If you are fanatical about reducing waste you may remember to mention that it annoys you that the rulers you purchased for your students come individually wrapped in plastic to the supplier. People around you will remember the goal of reducing the volume of trash— if only to stay on your good side but maybe when they have the chance to make a big decision that idea will be closer to the surface.
It’s not that your actions alone will save the world. Your actions are another way to speak.