18 June 2018

Buildings: from wreckage to resource

Achieving 70% recycling of building debris by 2020 demands better structuring of the demolition process and associated sectors; moreover, this dimension must be inbuilt at the design stage. A new circular economy is taking shape.

Dismantling revisited

For a 3- or 4-storey concrete building, out of the 1000 tonnes of waste left after demolition, 10% is “dead-end” debris in the form of wood, plaster, insulation, etc., leaving 90% of recyclable waste, mainly from the structure. The potential is therefore considerable and promises substantial savings. A tonne of waste sent to landfill costs €100. Sorted and sent to the recycling platforms, it costs just €1.

The first issue is therefore to get project owners to tackle the dismantling/demolition phase from a diagnostic/inventory angle, with a view to recycling or re-using the site waste. An essential step before proceeding is the waste diagnosis, which identifies and records recoverable materials and ensures relevant waste disposal/recycling facilities exist in the region.

Once all this is established, the job must be organized per storey and per material. This avoids sorting everything at the base of the building, where items can easily become mixed together and end up in the skip. A project owner eyeing re-use as a solution will need a contractor with the skills to identify materials having inherent value, such as parquet flooring, frames, frontages, roof tiles, etc., and assess their re-usage options, either direct or with slight reconditioning. In this habit-overturning context, the new “Guide”—drafted by ADEME, France’s state environment agency, to help contracting authorities and contractors compose the “waste” brief of major refurbishing or demolition contracts—is just what the doctor ordered.  Recommendations for the classification of waste and its selective disposal figure largely therein.

Use of construction systems facilitating value recovery

On the horizon of this thoroughly circular approach is the notion of buildings as a materials bank for future constructions, a key requirement in the upcoming French E+C–¹ regulations.

 

This assumes that construction methods and materials facilitating re-use or recycling be envisioned right from the conceptual design phase of buildings. That’s the whole purpose of the DEMODULOR approach developed by the MECD Institute in response to ADEME’s “Waste Management” project contest.

 

The proposed solutions avoid waste production by means of a systematic “enabled dismantling” approach aimed at facilitating the separation of systems, components, and materials with a view to recycling or optimized disposal and where possible re-use or re-purposing of materials and components. Four construction systems have thus been designed by researchers at the laboratories involved: a brick wall pre-stressed by steel sections and tie-bolts (with components that can be manually handled and re-used in housing), a glueless floor (steel tray, wooden boards, concrete slabs assembled by mechanical fastenings), a timber-frame frontage assembled with steel strapping, and a mixed steel-concrete floor. These systems are ready and waiting to be tested.

 

¹E+C–: higher energy efficiency, lower carbon output

 

Potential gans in figures

  • Generating a total of 247 million tonnes of waste per year, the building sector accounts for over two thirds of French waste

  • Out of 10 million tonnes of second-fix waste, half of it is inert (wall tiles, bricks, floor tiles, etc.), 45% is non-inert (slabs, door & window frames, plaster, etc.), and 5% is potentially hazardous (treated wood, electrical fittings, lead-based paint, etc.)
    Only 3 million tonnes are reclaimed each year.

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