Kristen Fritsch, in the thread about ipe wood, asked about resources comparing the carbon footprint of transporting building materials vs the transport mode. There are people who spend their lives on this topic that I won't presume to speak for, but I'll share a few observations:
Even though freight transport is something like 7% of global emissions, I think transportation of building materials a lot harder for architects to influence in a positive way than the 500mile rule would imply. We all know carbon impact is extremley dependent on mode of transport, and mode choice is usually determined by site location. Estimates of the carbon impact of shipping:
- ocean shipping averages 6 g CO2 / t-km
- rail freight ranges from 20 -50 g/t-km
- freight by truck range from 30 - 450 g/t-km
So if I ship 1 t (1000kg) from China to LA (12,000 km) and then 250 mi (400km) by truck the boat portion leads to 72kg CO2 while the truck impact ranges from 12kg to 180kg. If that 1 tonne was steel, its carbon footprint of manufacture might be 1900kg CO2. So transport was at most 10%) My colleague here at EDR, Kelsey Wotila, shared her conclusion (after looking at it over the course of a year) that the carbon of transport very rarely is a significant part (>10%) of the embodied carbon of a building materials.) Sources: L. Kaack et al.; IEA.
It is probably coincidence, but when I compiled these numbers I was reminded of a passage in the book The Ancient Economy by historian Moses I. Finley about ancient Rome that...
"There were also certain constants, the ox to begin with. The ox was the chief traction animal of antiquity, the mule and donkey his near rivals, the horse hardly at all. All three are slow and hungry. The transport figures in Diocletian's edict of maximum prices [301 AD] imply that a 1200-pound wagon-load of wheat would double in price in 300 miles, that a shipment of grain by sea from one end of the Mediterranean to the other would cost less (ignoring the risks) than carting it seventy-five miles."
