Metal recovery from bottom ash was deemed to be significant to achieve a higher stability of bottom ash and recycle valuable extractable metals. In China, the existing rugged industrial production ignores the actual metal distribution and thus fails to exploit the utilization potential of recoverable metals in bottom ash. Based on these findings, this work was proposed to obtain a comprehensive and in-depth study on the recoverability of metals in bottom ash. First, the particle size distribution and elemental composition of the bottom ash were analyzed. Then, complete information on the recoverable metals in bottom ash fractions with different sizes was obtained by washing, sorting, crushing, density separation and XRF (X Ray Fluorescence) analysis. The results showed that the smaller than 5 mm fraction accounted for up to 60% of the bottom ash, and the 5–20 mm fractions accounted for about 15%. The material characterization revealed that the contents of recoverable Fe, stainless steel, Al and Cu in bottom ash were averagely 9.01%, 0.136%, 0.78% and 0.08%, respectively. About 50% of Fe, 68% of Al, 61% of Cu, and 22% of stainless steel were distributed in smaller than 10 mm fraction. Particularly, Fe was evenly distributed among 0–2 mm, 2–5 mm, 5–10 mm fractions, and the content was between 5.41% and 7.5%. Non-magnetic stainless steel was mainly distributed in 20–40 mm and larger than 40 mm fractions. The highest share of Al was present in the fractions between 5 mm and 20 mm, accounting for 48% of the total aluminum. About 45.6% of the Cu was enriched in the 5–10 mm fraction. However, the Zn content was less than 0.01%. This work provides an in-depth understanding and information on metal recovery as well as promisingly guide ash utilization.

The challenges in the current energy consumption patterns and demand–supply gap are driving the need to develop commercially viable and sustainable alternative fuels that are eco-friendly and efficient. Given the existing alternatives, hydrogen is regarded as the ultimate carbon-less clean and green fuel with high energy density. Considerable efforts are being made to develop catalysts/photo-catalysts for the efficient production of hydrogen from abundantly available water resources via water-splitting process. In this review, the photocatalytic activity of tin oxide-based hybrid photocatalytic materials for increased hydrogen production has been studied. The existing bottlenecks and proposed solutions have also been discussed.

Fly ash, as a byproduct of municipal solid waste incineration, contains several kinds of pollutants, especially dissolvable salts that cause a severe challenge for fly ash disposal. Washing combined with cement kiln co-processing for fly ash disposal has been applied in China. After washing, the wastewater was evaporated to produce fly ash salt (FAS). In this study, FAS was mixed the KCl and LiCl to be used as molten chloride salt for energy storage material. Twenty-three types of molten salts with various ratios of FAS-KCl-LiCl were evaluated. Thermophysical properties (melting point and latent heat) and thermal stability of these salts were characterized. The increase in FAS fraction decreased the latent heat of molten salts. Among the tested samples, the best compatibility ratio of FAS:KCl:LiCl was 10:50:40 (%, in weight), with latent heat of 108.7 J/g and melting point of 333 °C. This molten salt also showed good thermal stability after 1–13 h of thermal experiments, and the mass loss was less than 2% after 5 heating cycles at 600 °C. By corrosion test, FAS-KCl-LiCl (10:50:40, % in weight) could be more safely used in vessels made of nickel-based alloy, but it might cause corrosion risk for stainless steel.

Hydrothermal carbonization (HTC) of food waste can produce hydrochar for further utilization as high-quality fuel or carbon materials, but the by-product of liquid effluent, named HTC wastewater, has a high chemical oxygen demand (COD) content and other organic pollutants. This study focused on the feasibility of Fenton oxidation combined with activated carbon (AC) to reduce COD in HTC wastewater. The effects of different parameters including pH, dosage of hydrogen peroxide, molar ratio of Fe2+/H2O2, and reaction time were tested and discussed. Eventually, through the optimized Fenton oxidation (pH = 3, H2O2 dosage = 1.5 mol/L, Fe2+/H2O2 = 1:15, reaction time = 60 min) combined optimized AC adsorption process (AC dosage = 30 g/L), the COD value reduced from 42,000 mg/L to 3075 mg/L, indicating a COD removal efficiency of 92.7% and a color removal ratio of 91.9%, respectively. The comparison of GC/MS (gas chromatography mass spectrometer) and FTIR (Fourier transform infrared spectrometer) of liquid residual from different treatment methods also indicated that the types of organic substances in HTC wastewater were significantly reduced through Fenton oxidation and AC adsorption.

The production of biohydrogen from biological processes is cleaner and more sustainable than that of fossil fuel-based hydrogen. The drive for cleaner and sustainable energy sources is an important facet of the bioeconomy. Based on these findings, this paper aimed to examine the significance and impact of biohydrogen on the bioeconomy. These bioprocessing strategies are primarily biophotolysis, fermentation and bio-electrolytic systems. Considering that biological processes are slow compared to other thermochemical production processes, production volumes cannot match that of the latter. The inherently slow nature of biochemical reactions taking place in living organisms is a challenge that puts biohydrogen at a disadvantage. Biological processes are also very sensitive to temperature and pH, thereby requiring more intricate process monitoring and control. To obtain equivalent volumes of biohydrogen compared to production strategies, larger and more intricate facilities would be needed, implying more cost implications. It is surmised that biohydrogen will continue to play an important role in the drive for a sustainable bioeconomy despite the current challenges it faces.

The coal-fired flue gas spraying wastewater is a kind of refractory mixed wastewater with poor biodegradability. In this study, the degradation of model coal-fired flue gas spraying wastewater was studied by using discharge free radicals produced by double-dielectric barrier discharge. The degradation rate of pollutants, chemical oxygen demand removal rate and other indicators were detected, and the influence of different conditions on the degradation effect was analyzed. The optimal parameters are as follows: residence time 120 min, input power 170.0 W, initial pH value 3.79, and aeration rate 1.8 mL/min. The initial concentrations of acetone, formaldehyde, chloroform, benzene and toluene were 100, 100, 100, and 100 mg/L, respectively. Furthermore, it is proved that the discharge area is independent of the degradation rate. Through the analysis of the mechanism, it is found that ·OH is an important factor affecting the degradation rate of pollutants in model coal-fired flue gas spraying wastewater.

Energy is a vital input to the economic growth and development of any economic sector. One of the best-known and longest-used sources of renewable energy is biomass. Generating energy from forest resources opens the opportunity for woodlands and other tree areas that can offer natural, environmentally-friendly energy to meet the needs of distant regions that would help protect forest resources. On the other hand, the increases in wastewater for brewery treatment plants could result in a large amount of brewery wastewater sludge (BWWS) generation, which requires proper management before disposal. This research aimed to characterize and produce briquette fuel from the combination of sawdust and BWWS brewery using molasses as a binder. The Composite Briquitte was produced by varying the mixing ratio of sawdust to BWWS 100:0, 90:10, 80:20, 70:30, and 60:40, using 0 to 10% molasses as a binding agent. The proximate, ultimate and calorific value analyses of all composite briquettes were performed according to the American Society Testing of Material standard. It was observed that moisture content increased from 6.2% to 10.2%, fixed carbon decreased from 64.5% to 50.9%, and the caloric value decreased from 24.8 MJ/kg to 14.8 MJ/kg as the proportion of BWWS mixture in composite briquette increased. The binder ratio, hold time, and pressure effects and their interaction on the density and durability index of briquettes were investigated. The findings showed that the optimum density and durability indexes were 1019.99 kg/m3 and 97.274%, respectively, for the binder of 10%, hold time of 4.126 min and pressure of 6.076 MPa. It was concluded that the composite briquettes produced from 10%–20% BWWS proportion sawdust and the sawdust alone have high calorific values ranging from 20.9 MJ/kg to 24.8 MJ/kg, fixed carbon is from 61.18% to 64.5%, ash content is from 4.65% to 10.1%, volatile matter is from 20% to 24.85%, and moisture content is from 6.2% to 8.32%, which is guaranteed to be used for household cooking.

Correction to: Waste Disposal & Sustainable Energy (2022) 4:157–167 https://doi.org/10.1007/s42768-022-00097-0 In this article, the affiliation details for Author Chi Sun Poon were incorrectly given as 'State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China' and 'State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China' but should have been 'Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China' and 'IRSM-CAS/HK PolyU Joint Laboratory on Solid Waste Science, Kowloon, Hong Kong, China'. The original article has been corrected.