How Can We ‘Close the Loop’ on Construction Waste?

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Marlene Thorman Member Name

Operations Manager

Maud Söderberg Member Name

Senior Environmental Consultant

Throughout Scandinavia, the ‘circular economy’ is recognised as a key sustainability goal. In a circular or ‘closed loop’ system, maximum value can be extracted from existing materials through reuse which reduces the need to exploit new resources and creates less waste. Rather than the wasteful linear model of take–make–use–dispose, the circular model prioritises returning, sharing and reusing.

Construction and demolition waste make up around one-third of all waste in the EU, and building materials account for approximately half of a building’s carbon footprint. If also targeted other constructions such as bridges, viaducts, and pylons the waste from construction and demolition is even larger. This makes it very beneficial to keep construction materials circulating rather than heading to incinerators or landfill. Reuse avoids the greenhouse gases generated when new materials are created and considerably reduces freight-related emissions.

Concrete is often crushed and reused as fill or in major infrastructure projects, yet some barriers still inhibit the reuse of other demolition waste (such as wood, bricks, metals, glass, gypsum, soil, etc.) and materials used temporarily on construction sites (primarily timber for footboards, supports, hoarding, etc.). In Denmark alone, temporary materials account for approximately 50 000 tonnes per year of timber disposed of as combustible waste.

What can we do to encourage and facilitate greater reuse of construction and demolition waste without introducing risk?

Confirm the safety and composition of recycled materials

In the demolition process, any potentially hazardous materials (such as impregnated wood, paint, varnish, sealants, etc.) must be carefully identified and separated. Remaining materials that are identified as having potential for reuse must be confirmed to be free of hazardous contaminants such as PCBs (polychlorinated biphenyls), absorbed chemicals from historical uses, and heavy metals – otherwise pollution issues are shifted rather than resolved and risks to health remain. Materials identified for reuse should also be confirmed as meeting the required performance standards for new construction.

Attaining a higher level of reuse cannot come at the expense of contaminating new buildings or the environment, nor risking the health and safety of the community. It is understandable that the building industry and community should be concerned about the risk of pollution if construction and demolition waste is used for anything other than fill. However, a specialist sampling and testing strategy can minimise risk and assist in alleviating these concerns.

Identifying the level of risk and the condition of materials at the earliest stage of a project will allow owners, developers, architects, and builders of constructions such as buildings to plan for effective reuse of materials. Sampling and testing will not be adequate in isolation. Specialist support will be necessary to confirm whether the sampling is suitable and to advise on the implications of the testing results. This means starting the process early with an inventory of the historical use of the construction/building, including the chemicals used. This will indicate what and where to sample by identifying specific risks for contamination and/or hazardous materials.

A little extra time and money spent at this early stage will be a sound investment and is likely to produce a better result. Specialist interpretation and identification of an appropriate approach for safe and economical handling may avoid a range of complex and expensive problems further along the journey. Issues identified late, such as discovering unaddressed hidden tar layers in a concrete slab during demolition, could greatly interrupt and delay a project as well as incur extra costs for urgent handling.

Improve communication and collaboration among all industry participants

Architects, developers, and builders in Scandinavia are increasingly interested in the circular economy, and most have the desire and intention to reuse materials to create new, sustainable buildings that include layers of heritage and history. However, there is room for improvement in the chain of communication among all the participants in the construction process. Circularity, by its very nature, requires information, negotiation, collaboration and coordinated action, and is unlikely to be achieved if the sector is fragmented.

Good communication and clear expectations among the building/construction owner/developer, architect, engineer, builder, demolition contractor and waste manager are necessary from the earliest point in the design and planning process. When there is shared understanding of the goals and benefits (and potential profits), each participant is likely to be more motivated to optimise their management of materials. Better communication and coordination throughout the sector will also facilitate knowledge sharing and up-skilling, which lowers risk and increases the likelihood of positive outcomes. It will be even more beneficial if communication and coordination can extend beyond contractors, builders, and environmental specialists to also include regulators, municipalities, and suitable research institutions.

Incorporate clear expectations into the tender documentation

It is one thing to agree theoretically with a sustainability principle, but will that be enough incentive to overcome inertia, change habits, create a sense of urgency for change, and foster innovation? If recycling requirements and expectations are incorporated into the tender documentation, all players are likely to achieve a clearer understanding of the project and to compete on even terms.

The Nordic countries have various guidelines for handling resources and construction waste with the objectives of optimising material flux, minimising the amount of waste, and ultimately achieving a circular economy to benefit society. The use of these, or similar, guidelines can be incorporated in the tender documents. Expectations can also be built into contracts to optimise transport in demolition and (re)building processes, such as expectations that trucks not travel without loads. The coordination will be challenging, but not insurmountable.

Make cost-competitive materials available when and where needed

In practice, greater recovery of materials during demolition and increased reuse of these materials in new construction will depend on the materials being easily available and cost-competitive and will require solutions to the substantial challenges of logistics and coordination. We will need efficient transport, temporary material storages, information exchanges or ‘matching’ systems that can connect availability and need, and markets where material can be sourced – whether these markets are virtual (e.g. via a website, database or app) or physical. An example is the collaborative project GENTRÆ, which enables checking of reusable construction timber, efficient transport (as new materials are delivered to site, the recyclable materials are transported away, optimising the truck’s journey), and resale at a construction market. The key is to have these markets easily available and not too distant.

When all participants in the construction sector are enthusiastic about greater circularity, and can be confident of the safety, quality, availability and cost-effectiveness of recycled materials, together we can create a paradigm shift towards a more sustainable built environment and a better future.

About the Authors

Marlene Thorman Member Name

Operations Manager

Maud Söderberg Member Name

Senior Environmental Consultant

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