Industrial ecology considers industrial activities as ecosystems in themselves, composed of flows of materials, energy and information. It uses knowledge on how ecosystems function, in order to formulate proposals to reorganise the industrial system, making it compatible with the biosphere and sustainable in the long term. Industrial ecology therefore aims at solving the question, "How can sustainable development be made operational and economically viable?" It provides a conceptual framework and tools to plan economic development and propose ways of optimising the use of limited resources and protect the environment.