Life cycle assessment of three different management options for spent alkaline batteries

The reduction of the carbon footprint of municipal solid waste management via source classification and supporting strategies: An analysis for the megacity of Shenzhen

Municipal solid waste (MSW) management is a critical concern in megacities that depend heavily on external material and energy inputs but lack space for waste disposal. MSW treatment is a significant contributor to carbon emissions. The implementation of source classification improved the overall MSW management system and enhanced resource recovery from MSW. However, the precise contribution of source classification to carbon emissions reduction remains unclear. This study aimed to analyze the carbon emissions evolution in the MSW management of Shenzhen, a prototypical megacity in China, using data from 2006 to 2020 and employing carbon footprint assessment methodologies. The results demonstrated that source classification reduced the carbon emissions from 0.19-0.25 to 0.14-0.18 t CO2-eq/t MSW when considering the contribution of the urban environmental sanitation management department. The entire MSW management system becomes a carbon sink when considering recyclables collected by commercial enterprises. Although the source classification complicated the collection and transportation of MSW, the carbon offset effect of recycling food waste and recyclables was more significant than that of carbon emissions from collection and transport. Moreover, the landfill gas recovery rate critically influenced the carbon emissions of landfill-based MSW management systems. In contrast, the recovery of plastics was crucial for determining carbon emissions from incineration-based MSW management systems.

The (un)shared responsibility in the reverse logistics of portable batteries: A Brazilian case

The Brazilian National Solid Waste Policy (BNSWP) determines that reverse logistics (RL) of waste batteries is mandatory and adopts the principle of shared responsibility among stakeholders. In this work, we sought to diagnose the current state of the RL chain for batteries in Vale do Aço, Brazil, and identify challenges and potentialities related to its improvement. Data were obtained by means of questionnaires sent to the main stakeholders involved in the batteries RL chain and by consultation of official Brazilian databases. The results showed that the main obstacles to the implementation of the RL of portable batteries in the region are: the lack of information by consumers and retailers regarding the BNSWP and management of waste batteries; the existence of few collection and consolidation points in the region; lack of municipal waste management plans; and lack of sustainability of waste picker organizations. The identified potentialities were: the good receptivity of environmental education actions by the population; the possibility of taking advantage of direct logistics of local retail chains to collect waste; the existence of a special waste management and transportation company in the region; and the existence of waste picker organizations interested in integrating the RL system. Finally, by a SWOT analysis, strategies for the implementation of a more effective RL system were drawn up. This work can serve as a basis for the structuring and implementation of the batteries RL system at the Metropolitan Region of Vale do Aço (MRVA) and can be a reference for other settings.

Direct recovery of Zn from wasted alkaline batteries through selective anode's separation

In the present study, a leaner process for recovering zinc from spent alkaline batteries is studied at a laboratory scale. Such process is part of a diagram, under development, that aims at maximizing the value of all the battery components while reducing the costs of treatment and the environmental footprint involved in recycling this waste. It starts by a physical and selective pre-treatment stage that separates the anode from the remaining components followed by neutral leaching (three washing cycles at room temperature, S/L ratio of 1/5 (w/v), magnetic stirring for 15 min and settling during 45 min), acid leaching of the washed solid (4 mol/L of sulphuric acid, S/L ratio of 1/3 (w/v), 120 min at room temperature under magnetic stirring) and, finally, electrowinning of zinc from the pregnant leach solution (100 mA/cm², 120 min under slow magnetic stirring). By leaching the anode alone, it is possible to obtain a solution rich in zinc (86 g/L), with very low concentration of other metals (<0.08 g/L). Such solution was adequate for zinc electrowinning, allowing an average recovery rate of 58%, without applying any purification stages, at the same time regenerating sulphuric acid for its recirculation. In conclusion, the results demonstrate that a more specific physical pre-treatment stage is highly desirable to recycle spent alkaline batteries in order to reduce the number of stages involved and the overall complexity, thus, reducing the costs involved and the potential environmental impacts, while maintaining high recovery rates of zinc.

Environmental Trade-Offs of Downcycling in Circular Economy: Combining Life Cycle Assessment and Material Circularity Indicator to Inform Circularity Strategies for Alkaline Batteries

The application of circularity strategies to improve resource use and recovery should be considered with their potential impacts on the environment. Their effectiveness could be evaluated by combining the material circularity indicator (MCI) and life cycle assessment (LCA) methods. Environmental trade-offs may be underestimated for some strategies given that the loss of material quality with recycling has not been captured within the methodological framework of MCI. The current study demonstrates how significantly this limitation may influence the trade-offs in a case study. The methods are applied to several scenarios for the circularity improvement of alkaline batteries. The joint interpretation of MCI and LCA scores is carried out using waterfall charts and normalized indicator scores. Results suggest that improving circularity generally reduces environmental impacts, although there is large variability among two sets of values. For example, an increase of MCI score by 14% for two recycling scenarios translates to a small reduction of impacts in one case (0.06–1.64%) and a large reduction in another (9.84–56.82%). Observations from the case study are used to discuss the design and scope of MCI use and its combining with LCA. Lastly, we draw on the opportunities of the new comparative approach.

Simultaneous recovery of Zn and Mn from used batteries in acidic and alkaline mediums: A comparative study

A parallel study of acidic and alkaline leaching for the recovery of Mn and Zn from spent alkaline batteries is outlined. Using H₂SO₄ as solvent and selecting appropriate conditions of temperature and concentration, all residues were dissolved except carbon. The separation and recovery of the two components were performed by electrodeposition with satisfactory results at pH values above 4 (current efficiency above 70% for Zn and Mn) but rather lower efficiencies as the pH decreased. Most of the Zn was selectively dissolved by alkaline leaching using a 6.5M NaOH solution, and its recovery was examined by means of both electrochemical and chemical processes. The expected formation of pure Zn by electrowinning failed due to the formation of ZnO, the content of which was highly dependent on the electrodeposition time. For short periods, Zn was the main component. For longer periods the electrodeposit consisted of agglomerated microparticles of ZnO with a minor fraction of Zn metal (barely 3% as measured by X-ray diffraction). A chemical reaction of the element with oxygen released at the anode surface might be responsible for its conversion to ZnO. A simple chemical route is described for the first time for the direct conversion of Zn(OH)₄^2- solution to nanostructured ZnO by lowering the pH to values around 12 using 2M HCl solution.

Recovery of zinc and cadmium from spent batteries using Cyphos IL 102 via solvent extraction route and synthesis of Zn and Cd oxide nanoparticles

The overall aim of this study is to separate and recover zinc and cadmium from spent batteries. For this purpose Cyphos IL 102 diluted in toluene was employed for the extraction and recovery of Zn and Cd from Zn-C and Ni-Cd batteries leach liquor. The influence of extractant concentration for the leach liquors of Zn-C (0.01-0.05mol/L) and Ni-Cd (0.04-0.20mol/L) batteries has been investigated. Composition of the leach liquor obtained from Zn-C/Ni-Cd spent batteries is Zn - 2.18g/L, Mn - 4.59g/L, Fe - 4.0×10^-3g/L, Ni - 0.2×10^-3g/L/Cd - 4.28g/L, Ni - 0.896×10^-1g/L, Fe - 0.148g/L, Co - 3.77×10^-3g/L, respectively. Two stage counter current extraction at A/O 1:1 and 3:2 with 0.04mol/L and 0.2mol/L Cyphos IL 102 for Zn and Cd, respectively provide more than 99.0% extraction of both the metal ions with almost negligible extraction of associated metal ions. A stripping efficiency of around 99.0% for Zn and Cd was obtained at O/A 1:1 using 1.0mol/L HNO₃ in two and three counter current stages, respectively. ZnO and CdO were also synthesized using the loaded organic phase and characterized using XRD, FE-SEM and EDX techniques. XRD peaks of ZnO and CdO correspond to zincite and monteponite, respectively. The average particle size was ∼27.0nm and ∼37.0nm for ZnO and CdO, respectively. The EDX analysis of ZnO and CdO shows almost 1:1 atomic percentage.

Using life cycle assessment to address stakeholders' potential for improving municipal solid waste management

Because the consumption of materials is generally higher than their recovery rate, improving municipal solid waste (MSW) management is fundamental for increasing the efficiency of natural resource use and consumption in urban areas. More broadly, the characteristics of a MSW management system influence the end-of-life (EOL) impacts of goods consumed by households. We aim to indicate the extent to which greenhouse gas emissions from a MSW management system can be reduced by increasing waste paper recycling. We also address the stakeholders' contribution for driving transition towards an improved scenario. Life cycle assessment (LCA) addresses the EOL impacts of the paper industry, driven by the characteristics of MSW management in Florianópolis, Brazil, by varying the level of stakeholders' commitment through different recycling scenarios. The results show that 41% of the climate change impacts from waste paper management could be reduced when increasing the waste paper recycling rates and reducing waste paper landfilling. To achieve such emissions reduction, the industry contribution to the MSW management system would have to increase from 17% in the business-as-usual scenario to 74% in the target scenario. We were able to measure the differences in stakeholders' contribution by modelling the MSW management system processes that are under the industry's responsibility separately from the processes that are under the government's responsibility, based on the Brazilian legal framework. The conclusions indicate that LCA can be used to support policy directions on reducing the impacts of MSW management by increasing resource recovery towards a circular economy.

Enhanced recycling network for spent e-bicycle batteries: A case study in Xuzhou, China

Electric bicycles (e-bicycles) are a primary means of commuting in China because of their light weight, speed, and low maintenance costs. Owing to short service life and environmental pollution hazards, recycling and reuse of e-bicycle batteries has always been a focus of industry and academia. As a typical case of both production and use of large electric bicycles, 113 major sellers, 378 corporate and individual buyers, 147 large e-bicycle repair centers, and 1317 e-bicycle owners in Xuzhou City were investigated in order to understand the sales, use, recycling, and disposal of spent e-bicycle batteries. The findings show that the existing distempered recycling system is the main limitation of spent battery recovery, and the actual recovery rate of spent batteries is lower than the estimated output (QW) for the years 2011-2014. Electric bicycle sellers play a fundamental role in the collection of spent batteries in Xuzhou, accounting for 42.3±8.3% of all batteries recovered. The widespread use of lithium batteries in recent years has resulted in a reduction in spent battery recycling because of lower battery prices. Furthermore, consumer preferences are another important factor affecting the actual recovery rate according to survey results evaluated using canonical correspondence analysis. In this paper, we suggest that a reverse logistics network system for spent battery recycling should be established in the future; in addition, enhancing producer responsibility, increasing publicity, raising of public awareness, developing green public transport, and reducing dependence on e-bicycles also should be pursued. This study seeks to provide guidance for planning construction and management policies for an effective spent battery recycling system in China and other developing countries.

Selective leaching of Zn from spent alkaline batteries using environmentally friendly approaches

The main aim of this work was to evaluate the possibility of using microwave or ultrasound to assist the efficient and selective leaching of Zn from spent alkaline batteries and compare the results with those obtained using the conventional method. Two different strategies were applied: acid leaching of a washed residue and alkaline leaching of the original residue. In both (acid and alkaline) approaches, the use of microwave- or ultrasound-assisted leaching increased the extraction of Zn compared with the best results obtained using conventional leaching [acid leaching (1.5mol/L H₂SO₄, 3h, 80°C), 90% of Zn extracted; alkaline leaching (6mol/L NaOH, 3h, 80°C), 42% of Zn extracted]. With acid leaching, 94% of the Zn was extracted using microwave-assisted leaching (1 cycle, 30s, 1mol/L H₂SO₄), and 92% of the Zn was extracted using ultrasound-assisted leaching (2min, 0.1p, 20% amplitude, 1mol/L H₂SO₄). Ultrasound-assisted leaching resulted in a more selective (Zn/Mn ratio of 5.1) Zn extraction than microwave-assisted leaching (Zn/Mn ratio of 3.5); both processes generated a concentrated Zn solution (⩾18.7g/L) with a purity (83.3% and 77.7%, respectively) that was suitable for electrowinning. With alkaline leaching, microwave- (1 cycle, 3 min, 4mol/L NaOH) and ultrasound-assisted (14min, 0.1p, 20% amplitude, 4mol/L NaOH) leaching extracted about 80% of the Zn and less than 0.01% of the Mn, which resulted in lesser concentrated Zn solutions (approximately 16.5g/L) but with high purity (>99.5%) that was suitable for the recovery of Zn by precipitation. The microwave- and ultrasound-assisted leaching strategies used in this work proved to be efficient and environmentally-friendly approaches for the extraction of Zn from spent alkaline residues since a concentrated Zn solution with adequate purity for subsequent Zn recovery was obtained using significantly decreased leaching times and concentrations of chemicals.

A facile chemical route for recovery of high quality zinc oxide nanoparticles from spent alkaline batteries

Recycling of spent domestic batteries has gained a great environmental significance. In the present research, we propose a new and simple technique for the recovery of high-purity zinc oxide nanoparticles from the electrode waste of spent alkaline Zn-MnO2 batteries. The electrode material was collected by the manual dismantling and mixed with 5M HCl for reaction with a phosphine oxide reagent Cyanex 923® at 250°C for 30min. The desired ZnO nanoparticles were restored from the Zn-Cyanex 923 complex through an ethanolic precipitation step. The recovered particle product with about 5nm diameter exhibited fluorescent properties (emission peak at 400nm) when excited by UV radiation (excitation energy of 300nm). Thus, the proposed technique offered a simple and efficient route for recovering high purity ZnO nanoparticles from spent alkaline batteries.