Day after day, you pump carbon dioxide into the atmosphere, whether you’re driving or turning on lights or eating meat. You can’t help it, because really, no human can. But I bet you haven’t stopped to think about how the simple act of pooping is also part of the problem: Worldwide, wastewater treatment facilities account for 3 percent of electricity consumption and contribute 1.6 percent of emissions. A drop in the horrifying bucket that is climate change, you might say.