from our immediate environments. As noted above in the previous section, reuse-based production and secondary materials industry is much efficient when local and regional. Closed-loop production is not just more local than conventional industrial mass production, it is also more diverse and less monocultural. If all by-products of manufacturing are to be used creatively and benignly, this requires that a variety of firms and processes be grouped together that can complement each other. As in nature, this works best with intentionally multi-functional design where any process always has multiple and overlapping effects. So while it is true that green manufacturing tends to be more decentralized than conventional brown industry, this is not an arbitrary and chaotic dispersal of production units. The importance of symbiotic and complementary relationships demands new levels of cooperation and the intelligent clustering of firms. Over the last ten years the parallels between nature and sustainable production systems have been explored most deeply by the emerging discipline of industrial ecology. One of its pioneers, Robert A. Frosch (1992, p. 800), describes these connections: The idea of an industrial ecology is based upon a straightforward analogy with natural ecological systems. In nature an ecological system operates through a web of connections in which organisms live and consume each other and each other's waste. The system has evolved so that the characteristic of communities of living organisms seems to be that nothing that contains available energy or useful material will be lost. There will evolve some organism that will manage to make its living by dealing with any waste product that provides available energy or usable material. Ecologists talk of a food web: an interconnection of uses of both organisms and their wastes. In the industrial context we may think of this as being use of products and waste products. The system structure of a natural ecology and the structure of an industrial system, or an economic system, are extremely similar.