Comparison of different post-demolition autoclaved aerated concrete (AAC) recycling options

Autoclaved aerated concrete (AAC) is used as masonry blocks and prefabricated reinforced elements preferably in residential buildings. Due to its porous structure and mineral composition, it combines low thermal conductivity and fire resistance properties. Consequently, the popularity of AAC increases. However, due to significant AAC production volumes in many European countries since the 1960s and 1970s and given building lifetimes, strongly increasing post-demolition AAC waste volumes can be expected in the following decades. Recycling these post-demolition AAC wastes could protect primary resources and landfill capacities and reduce greenhouse gas emissions. But, recycling of post-demolition AAC is not yet established. The majority of the waste is landfilled even though landfill capacities have decreased and the legal framework conditions in Europe regarding a circular economy are becoming stricter. Therefore, new recycling options are needed. Current research approaches propose different open-loop recycling routes for post-demolition AAC, e.g. lightweight aggregate concrete, lightweight mortar, no-fines concrete, floor screed, animal bedding, oil- and chemical binders, and insulating fills for voids and interstitial spaces. Additionally, closed-loop recycling is possible and under research. Finely ground post-demolition AAC powder can be directly used in AAC production or can be chemically converted to belite (C2S) clinker to substitute primary cement in AAC production. These promising recycling options are compared regarding environmental and economic aspects. We find that the resource consumption is lower in all recycling options since post-demolition AAC helps to save primary resources. Furthermore, greenhouse gas emissions associated with the substituted primary resources are saved - especially when substituting primary cement in closed-loop recycling. In economic terms, increasing landfill costs could be avoided, which leaves a considerable margin for the cost of pre-processing, transport and recycling. The results can help decision-makers to implement circular management for AAC by fostering post-demolition AAC recycling and reducing its landfilling

Comparison of building thermography approaches using terrestrial and aerial thermographic images

Thermography is commonly used for auditing buildings. Classical manual terrestrial thermography records images of individual buildings at a short distance. When auditing a large number of buildings (e.g. whole city districts) this approach reaches its limits. Using drones with thermographic cameras allows images to be recorded automatically from different angles, with faster speed and without violating property rights. However, an airborne camera has a significantly greater distance and more varied angles to a building compared to terrestrial thermography. To investigate the influence of these factors for building auditing, we perform a study evaluating seven different drone settings of varying flight speed, angle, and altitude. A comparison is drawn to manually recorded terrestrial thermographic images. While we find that a flight speed between 1m/s and 3m/s does not influence the thermographic quality, high flight altitudes and steep viewing angles lead to a significant reduction of visible details, contrast, and to falsified temperatures. A flight altitude of 12m over buildings is found to be the most suitable for the qualitative and quantitative analysis of rooftops and a qualitative analysis of façades. A flight altitude of 42m over buildings can only be used for qualitative audits with little detail

Prioritising urban green spaces using accessibility and quality as criteria

Urban green spaces are a critical component of cities, providing environmental, social, cultural, and economic benefits. To support smart(er) decisions by city planners and managers, this study aims to investigate how open data sources could be integrated into urban green space management. Specifically, it proposes a novel GIS-based method to prioritise urban green space in a resource-constraint scenario so that social benefits are maximised. To quantify the social benefits, the methodology is based on the WHO indicator, which recommends access to at least 0.5-1 ha of green space within 300 metres\u27 linear distance to all the city residents. The approach assigns each urban green space an \u27accessibility score\u27 based on its significance in the city, and a \u27quality score\u27 based on its performance on different quality parameters (size, greenness, quietness, and safety). Urban green spaces are ranked with respect to these two scores, enabling to prioritise spaces under resource constraints such as water shortage, limited staff, or budget. This approach is demonstrated through a case study on a mid-size German city and is transferable to other cities worldwide with varying weightage factors

Return Rates and Recovery Options of Used Electric Vehicle Traction Batteries in Germany = Rücklaufmengen und Verwertungswege von Altbatterien aus Elektromobilen in Deutschland

Die Elektromobilität wird als Schlüsseltechnologie zur Senkung der CO$_{2}$-Emissionen im Straßenverkehr gesehen. In der Diskussion um die Klimabilanz der Elektromobilität wird allerdings der hohe ökologische Fußabdruck in der Herstellung batterieelektrischer Fahrzeuge wenig adressiert, der sich insb. durch die ressourcenintensive Traktionsbatterie ergibt. Neben der Bereitstellung von regenerativem Ladestrom ist eine effiziente Kreislaufführung der Batteriematerialien und eine möglichst lange Nutzung der Batteriesysteme und Komponenten Voraussetzung für die nachhaltige Gestaltung der Elektromobilität. Der vorliegende Beitrag gibt einen Überblick zur kreislaufwirtschaftlichen Wertschöpfungskette von obsoleten Traktionsbatterien aus Elektromobilen. Mithilfe eines systemdynamischen und eines ereignisdiskreten Simulationsansatzes werden zukünftige Rücklaufmengen obsoleter Traktionsbatterien auf Basis aktueller Diffusionsszenarien abgeschätzt sowie unterschiedliche Verwertungsoptionen von 2nd-Life-Konzepten bis hin zu alternativen Recyclingverfahren dargestellt und diskutiert

Deconstruction Project Planning Considering Local Environmental Impacts

At present deconstruction project planning and related research focus mainly on economic issues including costs for equipment, workers and material disposal. Nevertheless, deconstruction of buildings can have major impacts on the local environment in terms of noise, dust and vibrations. Usually these environmental concerns are not included in deconstruction planning. But they can be harmful for humans, animals and the surrounding built environment. Analyses of different deconstruction techniques show major differences in noise, dust and vibrations. To use this potential to mitigate local environmental impacts, principals and deconstruction managers have to perform environmental conscious detailed deconstruction planning. In support of balancing these environmental issues with economic and technical aspects, a multi-criteria decision approach can help in the planning phase. In this paper a combination of the multi-criteria decision analysis methods Analytic Hierarchy Process (AHP) and Multi-Attribute Value Theory (MAVT) is embedded in a system for the planning of deconstruction projects based on deconstruction techniques applied to single building components. The structure of this system is described in detail, encompassing the procedure of modelling the overall planning and decision making process as well as the application of the decision making logic. Expert knowledge and experimental noise, dust and vibration measurements related to different deconstruction techniques form the system database. The system is exemplarily applied to deconstruction planning of a small one-level building. Finally, its possible future practical implementation is addressed

A Reverse Logistics Network Model for Handling Returned Products

58827Due to the emergence of e-commerce and the proliferation of liberal return policies, product returns have become daily routines for many companies. Considering the significant impact of product returns on the company’s bottom line, a growing number of companies have attempted to streamline the reverse logistics process. Products are usually returned to initial collection points (ICPs) in small quantities and thus increase the unit shipping cost due to lack of freight discount opportunities. One way to address this issue is to aggregate the returned products into a larger shipment. However, such aggregation increases the holding time at the ICP, which in turn increases the inventory carrying costs. Considering this logistics dilemma, the main objectives of this research are to minimize the total cost by determining the optimal location and collection period of holding time of ICPs; determining the optimal location of a centralized return centre; transforming the nonlinear objective function of the proposed model formulation by Min et al. (2006a) into a linear form; and conducting a sensitivity analysis to the model solutions according to varying parameters such as shipping volume. Existing models and solution procedures are too complicated to solve real-world problems. Through a series of computational experiments, we discovered that the linearization model obtained the optimal solution at a fraction of the time used by the traditional nonlinear model and solution procedure, as well as the ability to handle up to 150 customers as compared to 30 in the conventional nonlinear model. As such, the proposed linear model is more suitable for actual industry applications than the existing models.S

Editorial for special issue: interfaces in supply chains

Editorial for special issue: Interfaces in Supply ChainsRainer Lasch, Frank Schultman