Intensive land use has several detrimental effects on land function and imposes an undue burden on the environment. Continuous farming and pollution by heavy metals have negatively influenced many soils. Biochar is now gaining attention as a major research subject in the areas of agriculture, environment, and energy as an eco-friendly soil conditioner. The use of biochar for agricultural and environmental purposes has been widely studied and reviewed. Unfortunately, there are few reviews on biochar structures and other biochar uses. This review presents an overview of current developments in the effects of numerous biochar physicochemical properties and biochar uses, such as utilization as a soil microbial activity, contaminant adsorbent, ion exchange, soil amendment, gas storage and water retention. The physical, chemical and biological properties have been discussed following amendments to the soil and conditions of preparation. However, scientific observation and research are required to identify the negative effects of biochar in preparations and applications. It is envisaged that further in-depth studies of biochar amendment will lead to a deeper understanding of biochar's relationships with soils and that reviews of the negative impacts of biochar could reveal ways in which they might be mitigated.

Ammonia (NH3) synthesis via electrocatalytic nitrogen reduction generally suffers from low NH3 yield and faradaic efficiency. Compared with activating stable, low-solubility N2, the electrochemical conversion of nitrates to ammonia provides a more reasonable route for NH3 production. Herein, we introduce Ar-plasma to enhance the interaction between copper-nickel alloys and carbon substrate to improve the performance of NH3 production. The NH3 faradaic efficiency from nitrate is nearly 100% and the yield rate is over 6000 \({\mathrm{\mu g}}_{{\mathrm{NH}}_{3}}{\mathrm{cm}}^{-2}{\mathrm{h}}^{-1}\). DFT (density functional theory) calculation reveals the high performance of Cu50Ni50 originates from the lower energy barrier on the reaction path and the closer position to the Fermi level of the d-band center. This work offers a promising strategy for plasma-modified electrocatalyst to promote ammonia synthesis via nitrate reduction.

A novel selective catalytic reduction (SCR) catalyst with high catalytic activity on chloroaromatic organics at lower temperatures (160–180 ℃) is critical for municipal solid waste incineration (MSWI) plants. This study prepares a series of honeycomb-type VOx/TiO2 catalysts and finally develops a new low-temperature catalyst with high catalytic activity in eliminating chloroaromatic organics. Based on the conversion efficiency (CE) of 1,2-dichlorobenzene (1,2-DCB) and CO2 selectivity, the optimal VOx content of 4.06% (in weight) in VOx/TiO2 catalyst is first confirmed. By modifying CeOx and WOx, a novel honeycomb-type catalyst of VOx–CeOx–WOx/TiO2 achieves the highest CE (93.1%–93.6%) and CO2 selectivity (40.9%–60.7%) at 150–200 ℃. It was found that the CeOx and WOx can improve the catalytic activity by enriching the surface content of V and O, increasing the proportion of V5+ and Osurf, enlarging the supply source of reactive oxygen species and their storage capacity, and accelerating the redox cycle of VOx, CeOx, WOx, and reactive oxygen species. This study can guide the development of monolithic low-temperature catalysts with high catalytic activity in eliminating chloroaromatic organics in MSWI flue gas.

Coal fly ash (CFA) is the main combustion residue of fine ground coal in the process of coal-fired thermal power generation, and crude glycerol (CG) is the byproduct of biodiesel production. The novel polyurethane/CFA (PU/CFA) foam composites were prepared from CFA and CG. Two kinds of CFA, CFAI and CFAII were used as fillers for the property enhancement of PU/CFA composites, and the effects on foaming behavior and the reinforcement for the PU/CFA composites were investigated. It was found that the addition of CFA can prolong the rising time and tack-free time, and the maximum rising time and tack-free time increased to 40 s and 42 s. Meanwhile, the maximum compressive strength of PU/CFAI and PU/CFAII increased to 0.2186 MPa and 0.2284 MPa with the addition of CFA. The thermogravimetric analysis showed that the PU/CFA composites underwent three stages of thermal decomposition, and the amount of carbon residue increased from 23.11% to 67.91% with increasing CFA dosage. Moreover, the values of the limit oxygen index increased from 21.5% to 23.7% with the incorporation of CFA into the PU foam matrix, indicating that CFA improved the thermal stability and flame retardant performance of the composites. This study provided a new method for the recycling and high-value utilization of CG and CFA.

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.

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.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.

Microwave steam pyrolysis (MSP) is an innovative thermochemical approach to converting biomass into high-quality biochar using steam to improve the dielectric heating of microwave radiation. Biochar shows high fixed carbon and carbon contents at a maximum temperature of 550 °C in 10 min. The MSP achieved a heating rate of 112 °C/min from 200 °C to 400 °C to produce biochar effectively. Furthermore, the thermal properties of biochar in microwave heating were investigated in this study to explore its potential as a microwave heat-absorbent material. Microwave is able to perform volumetric and controllable heating to the biochar. Moreover, biochar shows good microwave heat absorbency, storing and transferring heat effectively. The temperature profile of three different sizes of biochar was investigated to examine the efficiency of biochar in heat absorption from microwave radiation. It was found that the powder form of biochar showed a higher heat transfer rate of 40 °C/min and a low cooling rate of 7.5 °C/min. The presented results are useful for evaluating the application of biochar as a promising medium for heat storage systems.

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.

Solid waste management is a severe challenge in India due to massive and rapid growth in waste generation rates, environmental difficulties, and financial constraints for proper treatment. Poorly managed municipal solid waste (MSW) has substantial negative consequences for society, including financial and aesthetic harm, contamination of natural resources, environmental pollution, and severe health danger. Both qualitative and quantitative factors are required to select the appropriate solid waste treatment and disposal technologies. Multi-Criteria decision-making tools helped in analyzing solid waste in terms of qualitative and quantitative factors. In this paper, seven criteria and their sub-criteria are selected for ranking solid waste treatment and disposal technology using fuzzy-analytic hierarchy process. The results showed that composting is the most suitable option for solid waste treatment and disposal technology, followed by refuse-derived fuel. The incineration and sanitary landfills are the least preferred MSW management alternatives. The sensitivity analysis reveals a high consistency, robustness, and stability level.

Empty fruit bunch (EFB) is an industrial waste that is abundantly available in Malaysia. Traditionally, EFBs were burned and dumped on the plantation site, resulting in global warming pollution from methane and carbon dioxide. In this study, the EFB was transformed into a high-surface area of activated biochar through a microwave physicochemical approach involving the combination of steam followed by a hydroxide mixture for palm oil mill effluent (POME) treatment. It was found that BET (Brunauer–Emmett–Teller) surface area and total pore volume of activated biochar were 365.60 m2/g and 0.16 cm3/g, respectively. The surface morphology of activated biochar revealed the formation of well-developed pores that can potentially be used as adsorbents to treat POME. The removal efficiency of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of POME achieved 75%–55%, respectively. This study offers insight into the transformation of industrial waste into value-added products for sustainable environmental remediation.

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.

Decentralized solid-waste incinerators (DSWIs) have certain advantages for waste disposal from villages and towns. However, the incineration condition is always affected by the distribution of temperature and oxygen concentration, which causes difficulties in operation and maintenance. In this study, the temperature and oxygen concentration distribution of DSWI were characterized using different air flow rates and bottom ash volumes. The results showed that the adjustment of air flow has no significant influence on the heating process of the DSWI, while the retention of bottom ash did affect the temperature and oxygen concentration fields in the furnace. When the air flow rate was increased without the retention of bottom ash, 99% of the furnace volume temperature was observed between 780 °C and 800 °C. However, once the bottom ash was retained, the whole furnace temperature was steadily maintained between 800 °C and 850 °C. When the air flow rate was increased without bottom ash, the highest furnace volume percentage of oxygen concentrations higher than 3% maxed out at 11% volume, while it could reach 100% when bottom ash remained. The distribution of the temperature and oxygen concentration in the DSWI characterized by this research provides strong support for the operation and management of such systems.

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.

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.

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.

The vastly increasing generation of plastic packaging waste has outgrown the infrastructure capacity to manage this waste effectively, resulting in critical aquatic and terrestrial pollution. In 1994, the European Commission implemented the Packaging and Packaging Waste Directive 94/62/EC, responding to growing concerns regarding the environmental impact of packaging and safe waste management. This study analyses how Germany, Spain, France, Italy, and Poland—the five most populous countries in the EU (European Union)—manage their plastic packaging waste, and evaluates their established Extended Producer Responsibility (EPR) schemes, which are mandatory for all EU Member States by the end of 2024. This research shows that EPR schemes improve the financial and operational viability of plastic waste management in the scope countries, resulting in higher collection and recycling rates. Take-back requirements can incentivise producers to put less plastic packaging on the market, and advanced disposal fees can encourage eco-design. The Producer Responsibility Organisation plays a crucial role in both producer and consumer awareness, and in ensuring that plastic waste is safely managed. However, the local recycling infrastructure of 6.5 Mt in 2018 is a major barrier to reaching 50% recycling of plastic packaging in the EU by 2025. The European recycling capacity only covered about 23% of the cumulative post-consumer plastic waste generation, delaying the transition to the EU circular plastic economy. The recycling capacity has increased by 3 Mt between 2018 and 2020 and needs to continue its rapid expansion to become autonomous in reaching the recycling targets.

In this study, coal slime was mainly utilized to conduct experiments on a 30 kW preheating combustion test rig to analyze the conversion pathway of sulfur during the experiment, aiming at reducing slime pollution, controlling sulfur emission reasonably, and providing theoretical support for the preheating combustion technology. The results showed that after the coal slime was preheated, a large number of elements were released. The maximum release rates for H and S were 94.0% and 73.3%, respectively. The released S was converted into the sulfur-containing gases like H2S, COS, CS2, and the rest existed in the solid in the five forms of mercaptan, thiophene, sulfoxide, sulfone, and sulfate. Besides, during the combustion process, the gas was oxidized continuously and finally converted into SO2, leaving only the sulfate in the fly ash. In the preheating combustion process, 26.7% of the S was released from the coal, 73.3% of the S was retained in the semi-coke, and the final SO2 emission concentration of combustion was 959 ppm.

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.

Antibiotics and their metabolic byproducts are found in wastewater and natural water as a result of increased consumption, posing a major threat to humans and other living organisms. One of the most promising methods for their removal is adsorption using biochar because it offers excellent adsorption potential and is both affordable and environmentally beneficial. However, raw biochar frequently has a low adsorption capacity due to its limited pore structure and unfavorable surface characteristics. Biochar surface modifications using modifiers such as H3PO4, KOH, and NaOH have improved the surface area and thereby the adsorption capacity. Experimental methods for assessing the effectiveness and adsorption mechanism of modified biochar are costly and time-consuming. Density functional theory (DFT) was used to investigate the interfacial interactions and adsorption mechanism of tetracycline (TC), a widely used antibiotic for personal care and veterinary medication, on unmodified and modified biochar. The DFT calculations showed that the adsorption energy of TC on unmodified and modified biochar is in the following order: KOH-modified biochar (− 2.38 eV)