It is widely accepted by now that the “normal” supply chains of material use — producing materials, using them, and then discarding them into landfills, other countries, or rivers and seas — are wasteful and damaging to the environment. As an extreme example, in 2019 oceanographers found a plastic bag in the Mariana Trench, the deepest known point in the world’s oceans. It’s easy, therefore, to see why consumers and policymakers have become interested in the concept of the “circular” supply chain, in which at least a large fraction of materials is recycled and reused in the product.