Waste Disposal & Sustainable Energy最新文献

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.

Graphical abstract

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.

Graphical abstract

The present research work aims to explore the potency of piranha solutions at the best-optimized concentrations, i.e., 40% and 30% to reduce the recalcitrant and heterogeneous structure of wheat straw, and the treated wheat straw was denoted as WS40 and WS30. The effect of pretreatment on wheat straw was determined by anaerobic digestion (AD) in a batch mode, followed by the analysis of soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFAs). After pretreatment, the surface fibers shattered and detached, showing a distorted surface of wheat straw. An increase in the crystallinity of wheat straw after pretreatment was also observed due to the removal of amorphous cellulose and lignin. Enhancement in methane yield was obtained on the 9th day, which was 103±6.92 and 99.33±0.57 mL/d for WS40 and WS30, respectively. Displaced water measurement revealed that the pretreatment of wheat straw minimized the hydrolysis period by 14 days. It also improved the methane yield by 2.65 (WS40) and 2.45 (WS30) fold in comparison with the control which yielded 35.66 mL/d methane on the 23rd day. The modified Gompertz model (MGM), logistic function model (LFM) and transference function model (TFM) adequately described the degradation process and explained the kinetic behavior of the cumulative methane yield. Among the three models, MGM was found to fit best for the methane yield of WS40 and WS30.

Graphical abstract

As one of the main oxygen-containing organic products generated from the hydrothermal conversion of biomass, levulinic acid (LA) has the potential to be further upgraded. This work investigated the steam reforming (SR) process of biomass-derived LA to produce H₂. A series of Ni catalysts supported by various spinels were synthesized via co-precipitation and impregnation. The Ni active metal dispersed well on the NiAl₂O₄ catalyst with high specific surface area, thereby exhibiting high catalytic activity. Among all the catalysts tested, 15Ni/NiAl₂O₄ showed the best performance for SR of LA, resulting in high carbon conversion of 96.3%, H₂ yield of 92.8%, and H₂ concentration of 67.9% at a reaction temperature of 800 °C. Additionally, the influences of reaction temperature, steam-to-carbon ratio (S/C), and liquid hourly space velocity (LHSV) were also examined. Moreover, during the 40-h continuous SR process of LA, the 15Ni/NiAl₂O₄ catalyst maintained its outstanding catalytic activity. This study provides an encouraging route for upgrading biomass-derived LA into eco-friendly and high-value fuels, thereby advancing the sustainability of the biomass refining process.

Graphical abstract

Elevated price of chemical fertilizers and poor nutrient content in conventional organic sources such as municipal solid waste (MSW) compost necessitate the production of nutrient enriched compost which could serve as a potential alternative organic fertilizer option. We studied three types of amended compost that were prepared by mixing 20% mustard oil cake (MOC) and 30% poultry manure (PM) or cow dung or sugarcane press mud (SPM) with 50% MSW compost. Trichoderma viride was inoculated into every type of compost. The rate of amended or unamended MSW compost application was 10 t ha⁻¹. The use of different amendments improved the nutrient level of MSW compost, of which the N increment was remarkable, ranging from 1.14% N (unamended compost) to 2.9%–3.22% N depending on the types of amendment. A field experiment was conducted to evaluate performances of the amended MSW composts on the yield and nutrient content of potato (variety BARI Alu25). All compost treatments except the sole MSW compost treatment produced significantly higher tuber yields than the sole fertilizer treatment. The press mud based MSW compost + fertilizer treatment produced the highest tuber yield of 31.6 t ha⁻¹ (65% increase over 100% fertilizers and 57% increase over 100% compost treatment). The tuber N concentration varied from 0.128% to 0.594%, P from 0.018% to 0.035%, K from 0.213% to 0.313% and S from 0.020% to 0.053%, with the highest result recorded with press mud + fertilizer treatment. The use of amended composts had residual effects on soil N, P, K and S contents. Thus, the treatment containing 50% fertilizer+50% compost mixture (MSW:MOC:SPM in a ratio of 5:2:3) performed the best followed by PM amended compost. It is concluded that integrated use of 10 t ha⁻¹ organic amended MSW compost with chemical fertilizers can ensure higher crop yield, nutrient content and sustained soil fertility in nutrient-deficient sub-tropical soil.

This study was carried out in a full-scale (50 t/d) rotary kiln incinerator to explore the removal characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) by different units of air pollution control devices (APCDs), and special interest was focused on the “memory effect” phenomenon of PCDD/Fs in the wet scrubber (WS), which usually caused an undesirable rise in PCDD/F emission concentrations. The general removal efficiency of PCDD/Fs by APCDs was 99.4% (from 14.11 at exhaust heat boiler (EHB) outlet to 0.09 ng I-TEQ/Nm³ at stack) under medical waste (MW) incineration condition, and 99.2% (from 19.91 to 0.16 ng I-TEQ/Nm³) under hazardous waste (HW) incineration condition. The PCDD/F concentrations in flue gas decreased along the APCDs except for WS, in which the “memory effect” was observed. In detail, WS largely increased the I-TEQ concentration of gas-phase PCDD/Fs from 0.047 to 0.188 ng I-TEQ/Nm³ in the flue gas, and the concentration of particulate-phase PCDD/Fs increased from 0.003 to 0.030 ng I-TEQ/Nm³. In addition, this study found that phase migration promoted the accumulation of PCDD/Fs in scrubbing water, and the flow entrainment phenomenon played a great role in causing the “memory effect”. The PCDD/F concentrations of fly ash collected from cyclone and fabric filter (FF) were as high as 4.23 and 6.99 ng I-TEQ/g, respectively, which had exceeded the national landfill limitation (3 ng I-TEQ/g) in China. The system balance calculations revealed that APCDs promoted the migration of PCDD/Fs from the gas-phase to the particulate-phase, which caused fly ash to be the main carrier of PCDD/Fs and led to excessive emissions. The results of this study can contribute to the optimized design of combustion conditions and system cleaning for controlling PCDD/F emissions from rotary kiln incinerators.

One of the most misunderstood technologies in some parts of the world and widely adopted technologies in others is the recovery of energy and materials by the controlled combustion of post-recycling wastes. This technology is commonly called waste-to-energy, or simply WTE. After all possible efforts for recycling or composting wastes, there remains a large post-recycling fraction that is either landfilled or used as fuel in WTE power plants that also recover metals and minerals. Several nations, e.g., Switzerland, Japan, Sweden, Belgium, Denmark, and Germany, have succeeded in phasing out landfilling by processing all theãir post-recycling municipal solid wastes (MSW) in WTE power plants. This paper reviews the evolution and importance of WTE in the twenty-first century, with special focus on the world’s largest economies: the EU, US, and China.

Graphical abstract

The pyrolysis of poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) catalyzed by five alkaline earth metal-based minerals/wastes, namely calcined dolomite, calcite, magnesite, calcium carbide slag (CCS), and ophicalcitum, was conducted by a pyrolyzer-gas chromatography-mass spectrometer (Py-GC-MS) with the objective of recovering benzenes-enriched oil. Compared with magnesium-based catalysts and pure CaO, the calcium-based catalysts with calcium hydroxide as the main component performed better catalytic effect, which could simultaneously promote the hydrolysis of ester products and the decarboxylation of aromatic acids after hydrolysis. For PET, the addition of solid base catalysts at 600 °C promoted the complete degradation of aromatic acids and aryl esters, which accounted for 32.6% and 30.7% of the pyrolysis oil, respectively. The content of benzene in oil increased from 8.8% to 31.7%–78.8%. For PBT, the addition of solid base catalysts at 600 °C completely decomposed the aromatic acids, which accounted for 67.1% of the pyrolysis oil, and the content of benzene in oil increased from 12.3% to 34.5%–81.0%. During the deoxygenation of polyester pyrolysis products, increasing temperature was more effective for the decomposition/conversion of acetone and tetrahydrofuran, while increasing the alkalinity of the reaction environment contributed to the rapid decrease in acetaldehyde and aryl ketone contents.