Question and context

For the Amsterdam Metropolitan Area, extensive research was carried out into urban mining of residual streams from construction and demolition: recovering valuable materials from buildings that are renovated or demolished. The key conclusion is that substantial value is stored in the region and that large volumes of material become available every year. For construction and demolition, that value amounts to around €688 million per year. Currently, around 50% of it is lost because the material ends up in processing methods considered low-value, which do not make optimal use of the material’s worth.

At the regional scale, scientific data was combined with market knowledge to map the potential value of residual streams per MRA municipality. This makes it possible to test concrete solutions for feasibility and calculate the value-creation potential per material stream. For five material streams with significant potential financial value and environmental benefit, concrete business cases for collection, recycling and reuse were explored together with businesses.

The database and methodology

The geographic scope covers all 33 municipalities of the Amsterdam Metropolitan Area. Earlier urban mining research shows that the largest fractions of construction and demolition waste consist of sand and gravel, concrete, brick, stone, ceramics, glass, gypsum, steel and iron, copper, other metals, wood, paper, plastics, bitumen and insulation. These fifteen sub-streams form the material scope.

To provide insight into the scale across the whole chain, the sub-streams were quantified across nine chain steps: material input (new construction), stock, renovation, demolition, processing, downcycling, recycling, non-reusable, and not collected or untraceable. The basis is a distinction from Statistics Netherlands (CBS, 2017) between the stock of homes and non-residential buildings per municipality, multiplied by material-specific benchmark figures from urban mining reports. In an iterative process, the database was enriched with interviews with companies and processors across the chain, and with desk research.

Fifteen sub-streams by volume, value and environmental impact

The fifteen sub-streams differ sharply in volume, financial value and environmental impact. Concrete dominates the volume, but value is concentrated in a handful of streams: wood and insulation together account for almost 80% of the total material value. Copper has the highest relative environmental impact.

Annual volumes within the MRA area. Amounts based on primary (virgin) material value. Environmental impact as a share of the total impact of construction and demolition waste.

Five promising cases

Not all valuable streams are equally promising to develop further. For concrete, copper and other metals, many processors and processes already exist in the MRA. The research therefore focuses on promising streams for which no constant, local processing yet exists: ceramics, gypsum, wood, bitumen and insulation. Although these polluting fractions together make up around 10% of the volume, they represent around 51% of the value. Because they are partly processed at low value, an estimated €34 million per year is lost.

• Wood — processing into chipboard and OSB, or direct reuse of A and B wood.
• Insulation — one-to-one recycling is technically possible; growing demand gives this case significant potential.
• Gypsum — processing used gypsum boards into new, circular gypsum boards; rising demand makes this promising.
• Ceramics — part of separately capturing polluting fractions, so that clean mono-streams result.
• Bitumen — dropped: high-value processing proved not yet feasible in practice or cost terms, due to the purification technology required.

For all valuable residual streams, separate collection is essential to enable high-value processing. Clean mono-streams are worth more than polluted, mixed streams.

Wood: 30% of the value, largely incinerated

Wood makes up around 10% of the mass of construction and demolition waste, but equals around 30% of the total material value: €206 million. Around 54% of that wood stream is currently still incinerated or landfilled — a potential loss of around €111 million per year.

There are three wood categories. A-wood is untreated and has the highest value; B-wood is painted, varnished or glued; C-wood is impregnated or preserved and treated with substances such as copper, chromium and arsenic compounds that are harmful to people and the environment. A and B wood can be reused and recycled into wood products, but are currently often processed at low value into pallets or co-fired as biomass. C-wood is not recyclable and may only go to specialised energy-recovery installations. The promising routes for A and B wood are processing into high-value chipboard and OSB, reapplying fibres, and direct reuse of old floors, beams and doors.

Harvesting at the source

To make better use of the value in residual streams, fourteen solution directions were put forward in total. Selective demolition yields larger, clean mono-streams that are worth more than polluted, mixed streams. Four directions were explored for separately capturing valuable fractions at the source:

Source separation yields higher-value residual streams, but requires a substantial investment and is not always yet profitable: it is labour-intensive and requires time and space at the demolition site. A demolition advisor (solution 2) should be part of source separation (solution 1). The marketplace for direct reuse (solution 4) generates the most energy among chain partners: the potential value of reusable construction products is many times higher than the raw-material value.

Feasibility and barriers

In two working sessions with construction and demolition companies, waste collectors and processors, the feasibility of the solutions was discussed. Source separation is seen as promising, but high labour costs and the lack of space and time at demolition sites are significant barriers. At this stage, post-separation often still pays off more than source separation, even though post-separation typically leads to downcycling and value loss.

The main barriers named by chain partners:

• Surpluses of B-wood, aluminium and steel push down market prices, making landfilling cheaper.
• Virgin gypsum is cheaper and easier to process than secondary material.
• Perverse price incentives often make high-value processing unprofitable; financial incentives are needed for streams with negative value.
• Constant, clean residual streams are crucial for recycling and production, but volume is often insufficient.
• Producer responsibility around demountable construction will improve processing in the future.

Open database and calculation model

Both the database and the calculation model used to estimate the volume and value of construction materials have been made public. This makes visible to everyone how large the financial potential is when a circular business model is applied to these streams, for the MRA as a whole and for individual municipalities.

The calculation model is activity-based, both horizontally across the chain and vertically per activity within a chain step. For each step, a distinction is made between variable costs, fixed costs, investments and processing percentages. This produces a break-even volume, which is compared with the available volume in the MRA. This makes visible how much volume must be used at minimum to make a processing route profitable, and how investments early in the chain translate into higher value at the end.

Recommendations for the MRA

1. Invest in pilot projects. Start with concrete pilots, for example around selective and circular demolition, to test the solutions in practice.
2. Arrange distribution and reverse logistics. Organise logistics within the region, potentially via one or more construction depots where secondary materials can be temporarily stored.
3. Open up data at project level. Make data on construction and demolition projects and the materials released available at project level, so that supply and demand for residual streams can be matched.
4. Encourage source separation through policy. A levy on new raw materials and requirements for high-value reuse and demountable construction make source separation more profitable.

A single marketplace for supply and demand is preferred over separate, parallel systems: chain partners advocate jointly opening up and managing data on material streams released and needed.

Method and sources

This exploration maps the circular value of residual streams through urban mining: recovering materials from the existing built environment. It shows how construction and demolition can move from low-value processing to high-value reuse — a step towards regenerative construction. Read also the parallel exploration of e-waste in the MRA.

How to cite

New Economy and Metabolic (2018). Circular business cases in the MRA — construction and demolition waste. Exploration of urban mining for the Amsterdam Metropolitan Area. Available via neweconomy.eco.

Download the report

• Circular Business Cases in the MRA — Construction and Demolition Waste (PDF)The full report with the sub-stream analysis, the five cases, the solution directions and the recommendations. Download the report (PDF)