In the circular economy of building materials, raw earth occupies a paradoxical position: it's probably the lowest-environmental-impact material available, yet the contemporary construction system systematically treats its raw material as waste to be disposed of, not a resource to be put to use. The paradox has a precise technical name — excavated earth — and understanding it is the key to understanding why raw earth, despite an almost unbeatable environmental balance sheet, remains marginal in current European construction.
The paradox: paying to throw away the raw material
Every site that builds foundations, basements or below-grade works inevitably produces a volume of earth in excess of what's reused on site for backfill or grading. In current practice, this earth is almost always classified as waste or spoil and disposed of at landfill or a storage site, with a direct economic cost for the contractor (typically tens of euros per tonne) and an indirect environmental cost tied to road transport to the disposal site, often not especially close by. It's exactly the same earth that, with proper particle-size characterisation and minimal treatment, could become the raw material for CEB, plasters or rammed-earth masonry — a material people today pay to haul away, while elsewhere it's bought to build with.
The scale of the problem, and of the opportunity
The scale of this material flow is enormous relative to the potential demand from raw-earth construction. Large infrastructure sites alone — high-speed rail lines, tunnels, hydraulic works — generate volumes of excavated earth on the order of tens of millions of cubic metres a year nationally in a country like Italy, today disposed of almost entirely at landfill or reused at very low added value as road embankment fill. Even converting a tiny fraction of this flow — on the order of a few percentage points — into construction material for CEB, plasters or stabilised masonry, the theoretical potential would be enough to supply the entire demand of an entire country's rural and natural-building sector for years, without opening a single new quarry.
Why it isn't happening at scale already
If the potential is so obvious, why does reusing excavated earth as a building material remain an experimental exception rather than standard practice? The reasons are more bureaucratic and logistical than technical. First: not every excavated earth has a particle-size distribution suited to construction — this would require systematic characterisation of the material leaving each site, a step almost no specification requires today, because the earth is simply classified as waste to be disposed of, not raw material to be qualified. Second: construction-and-demolition waste regulation, designed to manage the risk of pollutant contamination on industrial sites, treats excavated earth with a level of bureaucracy proportioned to that risk, even when the earth comes from a clean residential site — a mismatch between the actual risk and the procedural cost of putting it to use. Third: especially in Europe, the industrial supply chain is still missing — characterisation facilities, CEB producers at scale, widespread laying expertise — capable of absorbing these volumes even where the bureaucracy allowed it more easily.
The first signs of change
Some public research programmes, in Italy and elsewhere, have begun explicitly trialling the reuse of urban excavated earth as raw material for CEB and finishing plasters, with the stated aim of demonstrating the technical and economic feasibility of the approach at real scale, not just in the laboratory. These are early steps, not yet a market transformation — but they signal that the paradox of excavated earth is now recognised as a solvable systemic problem, not an unchangeable feature of the construction sector. The day a tender specification treats excavated earth as a resource to be qualified rather than waste to be disposed of will be the day the circular economy of raw earth stops being an experimental exception.