Dog poo specific bags are biodegradable, so that's an important factor if you're a "greenie", I guess.
They even sell some that are "flushable", but over here I'm told we're not supposed to flush doggy doo as it apparently has different bacteria to what the public sewer system is normally used to & causes all sorts of problems at the treatment plant.
You don't even want to think about what folks flush down their toilets ....... ewwwwwww
Sigh, nor are we supposed to put it in our big green wheelie bins that the trucks come for, so I'm damned if I know what the heck they want us to do with it. In fact I think I'll search out that info right now whilst I'm thinking of it.
Our local parks have dispensers that give you the infamous dogi-dogi bags. We collect in the dogi-dogi bag, and will often put the results in the waste bins in the park, which contain many other such bags. If we take a bag home, we will double wrap in a supermarket plastic bag, and leave it in the large trash bin (which itself has a plastic liner) for Republic Waste Disposal to pick up. As far as I know, this is legal, but I have never specifically asked.
Chihuahuas are small dogs, and therefore we are saving the planet by producing less waste. Compared to a Great Dane, we are saving hundreds of pounds of poop per year!!!