Of course, quantifying the question of “How green is a chemical process?” is not always easy to answer! Even in simply comparing a set of alternative processes, it can still be difficult to determine which is better since each may have advantages and disadvantages for different aspects of human health and the environment.

A life-cycle analysis, or LCA, is a tool used to evaluate and compare the effects of a product on the environment. As the name implies, this includes everything that happens between the time the product is created until it is disposed of. Of course, this is no small task! Typically it involves identifying all relevant materials that go into the production of a product, as well as all of the waste produced during the course of using the product, including things like emissions into the atmosphere, soil, and water, as well as the solid waste produced. Then one needs to evaluate the environmental impact of each of those materials and waste products, hopefully in a manner that allows for the results to readily be compared to those from other products or services. The total of these environmental impacts describes the life-cycle impact of the product.

These inputs and outputs are then converted into their effects or impact on the environment. The sum of these environmental impacts represents the overall environmental effect of the Life Cycle of the product or service. Conducting LCAs for alternative products allows comparison of their overall environmental impacts.