In view of the problem of sustainable development, the issue of waste is crucially important because our very existence is probably threatened as much by the amount of waste we generate as by the resources we deplete. While CO2 may be the waste currently in the headlines, with its dangers being actively debated, others that are just as menacing also exist. For example, the various forms of active nitrogen in circulation have profound effects, both at the local level (nitrification of groundwater, green algae, air pollution, etc.) as well as at the global level (climate change, acidification of oceans, etc.). This chapter questions and refines our understanding of the notion of waste. And it takes a long historical perspective to highlight the need to fully account for waste production in assessing the implications of our development path, and notably of agrichain development.