 The sooner you can kill a chicken, the less carbon it will use in its lifetime. It's a pretty brutal kind of maths, but it checks out. The shorter the chicken's lives, the better for the environment. For me, this is really unsettling. I buy the highest welfare chicken I can, the ones that live for 12 to 14 weeks. Now I'm learning that these birds are the ones that might be hurting the environment the most, simply by living longer.