That's right: There's nothing more energy efficient than a dead cat!
"Here kitty, kitty. Dinnertime."
"That's your cat?"
"Yup! His name is Basil."
"Huh. That's pretty thoughtless."
"What? His name?"
"No, the fact that you keep him alive."
"It's just that I thought you considered yourself environmentally aware. And yet you're ballooning your carbon footprint with this walking CO2 machine."
"That's ridiculous! What, you think I should put my cat down for the sake of the climate?"
"Sure, as a first step."
"Well, it would be wasteful to just dispose of the body, but you could kill two birds with one stone (so to speak) and burn it for home heating instead of your nasty oil furnace."
"I think I'm going to be sick."
"Of course, you wouldn't want to burn the hide. That makes excellent weather-stripping for doors."
"--and it would be a shame to let all the nitrogen in the ashes go to waste. So you'd want to sprinkle that in your garden as fertilizer."
"I don't have a garden."
"You don't?? What kind of monster are you?"