Platinum: Embodied Land from Urban Harvesting
This is an example of a interesting re-generation route for the metal Platinum.
A car catalyst contains platinum, which is slowly used and lost during driving. It ends up as dust in the streets. Which can be a source in itself for harvesting platinum, as was subject of research some years ago by Angela Murray in the UK. She found that “If a road sweeper went along a city street 3km long for a year we could produce 30g of platinum.” “This would be enough to make into a ring that might sell for £2,500.”
Recalculated this would provide , with a street 3000 mtr long and an estimated 8 mtr wide, imply 0,00125 gr/m2 each year or , in other words, it requires 800 m2-year/gram. Since the road is primarily to support traffic, the harvest area would not have to count for Embodied Land, but the energy and equipment invested would. ( not calculated, anybody?)
In fact this can count as a reference environment for platinum: a diluted and dispersed form, a high entropy environment in exergy/thermo-dynamical terms. And as such a measure for compensating depletion, or regeneration.
Interesting is that this has actually led to application: Veolia in UK, contracting city cleaning, has build facilities for this. In fact for economical reasons of course; they have the dust already, so adding the filtering can give them an economical profit, see http://www.reuters.com/article/britain-environment-dust-idUSL6N0TM38A20141202