La reutilización y reciclaje de residuos en el sitio de construcción

Waste reuse and recycling on the construction site consists of sorting, treating and reincorporating surplus or demolished materials within the site perimeter itself, minimizing transport to landfill and demand for virgin raw materials. The Waste Framework Directive 2008/98/EC establishes a hierarchy that prioritizes prevention, followed by reuse, recycling, energy recovery and, as a last resort, landfill disposal. For construction and demolition waste (CDW), the European target is to achieve a 70% recovery rate by weight, a threshold met by 18 of the 27 Member States in 2022 (Eurostat). In Spain, Royal Decree 105/2008 requires preparation of a Waste Management Plan for every project with a budget exceeding 75,000 EUR, specifying estimated quantities by fraction (concrete, ceramics, wood, metals, plastics, hazardous waste), intended destinations and on-site separation measures. Data from the MITECO Register of Waste Producers and Managers indicate that in 2022, 38.9 million tonnes of CDW were generated in Spain, of which 68% was recovered, up from 40% in 2012.

Selective separation on the construction site is the primary prerequisite for effective reuse and recycling. Best practice technical standards require a minimum of 5 differentiated containers: clean stone materials (concrete, brick, ceramics), wood, metals, plastics and packaging, and hazardous waste (paints, solvents, asbestos). Documented experience shows that source separation achieves purities of 90% to 98% per fraction, compared to the 60% to 75% obtained at external sorting plants from mixed CDW (LIFE CIRC-ELV Project, 2021). The additional cost of on-site separation is estimated at 2 to 5 EUR per m² of constructed area, offset by reduced landfill fees (15 to 80 EUR per tonne in the EU), revenue from recyclable material sales (steel: 200-400 EUR/t, aluminum: 800-1,200 EUR/t, copper: 5,000-7,000 EUR/t) and reduced transport costs. A BRE (Building Research Establishment, 2020) study across 50 UK construction sites demonstrated average net savings of 4.50 GBP per m² of constructed area when selective separation with at least 7 fractions was implemented.

In-situ crushing of stone waste (concrete, brick, ceramics) constitutes the recycling technique with the highest volume of application on the construction site. Mobile jaw crushers (capacity: 50 to 300 tonnes per hour, weight: 25 to 45 tonnes, power: 150 to 350 kW) produce recycled aggregate in particle sizes of 0-20 mm, 20-40 mm and 40-80 mm, directly usable as base and sub-base for internal site roads, trench backfill, pipe bedding and ground stabilization. Standard EN 13242:2002 and the technical guide from the Comunidad de Madrid for recycled aggregate use permit their application in pavement layers with impurity content (gypsum, wood, plastic) below 1% by weight. The savings are twofold: the cost of transporting and disposing of waste is avoided (15-30 EUR/t for transport plus 15-80 EUR/t for disposal fees) and the purchase and transport of natural aggregate is eliminated (8-15 EUR/t plus 10-20 EUR/t for transport), yielding total savings of 40 to 130 EUR per tonne. On a 10,000 m² building project typically generating 800 to 1,500 tonnes of stone CDW, the savings reach 30,000 to 150,000 EUR.

In-situ recycling requires quality control to ensure the performance of the aggregate produced. Minimum testing includes: particle size distribution (sieving per EN 933-1, minimum frequency of 1 test per 500 tonnes), Los Angeles coefficient for fragmentation resistance (limit of 40 for road bases, EN 1097-2), flakiness index (limit of 35%, EN 933-3) and water-soluble sulfate content (limit of 0.8% to prevent expansive reactions, EN 1744-1). Modern crushers incorporate magnetic separators for steel extraction (recovery of 95% to 99%) and vibrating screens with interchangeable meshes for particle size classification in a single pass. Dust emissions during crushing are controlled through sprinkler systems (water consumption: 5 to 15 liters per tonne crushed), wind barriers and partial encapsulation of the crushing zone, maintaining PM10 concentrations below 50 µg/m³ at the site perimeter as required by Directive 2008/50/EC. A documented case is the demolition and reconstruction of Wembley Stadium (London, 2003-2007), where 23,000 tonnes of concrete from the original stadium were crushed in-situ to produce recycled aggregate used as sub-base for the new building, avoiding 2,300 truck trips and saving 1.2 million GBP.

Direct reuse, without industrial transformation, represents the highest level of the waste hierarchy applied to the construction site. Materials with the greatest reuse potential include: clean excavation soils (reuse as fill, landscaping or earthworks in 60% to 90% of cases when prior geotechnical characterization is performed), timber formwork and shoring (service life of 5 to 15 uses with proper maintenance, saving 3 to 8 EUR/m² of formwork), pallets and packaging (return to supplier or internal reuse: 100% reduction in packaging waste), metal elements such as props, scaffolding and temporary profiles (service life exceeding 20 years with periodic inspection), and surplus ceramic and stone pieces from offcuts (reuse as flooring in secondary areas, landscaping or donation to social projects). A project documented by Lendager Group in Copenhagen reused 1,400,000 bricks dismantled from demolished buildings to construct the facades of the Resource Rows residential complex, achieving a 70% emission reduction in the facade component at a cost comparable to new brick.

Excavation soil reuse deserves special attention due to its volume: a basement construction project of 2,000 m² with 3 underground levels generates between 15,000 and 25,000 m³ of soil, equivalent to 25,000 to 45,000 tonnes. Conventional management involves transport to landfill (cost: 8 to 20 EUR/m³ for transport plus 3 to 10 EUR/m³ for disposal fees), while in-situ or nearby-site reuse eliminates these costs and the associated transport emissions (a 25-tonne truck emits 0.1 kgCO₂ per tonne-kilometer). Spanish regulations (Royal Decree 1/2016 on soil management) permit reuse of clean soils (contaminant levels below the Generic Reference Levels of RD 9/2005) without specific authorization, provided that analytical characterization is documented. Digital soil exchange platforms (such as the Bolsa de Tierras of the Comunidad de Madrid) connect surplus sites with sites in need within a 30 km radius, achieving reuse rates of 40% to 70% of generated soils. Across all material types, waste reuse and recycling on the construction site transforms the project from a waste generator into a node of material circularity that optimizes resources and reduces the environmental footprint of building construction.

The quantified benefits of on-site reuse and recycling span the economic, environmental and social dimensions. In economic terms, the WRAP program (Waste and Resources Action Programme, United Kingdom) documented across 300 construction sites that implementing waste management plans reduces total CDW management costs by 30% to 50%, with average savings of 8.50 GBP per m² of constructed area. In environmental terms, diverting waste from landfill avoids methane emissions (0.05 to 0.1 tCO₂eq per tonne of organic waste not landfilled), reduces natural resource extraction (each tonne of recycled aggregate avoids extraction of 1 tonne of natural aggregate and associated emissions of 5 to 10 kgCO₂) and decreases transport emissions by 60% to 80% when recycling is performed in-situ. The life cycle analysis from the European SB-Alliance project demonstrated that projects with recycling rates above 80% reduce their total carbon footprint by 5% to 12% compared to equivalent conventional projects.

Barriers to implementation include technical, economic and cultural factors. Lack of space on site is the most frequent limitation in dense urban areas, where installing 5 to 7 separation containers and a reusable material storage area requires 100 to 300 m² of surface area — a scarce resource on plots smaller than 1,000 m². The sector's resistance to modifying established practices results in effective separation rates below 50% when no environmental supervision is present on site (WRAP, 2020). The absence of mature markets for certain recycled materials (gypsum, mineral wool, flat glass) reduces the economic incentives for their separation. Documented solutions include: designation of an on-site environmental manager (cost: 2,000 to 4,000 EUR per month, offset by generated savings), specific worker training (4 to 8 hours per worker, with increases of 20% to 40% in correct separation rates after training), incorporation of waste management clauses in subcontractor contracts (penalties of 500 to 2,000 EUR per contaminated container) and use of digital waste traceability platforms that document flows in real time and generate the monitoring reports required by regulations.