Are biodegradable or compostable dog poop bags actually better for the environment?

It depends on disposal. Reviewers and sustainability-focused commentary we read repeatedly note that 'biodegradable' bags thrown in a landfill won't meaningfully break down, and that only ASTM D6400 / EN 13432 certified bags composted in the right facility (or, for home-compostable variants, in a properly managed home pile that doesn't include the waste itself) deliver on the claim. Bags labeled simply 'biodegradable' without certification are widely criticized as greenwashing.