Thanks for the thoughtful response. My own original thinking was along these lines as well.

However, some thoughts that did occur to me along the lines of cleaning the air and water that we each consume, as well as carbon sequestration. Much in the same spirit that someone launches other local public goods (tor node, public wifi, etc.), perhaps a generous neighbor/employer decides to undo all of the carbon or water pollution, or air pollution that they've ever created--thereby creating a "blast radius" of positive effects around their cleaning apparatus. Such technologies currently exist, but are energy intensive.