As for the OP, yeah, everything we do uses up energy and resources. It's not very productive to try to come up with a lifestyle that's zero impact, because that's impossible. A better way of determining the environmental benefit of something is to compare it to alternatives. For example, one can ride a bike instead of driving, and that is probably a big improvement from an environmental standpoint. If riding the bike is replacing walking trips, though, in that context it's either a little worse or a wash (assuming you would already have purchased a bike for other purposes, and are not solely using where you would have walked instead). If you are riding the bike instead of going to the gym, you would have to weigh the environmental costs of the bike, both the manufacture and the use costs) with those of the gym (whatever proportion of its energy maintenance costs, plus some portion of all the environmental costs associated with the making of the building and the equipment inside). Clearly it would be a complicated calculation, but it is probably safe to assume that the bicycle is a good choice, environmentally speaking, for most people.