| Requires | Unit of comparison and boundaries |
|---|---|
| Includes | Stages and stated assumptions |
| Limit | Results depend on the scenario |
Definition and context
A life cycle assessment organizes inputs, outputs, and effects associated with the stages of a product or service. A comparison needs to define the service each alternative provides and which stages it includes. Material extraction, manufacturing, transport, use, and waste management can each make different contributions.
A result depends on data, assumptions, and boundaries. If a fictional comparison includes cleaning for one option and omits it for another, we still do not know whether the comparison is equivalent. We must also review the destinations of recovered materials and how burdens and benefits are allocated. Models help explore scenarios; they are not direct measurements of every specific case and do not justify transferring figures between systems without review.
What we know and its limits
Introductory reference sheet. Properties and applications depend on measurement conditions; consult the sources before making comparisons.
Follow the evidence
The original sources for exploring this explanation and its limits.
- Non-Hazardous Materials and Waste Management Hierarchy
U.S. Environmental Protection Agency
Hierarchy of prevention, reuse, recycling, and other forms of management. - Basic Information about the Waste Reduction Model
U.S. Environmental Protection Agency
Comparative modeling of energy use and emissions for waste management strategies.
Image credits
SciClue · AI-generated illustration (OpenAI) · Original source · Recurso editorial de SciClue · generado con IA