The management of the C&DW
6/06/2015
According to the European Commission, construction & demolition waste (C&DW) accounts for a third of the EU’s total waste production per year, amounting to some 450-500 million tonnes.
At least a third of this is concrete (the subject of this column). Of this amount, the part which ends up being recovered for recycling or reuse varies significantly across the EU, from just 30% in some countries to over 90% in others.
Why is concrete C&DW not recycled to a greater extent? It is primarily down to a lack of efficient sorting and collecting of C&DW, and an insufficient demand for, and confidence in, recycled materials.
These aspects are two sides of the same coin. Often, the infrastructure is not in place to allow for quality recycled materials to cost-efficiently reach a potential client.
There are various ways to encourage better recycling rates. The European Commission has just launched the process to write, with industry, a Protocol for C&DW management.
“Management” is the key word here, since it is primarily the processes collecting, sorting, treating and assuring the quality of recycled material that are lacking (rather than the technical basis).
Fortunately for concrete, recycling is not technically difficult. Concrete can be 100% recycled after demolition. Recycled aggregates from demolition concrete are traditionally used in unbound applications such as for road base, and they are also used as aggregates for new concrete.
Should there be a preference between these two uses? There are those who talk of “closed-loop” recycling (recycling back into the same application) as if it were the best (or only) way.
Alternative options, referred to as “open-loop recycling” or even “downcycling”, are cast in a negative light. But, in the case of concrete, there is no reason why this should be the case. Neither option is the clear winner from an environmental perspective in all cases.
We sometimes hear of proposals by the legislator to set minimum requirements on recycled content of construction products such as concrete.
Given the variable supply of materials coming from C&D, it is doubtful that this measure would be beneficial or even feasible.
One would not wish to see a situation whereby recycled aggregates travel long distances (translating into an increase in transport-related CO2 emissions), even when virgin aggregates are available nearby.
All this to say that it is impossible to generalise about how best to use recycled concrete aggregates. But one thing is clear: better processes for demolition, collection and sorting of C&DW will help with providing a consistent supply of good quality recycled aggregates.
The European concrete industry welcomes the initiative by the Commission to write a C&DW management Protocol and will contribute actively to its development.
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