Circular Economy

Circular Economy: what is it?

The Ellen MacArthur Foundation, which has been working for years to accelerate the transition to the circular economy, defines it as "an economy designed to regenerate itself" and adds that "in a circular economy, material flows are of two types: biological, capable of being reintegrated into the biosphere, and technical, intended to be revalorised without entering the biosphere".

Circular Economy: why is it important?

One of the most important issues we are facing today is the reduction of the natural resources consumption (fossil fuels and raw materials) and the managing and disposing of large quantities of industrial waste and scraps (in order to reduce also the related environmental and non- environmental costs).

Both issues can find a common solution thanks to the adoption of models inspired by the Circular Economy concept, such as the use of waste and industrial scraps as resources to be reintroduced into the production process as secondary raw materials, thus promoting a more sustainable development from an economic, social and environmental point of view.

How to adopt a “circular” waste management

According to the waste management hierarchy, landfilling must be considered as the last option and should be limited to the minimum necessary. Other management methods should be adopted for waste treatment:

1. Waste prevention by limiting production waste, which is implemented by many companies today.
2. The reuse of waste, a widespread practice, for example, in the ceramics and plastics industries.
3. The recycling of waste, one of the most interesting approaches that offers various new possibilities according to a circular economy approach (which we will explore in the last paragraph).
4. Waste incineration, which can be divided into:
   - incineration with material and energy recovery (depending on the calorific value of the material, as if it were a fossil fuel. In some cases, at the end of the incineration phase, a part of material remains in order to be reused, but with different characteristics to the original material);
   - incineration with energy recovery only;
   - incineration without energy recovery.
5. Finally, landfilling, which, as already mentioned, occurs when the previous options are not feasible due to particular characteristics of the waste (as, for example, in the case of composite materials that cannot be separated).

Circular Economy for sustainable construction industry

According to the European Commission Communication on "A new action plan for the circular economy. Towards a cleaner and more competitive Europe" (COM 98, 2020), the construction sector consumes about 50% of total material extraction and produces more than 35% of the total waste generated across Europe each year.

Furthermore, it is estimated that the extraction of materials for construction, together with the production of construction products and the building construction and renovation, are responsible for the 5% to the 12% of the total greenhouse gas emissions.

Currently, the scarcity of raw materials and their high costs have led to look at industrial waste and scrap as possible solutions to the problems listed above, considering them as secondary raw materials used to produce innovative and sustainable construction materials, through an approach based on the circular economy.

There is a need to understand how to do this and how to produce sustainable products while also ensuring a high level of quality, safety and performance.

For some production sectors (not currently including the construction sector) there is a dense network of legislation limiting the amount of waste that can be landfilled, such as the Council Directive 1999/31 / EC of 26 April 1999 relating to waste landfills in the case of organic waste and composite materials. In the automotive sector, since 2015, 85% of the weight of vehicles at the end of their useful life has to be reusable or recycled, and the remaining 15% only a fraction of it (5%) can be landfilled.

For the construction sector, a push towards the adoption of the solutions listed above was given by the introduction of CAM or Minimum Environmental Criteria, mandatory since 2017 for public administrations. The introduction of these criteria aims to reduce the environmental impact of building interventions (both new construction, renovation and maintenance) through the adoption of new environmentally sustainable solutions and products. CAM, for example, prescribes, among other things, the minimum recycled content that building materials must contain to be considered sustainable.

How to sort and evaluate waste or industrial waste?

Even if it is difficult in practical terms to define an ideal waste in absolute terms and to establish a possible reuse, it is possible to define what issues are faced when reusing a waste and what makes a waste a potential secondary raw material.

These are the characteristics that have to be taken into account in order to properly assess the waste reuse.

• The waste chemical composition, i.e. assessing whether it contains any harmful substances, substances that may react with others or substances that may degrade rapidly.
• The variation of the waste composition during the annual production, as the characteristics and composition of the waste must be constant over time in order to have a quality product.
• The waste condition (i.e. purity, particle size, moisture content, presence of slurry or undesirable components, etc.), which can greatly influence the possibility of reusing this material.
• The work and processes required for reuse (sorting, screening, grinding, washing, filtering, heat treatment, etc.): the less work and processes that are required for this waste/waste to be reused, and the lower the costs involved, the greater the possibility of reusing this material.
• The waste classification and the conditions of its disposal, as according to its EWC code (European Waste Catalogue) and its level of hazardousness, the reuse of the material may be limited to certain uses or quantities.
• The waste availability, i.e. checking that the production volume is compatible with the availability of the waste to be used in production.

From waste to secondary raw material: practical examples in the construction industry

Among the possibilities of reusing waste or industrial waste, it is important to mention the possibility of producing cement conglomerates by integrating waste materials. This type of production process offers a number of significant advantages, such as:

• the possibility of using large quantities of waste;
• multiple possibilities of reuse, for example in the production of mortars, screeds, sub-bases, panels, plasters and concrete;
• the possibility of using different sizes and types of waste (powder, fine or coarse ground, fibers, etc.);
• the applicable quantities and related controls which vary depending on the intended use of the waste materials (e.g. for structural concrete only the use of material from selective demolition is permitted, with specific controls);
• the increase in market demand for products containing industrial waste, also due to regulations that increasingly require materials with these characteristics.

The procedure to be followed in order to develop innovative and sustainable mixtures, that partially or totally replace aggregates and/or cement with secondary raw materials, involves the following steps:

• it starts with the characterisation and assessment of the waste, through chemical and physical analysis of the waste;
• a feasibility study, used to develop and implement a mix of secondary raw materials (as aggregate and/or binder) in terms of type and quantity;
• the experimental validation and engineering of the product, through experimental characterisation according to the reference norms and EU standards, in order to assess the performance and durability of the product, including comparison with traditional products already on the market (to verify that they possess qualities in line with them, in order to be presented on the market as real alternatives).

Below are listed other case studies about the reuse and valorisation of processing waste, followed by Certimac's team of Materials Science experts, to provide further insights into the potential of this type of application as part of the Circular Economy concept.

• Reuse of shells (mussel farming waste) and ceramic powder (ceramic industry waste) for the production of sustainable mortars and plasters.
• Re-use of ground tyres (used/end-of-life) and ceramic powder (ceramic industry waste) to produce sustainable screeds.
• Production of sustainable mortars using black foundry slag (foundry waste) and ceramic powder (ceramic industry waste).
• Use of fibreglass powder and ground fibreglass, obtained by grinding the waste from the processing of fibreglass composites, for the production of two types of products:
  - cementitious mortar (the powder is used to partially replace aggregate and cement);
  - concrete (the powder is used to partially replace cement, while the coarser fragments are used to replace gravel).
• Eggshells (calcined and ground) have also been re-used to make sustainable mortars and cements. The process of incubating chicks and the food industry both produce a huge amount of waste in the form of eggshells (millions of eggs per week). This waste is composed of very pure limestone which can be used as:
  - filler for cement mixes, replacing common limestone fillers;
  - addition for cements, to produce cement from limestone.
• Finally, recycled ground glass (from separate waste collection) can also be used to make sustainable mortars and plasters.