This concept of Spatial Justice has overtaken me. The combining of economics, urban planning, environmental issues, transportation, food politics and social theory is amazing.
For instance, what if considered that every poorly designed building (i.e. one that did not try to minimize its environmental impact -- if we are using that metric) is actually an injustice to the world and those who do not have enough? That the building is taking away life from others? Now. It doesn't just bleed energy and cost the owner money. Now it's a baby killer.

Phases of pollution, as seen in Slow Death By Rubber Duck:
1) Death by Direct Exposure
2) Belching and Spewing Industrial Phase
3) Workplace Exposure
4) Subtle Poisioning of the entire population with tiny, invisible amounts of toxins in our food and water.

Thinking about the correct use for the correct tool, based on efficiency. For instance, it is very carbon intensive to bring together the materials and then produce a backhoe. The shipping from factory to customer is another great intensive act - the truck uses gas, but the highway had to be built for the truck to drive on. Then there is the operation and eventual lifecycle end of the backhoe. All greatly intensive uses of carbon.
However, the backhoe is so efficient at what it does, maybe it cancels all that out?
Take that idea and apply it to small powered tools - like a lawnmower. The same relative amount of energy intensivity happened to put that mower in your hands, but the tool's efficiency ratio compared to doing it by hand isn't as much.