Waste on the return trip: how consolidation centres make waste separation possible on cramped inner-city construction sites.

The Netherlands recycles most of its construction waste, but the bulk of it is downcycled into road foundations rather than returned to high-value use. Better recycling starts with separating waste where it is produced, which on inner-city projects is often impossible. There is no room for a row of large containers, so the varied waste of the finishing stage, from plasterboard and insulation to wood and packaging, goes into one mixed container and is sorted mechanically at a recycling facility.

The EaSiCon project develops a digital twin that gives a real-time virtual representation of construction processes and their connected supply chains, supporting tactical and operational planning to improve efficiency and sustainability. This article presents research into waste management on inner-city sites, which examines whether a construction consolidation centre (CCC) can make on-site waste separation viable. A CCC is a hub on the edge of the city where materials from many suppliers are bundled and delivered to the site in fewer, fuller trucks. The research resulted in a decision support tool, tested on three projects.

Three sites, one mixed container

The projects were a former music venue in central Utrecht, a hotel in central Amsterdam renovated while still open to guests, and a residential tower on the edge of Utrecht. At the two city-centre sites, waste storage was limited to a few dozen square metres. In Utrecht all waste had to pass through a corridor two metres wide and was collected as one mixed stream up to three times a day. In Amsterdam workers used material delivery boxes as makeshift bins. The tower did separate its waste, but only because the project rents extra land for the containers.

Using the delivery truck on its way back

The integrated approach replaces the one large container with several small ones, each for a single waste stream. Collecting them would normally mean many extra trips, but a CCC already sends frequent, planned deliveries to these sites. The truck that brings in materials takes full waste containers and empty packaging back to the hub on its return trip.

Week by week, the model forecasts the waste produced, matches it to scheduled deliveries and decides which containers ride back with each truck.

Sorting at the source pays off

On all three projects the integrated approach is cheaper than a single mixed container, despite higher transport and rental costs. The savings come from avoiding the costly sorting of mixed waste at a recycling facility, which also lowers emissions. The larger environmental gain is quality, since source-separated streams are cleaner and better suited to high-value recycling.

The trade-off is social. Several small containers need somewhat more trips than one large one, which means more traffic, noise and safety risk in the street. At the tower, where the CCC is close and the recycling facility far away, shorter waste journeys more than offset the extra trips.

When the approach makes sense

Project size is the deciding factor. Small projects do not produce enough waste to cover the extra logistics, and the break-even point is similar in all three cases. Storage space is less of an obstacle than expected. On two of the three sites, about 20 square metres for waste containers was already enough.

The decision support tool is built for project managers and logistics planners during procurement and planning. Users enter the weekly material planning, project address, floor area and space for waste. The tool compares both approaches on cost, emissions and number of trips, and produces a weekly logistics plan. Test users rated it as easy to use.

Conclusion and recommendations

For inner-city projects, the barrier to waste separation is logistical, not technical. Linking waste collection to material deliveries through a CCC removes that barrier. Practitioners can make the most of it through:

• choosing the waste strategy during procurement rather than on site
• small, stream-specific containers collected on return trips
• clear labelling and instruction so separated streams stay clean
• extra attention to trip numbers where the CCC is far from the site
• take-back agreements with manufacturers of gypsum and insulation

The next step is better data. Dutch waste forecasts and a link to the material quantities in a building information model (BIM) would sharpen the predictions. Connected to a construction digital twin, the same information can support material passports and help close the material loop.

For more information, please contact:

Ragnar Klabbers

Ivo Agricola

Kees Jan Roodbergen

Michael Dienstknecht

Jeroen Laarman