Technology readiness levels describe progress from scientific principles toward an operational system. The rating is meaningful only when the technology boundary, scale and test environment are specified. A component and the integrated plant can have different readiness levels. DOE/NETL TRL definitions
A practical evidence ladder
| Evidence | Useful question |
|---|---|
| Laboratory experiment | Were results reproducible under specified conditions? |
| Relevant-environment test | Did realistic contaminants, loads and feeds change performance? |
| Integrated pilot | Did recycle, separation and controls work together? |
| Demonstration | Was meaningful scale sustained for the required duty? |
| Commercial operation | Are output, quality, uptime and costs evidenced? |
A readiness label does not establish financing, qualified demand, unit economics or lifecycle performance. Those are separate questions. An announced plant is evidence of intent; continuous production requires operating evidence.
Analyst reading rule: retain the source’s TRL as reported, identify the subsystem it applies to, and avoid assigning one number to an entire pathway. Unknown is preferable to an unsupported rating.