11.1. Circular construction

A circular economy is based on the principles of designing out waste and pollution, keeping products and materials in use, and regenerating natural systems [10]

The circular economy, as such, is seen as a new way of creating value and prosperity, by extending the life of products and moving waste from the end to the beginning of the supply chain. It uses two different cycles – biological and technological. The biological cycle refers to the consumption of food and bio-based materials designed to be returned to the environment through composting and anaerobic digestion processes (e.g., wood products), or transformed into energy. The technological cycle involves the design of products that can be reused and restored as whole products, components, and resources (e.g., buildings, airplanes...) [10]. In other words, in the circular economy, products are manufactured in such a way that they can be disassembled and materials can be broken down by nature or returned to nature, with the goal of not throwing anything away and reducing the need to buy new goods [11]. Ultimately, resources are used more efficiently by using them more than once, which should lead to less waste [5].

On the supply side, the circular economy focuses mainly on production chains in: electronics and ICT, batteries and vehicles, packaging, plastics, textiles, construction and buildings, and food, water and nutrients. While looking from the demand side, it should provide citizens with high-quality, functional and safe products that are efficient, affordable, last longer and are designed for reuse, repair and high-quality recycling [2].

Circular construction, the application of the circular economy to the construction industry, aims to close building material loops by reusing, sharing, leasing, repairing, refurbishing, upcycling or recycling rather than continuing the traditional take-make-consume-dispose process. It is about considering how to maximise the lifespan and reusability of entire buildings or materials at the very start of the design process (Fig. 2).

A true circular building is made of components of fully recyclable, non mixed technocycle materials, that can be 1 on 1 upcycled in the end of life (e.g. concrete columns), combined with building components that are fully fitting with the biocycle (e.g. prefab CLT components) that may recycled and even downcycled (particle board, bio-energy). Also it is important to use as many fully non-toxic materials as possible, proven by C2C (Cradle to Cradle) Gold / Platinum certification [13]. Ideally these building components are leased and there is an accurate overview of the materials used in a Material Passport of the building, this way a building becomes a material bank as shown in the BAMB2020 project [14]. In the Netherlands, Venlo City Hall [15] and Circl Pavillion [16] ABN AMRO bank Amsterdam WTC are showcases of a circular building project.