Although geographic proximity is often associated with industrial symbiosis, it is neither necessary nor sufficient—nor is a singular focus on physical resource exchange. Strategic planning is required to optimize the synergies of co-location. In practice, using industrial symbiosis as an approach to commercial operations—using, recovering and redirecting resources for reuse—results in resources remaining in productive use in the economy for longer. This in turn creates business opportunities, reduces demands on the earth's resources, and provides a stepping-stone towards creating a circular economy. The industrial symbiosis model devised and managed by International Synergies Limited is a facilitated model operating at the national scale in the United Kingdom (NISP—National Industrial Symbiosis Programme), and at other scales around the world. International Synergies Limited has developed global expertise in IS, instigating programmes in Belgium, Brazil, Canada, China, Denmark, Finland, Hungary, Italy, Mexico, Poland, Romania, Slovakia, South Africa and Turkey, as well as the UK. Industrial symbiosis is a subset of industrial ecology, with a particular focus on material and energy exchange. Industrial ecology is a relatively new field that is based on a natural paradigm, claiming that an industrial ecosystem may behave in a similar way to the natural ecosystem wherein everything gets recycled, albeit the simplicity and applicability of this paradigm has been questioned.