How much crushed rock you get through in a year?
Take a guess, then read on.
Construction aggregate (crushed rock, sand, gravel, slag) is one of the many taken-for-granted commodities that underpin rich nation lifestyles. It’s mainly used for building (e.g. concrete, foundations, drains) and for roading (both for road beds and, mixed with/covered in asphalt, for road surfaces. In New Zealand, according to the New Zealand Mineral Industry Association, 56% of that aggregate is used for roading, and 29% for concrete.
And how much do we use each year? “Per capita consumption in most developed countries is between 3 and 8 tonnes per annum” (Tony Christie, Bruce Thompson and Bob Brathwaite, Mineral Commodity Report Report 22 -aggregate, 2001). Currently, in New Zealand, we use about 7 metric tonnes per person per annum, and as the Chief Executive of the NZ Minerals Industry Association says, “this is just to maintain our current standard of living.” (Douglas Gordon, Chief Executive, Minerals Industry Association, New Zealand Quarrying & Mining, January, 2008, p.32)
We have a lot of mountains, and hills, but still, that’s a lot of rock. And it’s a lot of environmental impact. Aside from the direct local impacts of quarrying, transporting aggregate – which is heavy – uses a lot of fuel. It is certainly a material to conserve and source as locally as is feasible.
If a person lived 75 years, and the seven tonnes per person per annum use was kept up for their entire life, their life share of aggregate would be 525 tonnes, with 294 tonnes (at the 56% use rate cited by NZMIA) of that being used to provide the roads you drive on and that bring you the goods you enjoy.