Cleantech is a term used to describe knowledge-based products or services that improve operational performance, productivity, or efficiency while reducing costs, inputs, energy consumption, waste, or pollution. Its origin is the increased consumer, regulatory and industry interest in clean forms of energy generationspecifically, perhaps, the rise in awareness of global warming and the impact on the natural environment from the burning of fossil fuels.

Sustainability is a characteristic of a process or state that can be maintained at a certain level indefinitely. The term, in its environmental usage, refers to the potential longevity of vital human ecological support systems, such as the planet's climatic system, systems of agriculture, industry, forestry, fisheries, and the systems on which they depend. In recent years, public discourse has led to a use of "sustainability" in reference to how long human ecological systems can be expected to be usefully productive. In the past, complex human societies have died out, sometimes as a result of their own growth-associated impacts on ecological support systems. The implication is that modern industrial society, which continues to grow in scale and complexity, will also collapse.

The implied preference would be for systems to be productive indefinitely, or be "sustainable." For example, "sustainable agriculture" would develop agricultural systems to last indefinitely; "sustainable development" can be a development of economic systems that last indefinitely, etc. A side discourse relates the term sustainability to longevity of natural ecosystems and reserves (set aside for other-than-human species), but the challenging emphasis has been on human systems and anthropogenic problems, such as anthropogenic climate change, or the depletion of fossil fuel reserves.