The best way to optimize for CO2 is to ask the user to do it at the right time of day for their grid. Otherwise it's the same thing as using less energy which i

The best way to optimize for CO2 is to ask the user to do it at the right time of day for their grid. Otherwise it's the same thing as using less energy which is ~ the same thing as being faster (assuming fixed resources). But watch out for induced demand (the user turning the graphics settings up because you made the FPS better.)