We have all been hit with the mantra that recycling is green and sustainable (and I am not disputing that, particularly when compared to using brand new materials). However, the carbon emissions resulting from the processing of recycled materials need to be taken into consideration. An article published by Wired has highlighted a possible greener alternative for the construction industry. That is urban mining.
Urban mining is stripping materials from obsolete buildings and, instead of sending them to be recycled, re-using them in their existing form. It is expected that this could save on 93% of carbon emissions when compared to the recycling process.
The practice of urban mining is not currently mainstream and it is easy to see why. Construction materials need to comply with certain minimum requirements and it will often not be possible to ascertain whether those requirements are met by materials mined from other buildings. There are storage considerations and cost considerations. In addition, the buildings being mined will not have been built with ease of extraction in mind.
An EU research project in 2020 called Buildings As Material Banks envisages that in the future all buildings will have a passport, so the qualities of each building's materials are known for the purposes of urban mining when those buildings reach the end of their useful lives. We might then see marketplaces for second hand building materials pop up, where companies specialise in buying, storing and selling these materials at a large scale, resulting in cheaper prices than buying new.
Factoring in a small amount of carbon for cleaning, transporting and refabricating, Webster estimates that steel reuse would generate less than 50 kilos of carbon per metric ton reused, which is 7 percent of the recycled content approach. “It cuts emissions to almost nothing,” he says.
