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End-of-Life Household Materials (EoLHM) can be defined as household waste materials that still possess exploitable properties, thus making them suitable for reuse. There are several studies in the literature that address the recycling of these materials. When it comes to their reuse, unfortunately, only a limited number of studies are available.
Household end-of-life material (EoLHM) can be destined for reuse, recycling, and incineration, with or without energy recovery, or landfill. According to the survey by Eurostat [1], municipal waste includes household waste and waste similar in nature and composition to household waste: in Figure 1, it can be observed that municipal waste is destined for landfill and, in a small part, to recovery operations. Landfill is the most common practice in OECD countries (Figure 1). Except for reuse and recycling, the other disposal methods determine the material end-of-life with a consequent footprint. Indeed, new raw materials must be extracted and processed. Finished goods must be transported and supplied. The amount of recycled packaging depends on the material and on the country [2]. Waste is often shipped overseas (with additional emissions due to the transportation) towards regions where waste disposal rules are sometimes unclear. In these countries, waste is often mismanaged (not formally managed and includes disposal in dumps or open, uncontrolled landfills, where it is not fully contained) with consequences for the environment and the health of native people [3][4]; incorrect waste disposal and abandonment are critical, with consequent soil, air and water pollution. If recycling is energy-consuming, reuse (intended as the reuse of the object for the same purpose for which it was designed, or assigning the object to another use) is probably the option with the lowest environmental impact.
Figure 1. Municipal waste produced in 2018 in EOCD, and waste treatment [5]. Recovery indicates any operation whose objective is to use waste as a substitute for other materials to perform a particular function [6].
While the building design in the past was aimed at structural aspects only, it is now a multidisciplinary process that embraces socio-economic and environmental issues. According to the European Energy Poverty observatory [7], energy poverty occurs when a household suffers from a lack of adequate energy, that is, the lack of adequate warmth, cooling, lighting and energy to power appliances. In the EU, energy poverty affects more than 50 million families that cannot afford proper interventions to improve their dwellings energy performance [8]. There is a close correlation between poverty and precarious indoor comfort conditions, which are affected by age, education level, salary of the occupants, dwelling size, and age of the building [9][10]. Mainly elderly people, disabled people and long-term-unemployed are often forced to live in unhealthy spaces and in conditions of total discomfort, including conditions causing the death of the tenants. For example, in Spain, there are about 6000 excess winter deaths related to cold dwellings [11]. Since energy poverty is related also to social isolation, people living in poor neighborhoods should be involved in the renovation process to give them the possibility to have experience in the construction sector. The idea is that this could help marginalized people to find a job. Examples of the combination of engineering and social aspects are reported in [12][13][14]. One of the test cases is the construction of a psychiatric hospital in Czech Republic: the hospital was built by people with mental diseases. In Germany, homeless and unemployed people were hired in a construction site and a certification proving the acquired knowledge was released, so that the people participating to the experiment could enter the work world more easily.
Given their huge quantity and presence in every part of the world, the reuse of EoLHM enables low-income people to refurbish their houses with free products in contexts where commercial insulating materials cannot be purchased. In addition, low-cost or even free insulating materials would incentivize buildings refurbishment, and it would facilitate the achievement of energy and environmental international goals [15][16], as buildings are responsible for approximately 40% of EU energy consumption and 36% of the CO22emissions [17][18]. Since about 35% of the EU’s buildings are over 50 years old, and only about 1% of the building stock is renovated each year [19], revamping the existing building stock is a key factor.
We investigated the possibility of converting end-of-life household materials (EoLHM) into low-cost insulating materials. The limited number of articles found in the literature related to reuse has highlighted the necessity of bringing some innovation in this sector. From the information so collected, tables that qualitatively evaluate important aspects in the choice of insulating materials have been proposed to highlight the potential of EoLHM and the aspects that need to be improved to achieve the performance of commercial materials. The conversion of EoLHM into insulating materials is possible, and it must be stimulated, in order to push the circular economy and discourage the abandonment of EoLHM. However, there are some aspects, such as the collection and storage of the materials to be used, that need to be further investigated. Since a large number of elements must be collected in order to carry out interventions even on small surfaces, EoLHM collection and storage should be done at the neighborhood or at city level by means of an extensive collecting system. Furthermore, some of these materials (such as glass bottles) are poorly adaptable or offer poor thermal resistance/insulation (such as egg-boxes). Nevertheless, the peculiarities of each material can be exploited to create insulating panels composed of several materials. Egg-boxes can, for example, contain materials characterized by low thermal conductivity but without structural stiffness (such as clothes). Given the wide availability of these materials, these solutions should be used to renovate buildings in disadvantaged contexts. If properly trained, people living in these realities could implement the interventions directly. Indeed, the realization of insulating panels made of EoLHM does not require particular skills and tools. In spite of this, an introduction to the thermal insulation in buildings and its principles is very important to show how to make these panels. On the other hand, a course or set of guidelines should be defined to make participants aware of the best practices. A further benefit of a possible collaboration between professionals and people living in these contexts can be a better integration of the marginalized population and the creation of work opportunities.