A new study from TU Delft researchers, published in Urban Planning (2026), offers practical insights into how cities can use urban space — including temporarily vacant plots — to keep materials circulating rather than ending up as waste.
The research examines three cases in Amsterdam where the municipality used storage spaces of varying scales and durations to facilitate the reuse of materials from outdoor public spaces (OPS): such as concrete pavers, lampposts, benches, and playground equipment.
The three storage models
The City-Scale Storage (CSS) operates as a semi-permanent, centrally managed depot near Amsterdam Sloterdijk. It serves the entire city, holding a diverse inventory from bicycle racks to bollards. Its scale enables professionalized management, long-term supplier collaborations, and ad hoc replacements when residents need quick fixes — avoiding the weeks-long lead times for ordering new materials.
The Neighborhood-Scale Storage (NSS) exploits a temporarily idle development plot in Buiksloterham (Amsterdam-North), made available by a delayed real estate project. Pavers and concrete tiles stockpiled there directly feed a local ambition to build 80% of new outdoor public spaces from circular materials. Duration: two to four years, after which construction begins.
The Project-Scale Storage (PSS) is the most tactical model — a parking lot 850 meters from a sidewalk maintenance project, occupied for roughly eight weeks. Simple, low-cost, and highly local.
Why this matters beyond municipal housekeeping
The study’s key argument is that space itself is a logistics resource. Without intermediate storage, circular material flows break down: projects can rarely exchange materials directly, quality-approved surplus has nowhere to go, and contractors default to ordering new. Storage bridges the timing mismatch between supply (demolition or replacement) and demand (the next project).
The value created spans four domains. Environmentally, reuse avoids the embodied carbon of producing new concrete, steel, aluminum, and clay products. Economically, avoided procurement costs are high — especially for high-value items like outdoor sports equipment and baked clay pavers. Socially, refurbishment activities create employment pathways for people distanced from the labor market. And, publicly, reuse supports municipal circularity targets and can preserve neighborhood character — in one case, residents actually complained when new pavers were mixed in with old ones.
The logistics takeaway
The paper reinforces a principle familiar in supply chain thinking: inventory positioning determines flow efficiency. A layered storage network — permanent city depot, medium-term neighborhood buffer, short-term project site — mirrors the logic of tiered warehousing. The difference is that the “product” is reclaimed public infrastructure, and the “warehouses” are often opportunistic. Amsterdam’s “reuse, unless” policy creates the demand signal; the storage network enables fulfillment.
The study maps value creation thoughtfully but remains qualitative where numbers matter most. Actual reuse rates, cost comparisons between reused and new materials, transport distances saved, and carbon calculations are either absent or unverified — the authors themselves admit exact activity costs are unknown. There is no breakeven analysis showing when reuse becomes economically inferior to procurement, nor any data on material rejection rates due to quality failures. Without these figures, practitioners cannot make a business case. The framework reads more as a municipal advocacy tool than an evidence-based decision guide.