The construction industry generates enormous quantities of waste. In spite of the high volumes of construction and demolition waste (CDW) being generated, recycling rates vary substantially in different countries around the world. Countries such as The Netherlands, Ireland, and Hungary reported recovery rates of 99 to 100 percent in 2017, while figures for other nations ranged from 0 to 69 percent.
In all cases, most of the recovered materials are downcycled – mainly used for backfilling in road construction, building foundations, or embankments – or sent to landfill. This means that the recovered materials do not replace or significantly reduce the use of raw materials in the production process, hindering an effective circular economy.
"This represents a huge untapped potential," says Juan Carlos Hernández Parrodi, senior project manager of research and development at STADLER. "Typically, CDW is made up of concrete, wood, metals, glass, masonry rubble, stones, soil, sand, gypsum, plasterboard, asphalt, plastics, insulation, paper, cardboard, and salvaged building components. There is very little that can't be recycled - the recycling potential of this waste can be higher than 90 percent."
Recovered materials from CDW can be recycled in a variety of applications. For example, today less than 5 percent of recovered aggregates are used in the production of new concrete. However, recovered aggregates are said to be suitable for the substitution of 10 to 20 percent of virgin aggregates for many concrete applications, which range from pipe bedding to concrete and block construction.
"Some previous studies have pointed out that, if appropriately processed to remove moisture and impurities, recovered aggregates can even have advantages over raw materials in some cases, such as higher compressive strength and a wider range of applications in the construction industry," explains Hernández Parrodi.
The effective management of CDW is becoming an increasingly urgent issue. As natural resources are depleted and the demand from the construction industry continues to grow, recycling CDW to replace raw materials is fast turning into a necessity.
"Even if we were to recycle 100 percent of the generated CDW, we would not be able to meet the current demand of construction materials," says Hernández Parrodi.
However, awareness among governments, environmental organizations, educational institutions, and the general public is growing. The gradual implementation of ordinances and directives in the EU and around the world is diverting increasingly significant amounts of CDW from landfill toward recycling and material recovery plants.
"This evolution is accelerating," says Hernández Parrodi. "Legislation regulating the amounts of CDW that can be disposed of in landfill is increasingly restrictive and aims to promote the recovery of secondary materials and recycling. At the same time, new regulations are setting high standards for recycled construction materials, encouraging a shift from downcycling to recycling and upcycling. All these factors are driving a fast growth in the demand for technology innovation and facilities capable of recovering high-quality materials from CDW."
The effective sorting of CDW is key to achieving the high-quality levels required for successful recycling and upcycling in a broad range of construction applications. The composition of this type of waste and the requirements for the targeted output fractions varies significantly from country to country, and sometimes even at regional levels.
"Similarly to other waste streams, such as municipal solid waste or packaging waste, there is no standard recipe for processing CDW," explains Hernández Parrodi.
STADLER is able to bring its experience in the design of advanced sorting plants to the construction sector, developing tailored solutions to match the individual situations: "The consideration of all the specific factors, together with our know-how, enables us to provide effective, efficient, and high-quality sorting facilities. Since we produce and assemble most of our equipment ourselves, we can be very agile in project planning, development, and execution. Also, we employ the latest sorting equipment available in the market, such as sensor-based and robotic sorting systems."
CDW sorting processes need to be flexible, robust, and capable of handling high throughputs with considerable fluctuations. STADLER's machines are conceived to process large amounts of mixtures of diverse materials in challenging conditions, such as the presence of fines and humidity, as well as heavy and bulky objects.
STADLER has successfully applied its waste sorting know-how in a number of CDW projects – the most recent ones for Sogetri in Switzerland and Remeo Oy in Finland. The latter is a pioneering facility that combines a CDW plant capable of processing 30 tph and a C&I plant with 15 tph capacity, featuring artificial intelligence (AI) technology from partner ZenRobotics, cutting-edge processes, and a high level of automation.
STADLER's sorting plants enable the separation of CDW into different fractions, which can have a broad range of applications. They can substitute raw construction materials such as sand, gravel, metal, wood, and many more. Recovered concrete can be used to produce recycled concrete. Recovered fractions from CDW can also be utilized to innovate and produce new materials, such as inorganic polymers and glass-ceramics.
"This means that with recovery not only is it possible to close the loop in material life cycles and move toward a circular economy," concludes Hernández Parrodi, "but it also enables upcycling, consequently expanding the applications and increasing the added value of recovered materials."
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