Since 1989, efforts to understand the nature of interfirm resource sharing in the form of industrial symbiosis and to replicate in a deliberate way what was largely self-organizing in Kalundborg, Denmark have followed many paths, some with much success and some with very little. This article provides a historical view of the motivations and means for pursuing industrial symbiosis-defined to include physical exchanges of materials, energy, water, and by-products among diversified clusters of firms. It finds that "uncovering" existing symbioses has led to more sustainable industrial development than attempts to design and build eco-industrial parks incorporating physical exchanges. By examining 15 proposed projects brought to national and international attention by the U.S. President's Council on Sustainable Development beginning in the early 1990s, and contrasting these with another 12 projects observed to share more elements of self-organization, recommendations are offered to stimulate the identification and uncovering of already existing "kernels" of symbiosis. In addition, policies and practices are suggested to identify early-stage precursors of potentially larger symbioses that can be nurtured and developed further. The article concludes that environmentally and economically desirable symbiotic exchanges are all around us and now we must shift our gaze to find and foster them.
