A play on the phrase "ego-trip" referring to the superiority one feels when going green, being green, or living green.
Militant recycling, composting, farmers markets', CSA shares, organic food, solar panels, bio-diesel, and the purchase of a Prius or Smart Car can all trigger an eco-trip.
He thinks he is saving the environment single-handedly because he bathes in collected rain water instead of taking showers.
I know, he is on such an eco-trip.