Waste management最新文献

Manure is a renewable feedstock, whose theoretical potential for biogas production is scarcely deployed due to modest methane yields that prevent economic feasible operation of anaerobic digestion plants. Steam explosion pretreatment has the potential to improve the digestibility of manure, however it is energy intensive, and the optimal conditions depend on the feedstock. In this work, the solid and the liquid fraction of separated dairy cattle manure were pretreated between 130 and 210 °C for 5 to 40 min by steam explosion to individually determine the optimal conditions for each fraction. Additionally, mass balances for volatile solids (VS), cellulose, hemicellulose and proteins were performed to better understand the effects of the pretreatment. For the manure solids, a pretreatment at 130 °C for 20 min was most effective, the biomethane potential (BMP) improved by 40 %. In contrast, the BMP of the liquid fraction could not be improved at any pretreatment condition. The mass balances showed that at more severe conditions up to 18 % of the VS were lost by decomposition and/or evaporation, with the proteins being the most thermolabile fraction. Based on the observation, that a pretreatment of the liquid phase can be omitted, a heat integrated plant concept is suggested where the necessary heat input is only as large as in conventional anaerobic digestion. Taken together, this work underlined the benefits of steam explosion pretreatment of manure and identified the prevention of VS loss as a promising avenue for further improving the process.

In contemporary times, global plastic waste production has doubled in comparison to two decades ago, with only 9% effectively recycled. The polymer industry is undergoing a transition to address the disparity between plastic production and end-of-life waste management. Chemical recycling offers a solution by converting plastic waste into its constituent building blocks, or monomers, which can be utilized in the production of new, high-quality plastics. This concise review provides an overview of conventional chemical recycling technologies employing heated reactors, before delving into ongoing efforts towards electrifying the chemical recycling process. A conceptual framework for a fully electrified value chain aimed at achieving plastics circularity is outlined and analyzed. Additionally, attention is given to the challenges posed by industry inertia towards adopting electrified technologies, as well as performance issues stemming from the intermittent nature of renewable energy sources and the availability of long-duration renewable electricity storage options.

Micro-aeration pretreatment has emerged as a promising technology for improving the performance of anaerobic bioreactors in the treatment of lipid-rich organic waste, particularly in mitigating the accumulation of long-chain fatty acids (LCFAs). Micro-aeration intensity is a critical factor in optimizing substrate hydrolysis and methanogenesis efficiency. In this study, optimal micro-aeration intensities for acetoclastic (30 mL-air/g-COD) and overall methanogenesis (7.5 mL-air/g-COD) were initially determined using acetate and glucose as substrates, respectively. Subsequently, the addition of 0.5 mM oleate (a typical LCFA) increased cumulative methane production by 22.1 % when acetate was used as the substrate after 30 mL-air/g-COD micro-aeration pretreatment. Conversely, it decreased cumulative methane production by 17.3 % when glucose was used as the substrate after 7.5 mL-air/g-COD micro-aeration pretreatment. Additionally, the population of facultative hydrolysis microorganisms, such as the genus Pseudomonas, increased by 25.7 % and 27.8 % when acetate and glucose were used as substrates, respectively. Furthermore, the predominant methane-producing archaea, including the genus Methanosarcina, increased by 27.3 % when acetate was used as the substrate, while the genus Methanosaeta decreased by 65.3 % when glucose was used as the substrate. Collectively, these findings provide insights into the methanogenesis pathway under optimal micro-aeration pretreatment conditions, guiding future research in this field.

Incinerated sewage sludge ash (ISSA) with high P₂O₅ content is a potential phosphorus resource that can replace the non-renewable phosphorus rocks. However, extracting phosphorus from ISSA using hydrometallurgical methods also dissolves a large amount of impurity metals into the leachate. Therefore, this study proposes a new method combining high-temperature reaction with CaO addition, selective leaching, and chemical precipitation for efficient and low-cost phosphorus recovery from ISSA. During thermal treatment at 1050 °C, the addition of CaO significantly influenced the types and amounts of phosphate mineral phases in ISSA. When 20 % CaO was added, the Al/Fe-phosphate phases were completely converted into acid-soluble Ca-phosphate phases, while Al and Fe were retained in acid-insoluble phases (e.g., Al- and Fe-containing oxides and silicates). Subsequently, by controlling the pH of acidic leachate (2.0 to 1.5), Ca-phosphate phases were selectively dissolved. At a pH of 1.5, better selective leaching was achieved, with a leaching efficiency of 94.71 % for P and less than 10 % for Al, Fe and Si. The XRF results showed that the majority of SiO₂ (38.39 %), Al₂O₃ (33.26 %) remained in the post-leaching solid residue, which was expected to be further resource utilization. Without purification treatment to remove Al, Fe and Si, almost all phosphate ions were precipitated at pH = 8.5, with P recovery efficiency of 94.07 %. XRD results showed that the precipitate was mainly composed of HAP, with a P₂O₅ content of 37.51 % and low level of contaminants, thereby realizing the effective recovery of phosphorus from ISSA.

In the modern electronics industry, with the rapid development of technology and the quick turnover of electronic products, the production of electronic waste (e-waste) has also dramatically increased. Among these, discarded capacitors are a significant component of e-waste. These old capacitors not only contain harmful chemicals but are also rich in economically recoverable precious metals like Nb and Ag. This study specifically aims to enhance the classification of discarded capacitors to enable more efficient recycling and resource recovery.Traditional methods of capacitor classification mainly rely on manual identification, which is inefficient and limited in accuracy. To enhance the efficiency and accuracy of classification, this study introduces, for the first time, the combination of Laser-Induced Breakdown Spectroscopy (LIBS) technology and machine learning for the classification of capacitors. The Backpropagation Artificial Neural Network (BP-ANN) algorithms can be trained to automatically identify and classify discarded capacitors. To achieve better performance, we developed a novel algorithm called the Optimized Feature Extraction Variance Algorithm (OFEVA), which addresses the limitations of existing methods by significantly improving the accuracy of the classification model. Compared to training with principal component scores data from traditional Principal Component Analysis (PCA), training with OFEVA achieves higher classification accuracy and computational efficiency.This innovative approach not only helps increase the recycling rate of discarded capacitors and reduce environmental pollution but also provides significant technical support for the reuse of resources, thereby making an important contribution to the fields of environmental protection and resource recycling. In addition, the spectral lines of pure niobium have been calibrated for the first time in this paper, providing important data for further spectroscopic studies.

Polyvinyl chloride (PVC) is a polymer comprised of more than 50% chlorine that offers unmatched versatility at low expense. PVC is irreplaceable in several applications, such as construction materials, medical applications, and cables. This versatility and tunable properties come at the cost of complex formulations for the product and challenging end-of-life (EoL) options for PVC waste. Pure collected and sorted PVC is already recycled successfully to some extent, yet, when PVC ends up in a mixed plastic waste stream, it can be detrimental to the recycling process. PVC waste and its effects at various concentrations remain a focal point for both scholars and policymakers. In this review, the narrative begins at the naissance of PVC and continues to investigate the EoL valorization options when the products are inevitably discarded. Strategies for PVC waste recycling and the technical and legal challenges regarding each method are discussed, focusing on the European recycling market. An effective solution to handle EoL PVC requires a combination of policies and schemes for proper collection and sorting of specific waste streams and considering all available technologies to select the right tools. This review can support appropriate policies and the selection of suitable methods of recycling PVC waste.

Monitoring campaigns to collect and characterize urban park litter have been carried out in Italy annually from 2018 to 2023. A total of 274 urban parks in 108 cities (with 745 inhabitants to 2.7 million) were monitored. The citizen science approach was applied, and each campaign involved yearly an average of 416 volunteers coordinated by Legambiente. An adaptation of the sampling protocol proposed by the Marine Strategy Framework Directive (MSFD) Technical Group on Marine Litter (2008/56/CE) was applied. In total 161,293 (mean value 26,882.2 ± 4,743.4) items were collected within 42,300 m² (density 3.82 items/m²). Cigarette butts are the most widespread waste: 36.3 % ± 5.5 % and up to 25 butts/m² were found. Significant amounts of metal (16.2 %), glass/ceramics (13.0 %) and paper/cardboard (10.7 %) were found. Despite the COVID emergency having ended in 2021, during the 2022 monitoring campaign face masks only represent 0.2 % of the total waste items. No correlation was found between the amount of waste and the number of inhabitants or the geographical position of the city. The population density was poorly correlated with the quantity of waste collected while a slight correlation was evidenced by the presence of plastic bottles which seem to have decreased in recent years. Using the FTIR Spectroscopy 19 different polymers were identified. The most common were cellulose acetate (cigarette butts) polyethylene and polypropylene. Following the application of recent SUP regulations, polylactic acid and starch blended biopolymers were found (till 0.3 %). Finally, the presence of highly degraded polymers was observed.

Municipal solid waste (MSW) management has become a critical issue today, posing substantial economic, environmental, and social challenges. Identifying and analyzing dominant themes in this field is essential for advancing research and policies towards sustainable MSW management practices. This study aims to explore the key issues related to MSW management that have been addressed by both the scientific community and policymakers through funded projects. By doing so, the study seeks to guide the scientific community as a knowledge producer and the EU as a key funder. Two Latent Dirichlet Allocation (LDA) models were applied to analyze the themes from two corpora: one representing scientific literature and another focusing on EU-funded projects. Additionally, this analysis was complemented by a quantitative estimation of the similarity between the two corpora, providing a measure of alignment between the scientific community and policymakers. The results generally indicate that the two spheres are aligned and highlight the diversity of topics explored by the scientific community. Nevertheless, it is concluded that there are opportunities for further research on specific topics, such as leaching and the extraction of heavy metals. Additionally, the popularity of topics identified in European Union-funded projects has fluctuated considerably over time, focusing primarily on waste management rather than its prevention. In light of these findings, waste prevention emerges as a promising avenue for future EU-funded research initiatives.

Reducing CO₂ and pollutant emissions is a global priority. Waste glass recycling is more effective in achieving this goal compared to producing new glass. A crucial step in waste glass recycling is removing adhesive impurities from the glass surface. Hydraulic cleaning generates organic wastewater, leading to its gradual replacement in China by anhydrous cleaning, a novel technology that avoids wastewater generation. However, CO₂ and pollutant methyl methacrylate are still produced during anhydrous cleaning, and their formation mechanisms were previously unclear. This study explores these mechanisms and finds that the existence of glass interface increases the length of C≡N bond of binder by 0.239 Å, which promotes the bond's fracture and the formation of methyl methacrylate in exhaust gas. Iron in waste glass increases the length of C = O bond by 0.263 Å, facilitating the bond's fracture and reducing the proportions of methyl methacrylate and CO₂ by 7.31 % and 18.01 %, respectively. Therefore, it is recommended to modify the existing recycling process of waste glass by arranging iron removal after anhydrous cleaning to reduce CO₂ and methyl methacrylate production. This paper is the first time to report the mechanisms and approaches for reducing CO₂ emission and controlling gaseous pollutant in waste glass recycling.

Pyrometallurgy has proven to be a highly effective method for the large-scale recycling of waste printed circuit boards (WPCB) in industrial settings. This study focused on the fast pyrolysis characteristics of WPCB at smelting temperatures and characterized the gas product release behavior and solid product features in detail. The results indicate that the pyrolysis gas was mainly composed of H₂, CH₄ and CO, and the maximum yield of pyrolysis gas was obtained at 1300 °C, which was 233.66 mL/g. The retention of copper and tin decreased from 98.61 % and 92.39 % to 87.98 % and 70.66 %, respectively, when the temperature increased from 800 °C to 1300 °C. The structure of the glass fibers in the WPCB remained invariant, whereas the carbon fraction progressively tended to graphitize. The results of Py-GC/MS analysis indicate that high temperatures and extended residence times were more favorable for the formation of small molecules such as alkenes and aromatics and inhibited the production of brominated contaminants.