Waste Disposal & Sustainable Energy最新文献

Microbial electrolysis cell (MEC) is a potential technology to meet the increasing interest in finding new sources of energy that will not harm the environment. MEC is an alternative energy conversion technology for the production of biofuels. It is possible to produce hydrogen by fermenting biogenous wastes with hydrogen-producing bacteria. This study investigated the biohydrogen production from co-substrates using electrogenic bacteria such as Escherichia coli, Salmonella bongori, and Shewanella oneidensis in pure culture and as a co-culture, which has the potential to be used as co-substrate in MECs. Briefly, 150 mL working-volume reactors were constructed for batch biohydrogen production. The hydrogen production rate (HPR) from the co-substrate was maximum at a ratio of 75:25 g/L with a co-culture of 2.35 mL/(L h). Fabricated a single-chamber membrane-free microelectrolysis cell to evaluate the power density, current density, voltage, HPR, chemical oxygen demand (COD) removal efficiency and Columbic efficiency. Scanning electron microscope (SEM) imaging confirmed the binding of electrogenic bacteria to anode and cathode. The efficiency of electrical conductivity of MEC was analyzed by three different electrodes, namely, nickel, copper and aluminum. The HPR was high using nickel when compared to the other two electrodes. The HPR of a single chamber using a nickel electrode was 2.8 HPR ml/L H₂ d⁻¹ and provided a power density of 17.7 mW/m² at pH 7. This study suggests that the nickel cathode in a single chamber could be a promising sustainable source for stable power generation.

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Electrical and electronic waste (e-waste) has become a global crisis. Managing this ever-growing problem has become very critical and yet challenging, especially in the South Asian region; otherwise, it may undermine the sustainability of development and growth of numerous industries. Hence, to explore the current context of e-waste management, recycling, and strategies in Sri Lanka, we conducted a systematic literature review process using peer-reviewed research articles retrieved from Google Scholar Database. We searched for articles containing keywords such as “e-waste”, “management strategies and recycling”, and “Sri Lanka”. We screened out papers (n = 20) selected from papers (n = 327) initially retrieved over a 17 period of time (2005–2022). The analysis of the screened articles showed that the main challenges to successful e-waste management were a lack of management strategies, policies, and inadequate recycling practices as well as identifying the potential and opportunities to actively enhance the comprehensive awareness, collection, storage, proper disposal, and other e-waste management steps in Sri Lanka. Further, the study identified technological, financial, socio-economic, and institutional sectors as fundamental sectors to formulate a strategic plan for e-waste management. Also, the study suggests that enacting laws to practice and adopt e-waste management, establishing central command and management institutes to control all e-waste management bodies, providing financial assistance to informal e-waste collectors and recyclers, and introducing e-waste management to school curricula are some of the possible actions that can be taken along with enhancing the awareness of  e-waste management.

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Biobed is a smart bioremediation system used to treat point-source pesticide contamination. Biomixture is the main component of biobeds, and pesticide dissipation is affected by its composition. This study aimed to compare the effectiveness of compost-based (C) versus peat-moss-based (P) biomixtures of biobeds on tested pesticide dissipation. Three concentrations (25, 50, and 75 mg/kg) of chlorpyrifos, pendimethalin, and thiophanate methyl were added separately and as a mix to both biomixtures C and P. Our data showed the effect of biomixture type on the dissipation of the tested pesticides. For chlorpyrifos, its dissipation rate in biomixture P was more rapid than that in biomixture C. This result was confirmed by the mineralization kinetic experiment, since 25% of the initial ¹⁴C-chlorpyrifos concentration accumulated in the form ¹⁴CO₂ in biomixture P compared to only 14% in biomixture C. In addition, the chlorpyrifos dissipation rate was influenced by the initial concentration when applied individually in biomixture P. In contrast, biomixture C was more effective at pendimethalin dissipation than biomixture P, since >76% of pendimethalin was dissipated in biomixture C versus 67% in biomixture P at the same incubation time. For thiophanate-methyl, the abilities of both biomixtures C and P were similar and less efficient than those of the other tested pesticides. The addition of the three tested pesticides to biomixture C only had a positive effect on both chlorpyrifos and thiophanate-methyl dissipation, while pendimethalin dissipation was similar when applied separately or as a mix. Microbial activity was stimulated by the addition of separately or mixed pesticides to biomixtures C and P as measured by dehydrogenase activity.

The waste-to-energy (WTE) technologies are now recovering energy and materials from over 300 million tonnes of municipal solid wastes worldwide. Extensive studies have investigated substituting natural construction materials with WTE residues to relieve the environmental cost of natural resource depletion. This study examined the beneficial uses of WTE residues in civil engineering applications and the corresponding environmental standards in Europe, the U.S., and China. This review presents the opportunities and challenges for current technical approaches and the environmental standards to be met to stabilize WTE residues. The principal characteristics of WTE residues (bottom ash and fly ash) and the possible solutions for their beneficial use in developed and developing countries are summarized. The leaching procedures and environmental standards for pH, heavy metals, and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) are compared. The current practice and engineering properties of materials using WTE residues, including mixtures with stone aggregate or sand, cement-based or hot-mix asphalt concrete (pavement), fill material in the embankments, substitute of Portland cement or clinker production, and ceramic-based materials (bricks and lightweight aggregate) are comprehensively reviewed.

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Excessive construction activities generate huge quantities of waste that are disposed of in nearby sites, leading to environmental degradation. Recycling the concrete fractions of construction wastes for their utilization as aggregates has been predominant among industrialists and researchers in recent years. However, the smearance of cement mortar on the recycled aggregates affects the concrete properties. Fewer treatments were developed to remove the weak cement mortar or seal the micro-pores on the adhered cement mortar of recycled aggregates. This paper investigates the comparative efficiency of acid and carbonation treatment on recycled coarse aggregate (RCA) properties and its behaviour on recycled aggregate concrete (RAC). The RCA was treated with HCl acid at 0.1 mol/L, 0.5 mol/L, and 0.8 mol/L and CO₂ at 0.1 bar, 0.2 bar, and 0.4 bar and tested for their physical properties, and the concrete mixtures with treated recycled aggregates were tested for fresh and hardened properties. It could be observed that the properties of RAC were affected owing to the smearance of weak mortar, whereas for the concrete with carbonated (RACc) and chemically treated aggregates (RACa), the concrete properties tended to improve. The strength of RAC was 28.59% less than that of normal aggregate concrete (NAC), whereas the strength of RACc and RACa was enhanced by 16.44% and 9.7% compared to that of RAC at 28 days. The water absorption of RAC was 47.51% more than that of NAC, whereas the water absorption of RACa and RACc was 28.67% and 33.75% lesser than RAC. Pre-soaking the RCA with acids removes the adhered mortar due to its acidic activity. In contrast, in carbonation, the CO₂ reacts with the Ca(OH)₂ on the cement mortar to form CaCO_3, filling the micro-cracks in the cement mortar on the RCA.

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Activated carbon (AC) has attracted tremendous research interest as an electrode material for supercapacitors owing to its high specific surface area, high porosity, and low cost. However, AC-based supercapacitors suffer from limited rate performance and low power density, which mainly arise from their inherently low electrical conductivity and sluggish ion dynamics in the micropores. Here, we propose a simple yet effective strategy to address the aforementioned issue by nitrogen/fluorine doping and enlarging the micropore size. During the treatment, the decomposition products of NH₄F react with the carbon atoms to dope the AC with nitrogen/fluorine and simultaneously enlarge the pores by etching. The treated AC shows a higher specific surface area of 1826 m² g⁻¹ (by ~ 15%), more micropores with a diameter around 0.93 nm (by ~ 33%), better wettability (contact angle decreased from 120° to 45°), and excellent electrical conductivity (96 S m⁻¹) compared with untreated AC (39 S m⁻¹). The as-fabricated supercapacitors demonstrate excellent specific capacitance (26 F g⁻¹ at 1 A g⁻¹), significantly reduced electrical resistance (by ~ 50%), and improved rate performance (from 46.21 to 64.39% at current densities of 1 to 20 A g⁻¹). Moreover, the treated AC-based supercapacitor achieves a maximum energy density of 25 Wh kg⁻¹ at 1000 W kg⁻¹ and a maximum power density of 10,875 W kg⁻¹ at 15 Wh kg⁻¹, which clearly outperforms pristine AC-based supercapacitors. This synergistic treatment strategy provides an effective way to improve the rate performance and power density of AC-based supercapacitors.

Forced aeration is one of the promising ways to accelerate landfill reclamation, and understanding the relation between aeration rates and waste properties is the prerequisite to implementing forced aeration under the target of energy saving and carbon reduction. In this work, landfill reclamation processes with forced aeration were simulated using aged refuses (ARs) of 1, 4, 7, 10, and 13 disposal years, and the potential of field application was also investigated based on a field project, to identify the degradation rate of organic components, the O₂ consumption efficiency and their correlations to microbes. It was found that the removal rate of organic matter declined from 20.3% (AR₁) to 12.6% (AR₁₃), and that biodegradable matter (BDM) decreased from 5.2% to 2.4% at the set aeration rate of 0.12 L O₂/kg waste (Dry Matter, DM)/day. A linear relationship between the degradation rate constant (K) of BDM and disposal age (x) was established: K = − 0.0002193x + 0.0091 (R² = 0.854), suggesting that BDM might be a suitable indicator to reflect the stabilization of ARs. The cellulose/lignin ratio decrease rate for AR₁ (18.3%) was much higher than that for AR₁₃ (3.1%), while the corresponding humic-acid/fulvic-acid ratio increased from 1.44 to 2.16. The dominant bacteria shifted from Corynebacterium (9.2%), Acinetobacter (6.6%), and Fermentimonas (6.5%), genes related to the decompose of biodegradable organics, to Stenotrophomonas (10.2%) and Clostridiales (3.7%), which were associated with humification. The aeration efficiencies of lab-scale tests were in the range of 5.4–11.8 g BDM/L O₂ for ARs with disposal ages of 1–13 years, and in situ landfill reclamation, ARs with disposal ages of 10–18 years were around 1.9–8.8 g BDM/L O₂, as the disposal age decreased. The increased discrepancy was observed in ARs at the lab-scale and field scale, indicating that the forced aeration rate should be adjusted based on ARs and the unit compartment combined, to reduce the operation cost.

Oil-based drill cuttings (OBDCs) are hazardous wastes generated during shale gas exploration, and the rapid, efficient and safe disposal methods for OBDCs have attracted the attention of many researchers. Plasma pyrolysis technology is widely used in solid waste treatment due to its extremely high temperature and reaction activity. A laboratory-scale thermal plasma pyrolysis system was built to investigate the plasma pyrolysis mechanism of simulated OBDCs. The thermal decomposition characteristics of OBDCs were studied by thermogravimetric-derivative thermo gravimetric-differential scanning calorimetry (TG-DTG-DSC) analysis in the range of 50–1300 °C. The thermal decomposition process of OBDCs was divided into the following four stages: evaporation of water and light oil, evaporation and decomposition of heavy oil, carbonate decomposition, and phase change reaction from solid to liquid. The effects of the oil ratio, water content, and water/oil (W/O) ratio of OBDCs on the composition and gas selectivity of pyrolytic gas were investigated. The results show that thermal plasma can crack the mineral oil in the OBDCs into clean gases such as H₂, CO and C₂H₂, while water can promote the decomposition of the heavy oil molecules and enhance the H₂ production. The energy consumption model calculation for the pyrolysis and melting of OBDCs shows that the highest energy utilization and the lowest molar energy consumption of H₂ were achieved at a W/O ratio of 1:4. Based on the thermal plasma pyrolysis system used in this study, the commercial application prospects and economic benefits of the plasma pyrolysis of OBDCs were discussed.

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Extensive use of fossil fuel has led to an increase in solid and gaseous particulates in the environment, which in turn necessitated newer, effective, and economical control strategies to abate pollutants, particularly gaseous pollutants. In the current research work, focus has been placed on utilizing industry wastes to adsorb nitrogen oxides present in diesel engine exhaust, which is pre-treated by plasma. Sampled exhaust from a 5 kW diesel generator is exposed to discharge plasma where the oxidation of nitric oxide to nitrogen dioxide occurs, which is then made to flow through another reactor filled with industry wastes drawn from agriculture, foundry, utility, marine industry, etc., comprising mulberry waste, rice husk, wheat husk, areca nut husk, sugarcane bagasse, coffee husk, foundry sand, lignite ash, red mud, and oyster shells. While the adsorption of nitrogen dioxide was observed in all the wastes, reduction of nitric oxide was observed in metallic compound-based industry wastes. At about 184 J/L, specific energy plasma cascaded industrial waste red mud yielded 98% NO_x removal efficiency, and that with agriculture rice husk waste yielded 53% NOx removal. TiO₂/Fe₂O₃ present in industry wastes might have exhibited photo-catalysis in visible light resulting in the possible reduction of NO. A new pathway for recycling the waste can be expected through nitrogen dioxide adsorption, and the results are further discussed with respect to plasma-alone and cascaded plasma adsorbent systems.

Rice is the prominent food grain required by more than half of the world's population to fulfill their nutritional demand. With the continuous growth in the population at the global level, rice production has also been elevated. However, high rice production also creates a new problem in waste management worldwide. Rice straw, generated after rice harvest, possesses meager nutritional value, due to which it is less preferred as fodder and burned in the field. Paddy burning is one of the major causes of air pollution, leading to lung, heart, eye, and skin-related diseases and even premature death. This stubble burning also decreases soil fertility. In this review article, we have discussed the various economic uses of paddy straw which will help to reduce air pollution through the decline in paddy straw burning. Biochar is produced from paddy straw, which can be mixed into the soil to restore fertility and reduce toxic metals' bioavailability. The generation of biofuels such as biobutanol, bioethanol, and biogas from rice straw with their mechanism of synthesis is also discussed in this article. Rice straw can also be utilized in the preparation of solid fuel. Along with this, mushroom cultivation in paddy straw houses is also described. Paddy straw can be used for the pulp and paper industries, which will help to reduce the tree dependence of these industries. Apart from this, a bibliometric analysis of the Scopus database on rice straw uses for the last 20 years was done, including a bibliographic keyword analysis to show published documents' trends. This review will give an elaborated overview of the alternative uses of rice straw with a quantitative analysis of air pollution caused by paddy straw burning. This review will also help to improve the current uses of paddy straw for industrial and commercial benefits to make it more economical.

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