Feb 13, 2023

Construction-trash talk (or: the problem with circular construction materials)

Last week I had mentioned that we are running out of rocks and crushed stone to use in construction.

I dug deeper on how recycling and circularity of construction & demolition waste (CD&W) might or might not help fix the raw material shortage we are running into.

To understand this, I had to understand what waste is generated on construction sites, what the CD&W is made of, and where it goes.

(I focused this post on the US market; European and Australian markets will have different specifics but will be directionally same ballpark)

Construction & demolition waste increased by +340% compared to 1990. While – interestingly – municipal solid waste “only” icreased by +40%. We create disproportionately more construction trash than household trash.

The big 6 components that make up construction waste are:

All other materials fall into the “any others” bucket. An example of “others” would be asphalt roof shingles.

Concrete makes up 70% of all construction waste. 22% are asphalt pavements and wood. Bricks, clay, gypsum, metals, and any others together make up 8%.

When it comes to “where does it all go”, brief time for definition:

To the numbers:

20% are re-cycled. The majority here is asphalt pavement. Some concrete is recycled. Some minor recycling of wood and metals.

56% are down-cycled. Vast majority is concrete (mostly re-used as aggregate). Some down-cycling of pavement, wood, gypsum, bricks and clay.

24% are un-cycled and just dumped. Again, a good share of this is concrete, but surprisingly much is wood. The majority of bricks, clay, gypsum and any others goes here. Reasons are diverse, but two of the bigger reasons are that separation is too costly or that adverse materials are contained.

What all these numbers tell me is that creating a stream of homogeneous supply of recycled construction materials is really difficult – and really key. The two biggest levers to improve our recycling rate are (1) concrete and (2) wood.

Who’s fixing construction waste at scale using technology? I.p. looking for robotics and software-led approaches


EPA | General Kinematics | University of Michigan