WASTE DESIGN: Production of urban equipment by processing construction waste

Eurostat statistics reveal that in Europe, 36% of special waste is generated in the construction sector during excavation and demolition, renovation of existing buildings and construction of new ones. As summarized in Chapter 17 of the European Waste List, construction and demolition waste includes various types of materials such as wood, metals, glass, excavated material, asphalt and, in larger quantities, bricks, bricks and fragments of reinforced and nearby concrete . conglomerates.

With Directive 2008/98/EC, the member states of the European Union set the goal of achieving 70% recycling of construction waste and waste generated during the demolition of buildings by 2020, and for this purpose a series of tools are provided to promote more sustainable waste management . The directive introduced the concept of a "waste hierarchy", which prioritizes prevention, reuse and recycling instead of processing for energy and landfilling. It also provided criteria for determining the conditions under which "waste ceases to be waste", and at the end, it also provided the classification of hazardous waste and the possible procedures for removing and processing materials in order to enable member states to coordinate and harmonize waste management activities. This directive provided the legal basis on which each Member State formulated its own legislation in the field of waste processing and disposal, but it was insufficiently precise regarding the management of construction and demolition waste. Over the next ten years, the European Union has committed itself to defining procedures to facilitate the identification, collection and processing of construction waste and to strengthen confidence in recycled quality materials from this waste.

In particular, the "selective demolition" of buildings is encouraged as a preliminary process before processing, which enables the safe treatment of hazardous substances and facilitates the reuse and recycling of demolition waste, at least for wood, mineral fractions, metals, glass, plastic and plaster.

An analysis of the Italian situation shows that a lot of waste is still dumped in landfills or illegally in nature, which is a result of the inadequacy of the contractual provisions of public and private construction sites and regulatory gaps regarding the obligations and ways of using materials obtained through recycling, which represent a major obstacle for the development of the circular economy in the construction industry.

The recycling of construction waste and waste from the demolition of buildings is a complex activity due to the abundance and variety of waste produced. Therefore, it is first necessary to quantify the different types of construction waste and the recycled materials obtained from them, so that their availability can then be assessed. According to data from the Regional Environmental Protection Agency of Veneto (ARPA), construction waste in Italy is mainly bricks and reinforced and non-reinforced concrete, with smaller proportions of plastic, metal and paper. Below is a list with the proportions of generated construction waste and the most widespread methods of reuse in the construction industry.

Glass
Proportion: < 3.5%
The most common methods of recycling: Recycled glass can be reused in the construction industry in different ways, depending on the proportion of impurities. It can be used to make glass panels, doors or frames, or mixed with other materials to make ceramic products such as sanitary ware or tiles. In addition to cellular glass thermal insulation, it can also be used as an aggregate to reduce weight or as an additive.

Metals
Proportion: < 3.5%
The most common methods of recycling: Ferrous and non-ferrous metals can be easily recycled and reused in a wide variety of fields.

Paper
Proportion: < 2.5%
The most common ways of recycling: Cellulose paper fibers can be used to make insulation boards, interior partitions or linings.

Plastic
Proportion: < 2.5%
The most common recycling methods: Thermoplastic polymers can be heated and molded to create new products, while thermosetting polymers, which are non-melting and insoluble, can be broken up and used as filler. These processes can be used to make furniture, flooring, pipes and insulation materials.

Wood
Proportion: < 2.5%
The most common ways of recycling: Recycled wood can be used to make wood agglomerates (chipboards) for the furniture industry or wood-cement bricks used in bio-construction.

Asphalt
Proportion: < 5%
The most common methods of recycling: Asphalt can be completely recycled and reused for new road paving.

Excavated material
Proportion: 6%
The most common methods of recycling: Excavated material, depending on the grain size, can be used for filling and backfilling, foundation and soil transformation.

Reinforced and unreinforced concrete
Proportion: 30%
The most common methods of recycling: The most common method of recycling concrete is to reuse it to make materials with lower yields, such as bases, screeds and asphalt.

Bricks
Proportion: 50%
Most common ways of recycling: Bricks can be recycled to make fillers and stabilizers for infrastructure, aggregates for concrete, mortar or calcium silicate bricks.

Among the various materials listed above, inert stone waste is certainly the most widespread and best regulated by recycling legislation, so that several types of recycled inert aggregates can be obtained from them for further use in the construction industry. Materials such as paper, wood, metals, glass and plastic are intended for processing and are partly reused in the same sector. Due to the sharp increase in the use of plastics such as polyvinyl chloride (PVC), polystyrene (PS) and polyethylene (PE) in the construction industry, experts are studying various techniques for recycling polymers, which are quite challenging.

The success of managing construction and demolition waste depends on a number of factors, including the ability to identify and collect waste by different types, the development of protocols based on common regulations and the management of recovery processes, and the process itself begins with a design approach that takes into account the life cycle product cycle in order to minimize the impact of the latter on the environment. The first goal for sustainable design is therefore the longest possible lifetime of the product, which must therefore be made of quality materials and designed in such a way that it can be easily renewed or repaired during its life cycle. Urban equipment can thus be made of several removable or replaceable pieces or made of the same type of materials, which enable the restoration of surfaces and the easy removal of any damage caused by external factors by sanding. An additional topic relates to the need to establish closed production cycles that enable the recycling of products made from recycled materials. For this purpose, it is important to take into account in the design phase the need to separate the different materials that make up the product at the end of its life, giving preference to dry assembly techniques or easily separable materials that are environmentally friendly and not they pollute.