Waste Disposal & Sustainable Energy最新文献

The thermal treatment of waste using grate-based systems has gained global acceptance as the preferred method for sustainable management of residual waste. This is because the energy content of the waste is utilized and quality products and residues are produced. Modern Waste-to-Energy (WtE) plants are extremely complex. Sound knowledge of “fuel” waste and its effects on the design and operation of WtE plants is crucial for the successful planning and operation of these plants. To respond to new challenges and/or priorities, developing and implementing innovative technologies is necessary. With long-term global partnerships and innovative grate and combustion technologies, Martin guarantees that in future, residual waste will be treated following ecological and economic constraints and in compliance with international legal requirements.

Plastic has caused serious "white pollution" to the environment, and the highly inert characteristics of plastic bring a major challenge for degradation. Supercritical fluids have unique physical properties and have been widely used in various fields. In this work, supercritical CO₂ (Sc-CO₂) with mild conditions was selected and assisted by NaOH/HCl solution to degrade polystyrene (PS) plastic, and the reaction model was designed using response surface methodology (RSM). It was found that, regardless of the types of assistance solutions, the factors affecting PS degradation efficiencies were reaction temperature, reaction time, and NaOH/HCl concentration. At the temperature of 400 °C, time of 120 min, and base/acid concentration of 5% (in weight), 0.15 g PS produced 126.88/116.99±5 mL of gases with 74.18/62.78±5 mL of H₂, and consumed 81.2/71.5±5 mL of CO₂. Sc-CO₂ created a homogeneous environment, which made PS highly dispersed and uniformly heated, thus promoting the degradation of PS. Moreover, Sc-CO₂ also reacted with the degradation products to produce new CO and more CH₄ and C₂H_x (x=4, 6). Adding NaOH/HCl solution not only improved the solubility of PS in Sc-CO₂, but also provided a base/acid environment that reduced the activation energy of the reaction, and effectively improved the degradation efficiencies of PS. In short, degrading PS in Sc-CO₂ is feasible, and better results are obtained with the assistance of base/acid solution, which can provide a reference for the disposal of waste plastics in the future.

Guimarães is a middle sized city and municipality located in northern Portugal. The municipality has committed to reducing the annual amount of undifferentiated municipal solid waste (MSW) from 371 kg/capita in 2021 to 120 kg/capita by 2030 under the Zero Waste Cities Certification process. In the municipality of Guimarães, one of the constant fractions of MSW composition is textile waste (TW), which the revised EU Waste Framework Directive requires separate collection by 1 January 2025. Therefore, two indicators of TW generation were analysed to identify waste collection routes with a high level of textile waste generation for the priority implementation of separate collection: TW composition in the undifferentiated MSW stream and TW generation per capita. Basic statistical analysis methods were used to process the source data of TW composition in the undifferentiated MSW stream. Cluster analysis was applied to the data set on TW generation per capita, considering the area typology (urban, rural or mixed) of collection routes. It was considered that 39% of the industrial sector of Guimarães consists of textile and clothing production and represents small- and medium-sized enterprises, which can affect TW generation in the undifferentiated MSW stream. Causal-comparative research was used to define the correlation between TW generation per capita and the economic activity of the textile and clothing industry in the municipality. As a result, applying a multi-disciplinary approach, a project of the Textile Waste Generation Map was presented.

Excessive exploitation, negligence, non-degradable nature, and physical and chemical properties of plastic waste have resulted in a massive pollution load into the environment. Consequently, plastic entres the food chain and can cause serious health issues in aquatic animals and humans. The present review summarizes currently reported techniques and approaches for the removal of plastic waste. Many techniques, such as adsorption, coagulation, photocatalysis, and microbial degradation, and approaches like reduction, reuse and recycling are potentially in trend and differ from each other in their efficiency and interaction mechanism. Moreover, substantial advantages and challenges associated with these techniques and approaches are highlighted to develop an understanding of the selection of possible ways for a sustainable future. Nevertheless, in addition to the reduction of plastic waste from the ecosystem, many alternative opportunities have also been explored to cash plastic waste. These fields include the synthesis of adsorbents for the removal of pollutants from aqueous and gaseous stream, their utility in clothing, waste to energy and fuel and in construction (road making). Substantial evidence can be observed in the reduction of plastic pollution from various ecosystems. In addition, it is important to develop an understanding of factors that need to be emphasized while considering alternative approaches and opportunities to cash plastic waste (like adsorbent, clothing, waste to energy and fuel). The thrust of this review is to provide readers with a comprehensive overview of the development status of techniques and approaches to overcome the global issue of plastic pollution and the outlook on the exploitation of this waste as resources.

Agricultural wastes are environmental hazards, as these wastes can catch fire, resulting in the loss of human and animal lives and properties. Alternatively, the wastes are dumped in large spaces, which are already limited. Cementitious composites are quasi-brittle and develop cracks at the micro and nano level, which affect their strength, durability, and esthetics. Transforming agricultural wastes to biochar and using it as fibers in cementitious materials for crack arresting and enhancing fracture toughness is an environment-friendly approach. In this research, nano to microscale carbonaceous inert fibers (biochar) of millet and maize were prepared through pyrolysis followed by ball milling. The X-ray spectroscopy (EDX) revealed that 82.08% and 86.89% of the carbon content was retained in millet and maize, respectively. The scanning electron microscope (SEM) confirmed the presence of angular, flaky, and needle-like particles in the carbonaceous inerts, which may enhance the strength and the fracture response of the cementitious materials. These inerts were added individually to mortar specimens at dosage levels of 0, 0.025%, 0.05%, 0.08%, 0.2% and 1% by mass of cement. The dispersion of the synthesized nano inerts was ensured by UV–VIS spectroscopy. The compressive strength, flexural strength, porosity, and fracture toughness of cement mortar were evaluated. The carbonized nano intrusions reduced the porosity and density of the mortar specimens. The minimum porosity was noted with 1% and 0.08% dosages of millet and maize, respectively, whereas the minimum density was observed at 1% dosage for both. An increase in compressive and flexural strengths was also noticed. The compressive strength increased by 32% and 28% with 0.2% and 0.5% millet and maize, respectively. An increase of 168% and 114% in fracture toughness was noticed at optimized dosages of 0.5% and 1% of maize and millet, respectively. It is concluded that the addition of carbonaceous inert fibers of millet and maize resulted in light-weight porous mortars with enhanced strength and fracture toughness. The fracture toughness increases with dosage as the nanoparticles enhance the tortuosity.

The dual  bag filter (DBF) system is a new polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) emission control technology that has more efficient (PCDD/Fs) removal performance,  a higher activated carbon utilization rate and less activated carbon consumption compared with the traditional single bag filter system. Moreover, few studies have been relevant to the mechanism of the PCDD/Fs removal process in the DBF system, and the selection of operating conditions of the DBF system lacks an academic basis. This study established a PCDD/Fs removal efficiency model of activated carbon injection combined bag filter (ACI+DBF) system for hazardous waste incineration flue gas and predicted  the crucial effect factors. New adsorption coefficients k₁=532,145 Nm³/(mol s) and k₂=45 Nm³/(mol s), and the relationship expression between the number of available adsorption positions of recycled AC (A_AC′) and cycle times (n) are proposed in the model. The results verify that the model error was below 5%. In addition, the PCDD/Fs removal efficiency model predicts that in a certain range, the PCDD/Fs removal efficiency increases with increasing activated carbon injection concentration. The best cycle number of activated carbon was less than 3, and the ratio of circulating activated carbon to fresh activated carbon in second bag filter (SBF) should be controlled at 7–8.

Gasification technology can effectively realize energy recovery from municipal solid waste (MSW) to reduce its negative impact on the environment. However, ammonia, as a pollutant derived from MSW gasification, needs to be treated because its emission is considered harmful to mankind. This work aims to decompose the NH₃ pollutant from MSW gasification by an in-situ catalytic method. The MSW sample is composed of rice, paper, polystyrene granules, rubber gloves, textile and wood chips. Ni–M (M=Co, Fe, Zn) bimetallic catalysts supported on sewage sludge-derived biochar (SSC) were prepared by co-impregnation method and further characterized by X-ray diffraction, N₂ isothermal adsorption, scanning electron microscopy, transmission electron microscopy and NH₃ temperature programmed desorption. Prior to the experiments, the catalysts were first homogeneously mixed with the MSW sample, and then in-situ catalytic tests were conducted in a horizontal fixed-bed reactor. The effect of the second metal (Co, Fe, Zn) on the catalytic performance was compared to screen the best Ni-M dual. It was found that the Ni–Co/SSC catalyst had the best activity toward NH₃ decomposition, whose decomposition rate reached 40.21% at 650 °C. The best catalytic performance of Ni–Co/SSC can be explained by its smaller Ni particle size that facilitates the dispersion of active sites as well as the addition of Co reducing the energy barrier for the associative decomposition of NH species during the NH₃ decomposition process. Besides, the activity of Ni–Co/SSC increased from 450 °C to 700 °C as the NH₃ decomposition reaction was endothermic.

Many growing cities of Sub-Saharan Africa (SSA) are marred by the inefficient collection, management, disposal and reuse of organic waste. The purpose of this study was to review and compare the energy recovery potential as well as bio-fertilizer perspective, from the organic waste volumes generated in SSA countries. Based on computations made with a literature review, we find that the amount of organic wastes varies across countries translating to differences in the energy and bio-fertilizer production potentials across countries. Organic wastes generated in SSA can potentially generate about 133 million GWh of energy per year. The organic waste to bio-fertilizer production potentials range from 11.08 million tons to 306.26 million tons annually. Ghana has the highest energy and bio-fertilizer potential among the SSA countries with a total per capita of 630 MWh/year and 306.26 million tons, respectively. The challenges and technical considerations for energy and bio-fertilizer approaches in the management of organic waste in SSA have also been discussed. This study is of help to the readers and strategic decision makers in understanding the contribution of bioenergy and bio-fertilizer to achieving sustainable development goals, namely, 7 (Affordable and Clean Energy) and 13 (Climate Action) in SSA.