Material Mapping
These maps illustrate our current global steel recycling supply chains. Whilst the creation of employment elsewhere is not a bad thing in itself, the specialising of each economy - some to consultancy, some to processing, some to manufacturing - is risky as it narrows the society that economy creates, as well as making it less resilient. It also ‘others’ certain processes, allowing us to ignore the negative impacts of our actions. Out of sight, out of mind. Recycling still uses raw materials. For instance, the re-processing of steel in the far east uses sand from the South China sea. See https://www.sandstories.org/for detail.
Timber is a complex picture, since growing trees captures carbon. However, a fast throughput of timber - grow to use to waste - means the carbon is stored for a short time. Timber that is looked after either as a tree, or in a stable state in a building, holds that carbon. Currently a lot of our ‘waste’ timber is recyled into short-life products - mulch or biomass - which soon releases gasses with global warming potential: carbon dioxide and methane. Ideally, like all materials, timber should be kept in use as long as possible. Beyond this, if timber can become something else useful that is cared for after each ‘life’ in a cascade fashion, then those embodied gasses will stay out of the atmosphere.
Concrete contains cement, which is one of the most polluting materials made by our species. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactured material in the world. Low carbon cement uses the byproducts of coal burning, which itself needs to be phased out so is not a long-term solution. Concrete in-situ is very heavy, and the emissions from moving it are very high. The best thing to do is to leave it in place and maintain it. If this isn’t possible, then it should be reused as whole units as close to its original use as possible. Concrete ‘recycling’ by chipping it for use as aggregate only avoids 0.0043 kg CO2e/kg, whereas re-used concrete avoids 0.1 kg CO2e/kg.
Understanding why some materials work in a circular economy now and others don’t gives us an insight as to what needs to change to enable others to do so. Two key variables are market (financial) value, and whether the materials are fixed in place or loose. For example, white goods do get re-sold and re-used because they are loose, but are less likely to do so if they are cheap. Around this diagram are roles and processes that play a part in enabling greater circularity for the scenario in each quadrant.