Electrification, including emerging technologies such as structural supercapacitors, is critical in realizing carbon-neutral transportation. A fundamental challenge is the trade-off between mechanical properties and energy storage capabilities. We report the fabrication of structural supercapacitors with a novel fibre-fibre interface to improve the interlaminar strength and encapsulation while considering the effect of structural resin on energy storage performance. The synthesized graphene nanoplatelets-modified electrodes attain a high specific surface area of ∼231 m² g⁻¹ - outperforming comparable carbon-based electrodes. We learned that the use of a gel-polymer electrolyte (GPE) separator containing 60 wt% Li-salt eliminates the requirement of electrolyte infusion and showed the highest values for conductivity for the cell produced using GPE. The implementation of glass fabrics (GFs) into the GPE improved the flexural modulus by ∼22%, while retaining the mechanical strength of the cells. The multifunctional performance of the produced SSCs were on par or even outperformed the performances of SSCs reported in literature. A proof-of-concept prototype demonstrates that gel-polymer electrolyte cells can retain charges for longer than those with a glass fibre separator. Cumulatively, these offer the possibility of conventional composite manufacturing techniques to scale-up and eliminate delamination issues arising from different thermal expansion coefficients which also addresses the balance between mechanical stability and electrochemical performance. Our findings support the advancement of durable, lightweight energy storage and delivery systems for sustainable transportation, with potential applications in robotics and wearable technologies.

Carbon dioxide utilization is a key strategy for sustainable chemical production and climate change mitigation. Microbial electrosynthesis (MES) offers a promising approach to convert CO₂ into organic acids and multi‑carbon compounds, but its industrial application requires improved product recovery methods. In this study, we developed an integrated MES-sorption-distillation system for the recovery of pure hexanoic acid. Adsorption experiments identified conditions for C6-selective capture from C2–C6 carboxylate mixtures typically produced from MES. Subsequent desorption using CO₂ expanded methanol enriched hexanoic acid concentration by 13-fold compared to the aqueous feed, achieving 67 % recovery in a single pass, but 100 % overall, since recirculation of unrecovered carboxylates back to the MES reactor is proposed. This recirculation will enhance chain elongation, eliminate loss of unrecovered carboxylates, and reduce the need for external pH control during MES. Distillation of the desorbed mixture led to streams of pure products and reusable solvent, without losses. Notably, 87 % of the total energy demand for product formation is attributed to the MES stage, where electrical energy is directly supplied as electrons to drive microbial production. Thus, MES with the proposed recovery method enables pure hexanoic acid production with minimal losses of materials or energy and potentially allows the system to operate in a carbon-negative manner.

Defossilization of industrial processes has led to a growing interest in alternative biotechnologies capable of producing chemicals from renewable resources. Microbial electrosynthesis (MES) is an emerging technology in which electrotrophic microorganisms utilize electrons from a cathode and CO₂ to produce multi-carbon compounds. To reach industrial application, clearer insights into the interactions between underlying biological, electrochemical, and physicochemical processes are required. Although individual parameters have been widely studied, identifying the most influential factors and their interactions remains challenging. This study applies design of experiments (DoE) and mixed linear regression modeling (MLRM) to examine the influence of pH, CO₂ and H₂ partial pressures, acetic acid concentration, and the addition of tungsten and selenium on the production spectrum in biofilm-driven MES. The developed DoE-MLRM approach highlights the key role of pH and CO₂ availability in supporting carbon fixation and acetate production, while the trace metals selenium and tungsten mostly promote chain elongation.

Syngas fermentation is a promising bioprocessing method that utilises autotrophic organisms to convert C1 gases, such as CO and CO2, into valuable chemicals, offering both environmental and economic benefits. Despite these advantages, the industrial application of gas fermentation remains limited owing to challenges in productivity associated with gas substrates. While previous studies have focused on optimizing reactor design, mass transfer, and growth medium as solutions to these specific challenges, the direct correlation between cell viability and productivity remains unexplored. To address this gap, this study investigates the viability of the acetogenic strain Eubacterium callanderi KIST612 and its impact on acetate production across various operational modes. Unlike conventional single-reactor systems, a dual-reactor strategy was implemented to enhance viable cell retention, leading to improved process efficiency. This approach significantly increased the total carbon conversion rate to 9.30mmolh-1 and the specific productivity of viable cells to 0.13g gcell-1h-1, ultimately achieving the highest acetate titer (34.4gL-1) with >53% cell viability. These findings represent a major advancement over previous studies, demonstrating that maintaining cell viability is critical for optimizing acetate productivity. By integrating viability control into process operations, this study presents a scalable and efficient strategy to enhance gas fermentation performance, improve substrate conversion efficiency, and expand biochemical production potential for industrial applications.

The practical implementation of microbial electrosynthesis (MES) is currently limited by the slow microbial colonisation of the electrode and the need to suppress methanogenic activity. This study investigates a two-stage strategy to suppress methanogenesis and promote the rapid formation of an acetogenic biofilm in a directed-flow-through bioelectrochemical reactor. Four start-up regimes were compared: mixotrophic without heat pre-treatment (M), mixotrophic with heat pre-treatment (MT), heterotrophic without heat pre-treatment (H), and heterotrophic with heat pre-treatment (HT), each followed by a common autotrophic phase. Mixotrophy outperformed heterotrophy by accelerating and increasing acetate accumulation. However, adding heat pre-treatment (MT) introduced a short lag phase and resulted in less sustained chain elongation than mixotrophy alone (M). Under the mixotrophic regime, microbial analysis showed an enrichment of genera with acetogenic representatives such as Clostridium sensu stricto 12 and Sporomusa, alongside a reduction in facultative anaerobic and fermentative bacteria. Full biofilm colonisation of the electrode was achieved within 55 to 65 days, while acetate, butyrate, and caproate production was initiated within the first week, reaching concentrations typically observed only after approximately 70 days under autotrophic conditions. Methane remained undetectable for about 40 days and, when detected later, exhibited low coulombic efficiencies (< 1%). Taken together, these results indicate that mixotrophic start-up provides a promising route to accelerate electrode colonisation and enhance early-stage productivity in MES, while highlighting the need for further optimisation and a deeper understanding of microbial interactions.

Carbon capture and utilisation are crucial for reducing fossil fuel dependence and transforming the chemical and energy industries. Microbial electrosynthesis (MES) is a promising technology where electrotrophic microorganisms convert CO₂ into valuable biochemicals using electricity. Despite recent advancements, replicability in MES remains poorly understood, with scarce pre-inoculation abiotic data and limited exploration of abiotic and biotic performance correlations. This study introduces a novel miniaturised reactor, modelled after a state-of-the-art flat-plate directed-flow-through bioelectrochemical reactor (DFBR). Four miniaturised reactors were tested in parallel under abiotic conditions to evaluate the impact of electrode material, reactor design, and assembly on replicability of electrochemical behaviour. Using the dynamic time warping (DTW) algorithm, reactor similarity was quantified for the first time based on electrochemical performance. Kernel scatterplot smoothing on micro-CT data revealed that electrodes, particularly the commonly used carbon felt, are a significant source of variability in electrochemical performance, as further supported by additional abiotic electrochemical tests. Additionally, the miniaturised reactors were inoculated with an enriched mixed culture to examine microbial activity's effect on replicability, achieving concentrations up to 4.55 g L^-1 acetate, 0.96 g L^-1 butyrate, and 0.38 g L^-1 caproate after 60 days. Variations in abiotic conditions, including maximum reachable current density, onset potential, and porosity, influence biofilm growth and performance. The miniaturised DFBR effectively represents the serpentine DFBR, while the adaptable reactor design and proposed statistical methods set a new benchmark for MES research.

Carbon-based products are essential to society, yet producing them from fossil fuels is unsustainable. Microorganisms have the ability to take up electrons from solid electrodes and convert carbon dioxide (CO₂) to valuable carbon-based chemicals. However, higher productivities and energy efficiencies are needed to reach a viability that can make the technology transformative. Here, we show how a biofilm-based microbial porous cathode in a directed flow-through electrochemical system can continuously reduce CO₂ to even-chain C2–C6 carboxylic acids over 248 days. We demonstrate a threefold higher biofilm concentration, volumetric current density, and productivity compared with the state of the art. Most notably, the volumetric productivity (VP) resembles those achieved in laboratory-scale and industrial syngas (CO-H₂-CO₂) fermentation and chain elongation fermentation. This work highlights key design parameters for efficient electricity-driven microbial CO₂ reduction. There is need and room to improve the rates of electrode colonization and microbe-specific kinetics to scale up the technology.

Soil moisture monitoring is essential for a variety of applications including agriculture, forestry, and environmental monitoring. However, soil moisture sensors may be expensive and require batteries or other energy sources, making them unsuitable for remote or off-grid locations and farmers. Improper e-waste management of short-lived sensing components can reveal the contradictions of solutions aimed at environmental sustainability, which also degrade environmental health. Therefore, the development of low-cost, off-grid, biodegradable in-situ soil moisture sensing system (SMSS) is necessary for these regions. This article provides an overview of the current state-of-the-art in low-cost, off-grid, and biodegradable in-situ soil moisture sensing. It highlights low-cost SMSS components including hardware (microcontrollers and communication modules), software, and off-grid ambient energy sources. It also highlights the current research in biodegradable polymers used for moisture sensing. The challenges in combining low-cost, off-grid, and biodegradable soil moisture sensing are identified as a research gap. Finally, the underlining question of the “perfect” choice of SMSS is explored based on the trade-offs of performance, operational feasibility, and the newly proposed aspect of biodegradability, consequently suggesting context-specific decisions by consciously managing these tradeoffs.

Microbial electrochemical technologies (METs) employ microorganisms utilizing solid-state electrodes as either electron sink or electron source, such as in microbial electrosynthesis (MES). METs reaction rate is traditionally normalized to the electrode dimensions or to the electrolyte volume, but should also be normalized to biomass amount present in the system at any given time. In biofilm-based systems, a major challenge is to determine the biomass amount in a non-destructive manner, especially in systems operated in continuous mode and using 3D electrodes. We developed a simple method using a nitrogen balance and optical density to determine the amount of microorganisms in biofilm and in suspension at any given time. For four MES reactors converting CO₂ to carboxylates, >99% of the biomass was present as biofilm after 69 days of reactor operation. After a lag phase, the biomass-specific growth rate had increased to 0.12–0.16 days⁻¹. After 100 days of operation, growth became insignificant. Biomass-specific production rates of carboxylates varied between 0.08–0.37 mol_C mol_X⁻¹d⁻¹. Using biomass-specific rates, one can more effectively assess the performance of MES, identify its limitations, and compare it to other fermentation technologies.

In microbial electrosynthesis (MES), microorganisms grow on a cathode electrode as a biofilm, or in the catholyte as planktonic biomass, and utilize CO₂for their growth and metabolism. Modification of the cathode with metals can improve MES performance, due to their catalytic activity for H2 production, which can be consumed by microorganisms, or via modifying the cathode properties. On the other hand, metals can have an inhibiting effect on MES. While these single roles of metals and their oxides have been identified, an investigation of the simultaneous effects on MES is still lacking. Here, we modify activated carbon (AC) electrodes with nickel (Ni) at high (5%) and low (0.01%) loadings, to investigate its combined effects on MES. Upon Ni impregnation, multiple factors explained the MES performance, including electrocatalytic H2 production, trace element availability, metal toxicity, Ni leaching and redeposition/bio-crystalization. Instead, the electrode surface properties (i.e., surface area and pore structure) were not affected by Ni addition. Compared to unmodified AC, low Ni loading did not improve abiotic H2 production, whereas at high Ni loading a 6-fold increase was observed. During biological experiments, low Ni loading resulted in over a 3-fold increase of acetate production and 35% higher planktonic growth, compared to unmodified AC. Instead, high Ni loading resulted in 25-fold increase of acetate production, 21% decrease of planktonic growth, and improved biofilm growth. Unmodified AC, and low and high Ni loading each resulted in unique microbial community composition. The effect of Ni on MES is therefore concentration-dependent, with apparently different mechanisms of interaction being prevalent at low or high Ni loadings.

Electrocatalytic metals and microorganisms can be combined for CO2 conversion in microbial electrosynthesis (MES). However, a systematic investigation on the nature of interactions between metals and MES is still lacking. To investigate this nature, we integrated a copper electrocatalyst, converting CO2 to formate, with microorganisms, converting CO2 to acetate. A co-catalytic (i. e. metabolic) relationship was evident, as up to 140 mg L-1 of formate was produced solely by copper oxide, while formate was also evidently produced by copper and consumed by microorganisms producing acetate. Due to non-metabolic interactions, current density decreased by over 4 times, though acetate yield increased by 3.3 times. Despite the antimicrobial role of copper, biofilm formation was possible on a pure copper surface. Overall, we show for the first time that a CO2 -reducing copper electrocatalyst can be combined with MES under biological conditions, resulting in metabolic and non-metabolic interactions.

Up to now, computational modeling of microbial electrosynthesis (MES) has been underexplored, but is necessary to achieve breakthrough understanding of the process-limiting steps. Here, a general framework for modeling microbial kinetics in a MES reactor is presented. A thermodynamic approach is used to link microbial metabolism to the electrochemical reduction of an intracellular mediator, allowing to predict cellular growth and current consumption. The model accounts for CO₂ reduction to acetate, and further elongation to n-butyrate and n-caproate. Simulation results were compared with experimental data obtained from different sources and proved the model is able to successfully describe microbial kinetics (growth, chain elongation, and product inhibition) and reactor performance (current density, organics titer). The capacity of the model to simulate different system configurations is also shown. Model results suggest CO₂ dissolved concentration might be limiting existing MES systems, and highlight the importance of the delivery method utilized to supply it. Simulation results also indicate that for biofilm-driven reactors, continuous mode significantly enhances microbial growth and might allow denser biofilms to be formed and higher current densities to be achieved.

Microbial electrosynthesis (MES) allows carbon-waste and renewable electricity valorization into industrially-relevant chemicals. MES has received much attention in laboratory-scale research, although a techno-economic-driven roadmap towards validation and large-scale demonstration of the technology is lacking. In this work, two main integrated systems were modelled, centered on (1) MES-from-CO₂ and (2) MES from short-chain carboxylates, both for the production of pure, or mixture of, acetate, n–butyrate, and n–caproate. Twenty eight key parameters were identified, and their impact on techno-economic feasibility of the systems assessed. The main capital and operating costs were found to be the anode material cost (59%) and the electricity consumption (up to 69%), respectively. Under current state-of-the-art MES performance and economic conditions, these systems were found non-viable. However, it was demonstrated that sole improvement of MES performance, independent of improvement of non-technological parameters, would result in profitability. In otherwise state-of-the-art conditions, an improved electron selectivity (≥36%) towards n-caproate, especially at the expense of acetate, was showed to result in positive net present values (i.e. profitability; NPV). Cell voltage, faradaic efficiency, and current density also have significant impact on both the capital and operating costs. Variation in electricity cost on overall process feasibility was also investigated, with a cost lower than 0.045 € kWh⁻¹ resulting in positive NPV of the state-of-the-art scenario. Maximum purification costs were also determined to assess the integration of a product's separation unit, which was showed possible at positive NPV. Finally, we briefly discuss CO₂ electroreduction versus MES, and their potential market complementarities.