, and presents an example of its application. The calculator is specific to the mineral assemblage investigated at the Turnagain ultramafic complex in northern British Columbia but can be adjusted to study comparable deposits. The paper acknowledges that using waste rock in a mineral carbonation operation requires economic and practical decisions beyond the scope of the research.