La economía circular en la construcción. Reduciendo residuos y reutilizando recursos

The construction and demolition (C&D) sector is the largest waste generator in the European economy. Eurostat (2023) puts C&D waste production in the EU-27 at 374 million tonnes per year, representing 37% of all waste generated. In Spain, the National Waste Management Framework Plan (PEMAR 2016-2022) documented the generation of 38.5 million tonnes of C&D waste in 2022, of which 34% underwent material recovery operations and 66% was sent to landfill, failing to meet the 70% recovery target established by the Waste Framework Directive (2008/98/EC) for 2020. The average composition of C&D waste in Spain is 75% concrete and mineral materials, 8% wood, 5% metals, 4% plastics, 3% glass, and 5% other (CEDEX, 2022). The problem is not merely one of volume: the extraction of virgin materials for construction amounts to 3 billion tonnes annually worldwide, equivalent to 40% of total material resource extraction (UNEP-IRP, 2020), generating pressure on ecosystems, energy consumption from extraction and transport, and CO₂ emissions that are accounted for in modules A1-A3 of the building's LCA.

The economic potential of circularity in construction is quantifiable. The Ellen MacArthur Foundation (2021) estimated that applying circular economy principles to the European construction sector could generate savings of 360 billion EUR per year through reduced virgin material costs, waste valorization, and extended building service life. A study by Arup and the Ellen MacArthur Foundation (2023) analyzed 15 circular building projects in 8 European countries and documented material cost savings of 15-30% through the use of reused components and recycled materials, although with a 5-12% increase in design and logistics management costs. The net return on investment was positive in 12 of the 15 projects, with an average payback period for the cost premium of 3-7 years. The materials with the greatest circularity potential are structural steel (recyclable at 98% with a 74% energy saving compared to primary production), aluminum (recyclable at 95% with a 95% energy saving), structural timber (directly reusable in 60-80% of cases when design for disassembly is used), and concrete (recyclable as aggregate in 90% of cases, but with a 100% loss of the calcination energy of the cement).

Design for Disassembly (DfD) is the most effective strategy for maintaining material value at the end of a building's service life. The principles of DfD include the use of reversible mechanical connections instead of permanent chemical bonds, dimensional modularization, minimization of the number of different materials, complete documentation of materials and their connections, and accessibility of connection points. A study by Akinade et al. (2017), published in Waste Management, evaluated 34 buildings designed with DfD criteria against 34 equivalent conventional buildings and documented that DfD buildings allow the recovery of 72% of structural materials in conditions suitable for direct reuse, compared to 18% for conventional buildings. The additional cost of design for disassembly is estimated at 2% to 5% of the material execution budget, but the residual value of recoverable materials increases the building's end-of-life value by 15% to 20% of the initial construction cost. The most advanced example is the Circle House in Denmark (2023, 60 dwellings), designed entirely for disassembly with 1,100 components cataloged in a digital materials passport: 90% of materials are recoverable for reuse or high-quality recycling.

Materials passports and digital materials banks are enabling tools for circular economy at scale. The Madaster platform, launched in the Netherlands in 2017 and operational in 15 European countries since 2024, records the identity, location, quantity, and residual value of each material incorporated in a building, and has cataloged more than 2,500 buildings with a total documented materials value of 4.3 billion EUR. The European Protocol on Construction and Demolition Waste Management (2018) establishes guidelines for pre-demolition audits that increase the recovery rate from 40% to 70% in projects where they are applied. In Spain, Royal Decree 105/2008 requires a waste management study for new construction and demolition projects, but a report by MITMA (2023) revealed that only 22% of supervised construction sites effectively comply with the separation of waste into 5 fractions (concrete, metals, wood, glass, plastic) required by regulation, indicating an implementation deficit that limits actual recycling rates.

Direct reuse of building components avoids reprocessing and preserves 100% of the energy and carbon embodied in the original material. The European market for reused construction materials grew by 25% annually between 2019 and 2024, reaching an estimated volume of 3.2 billion EUR (Circular Economy Network, 2024). The components with the greatest reuse potential are structural steel beams and columns (the British standard BS 7488 permits direct reuse with batch tensile testing), clay bricks recovered from walls with lime mortar (85% of bricks from buildings predating 1960 are recoverable according to a study by the University of Leuven, 2020), aluminum and PVC window frames with insulating glass units (reusable at 70-80% with gasket replacement), and clay roof tiles (service life of 100-150 years, reusable in 90% of cases). The Belgian company Rotor Deconstruction, founded in 2014, has deconstructed and brought to market components from more than 200 buildings, documenting that the cost of reused materials is 20-50% lower than that of new equivalents with verified technical performance.

Urban mining considers the existing building stock as a strategic materials bank. A study by Kleemann et al. (2017), published in the Journal of Cleaner Production, quantified the material stock accumulated in Vienna's buildings at 380 million tonnes, equivalent to 200 tonnes per inhabitant, of which 270 million tonnes are minerals (concrete, ceramics, stone), 55 million are metals, and 25 million are wood. The annual flow of materials released through building demolition in the EU is estimated at 450 million tonnes, a figure that exceeds the annual natural aggregate production of many member states. Recycled concrete aggregates, standardized under EN 12620 and permitted by Eurocode 2 with substitutions of 20-50% of natural aggregates in structural concrete, are already used in 12% of concrete produced in the Netherlands, 8% in Germany, and only 2% in Spain (ERMCO, 2023). The difference is explained by natural aggregate availability: Spain is the third-largest European aggregate producer at 210 million tonnes per year, which reduces the economic incentive for recycling, while the Netherlands, with a geological scarcity of aggregates, applies a tax of 7.5 EUR/tonne on virgin aggregates that incentivizes substitution.

European regulation is advancing toward mandatory circularity in construction. The revised Construction Products Regulation (CPR, 2024) introduces the requirement to declare the recycled content and recyclability of construction products marketed in the EU, and establishes the legal basis for digital product passports. The revised Waste Framework Directive (2024) raises the C&D waste recovery target to 80% by 2030 and introduces for the first time a specific reuse target of 15% of non-hazardous C&D materials. The EU Green Taxonomy Regulation includes the circular economy as one of 6 environmental objectives and defines specific technical criteria for construction activities to be classified as "substantially contributing" to circularity: a minimum of 70% of non-hazardous construction waste must be recovered, at least 15% of the content of main materials must be recycled, and the project must incorporate a waste management plan and a materials passport. In Spain, Law 7/2022 on Waste and Contaminated Soil introduces the obligation to separate C&D waste into 7 fractions from 2024 and establishes a landfill levy of 40 EUR/tonne that will come into effect progressively through 2026.

Scaling prospects depend on the convergence of regulation, technology, and business models. Digital materials exchange platforms such as Materiom, Excess Materials Exchange, and the Spanish platform Brickstock facilitate the connection between supply and demand for reusable materials and have intermediated transactions worth 180 million EUR in 2023. 3D printing with recycled materials enables the fabrication of building components from C&D waste: the company WASP (Italy) has demonstrated the feasibility of printing habitable modules of 40 m² using mixtures of local earth and recycled fibers at a material cost of 900 EUR/unit and a fabrication time of 200 hours. Product-as-a-service business models applied to construction, where the manufacturer retains ownership of the material and recovers it at the end of the building's service life, are being implemented by companies such as Interface (textile flooring, with 2.3 billion m² recovered since 1994) and Royal BAM Group (structural steel as a service). The Ellen MacArthur Foundation (2023) projects that the circular economy in construction will grow from 5% of the sector's business volume in 2023 to 20-25% by 2040, driven by embodied carbon regulation, rising raw material prices, and the maturation of digital materials management platforms.