Life-cycle assessment
A method for assessing environmental burdens across stages of a product or service's life.
Example
It can compare alternatives that perform the same function.
The catch
Assumptions about lifespan, electricity and end-of-life treatment matter.
In more depth
Life-cycle assessment, explained.
A life-cycle assessment is only comparable with another when both use the same functional unit, the defined service each option must deliver, such as a litre of drink delivered to a shop. Get the unit wrong and a reusable bottle can look better or worse than a disposable one, depending on how many trips it is assumed to make.
Practitioners fix the goal and system boundary first, then build an inventory of inputs and emissions and convert it into impact categories such as climate change or water use. Sensitivity checks show how far the answer depends on assumptions. The scope label tells you a lot. Cradle-to-gate stops at the factory exit, while cradle-to-grave includes use and disposal. A carbon footprint is a life-cycle result reduced to a single impact category. Comparative claims made in public deserve an independent critical review.