This study introduces the integrative concept of Temporary Material Hubs (TMHs) as a newly adapted approach to enhance long-term improvement in circularity by storing prospectively valuable waste, under current conditions not feasible or possible to recover, for future recycling capabilities. TMHs aim to optimize resource recovery by prolonging the lifespan of materials in anthropogenic cycles and avoiding premature disposal. Unlike landfilling with subsequent landfill mining (disposal and later excavation), TMHs proactively store such materials in controlled "hubs" to preserve value and enable future high-quality recovery. The conceptual framework is complemented by the known final sink concept to maintain clean material cycles. Given the lack of a clear definition of recyclability, this paper further proposes recycling pillars as guiding principles in the context of TMHs: environmental and health protection, availability of adequate recycling technologies, and economic feasibility including the availability of markets. Exemplary candidate materials for TMHs currently envisage, e.g., end-of-life wind blades and incineration residues. A SWOT analysis was used to discuss the strengths of TMHs in promoting resource optimization through postponed recycling, while identifying weaknesses such as uncertain costs and current lack of accurate technical implementation concepts. Opportunities lie in supporting European circularity goals and reducing primary material extraction, whereas threats include future regulatory uncertainties and inaccurate estimations of future waste recyclability. This study prepares the ground for future research and risk-assessment on technical, economical, and societal factors necessary for implementing TMHs on an industrial scale to ensure better functioning of the circular economy and a sustainable future.

Older municipal solid waste (MSW) landfills that received organic waste over past decades struggle in aftercare with declining gas production and fluctuating gas quality, making gas extraction systems inefficient. Methane (CH4) oxidation systems, such as biowindows, provide a sustainable, cost-effective passive alternative for mitigating residual emissions. This study presents long-term monitoring of three pilot biowindows at an Austrian MSW landfill to replace gas extraction wells and reduce CH4 emissions. Over a 10-year period, CH4 emissions and their relationship with environmental factors were analyzed through periodic field campaigns during two monitoring phases (2014-2016 and 2021-2024). Monitoring included gas and temperature profiles, surface screenings, and chamber flux assessments. Statistical analyses, including Pearson correlation and decision tree modeling, identified key factors influencing CH4 emissions, which were driven by a combination of temporal trends, gas composition dynamics, and environmental factors like ambient pressure and temperature. Results revealed a 60 % reduction in median hotspot CH4 emission rates (from 162 to 70 g/m2 d) at one biowindow between the two monitoring phases, while another biowindow demonstrated high performance over the period. In contrast, the third biowindow, installed at a newer landfill section, exhibited hotspots and increased emissions (median 80-265 g/m2 d across campaigns), likely linked to formerly installed and still remaining leachate and gas collection infrastructure, highlighting the need for site-specific interventions to address localized issues and optimize performance. The study confirms that biowindows require minimal maintenance during their first decade of operation and can achieve considerable CH4 reductions under appropriate conditions and well-designed construction.

In-situ aeration is a widely recognized method for stabilizing waste in old landfill sites, aiming to reduce the aftercare phase, lower greenhouse gas emissions (especially methane), and mitigate environmental risks. While its immediate effects are well-documented, the long-term sustainability of its outcomes, particularly longer periods after the shut-down of an aeration-plant, remains underexplored. This study investigates the long-term impacts of in-situ aeration at an Austrian landfill site, utilizing monitoring data collected over a decade after the cessation of the aeration process and following the implementation of a final cover. The findings demonstrate that the positive effects of in-situ aeration persist, with reduced pollutant concentrations in leachate—particularly for ammonium nitrogen (NH4-N), biochemical oxygen demand over 5 days (BOD5), and the BOD5/COD ratio—meeting suggested stability thresholds compared to pre-aeration levels. Notably, annual substance loads meet all stability criteria, largely due to the final cover installed in 2016, which limited water infiltration, reduced leachate generation, and enhanced the containment of residual emissions. Furthermore, methane (CH4) emission assessments, based on surface CH4 concentrations, revealed minimal emissions, with no significant levels being detected during the final monitoring sessions, underscoring the lasting benefits for greenhouse gas mitigation. These results demonstrate that in-situ aeration, combined with appropriate post-aeration measures such as final cover installation, is effective in bringing landfills to a state of low current emissions and reduced future emission potential.

The potential of industrially processed fine brick fractions from construction and demolition waste (CDW) as partial cement replacements in standardized mortar systems was systematically evaluated. Two brick fractions - a dry-processed sieved fraction and a wet-processed fraction - were ground to Blaine fineness values of approximately 4500 cm2/g and 7500 cm2/g and tested as type II hydraulic additives according to O & uml;NORM B 3309-1:2010. Mortars were prepared with 5-25 wt% cement replacement, and compressive strengths were measured at 7, 14, and 28 days. Microstructural analyses were conducted using mercury intrusion porosimetry (MIP) and energy-dispersive X-ray spectroscopy (EDS). At low replacement levels (5-10 wt%), both brick fractions achieved 28-day activity indices >= 90%, and mortars with 5 wt% replacement exhibited compressive strengths comparable to the control specimen. Higher replacement levels (15-25 wt%) caused significant strength reductions due to clinker dilution, while increasing the fineness from 4500 cm2/g to 7500 cm2/g had no measurable effect at high substitution rates (25%). MIP revealed a slight increase in total porosity of 3.4% for 5 wt% replacement with dry-processed materials, and more pronounced increases of 11.5-11.6% for 10-15 wt% replacement. Long-term measurements at 56 and 90 days under constant consistency conditions, achieved by adapting the water amount, showed that 10 wt% dry-processed materials contributed to strength development up to 56 days, indicating participation in long-term hardening processes. These findings demonstrate that industrially processed brick CDW materials can act as reactive type II additives at low replacement levels, achieving compressive strengths compliant with the Austrian standard O & uml;NORM B 3309-1:2010.

Urban water scarcity and growing agricultural water demands underscore the urgent need for advanced, sustainable strategies in water and nutrient management. This study examines the potential of green wall treatment systems for on-site water and nutrient reuse to create local circular food systems. Two case studies are evaluated: Cambium eco-village (rural area of Styria, Austria) and Zukunftshof urban farm (city of Vienna, Austria), with scenarios involving green wall treatment systems as well as rainwater and compost use. A material flow analysis approach is used to investigate the efficiency of these scenarios in meeting agricultural water and nutrient demands.The findings show that these wastewater treatment and reuse systems can be integrated in different community projects, demonstrating their broader applicability beyond site-specific contexts. Local phosphorus fertilizer demand can be fully covered, as well as a considerable proportion of the nitrogen fertilizer demand (up to 90 % demand coverage rate). At Cambium, the reclaimed water of the green wall system can nearly supply all water demands, achieving up to 90 % coverage by utilizing only 20 % of the available wastewater, with the limitation being to prevent overfertilization due to the high nutrient content in reclaimed water. For larger areas, combining it with rainwater harvesting is recommended to fully address water needs. Reclaimed wastewater offers advantages over rainwater collection as source of water and composting as source of nutrients due to consistent availability and reduced storage requirements. Integrating anaerobic digestion further enhances nutrient recovery and supports sustainable energy generation. Overall, green wall treatment systems can effectively close local water and nutrient cycles, enhancing resilience and sustainability in local food production.

This study examines methane (CH4) emission factors from biogas and wastewater treatment plants, based on primary and secondary data collected from 109 facilities. Primary emission data were measured at 19 facilities representing prevalent plant configurations across Europe. Statistical analysis highlights two categorical variables, namely primary feedstock and plant size, expressed as CH4 production (<= 250 kg h(-1): small and medium-sized plants, > 250 kg h(-1): large plants), each of which has a significant impact on whole-site CH4 emissions. Additionally, digestate storage (gastight vs. not-gastight) has a meaningful effect when considering CH4 production as a continuous variable in the statistical analysis. Our results indicate that wastewater treatment plants have the highest average CH4 losses (7.0 % of CH4 produced, n = 31 or 0.10 kg population equivalent (PE)(-1) yr(-1), n = 28), followed by manure-based plants (3.7 %, n = 49), biowaste treatment facilities (2.8 %, n = 11) and energy crop-processing plants (1.9 %, n = 14). Furthermore, small and medium-sized plants have elevated emissions (5.6 %, n = 67) compared to larger counterparts (2.2 %, n = 42), primarily attributed to the absence of gastight digestate storage. Emissions tend to be lower with gastight digestate storage (2.7 %, n = 61) than not-gastight storage options (6.2 %, n = 48). Emission factors were determined for normal operating conditions, with a further investigation into other-than-normal operating conditions revealing temporal or constant emission peaks in eight out of 19 facilities. These peaks, suggesting potential areas for targeted mitigation strategies, were attributed to pressure relief valves, flare ignition problems and major leakages.

Compostable pre-collection plastic bags can foster the separate collection of biowaste from households and reduce pollution of conventional plastics. Test conditions proposed in certification procedures (e.g., EN 13432) used to show the compostability of such materials (and products) are made under controlled and optimal laboratory conditions and extended test periods that are rarely achieved in the composting practice. Thus, it is possible that some ‘compostable’ plastic products may not be degraded satisfactorily in technical composting plants under realistic conditions, which could leave microplastic fragments in composts. Therefore, in this study, the compostability of a certified compostable plastic bag was investigated under practical conditions in two state-of-art composting plants in Austria. Expected future plastic bag quantities (resulting in 0.95–1.19 kg biowaste per pre-collection-bag) were added to test windrows and were investigated during 12 weeks for fragment sizes > 0.2 mm. The results show that the investigated materials degraded within the first four weeks and left only tiny amounts of plastic materials in a size range 0.63–0.2 mm.

Cities are increasingly confronted with the need to provide shortterm and cost-efficient housing as several factors, such as natural disasters, migration due to political or climatic circumstances or other unpredictable events can result in a sudden and at times temporary need for additional housing. Providing affordable, and flexible but at the same time sustainable and re-useable housing concepts that are easy to construct and quickly to implement are thus requirements that cities must face. Currently there is limited research available in this field, as disaster architecture and temporary housing have not yet been widely researched in an interdisciplinary manner. The project “Urban pop-up housing environments and their potential as local innovation systems” has aimed at addressing this research gap by investigating in a highly interdisciplinary approach how and under which circumstances temporary housing solutions could be implemented under challenging framework conditions. The aim of the project was to systematically investigate and evaluate existing temporary housing options, and to develop and assess innovative and sustainable models for pop-up living systems in urban environments regarding resource uptake as well as social aspects, which may serve as incubators for urban innovation. From a technical perspective the models are focused on integrating aspects related to architecture, energy technologies, resources and materials, water as well as landscape design. Starting with a data pool of international examples, a classification and systematization of relevant typologies has been carried out in combination with user profiles for the different housing situations. On this basis, potential urban areas have been identified for selected scenarios and finally six theoretical temporary housing models have been created and subsequently assessed and analyzed in detail. The purpose of this paper is to present the key findings related to the scenarios and models, that have been developed within this basic research project and the methodologies that have been applied to assess them. The challenges of the scenarios and overall project results are summarized to provide an outline for potential implementation and future pilot projects.

The management of waste plays a pivotal role in achieving the Sustainable Development Goals (SDGs) set by the United Nations through both direct and indirect linkages. Directly, waste management issues are addressed in four SDGs (6, 11, 12, 14), while landfilling issues are only mentioned in SDG 6 reflecting water quality in connection with waste dumping. However, inadequate management and disposal of waste pose environmental, health and safety risks; thereby undermining more SDGs. Indirectly, waste management and landfilling influence various SDGs ranging from 4 to all 17 SDGs depending on the literature reference. Although not directly addressed in SDG 13 (Climate action), the waste sector contributes to climate change, with the biggest share of greenhouse gases emitted from landfills and waste dumps. According to the latest assessment report by the IPCC (Intergovernmental Panel on Climate Change), waste management—and thereby mainly landfills—are responsible for 64 Mt of CH4 per year worldwide. A waste-related assessment of the IPCC report series from 1990 to 2023 revealed a paradigm shift in the covered waste management strategies, transitioning from conventional technical disposal methods towards holistic approaches that align with the principles of sustainability encapsulated in the SDGs. The focus in the reports moves upwards the “waste management hierarchy”, fostering circular economy. Indirectly, this leads to seemingly less focus on landfills and waste dumps despite their high share of greenhouse gas emissions and particularly their strong representation in low/lower middle-income countries, which is still expected to increase during the next years.

Transition to circular economy for lithium-ion batteries used in electric vehicles requires integrating multiple stages of the value cycle. However, strategies aimed at extending the lifetime of batteries are not yet sufficiently considered within the European battery industry, particularly regarding repurposing. Using second-life lithium-ion batteries (SLBs) before subsequent recycling can offer several advantages, such as the development of sustainable business models, the reduction of emissions, and alignment with UN Sustainable Development Goals 7, 12, and 13. Using expert and problem-centred interviews along with an exploratory workshop, this study guides stakeholders in the battery sector by illustrating the necessary changes for a more holistic circular economy. Moreover, an extended political, economic, social, technological, environmental, legal, and additionally safety-related (PESSTEL) analysis approach is carried out, which has not yet been used in this context. In this process, barriers, as well as necessary institutional framework conditions and organisational requirements for a successful market entry of SLB applications are investigated. Among others, key barriers relate to the competition with first-life applications and safety concerns. SLBs require high manual labour costs for repurposing, along with expenses for expired warranties and re-certifications. Ownership structures in traditional business models often result in SLBs and their corresponding usage data staying under the control of the manufacturers. Market viability, however, requires a level playing field for both first-life and second-life operators as well as circular battery and data-sharing business models. Gathering data on the ageing performance and performing improved safety testing according to test protocols facilitates the reliable assessment of SLBs.

Gärreste stellen einen wesentlichen Abfallstrom dar, der (gemischt mit strukturreichen Abfällen) kompostiert werden kann und als Kompost gemäß der österreichischen Kompostverordnung Produktstatus erreicht. Gärreste erhöhen den Nährstoffgehalt im Kompost, ein erheblicher Anteil der organischen Ursprungssubstanzen wird durch den Rotteprozess in stabile Huminstoffe umgewandelt. Beim Inputmaterial in Biogasanlagen handelt es sich jedoch oft um Lebensmittelabfälle, die stark mit Lebensmittelverpackungsrückständen verunreinigt sein können. Kunststoffe stellen eine inerte Verunreinigung des Bioabfalls dar, die zu Problemen bei der Verwertung führen kann. „Große“ Kunststoffteile werden bei der Abfallbehandlung zu Mikrokunststoffen fragmentiert, die nicht mehr aus Gärresten bzw. Komposten entfernt werden können. Dieses Mikroplastik kann über die Anwendung der Komposte oder Gärreste in der Landwirtschaft die Böden über lange Zeiträume kontaminieren, und sogar in die Nahrungskette und ins Grundwasser gelangen. In der gegenständlichen Studie wurden Masse und Art von Makro- und Mikroplastik > 2 mm in Gärresten aus einer kommunalen Biogasanlage untersucht. Dazu wurden über ein Jahr in Zweimonatsintervallen Gärrestproben entnommen und auf Ballaststoffe, Schwermetall‑, Salz- und Nährstoffgehalte untersucht. Die häufigsten Polymere, die in den Gärresten gefunden wurden, waren Polyolefine, einschließlich der anderen häufig vorkommenden Kunststoffarten, woraus geschlossen werden kann, dass deren Quellen gängige Verpackungsmaterialien sind. Die Ergebnisse der Studie zeigen, dass kommunale Gärreste vor allem aufgrund der Verunreinigung mit Kunststoffen die Qualität bzw. Anwendbarkeit der daraus hergestellten Komposte stark beeinträchtigen. Schwermetall- und Salzgehalte hingegen lassen einen Anteil von mindestens 40

Vor dem Hintergrund hoher biogener Anteile im Restmüll und zu verbessernder Bioabfallverwertung wurde das Projekt „KüKeN – Küchenküberl für energetische Nutzung“ gestartet, das neue Wege bei der Sammlung und kaskadischen Verwertung von biogenen Abfällen aus Haushalten erproben soll. Der Fokus liegt dabei auf dem Einsatz digitaler Medientechnologie zur Steigerung der Motivation und zur Verbesserung der Sammelqualität. Als Grundlage für Entwicklungen im Rahmen dieses Projekts werden der Hintergrund zur Gamification, der Stand der Sensorik in Hinblick auf die technische Umsetzung des Küchenküberls sowie der Stand der Technik bei abfallwirtschaftlichen Apps dargestellt. Die Konzeption des interaktiven Küchenküberls in Kombination mit einer Motivations-App basiert auf einem nutzer:innenzentrierten Designprozess, wobei Nudging als Ansatz für die Trenn- und Sammelmotivation zur Anwendung kommt. Hauptzielgruppe der KüKeN-App sind Kinder und Jugendliche, die als Multiplikator:innen Kenntnisse und Engagement für das Thema Abfalltrennung in ihrem Umfeld verbreiten. Auf Basis von User- und Stakeholder-Workshops wurde die KüKeN-App mit drei Komponenten – ein ChatBot für Information, ein Spiel zur Wissensvermittlung sowie ein Spiel zur Aufrechterhaltung der Motivation – entwickelt. Nach der Vorstellung des Ergebnisses der Smartphone-Applikation gibt der Artikel einen Ausblick auf den bevorstehenden Einsatz der App in der Testregion.

With the rise of electric vehicles (EVs) and thus lithium-ion batteries (LIBs), the number of end-of-life (EoL) LIBs after their first life in EVs is about to increase significantly. These end-of-first-life (EoFL) EV LIBs still have sufficient energy density for less-demanding second-life applications like stationary battery energy storage systems (BESSs) or mobile applications (e.g., forklifts, tools). Repurposing EoFL EV LIBs extends their lifespan, offering sustainability benefits and supporting several United Nations (UN) Sustainable Development Goals (SDGs). However, prevailing market entry barriers, such as high repurposing costs, little information on battery history and aging, or lacking performance indicators, hinder the widespread implementation of second-life applications. Thus, this study aims to identify preconditions for considering and selecting useful EoFL LIBs and to determine key performance indicators (KPIs) to minimize economic risks for a successful second-life market launch. KPIs were rated according to importance using a Likert scale, and reference values were introduced. A mixed-methods approach, using expert interviews, an exploratory workshop, and an online survey, was applied. Twelve important preconditions were identified, with the "availability of information on battery specification" and "compliance with standards and regulations" considered very important. In addition, 12 KPIs were derived, covering six economic, three environmental, and three technical and safety-related indicators. The KPIs "state of safety (SoS)" and "resource savings (Rsav)" were rated as highly important. Overall, the findings provide performance measurement guidance for repurposing companies, facilitating the market launch and adoption of second-life applications. Future research can build on these results and investigate variations among different battery types, ultimately promoting a circular economy.

The degradability of conventional plastic packaging specimens made from PP and PET, that were produced with novel prodegradant additives, was investigated during biological waste treatment processes. The additives were merchandised to foster the degradation of commodity plastics by enzymatic or by abiotic processes. Four different plastic packaging specimens and two different additives were evaluated for their biodegradability during anaerobic and aerobic waste treatment conditions. Aerobic treatment was investigated in laboratory rotting tests, simulating conditions during composting in a plant according to the Austrian state-of-the-art, while anaerobic treatment was investigated in laboratory digestion reactors. The study shows that only the PET specimens showed a loss of mass of ca. 6.5%, during 50 days of digestion at 52 °C. None of the specimens degraded during the aerobic rotting process. None of the materials fragmented into microplastic particles of sizes > 1 mm under the investigated conditions. However, FTIR analysis revealed the oxidation in the case of PP specimens, which indicated a mediated oxidation process during composting, independent of the merchandised mechanism of predegradation. Under anaerobic conditions, the plastic specimens containing reactors produced more biogas within the first 20 days of digestion, that did not originate from an observable degradation of the plastics.

Due to its intense use of resources, the construction sector was identified as a priority sector in the European Green Deal. Construction and demolition waste (CDW) is one of the largest waste streams of the European Union. As it shows a high potential for recycling, the European Commission set a recovery target of 70% under the Waste Framework Directive. To control the performance and achievements of the member states, annual national reports to the EU are required. However, there exist different ways to specify and report these rates. Recovery rates published by EUROSTAT are calculated on the basis of waste treatment data of non-hazardous mineral CDW, generated according to the EU Waste Statistics Regulation. Limiting factors like non-unified methods of data collection, different waste coding systems and misinterpretations of the term ‘backfilling’ impede a cross-country comparison of the published EU recovery rates. In this study, factors that may have a misleading impact on reporting EUROSTAT CDW recovery rates were compiled and a detailed analysis using national quality reports of twelve selected EU countries as a data base were performed. The development of the reported recycling rates over five years was examined and the influence of the various factors was determined. The findings may enhance a more purposeful (scientific) discussion of CDW data and for evidence-based reporting of national recovery rates, and may assist the development towards an improved, uniform EU-wide data set. Finally, this will provide support to decision makers for future policy and governmental requirements.

The quantity and type of macro-and microplastics was investigated in rotting material during the composting process of two state-of-the-art composting plants in Austria. Microplastics >0.2 mm, were found already after the first turning event in both facilities. The generation of microplastics was more extensive in the plant that used shorter turning intervals during the first four weeks and generated approx. 21 particles per week and kg- 1 DM. After 4 weeks of operation less microplastic particles were detected, which suggested that particles were frac-tionated to smaller sizes during processing. In addition, a total of nine composts from three different facilities that were operated in various settlement structures were compared. 7 to 232 macro-and microplastic particles per kg DM were found, whereas the highest plastic burden was observed in the composts made from biowaste that originated from the most densely populated area.