Waste management最新文献

Olive mill wastes (OMW) management by composting allows to obtain valuable fertilizing products, but also implies significant fluxes of greenhouse gases (GHG). For a proper OMW composting, high C- and N co-substrates are necessary, but little is known concerning their effect on GHG emissions in OMW-industrial scale composting. In this study, different co-composting agents (cattle manure (CM), poultry manure (PM), sheep manure (SM) and pig slurry solid fraction (PSSF) as N sources and olive leaves (OLW) and urban pruning residues (UPR) as bulking agents and C sources) were used for OMW composting at industrial scale. Physico-chemical and chemical properties in the composting samples, and GHG (CO₂, CH₄ and N₂O) fluxes were monitored in 12 industrial-scale windrows. GHG emissions were firstly influenced by N source, with the highest accumulated global warming potential (GWP) associated with PM (512 kg CO₂eq pile^-1), since PM composts were associated with the greatest N₂O (0.33 kg pile^-1) and CH₄ emissions (15.67 kg pile^-1). Meanwhile, PSSF was associated with the highest CO₂ emissions (1113 kg pile^-1). UPR as a bulking agent facilitated 10 % greater mineralization of the biomass than OLW, however this C-source was not associated with higher GHG emissions. The results showed that while mineralization dynamics may be impacted by C sources, GHG emissions were mainly conditioned by the characteristics of nutrient-heavy feedstocks (PM and SM). Moreover, manures as nitrogen-laden co-substrates had widely differing effects on total GWP, and that of individual gases, but further research is necessary to understand the mechanisms explaining such differences.

Electric arc furnace dust (EAFD) represents hazardous solid waste that poses substantial environmental risks, necessitating the urgent development of green and efficient recycling methods. Biomass, a renewable and carbon-neutral resource, offers a viable solution. This study proposes a synergistic process that integrates biomass gasification with reducing EAFD. The kinetics of zinc removal during the process were examined, and the synergistic reaction mechanisms between biomass gasification and EAFD reduction were analyzed through PY-GC/MS, SEM/EDS, XRD, TEM, and thermodynamic calculations. The findings demonstrated an exceptional zinc removal efficiency of 99.88%, governed primarily by interfacial chemical reactions. The synergistic reactions mutually enhanced the reduction of EAFD and the reforming of pyrolysis products. Furthermore, the process achieved low carbon emissions owing to the carbon cycle established through coupling reactions between the dust and biomass.

This study compares several methods, such as sodium chlorite, nitric acid, and hydrogen peroxide treatments with alkali pre-treatments, for efficiency of extracting cellulose from spent ground coffee. The extracted cellulose was characterized by Fourier transform infrared spectroscopy (FTIR), x-ray diffractometry (XRD), thermogravimetric analysis (TGA), colour analysis, chemical composition, and particle size analysis. FTIR confirmed the removal of non-cellulosic components from coffee, which correlates with chemical composition and colour analysis results. The highest cellulose content (96.7 %) and the highest whiteness index (71.24) were obtained for the cellulose materials extracted using nitric acid-sodium chlorite and sodium chlorite with alkali pre-treatments, respectively. XRD data reveals that the treated coffee presented exhibited a higher crystallinity index compared to the untreated one. The highest increase in crystallinity index (from 54.9 % to 66.3 %) was achieved for the cellulose extracted using a 20 % hydrogen peroxide treatment with alkali pre-treatment. The maximum degradation temperature of the spent ground coffee increased from 292.0 to 310.5 °C after treatment with 10 wt% hydrogen peroxide and alkali pre-treatment. In summary, these findings highlight the great potential of spent ground coffee as a source of cellulose.

Dewatering plays an important role in kitchen waste reduction and resource utilization; however, the mechanism of water combination and removal remains unclear. In this study, dimethyl ether solvent was used to investigate the water occurrence state and dewatering pattern in kitchen waste, and the key organic components, hydrophilic functional groups, and water removal mechanism were clarified. The results showed that all the water existed in the state of organic-bound water, in which proteins were the key organic matters affecting dewatering and the hydrophilic functional groups CO/CN, CO, and amine-N. combined with water through hydrogen bonding were the key mechanisms. Through competition with hydrophilic functional groups, dimethyl ether released 54.83-87.85% of the water to the liquid phase, while the hydrophilic components and hydrophilic functional groups were retained in the solid phase. Simultaneously, the addition of additives verified that enhanced disruption of hydrogen bonding between water and hydrophilic functional groups could improve the dewatering efficiency. It was concluded that more attention should be paid to reducing or disrupting the hydrogen bonding of hydrophilic functional groups on the surface of the solid phase with water to improve the kitchen waste dewatering performance.

Friction cleaning can effectively remove the paint coating (adhesive organic impurities) on the surface of waste glass, and promote the closed-loop recovery of urban silicic acid resources in industrial applications. However, due to a large number of mechanical collisions and wear during use, it is easy to produce powder dust and organic waste gas, and the pollution characteristics and mechanism have not been studied. In this study, the ball milling experiment was designed and the pollutants were tested and evaluated. The results show that a large number of micro/nano meters glass particles with an average size of less than 4.5 μm are generated by low-speed ball milling, and the risk of inhalation is as high as 50.75 mg/kg·m³. Main organic waste gases include cyclopropane, hexane, but-2-ene, and benzene with the value of Incremental lifetime cancer risk reaching 3.4 × 10^-2 indicating definite carcinogenic risks for benzene exposure. The C-C bond between hydroxyl acrylic acid molecules and the C-O bond between phenolic propylene oxide molecules are easily broken to form small molecular chains, and the complex product is due to the complex cross-linking with the silane coupling agent. It is suggested that a special dust collector for micro/nano meters glass particles should be added while adopting an activated carbon catalytic combustion process to treat VOCs in the exhaust gas. This study revealed the contamination of micro/nano meters glass particles and benzene during friction cleaning to remove organic coatings in waste glass recycling.

This study presents finite element method (FEM) modeling with COMSOL Multiphysics to estimate the thermal properties of a waste landfill through back-analysis of temperature responses from buried thermistors during a full-scale multi-week active thermal response test. Field tests were conducted at the Loraas MSW landfill in Saskatoon, Canada, using instrumented equipment, including a vertical borehole heat exchanger and thermistor strings. The test consisted of two phases: a heat injection test during the summer and a heat extraction test in the winter. The study focused on a landfill 25 m deep, observing temperature changes at various depths over time. The effect of heat generation rate (HGR) on landfill temperature was investigated. Thermal conductivity and volumetric heat capacity increase with depth, with close alignment between summer and winter results, validating the tests. This research enhances the understanding of thermal parameters in MSW landfills by combining field tests and numerical modeling, offering insights into landfill behavior in cold climates. These findings hold significance for optimizing geothermal energy recovery from such landfills, calibrating thermal parameters for coupled models in landfills, and improving waste management practices.

The recycling of paper and board (PB) yields economic and environmental advantages compared to primary paper production. However, PB from lightweight packaging (LWP) waste is currently not comprehensively reintegrated into the paper value stream. To develop an adapted recycling process for PB from LWP, PB quantities, qualities, and fluctuations ranges in LWP are required. Currently, no sufficient database is available. Therefore, we developed a methodical approach and conducted a case study to access the PB potential in LWP sorting plants using manual analysis and sensor-based material flow monitoring. Differences resulting from seasonal variations, materials from different settlement structures, and fluctuation ranges in LWP composition over two weeks have been investigated. PB contents in the input of 6.5 wt% (ww) and 5.9 wt% (ww) were determined for winter and summer sampling campaigns, respectively. The PB product stream amounted to 5.7 wt% (ww, winter) and 4.8 wt% (ww, summer). Around 45 wt% (ww) of PB from the PB product stream was classified as misplaced by the consumer and should have been discarded in separate paper collections. Based on the determined PB quantities and qualities, a potential of usable and in the PB product stream available PB in LWP was determined. The technically available and usable PB potential in German LWP waste amounts to 89,000 to 100,000tons per year (average PB yield of around 65 wt% (ww)). The methodical approach can be adapted for sorting plant balances. The results can contribute to developing an adapted recycling process for PB from LWP.