Here's why:

* CO2 is released: Photorespiration involves the release of carbon dioxide.

* No ATP or NADPH production: Unlike photosynthesis, photorespiration does not generate ATP or NADPH. In fact, it consumes ATP.

* It's not a part of photosynthesis: Photorespiration is a competing process that reduces the efficiency of photosynthesis.

Let me know if you'd like more details about photorespiration!