-( Story related, cannot be missed )-
*While this is "flagged" as possibly story related, the real note is that... you could scrape by without having all 101 Power Cells early on. It would be in your best interest to avoid back-tracking at the end to get this for the final ending.
Level: Boggy Swamp
Located throughout the swamp are four tethers wrapped around boulders. You will need to destroy them with Yellow Eco shots. Each will give you a Power Cell, and the last one will also give you a scene of the zeppelin drifting away (and giving you this trophy).