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Appropriate management of waste containing mercury is important. However, reducing greenhouse gases (GHGs) associated with this process is equally important, warranting research into waste management methods that emit the least amount of GHGs. We evaluated GHG emissions from recycling systems of spent fluorescent lamps and dry cell batteries discarded by households in Japan using a life cycle assessment technique. The results show significant GHG reduction from resource recovery; therefore, it is essential to ensure that resource recovery is conducted properly. Regarding the spent fluorescent lamp recycling system, the transportation process contributes a large amount of GHG emissions if the waste is not crushed. It is recommended that they be crushed before being transported to improve transportation efficiency. The larger the population of a city, the lower the per-capita collection of waste containing mercury. Due to the hazardous nature of mercury, it is necessary to encourage its separate collection. The demand for mercury will decrease in the future, and it is possible that collected mercury will be disposed of through chemical stabilization. This study clarifies no significant, less than 0.01 kg-CO2e/kg-waste, increase in GHG emissions associated with the transition from mercury recycling to chemical stabilization.

This study presents a sustainable method for recycling zinc–carbon batteries by electrochemically exfoliating spent graphite electrodes to produce graphene oxide (GO), followed by green reduction with palm oil leaf extract to form reduced graphene oxide (rGO). GO sheets were exfoliated from graphite electrodes under varying applied potentials, and the palm oil leaf extract served as a green reducing agent for GO. The physical, morphological, and electrochemical properties of the rGO were characterized, revealing that exfoliation at 4.5 V yields high‐quality GO. The resulting rGO outperformed GO in supercapacitor applications, demonstrating a significantly higher specific capacitance of 35.5 F g −1 compared to GO’s 0.5 F g −1 . This eco‐friendly approach not only enhances the electrical conductivity and stability of the recycled rGO but also contributes to sustainable material development for high‐performance energy storage applications.

In lithium metal batteries, the cycle life relevantly declines with decreasing electrolyte amount. The capacity decay is kinetically reasoned as shown by rises in cell resistances, in particular for the discharge processes, as indicated by the full capacity recovery during a constant voltage step after discharge at the end of life (EOL). Interestingly, adding fresh electrolyte after EOL only partially recovers the capacity, suggesting a different and more crucial failure origin than the assumed loss of charge carriers due to the electrolyte “dry‐out”. Contrary to the cathode, the anode has higher resistances and a thicker surface layer post mortem, which is also observed in Li‖Li cells. In addition, the resistance portion of the electrolyte itself remains comparatively low during cycling, suggesting that resistance rise is dominated by the Li anode and is confirmed by exchange with fresh Li, where the capacities are recovered toward initial values, again. Based on the observations, a mechanism with a faster dry‐out of Li metal pores is proposed, which decreases the electrolyte‐accessible Li metal surface area, enhances local current densities, and facilitates high surface area and dead lithium. This continuously clogs and blocks the surface, reducing the practical accessible Li and eventually causing the rollover fade. The cycle life of lithium metal batteries decreases with decreasing electrolyte amount. This study shows that the rising cell resistance is not driven by electrolyte dry‐accessible Li metal surface area, enhances local current densities, and facilitates high surface area and dead lithout, but by Li metal pore depletion, which shrinks the active area, raises local current density, favors high‐accessible Li metal surface area, enhances local current densities, and facilitates high surface area and dead lithsurface‐accessible Li metal surface area, enhances local current densities, and facilitates high surface area and dead litharea Li deposition, and ultimately deactivates Li via clogging the surface by dead Li.

Indiscriminate disposal of dry cell battery (DCB) waste contributes to environmental and public health issues in developing countries such as Ghana, due to the toxic nature of this specific waste. Accordingly, a study was conducted in Accra, Ghana, to determine the socio-economic and demographic factors influencing handling DCB waste, aiming a sustainable environment. Using a random sampling technique, a descriptive cross-sectional survey was conducted, encompassing 367 respondents from the Accra-Tema Metropolitan areas and Tema West Municipal Assembly in Greater Accra, Ghana. Using descriptive and multivariate statistical methods, the survey data were analysed with the Statistical Package for Social Sciences (SPSS) version 27. The results of this study show that female gender and residential area are likely to positively influence the use of DCB at home. Education significantly affects the use of DCB and its proper disposal. The results also suggest that 78% of the respondents disposed of DCB waste in waste bins. The mean monthly income of the respondents stands at USD 270, which is average and likely partially to positively influence the disposal of the DCB. The data collected revealed that female gender, age group, family size, and education level influence the indiscriminate disposal of DCB waste and DCB waste recycling. The results highlight that educated females above the age of 55, with a monthly income, are likely to properly segregate DCB waste. This study contributes to the knowledge gap in relation to dry cell battery waste management (DCBWM) in developing countries, aiming to advance global sustainability. This study is expected to contribute to educate and create awareness in managing DCB waste to reduce its indiscriminate disposal which leads to environmental pollution and negatively affects human health and environmental sustainability in Ghana.

Maintaining the optimum growth rate and estimating the concentration of microalgae are critical in improving microalgae production. An efficient concentration assessment of microalgae is essential for a timely and effective determination of the harvest period. This study proposes the luminance and viscosity methods to predict the concentration of microalgae. Image analysis was applied to measure the concentration of native microalgae: Desmodesmus sp., Scenedesmus sp., Dictyosphaerium sp., and Klebsormidium sp. The experiments were performed using different concentrations of the dry cell weight (DCW) of these microalgae species. A dual-camera device was used to capture the images of the DCW solution in a flask. For the confirmation of viscosity, a viscometer was used to determine the concentration of microalgae. A comparative analysis was performed between the data from the image analysis and viscosity method. The results from the viscosity method showed a higher accuracy with R2 = 0.9784 and the luminance method with R2 = 0.8266. Further investigations revealed that the brightness of the DCW image had a limitation at a specific concentration where the color was unrecognized. The current image processing method has the potential to be applied in an outdoor cultivation facility for real-time data acquisition. Both methods have advantages in terms of required time and experimental costs. The image analysis method provides an alternative way to efficiently monitor the cultivation and harvesting of microalgae.

Transition metal compounds with a high affinity for oxygen in dry cell configurations, such as MnO 2 , Mn 3 O 4 , and Zn x Mn 3 O 4−x , exhibit exceptional electrocatalytic properties in the oxygen evolution reaction (OER). However, the disposal of these dry cell materials, unlike that of rechargeable batteries, poses environmental hazards. In this study, we focused on optimizing these manganese oxides for energy-related applications, specifically OER. To achieve this goal, we investigated the electrocatalytic behaviour of both used and fresh dry cells in OER. Our results show that the used dry cell material achieved a current density of 10 mA·cm −2 at an overpotential of 525 mV, whereas the fresh dry cell required an overpotential 100 mV higher to reach the same current density. We further characterized the nature of these fresh and used materials using various techniques, including x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and contact angle measurements. The enhanced activity of the used dry cell can be attributed to the formation of highly active Mn 3 O 4 from MnO 2 and graphene oxide under discharging conditions.

This work aims to study the production of oxyhydrogen gas by a small low-cost prototype consisting of six dry cells. Firstly, a molecular composition study of the gas was carried out, presenting concentrations of 67% H2 and 28% O2. The deviation from the stoichiometric yield is discussed to be caused by water vapor production and/or oxygen dissolution in the liquid phase. Secondly, an efficiency study was done, considering the ratio between the reversible voltage of an electrolytic cell and the voltage applied to the dry cell by an external power source. Different working conditions (electrolyte concentration, 3% (w/w) of KHO and 20% (w/w) of KHO) have been tested to analyze their effect on the efficiency of the system. The results show that a lower electrolyte concentration increases the applied cell voltage, and so the necessary power input for gas production to occur, resulting in lower cell efficiency. Overall, the efficiencies are below 69.8 ± 0.6% for the studied electrolyte concentrations and approach approximately the same value around 50% for higher powers.

SignificanceAlthough the electrochemical reduction of CO2 into chemicals has been actively explored to address climate change, the products are mainly limited to C1-3 products. Herein, we show that the integration of CO2 electrolysis with microbial fermentation can efficiently produce value-added multicarbon products such as poly-3-hydroxybutyrate (PHB) from gaseous CO2. This biohybrid system comprises electrochemical conversion of CO2 to formate and subsequent biological conversion of formate to PHB by Cupriavidus necator. Optimization of the system to secure suitable conditions for both conversions allowed continuous production of PHB with high titer and productivity which is two orders of magnitude higher than the reported values. This work proposes an exceptional strategy for lowering CO2 emission and producing environmentally friendly bioplastics. Converting anthropogenic CO2 to value-added products using renewable energy has received much attention to achieve a sustainable carbon cycle. CO2 electrolysis has been extensively investigated, but the products have been limited to some C1-3 products. Here, we report the integration of CO2 electrolysis with microbial fermentation to directly produce poly-3-hydroxybutyrate (PHB), a microbial polyester, from gaseous CO2 on a gram scale. This biohybrid system comprises electrochemical conversion of CO2 to formate on Sn catalysts deposited on a gas diffusion electrode (GDE) and subsequent conversion of formate to PHB by Cupriavidus necator cells in a fermenter. The electrolyzer and the electrolyte solution were optimized for this biohybrid system. In particular, the electrolyte solution containing formate was continuously circulated through both the CO2 electrolyzer and the fermenter, resulting in the efficient accumulation of PHB in C. necator cells, reaching a PHB content of 83% of dry cell weight and producing 1.38 g PHB using 4 cm2 Sn GDE. This biohybrid system was further modified to enable continuous PHB production operated at a steady state by adding fresh cells and removing PHB. The strategies employed for developing this biohybrid system will be useful for establishing other biohybrid systems producing chemicals and materials directly from gaseous CO2.

High-purity Mn is necessary for high strength steel production. However, the availability of metal Mn is limited to a few countries. Therefore, as an alternative to direct purchasing of metal Mn, a process for Mn recovery was investigated. Waste dry cell batteries are considered to be one of the most feasible Mn sources. We have developed a high efficiency chemical separation system. This system consists of a three-phase chemical treatment. In the first phase, the metal components of the waste dry cell batteries were dissolved by acid, along with a reducing agent. Afterward, the undissolved carbon particles were separated by filtration. In the second phase, the dissolved Mn was selectively precipitated as manganese oxide by O3 oxidation. Then, the precipitated manganese oxide was separated from the other metal components by filtration. Finally, in the third phase, the manganese oxide was reduced to high-purity Mn using an electric furnace.

Ectoine, a compatible solute synthesized by many halophiles for hypersalinity resistance, has been successfully produced by metabolically engineered Halomonas bluephagenesis , which is a bioplastic poly(3-hydroxybutyrate) producer allowing open unsterile and continuous conditions. Here we report a de novo synthesis pathway for ectoine constructed into the chromosome of H. bluephagenesis utilizing two inducible systems, which serve to fine-tune the transcription levels of three clusters related to ectoine synthesis, including ectABC , lysC and asd based on a GFP-mediated transcriptional tuning approach. Combined with bypasses deletion, the resulting recombinant H. bluephagenesis TD-ADEL-58 is able to produce 28 g L −1 ectoine during a 28 h fed-batch growth process. Co-production of ectoine and PHB is achieved to 8 g L −1 ectoine and 32 g L −1 dry cell mass containing 75% PHB after a 44 h growth. H. bluephagenesis demonstrates to be a suitable co-production chassis for polyhydroxyalkanoates and non-polymer chemicals such as ectoine. Halomonas bluephagenesis is a halophilic platform bacterium for next generation industrial biotechnology. Here, the authors employ a stimulus response-based flux-tuning method for coproduction of bioplastic PHB and ectoine under open unsterile and continuous growth conditions.