Green disposal of waste smartphone protective film: Efficiency, mechanism, bench-scale test and secondary waste reutilization.

The manufacture and obsolescence of smartphones produce numerous waste plastic accessories (e.g., waste smartphone protective film (WSPF)), possessing immense potential for recycling. However, available recycling technologies have limitations such as substrate damage and secondary pollutant generation. The present study aimed to develop a green disposal method that not only recycled polyethylene terephthalate (PET) from WSPF, but also reused the stripped polyacrylate (PAA) adhesive as an adsorbent to reduce solid waste generation. When the WSPF was treated in 1 mol/L NaOH solution at 90 °C, the PAA hydrolyzed to two main by-products of 1-butanol and 2-ethylhexanol, weakening the binding strength between PAA and PET and then efficient separation of them. Further bench-scale test revealed that over 97.2% of detachment efficiency toward PAA was achieved during continuous treatment of 17 batches of WSPF (200 g for each) without supplement of NaOH and generation of wastewater. Meanwhile, the economic evaluation indicated that the recycling method would generate a net profit margin of 647% for the second year without considering the incurrence of new cost and input. Additionally, the pyrolysis of waste PAA enabled its conversion into potential adsorbent, which showed 2 to 4 times enhanced adsorption capacity toward styrene and ethyl acetate after modification with NaOH solution. This study provides a green method for recycling waste plastics and inspires a referable solution for solid waste treatment in the smartphone industry.

Inhibition of jarosite heterogeneous crystallization on anglesite via in-situ formation of competitive substrate.

Heterogeneous crystallization is a common occurrence during the formation of solid wastes. It leads to the encapsulation of valuable/hazardous metals within the primary phase, presenting significant challenges for waste treatment and metal recovery. Herein, we proposed a novel method involving the in-situ formation of a competitive substrate during the precipitation of jarosite waste, which is an essential process for removing iron in zinc hydrometallurgy. We observed that the in-situ-formed competitive substrate effectively inhibits the heterogeneous crystallization of jarosite on the surface of anglesite, a lead-rich phase present in the jarosite waste. As a result, the iron content on the anglesite surface decreases from 34.8% to 1.65%. The competitive substrate was identified as schwertmannite, characterized by its loose structure and large surface area. Furthermore, we have elucidated a novel mechanism underlying this inhibition of heterogeneous crystallization, which involves the local supersaturation of jarosite caused by the release of ferric and sulfate ions from the competitive substrate. The local supersaturation promotes the preferential heterogeneous crystallization of jarosite on the competitive substrate. Interestingly, during the formation of jarosite, the competitive substrate gradually vanished through a dissolution-recrystallization process following the Ostwald rule, where a metastable phase slowly transitions to a stable phase. This effectively precluded the introduction of impurities and reduced waste volume. The goal of this study is to provide fresh insights into the mechanism of heterogeneous crystallization control, and to offer practical crystallization strategies conducive to metal separation and recovery from solid waste in industries.

Effects of steel slag mixed substrate on rooting of Hydrangea macrophylla cuttings.

To investigate the effect of steel slag used as substrate on the rooting of Hydrangea macrophylla cuttings, and to develop a new mixed substrate that can partially replace conventional cutting substrates and realize the high-efficient utilization of solid waste, we examined the physical and chemical properties of different mixed substrates containing 10% (T1), 20% (T2), 30% (T3), and 40% (T4) volume fractions of steel slag, and investigated the rooting of H. macrophylla 'Red Beauty' cuttings growing on these substrates, with conventional cutting substrates (peat and perlite) as the control (CK). The results showed that pH value, electrical conductivity, and bulk density of the mixed substrates were significantly higher than those of CK. The aeration porosity of T2 was higher than other treatments, while the total porosity and water holding porosity differed little from others. Both fresh weight and dry weight of all the four treatments were higher than those of CK, with stem diameter being higher than that of CK (except T4), plant height showing no significant difference compared to CK (except T4), and leaf chlorophyll content being significantly lower than CK. Root length ranked as T2>CK>T1>T3>T4, the root surface area and root volume both ranked as T2>T1>CK>T4>T3, the root tip ranked as T2>CK>T1>T4>T3. Both average root diameter and root activity were significantly higher than that of CK, with the highest value being observed in T2. Soluble sugar content in the leaves of T2 was the highest, followed by T4, T3, CK, and T1. The weight ranking of root growth indices was root activity > average root diameter > root volume > root surface area > root tip number > root length. Redundancy analysis indicated that pH value, electrical conductivity, aeration porosity, and water holding porosity of substrates were key factors influencing root growth and development of cuttings. Our results suggested that substrates mixed with 10% to 40% steel slag could be used for H. macrophylla cutting propagation, and 20% (T2) being the best one because it could significantly improve the survival rate, growth status, and root development of cuttings. Steel slag would be a novel substrate to partially replace conventional unrenewable substrates such as peat and perlite for flower seedling propagation, which could reduce agricultural production cost and provide a high-value utilization way of industry solid waste.

Assessment and management of construction and demolition waste in tier 2 cities of Karnataka, India: a case study of Hubli-Dharwad and Davanagere.

The present study examines the current practices for managing construction and demolition waste (CDW) in two tier-2 cities of Karnataka state: Hubli-Dharwad and Davanagere. The research highlights the quantification, characterization, and effective management strategies for CDW. CDW dumping sites were identified through field visits conducted across all wards of the cities and recorded using a mobile-based app. At each site, data were collected on the types of vehicles dumping CDW, the frequency of dumping, the volume of waste in the vehicles, and the quantity of CDW removed for reuse. The dumping sites were categorized into large, medium, and small based on the area and volume of waste. In total, 130 unauthorised dumping sites were identified in Hubli-Dharwad and 62 in Davanagere. The study estimated that Hubli-Dharwad generates approximately 607 tonnes per day (TPD) of CDW, while Davanagere produces around 287 TPD. The characterization of CDW revealed that in Hubli-Dharwad, CDW consists of 14.4% concrete, 25.5% brick and mortar, 39.1% soil and aggregates, and 20% other materials. In Davanagere, the composition includes 19% concrete, 29% brick and mortar, 38% soil, and 14% other materials. Based on these findings, the study proposes a system for the collection and transportation of CDW and recommends suitable recycling technologies. While the approach outlined in this paper is well-suited for urban local bodies to assess CDW, the data on CDW reuse and recycling is primarily based on informal practices. This makes accurate quantification challenging and subject to variation over time due to a lack of regulatory oversight. Additionally, the study provides only a snapshot of CDW generation and management at a specific point in time, potentially missing seasonal variations or long-term trends in waste handling.

Soil degradation around Orji municipal solid waste dump site: a spatial assessment.

The present study assessed the impact of municipal solid waste dump on the degradation of soil around Orji dump site. A total of 15 soil samples were collected for this study. Twelve soil samples were collected around the dump site at 0 m, 10 m, and 20 m distance and three from Imo State University (IMSU) research farm as control. The samples were collected from the east, west, north, and south of the dump site. The samples were subjected to laboratory analyses. The mean results obtained indicate that the values of the dump site soil parameters analyzed ranged from 86.67 to 89.00% (sand), 4.33 to 5.67% (silt), 7.00 to 7.67% (clay), 6.80 to 7.50 (pH), 4.33 to 7.00 dS m-1 electric conductivity (EC), 0.0028 to 0.0045 mg kg-1 (salinity), 2.36 to 3.76% soil organic matter (SOM), 24.13 to 38.93 cmolc kg-1 cation exchange capacity (CEC), 4.50 to 9.57 cmolc kg-1 calcium (Ca), and 1.0 to 2.25 cmolc kg-1 magnesium (Mg). At the control, mean values were 81.24% (sand), 6.39% (silt), 12.45% (clay), 5.69 (pH), 0.47 dS m-1 (EC), 0.0005 mg kg-1 (salinity), 1.99% (SOM), 5.08 cmolc kg-1 (CEC), 2.17 cmolc kg-1 (Ca), and 1.67 cmolc kg-1 (Mg). These values showed substantial enrichment. Correlations indicate that EC, salinity, and CEC majorly determined the availability of most of the parameters analyzed. Soil degradation index (SDI) was used to determine degradation around the dump site. It ranged from 2.546.61% (0 m) to 1573.50% (10 m) and 1.603.73% (20 m). Thus, distance affected the rate of soil degradation in all directions away from the dump site.

Unveiling the composition of bio-earth from landfill mining and microplastic pollution.

Landfill mining is the prominent solution for the recovery of resources from legacy waste. The bio-earth recovered from landfill mining is being utilized for a variety of applications like application as fertilizer. The presence of microplastic in the recovered bio-earth disrupts its usefulness. This study investigated the composition and microplastic pollution in bio-earth derived from landfill mining at the Bhandewadi landfill, Nagpur, India. Results provided insights into its characterization and presence of microplastic. The average moisture content of the bio-earth was 25.2 ± 1.1% with total organic carbon of 14.3 ± 0.6%. The bio-earth exhibited a C:N ratio of 16.9 ± 5.0, volatile solid content of 24.6 ± 1.0%, and ash content of 75.4 ± 1.0%. Bulk density was 434.3 ± 37.2 kg/m3, pH value 6.91 ± 0.28, and electrical conductivity 4.6 ± 0.7 dS/m. Total nitrogen content was 0.9 ± 0.3%, available phosphorus 2.1 ± 0.3 g/kg, and potassium and sodium contents of 12.7 ± 0.4 g/kg and 3.9 ± 0.3 g/kg, respectively. Heavy metals detected included Fe, Zn, Mn, Cu, Pb, Ni, Cr, and Cd. Microplastics in the bio-earth samples were assessed using attenuated total reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR). The amount of microplastics averaged 100,150 ± 29,286 items per kg (dry basis). Additionally, five specific polymer types were prominent as microplastics. Further research and mitigation strategies are necessary to ensure the safe and sustainable use of bio-earth in agriculture and horticulture.

Integrated municipal solid waste management using ArcGIS tools: A case of akaki-kality sub-city, addis ababa, ethiopia.

This study aimed to optimize the solid waste collection and transportation system using ArcGIS Network Analyst and location-allocation tools. The generated solid waste was characterized by proximate analysis. The generation rate and composition were determined according to standard methods. The average solid waste generation rates for households, commercial sites, institutions, and recreational places were 0.48 kg/c/day, 15.03 kg/fac/day, 9.32 kg/fac/day, and 22.8 kg/fac/day, respectively. The estimated total generation rate of the sub-city is 207,004.03 kg/day and 712.13 m3/day as discarded base. Composition analysis revealed that food waste is the major component of municipal solid waste, with estimated weight and volume of 134,696.08 kg and 299.46 m3, respectively. Proximate analysis indicated that food and textile wastes have relatively high moisture content and fixed carbon. Candidate pre-collection bin allocations were optimized based on factors such as road network, distribution of solid waste generators, and existing temporary dumping sites, resulting in 1052 potential bin locations. Transfer station allocation was optimized by considering land use-land cover, slope, and geology. Twelve transfer routes and four transport routes were established to efficiently serve the bins and final waste destinations. In conclusion, the study demonstrates that ArcGIS Network Analyst and location-allocation tools can effectively optimize the municipal solid waste collection and transportation system, providing a robust framework for improving waste management efficiency. However, further research is recommended to validate these findings through field application.

Influential factors in anaerobic digestion of rice-derived food waste and animal manure: A comprehensive review.

Utilization of organic community wastes towards deriving sustainable renewable energy and adequate disposal of the residual has been an important topic of investigation. Anaerobic digestion and co-digestion of rice-derived food waste and animal manure for sustainable biogas generation is crucial from the view-point of community consumption. This paper presents an extensive review of the important and recent contributions in the related areas. The critical physico-chemical parameters involved in such digestion process are analyzed, including temperature, carbon-nitrogen ratio, microorganisms, pH, substrate characteristics, organic loading rate, hydraulic retention time, volatile fatty acids, ammonia, and light/heavy metal ions. Studies implied that the optimum yield of biogas production could be achieved only when the values of the parameters exist in the specific ranges. Few recent studies highlighted the use of emerging techniques including micro-aerobic system, additives, laser radiation, bio-electrochemical field, among others for efficiency enhancement of the digestion process and optimum yield. The entire study provided a set of important conclusions and future research directives are as well proposed.

Biological methane potentials of food waste of different components: Methane yields, production kinetics, and element balance.

This study assessed the methane production from food waste (FW) with dominant components of Meat (MFW), Fruit &Veg (VFW), Grain (GFW), Dairy (DFW), and the mixed feed of these components (MixFW). The high protein and lipid content FW (HPLFW) of MFW, DFW, and MixFW showed the methane yields of 337.0 ± 3.0, 307.4 ± 0.8, and 297.1 ± 1.2 ml-CH4/gCOD, respectively, while those for the high carbohydrate content FW (HCFW) of VFW and GFW were 238.3 ± 1.2 and 171.2 ± 0.3 ml-CH4/gCOD, respectively. A modified two-component kinetic (MTK) model was demonstrated to be the best to describe the methane production kinetics of both HPLFW and HCFW types of feeds. The element balance analysis revealed the element formula of the FW feeds and the methane-conversion organic content. The results obtained from this study showed that the high lipid and animal protein content increased the methane yield and biogas methane composition.

Positive effects of appropriate micro-aeration on landfill stabilization: Mitigating ammonia and VFAs accumulation.

The slow stabilization process of landfill had brought obstacles to urbanization. The paper investigated the efficacy and mechanism of micro-aeration intensity for landfill stabilization. The micro-aeration intensity of 0.05 L/(h·kg) resulted in a significant increase of volatile fatty acids (VFAs) in the hydrolysis stage, and the NH4+-N concentration was reduced by 22.1 %. At the end of landfill, VFAs were rapidly degraded and organic matter was reduced from 36 % to 16 %, which was 55.5 % more efficient than the control group. In addition, the community succession and structure of bacteria and archaea were analyzed. The micro-aeration intensity of 0.05 L/(h·kg) increased the abundance of hydrolyzing functional bacteria such as Pseudomonas and Bacillus, and allowed methanogenic bacteria such as Methanobacterium and Methanothrix to gradually establish oxygen tolerance in the microaerobic environment. The appropriate micro-aeration intensity can accelerate the stabilization process of landfill, which has environmental and economic benefits.

Recent advances in thermochemical conversion technology for anaerobic digestate from food waste.

The thermochemical conversion technology for anaerobic digestate from food waste (ADFW) can reduce waste volume, eliminate pathogens, and recover energy through incineration, pyrolysis, gasification, and hydrothermal transformation. This paper comprehensively reviews the physicochemical features of anaerobically fermented digestate from food waste (FW), digestate treatment methods, and their advantages and disadvantages. In addition, the analysis and application of associated by-products from ADFW thermochemical conversion are also discussed. The main products include biochar, bio-oil, and biogas. Biochar can be used for soil improvement and biomedicine and bio-oil can be used forliquid fuel. Meanwhile, biogas mainly consists of CH4, CO2, and H2 and CO, which can be used in petrochemicals, metallurgy, and other fields. The catalytic pyrolysis/gasification for plastic-containing ADFW is proposed by adding iron-based industrial waste (red mud/copper) as catalysts under the CO2/CH4 atmosphere. This review helps to provide new guidelines for the ADFW utilization of desired products.

A new approach for the assessment of the environmental risk of a soil-like fraction in landfills due to PTE contamination.

In the context of the shift toward a closed-loop economy, soil-like fractions from landfills are increasingly seen as a potential raw material. Pollution, including potentially toxic elements (PTEs), limits the use of soil-like fractions. The study objective was to assess the level of contamination with PTEs and the ecological risk of the soil-like fraction from a landfill using an interval method on the basis of a quantile analysis. Quantile analysis allows visualization and interpretation of data based on statistical principles using a cumulative distribution function for the data. Quantiles divide the entire dataset into equal parts by probability, and they indicate the proportion of observations that have a value less than or equal to a given quantile. A study was conducted at a landfill in Volgograd. The contents of Cd, Ni, Pb, Hg, Cu, and Zn were studied in a soil-like fraction. The contents of Hg, Pb, and Zn were low and did not pose any risks to the environment. Cd, Ni, and Cu were the main reasons for the contamination of the soil-like fraction. Quantile analysis has shown that the soil-like fraction is polluted unevenly and is described by several contamination levels. The pollution level with PTEs in the soil-like fraction is low, with a probability of 27-31%. The other part of the soil-like fraction has a pollution level ranging from moderate to very high. The environmental risk of a soil-like fraction is associated with Cd and Ni. With a probability of 23.5%, a soil-like fraction is a high environmental risk and requires a responsible attitude and measures to ensure environmental safety. With probabilities of 29.4% and 47.1%, the complex potential environmental risks of a soil-like fraction are low and moderate, respectively. The soil-like fraction located at a depth of more than 2.5 m has a low level of pollution and a low environmental risk. Potentially, this part of a soil-like fraction can be isolated and, after detoxification, used. The significance of this research lies in providing a novel approach to evaluate the ecological risk of soil-like fractions from landfills, which can inform more effective sustainable waste utilization practices in landfill mining.

Megacity solid waste disposal suitability mapping in Dhaka, Bangladesh: an integrated approach using remote sensing, GIS and statistics.

Selecting suitable Megacity Solid Waste Disposal (MSWD) sites is a challenging task in densely populated deltas of developing countries, exacerbated by limited public awareness about waste management. One of the major environmental concerns in Dhaka City, the world's densest megacity, is the presence of dumps close to surface water bodies resources. This study employed the Geographic Information System (GIS)-Analytic Hierarchy Process (AHP) framework to integrate geomorphological (slope and flow accumulation), geological (lithological and lineament), hydrogeological (depth to groundwater table and surface waterbody), socioeconomic (Land use land cover, distance to settlement, road, and airport), and climatological (wind direction) determinants, coupled by land-use and hydro-environmental analyses, to map optimal dumps (MSWDO) sites. The resulting preliminary (MSWDP) map revealed 15 potential landfill areas, covering approximately 5237 hectares (ha). Combining statistical analysis of restricted areas (settlements, water bodies, land use) with AHP-based ratings, the MSWDO map revealed two optimal locations (2285 ha). Additionally, the hydro-environmental analysis confirmed the unsuitability of northern sites due to shallow groundwater (< 5.43 m) and thin clay, leaving 11 options excluded. Sites 12 (Zone A, 2255 ha) and 15 (Zone B, 30 ha), with deeper groundwater tables and thicker clay layers, emerged as optimal choices for minimizing environmental risks and ensuring effective long-term waste disposal. This study successfully integrates remote sensing, geospatial data, and GIS-AHP modeling to facilitate the development of sustainable landfill strategies in similar South Asian delta megacities. Such an approach provides valuable insights for policymakers to implement cost-effective and sustainable waste management plans, potentially minimizing the environmental risks to achieve Sustainable Development Goals (SDGs) 6, 11, 13, and 15.

Response of food waste anaerobic digestion to the dimensions of micron-biochar under 30 g VS/L organic loading rate: Focus on gas production and microbial community structure.

Biochar modification is an effective approach to enhance its ability to promote anaerobic digestion (AD). Focusing on the physical properties of biochar, the impact of different particle sizes of biochar on AD of food waste (FW) at high organic loading rate (OLR) was investigated. Four biochar with different sizes (40-200 mesh) were prepared and used in AD systems at OLR 30 g VS/L. The research results found that biochar with a volume particle size of 102 µm (RBC-P140) had top-performance in promoting cumulative methane production, increasing by 13.20% compared to the control group. The analysis results of the variety in volatile acids and alkalinity in the system did not show a correlation with the size of biochar, but small size has the potential to improve the environmental tolerance of the system to high acidity. Microbial community analysis showed that the abundance of aceticlastic methanogen and the composition of zoogloea were optimized through relatively small-sized biochar. Through revealing the effect of biochar particle size on AD system at high OLR, this work provided theoretical guidance for regulating fermentation systems using biochar.

Sustainable organic waste valorisation: A zero-waste approach.

The annual increase in global organic waste generation emphasises the need to develop a sustainable management platform to address environmental concerns. This study aims to explore sustainable treatments for the conversion of organic waste into energy in pursuit of zero-waste. The organic waste generated from the animal feed industry (referred to as WF) was used for the model compound in this study. 8.5 wt% of lipids were extracted from the WF, which contained unidentified impurities. Acid-catalysed transesterification yielded less than 80 wt% biodiesel might be due to the reversible reaction. In contrast, non-catalytic transesterification resulted in a significantly higher biodiesel yield (95.6 wt%), suggesting that this method was more effective at converting impure lipids into biodiesel compared to acid-catalysed transesterification. These results indicate the potential advantages of the non-catalytic approach, particularly when dealing with impure lipid sources. To minimise the generation of waste in the process, the WF residue produced after lipid extraction was converted into combustible gas (syngas) through pyrolysis. CO2 was used as a reactive medium in pyrolysis. In one-stage pyrolysis, the gas yield under CO2 was comparable to that under N2, indicating that CO2 did not react effectively with the volatiles derived from the WF residue. Enhanced CO2 reactivity was achieved via catalytic pyrolysis using a nickel-impregnated catalyst. Consequently, the combustible gas yield under CO2 was much higher than that under N2. This approach might contribute to maximising the efficiency of converting organic waste into renewable energy while simultaneously consuming CO2 during pyrolysis, thereby enhancing the sustainability of this approach.

Enhancing landfill efficiency to drive greenhouse gas reduction: A comprehensive study on best practices and policy recommendations.

This article investigates the pivotal role of non-hazardous waste landfills in achieving greenhouse gas (GHG) reduction objectives within the European Union (EU).1 This study leverages the experience of key stakeholders in the European landfilling, assesses the efficacy of 'best-in-class' landfill installations, evaluates their potential impact on GHG reduction, and offers concrete recommendations for operators and policymakers. 'Best-in-class' landfills exceed the commonly accepted best practices by implementing all the following practices: (1) an anticipated capture system during the operating phase, (2) prompt installation of the final cover and capture system, with use of an impermeable cover, (3) operated as bioreactor, keeping optimal humidity, (4) adequate maintenance and reporting, (5) recovery of captured gas and (6) treatment of residual methane emissions throughout the waste decomposition process. The main finding is that switching from the actual mix of practices to 'best in class' practices would reduce by ~21 MtCO2eq (-36%) the emissions due to the degradation of waste landfilled between 2024 and 2035, compared to the 'business-as-usual scenario', while also providing a renewable energy source, bringing potential avoided emissions and energy sovereignty. The findings underscore that in addition to implementing the organics diversion and waste reduction targets of the EU, adopting 'best-in class' landfill practices has the potential to bolster energy recovery, mitigate emissions and stimulate biomethane production, thereby advancing the EU environmental goals.

Overcoming China's animal waste disposal challenge brought by elevated levels of veterinary antimicrobial residues and antimicrobial resistance.

Direct application of animal waste on farmlands was banned in China recently, rendering organic fertilizer production a sound solution for disposing of animal manures and recycling their materials and nutrients. Due to the overuse of antimicrobials in livestock and poultry farms, manure-based organic fertilizers often contain elevated residues of antimicrobials and abundant antimicrobial resistance genes. Land application of such products has caused significant concerns on the environmental pollution of antimicrobials, and the transmission and development of antimicrobial resistance (AMR), which is a major global health challenge. China's recent attempt to restrict the contents of antimicrobial residues in organic fertilizers encountered strong resistance from the industry as it would hinder the utilization of animal manures as a raw material. Reducing and even eliminating the use of antimicrobials in animal farms is the ultimate solution to the challenge of manure disposal posed by the elevated levels of antimicrobial residues and AMR. Phasing out the non-therapeutic use of antimicrobials, developing substitutes of antimicrobials, enhancing animal welfare in farms, promoting diversification of animal farms, and developing antimicrobial removal and disinfection technologies for animal waste are recommended to improve the veterinary antimicrobial stewardship and manure management in China's animal agriculture. These concerted measures would enhance the sustainability of crop and animal farming systems in China and mitigate the impact of antimicrobials and AMR to agro-environmental quality and human health.

Leaching of per- and polyfluoroalkyl substances (PFAS) from food contact materials with implications for waste disposal.

Leaching of per- and polyfluoroalkyl substances (PFAS) during the post-consumer disposal of food contact materials (FCMs) poses a potential environmental threat but has seldom been evaluated. This study characterized the leaching behavior of PFAS and unidentified precursors from six common FCMs and assessed the impact of environmental conditions on PFAS release during disposal. The total concentration of 21 PFAS ranged from 3.2 to 377 ng/g in FCMs, with PFAS leachability into water varying between 1.1-42.8 %. Increasing temperature promoted PFAS leaching, with leached nine primary PFAS (∑9PFAS) reaching 46.3, 70.4, and 102 ng/L at 35, 45, and 55 â„ƒ, respectively. Thermodynamic analysis (∆G>0, ∆H>0, and ∆S<0) indicated hydrophobic interactions control PFAS leaching. The presence of dissolved organic matter in synthetic leachate increased the leached ∑9PFAS from 47.1 to 103 ng/L but decreased PFBS, PFOS, and 6:2 FTS leaching. The total release of seven perfluorocarboxylic acids (∑7PFCAs) from takeaway food packaging waste was estimated to be 0.3-8.2 kg/y to landfill leachate and 0.6-15.4 kg/y to incineration plant leachate, contributing 0.2-4.8 % and 0.1-3.2 % of total ∑7PFCAs in each leachate type. While the study presents a refined methodology for estimating PFAS release during disposal, future research is needed on the indirect contribution from precursors.

Of the first five US states with food waste bans, Massachusetts alone has reduced landfill waste.

Diverting food waste from landfills is crucial to reduce emissions and meet Paris Agreement targets. Between 2014 and 2024, nine US states banned commercial waste generators-such as grocery chains-from landfilling food waste, expecting a 10 to 15% waste reduction. However, no evaluation of these bans exists. We compile a comprehensive waste dataset covering 36 US states between 1996 and 2019 to evaluate the first five implemented state-level bans. Contrary to policy-makers' expectations, we can reject aggregate waste reductions higher than 3.2%, and we cannot reject a zero-null aggregate effect. Moreover, we cannot reject a zero-null effect for any other state except Massachusetts, which gradually achieved a 13.2% reduction. Our findings reveal the need to reassess food waste bans using Massachusetts as a benchmark for success.

High-solid digestion - A comparison of completely stirred and plug-flow reactor systems.

High-solid digestion (HSD) for biogas production is a resource-efficient and sustainable method to treat organic wastes with high total solids content and obtain renewable energy and an organic fertiliser, using a lower dilution rate than in the more common wet digestion process. This study examined the effect of reactor type on the performance of an HSD process, comparing plug-flow (PFR) type reactors developed for continuous HSD processes, and completely stirred-tank reactors (CSTRs) commonly used for wet digestion. The HSD process was operated in thermophilic conditions (52 °C), with a mixture of household waste, garden waste and agricultural residues (total solids content 27-28 %). The PFRs showed slightly better performance, with higher specific methane production and nitrogen mineralisation than the CSTRs, while the reduction of volatile solids was the same in both reactor types. Results from 16S rRNA gene sequencing showed a significant difference in the microbial population, potentially related to large differences in stirring speed between the reactor types (1 rpm in PFRs and 70-150 rpm in CSTRs, respectively). The bacterial community was dominated by the genus Defluviitoga in the PFRs and order MBA03 in the CSTRs. For the archaeal community, there was a predominance of the genus Methanoculleus in the PFRs, and of the genera Methanosarcina and Methanothermobacter in the CSTRs. Despite these shifts in microbiology, the results showed that stable digestion of substrates with high total solids content can be achieved in both reactor types, indicating flexibility in the choice of technique for HSD processes.