Could the tuning of the PID controllers have any effect on energy consumption and CO2 pollution? Absolutely!
This post explains how.
Any PID controller that adjusts the feed of fuel, steam or electrical current, has an immidiate effect on on energy consumption and therefore, usually, on CO2 pollution as well.
After better tuning of these PID controllers, you can adjust the setpoint of the PID controller, so that it consumes less energy!
To clarify this, consider the following example.
Suppose that the PID controller must maintain the temperature above 21 C while the temperature varies with +/- 1 degrees C around setpoint (at 22 C). After better tuning, the temperature varies with +/- 0.1 graden C around setpoint. Then, we can reduce setpoint to 21.1 C and the temperature will still not drop below 21 C!
Obviously, less heat will be consumed.
This example is fiction, but in this post we show that it is true and works in practice too.