The way I look at it, the answer is in the cost. Every process and product we build or buy has an energy cost that is reflected in the price we pay. Ultimately we're always paying for energy and not much else.

It's a good rule of thumb.

For example, it shows how absurd "food miles" are as a unit. Shipping something around the world on a giant ship is spectacularly fuel efficient, so it's not the distance that matters. If it weren't fuel efficient, those things would be expensive.

A somewhat better "green food" metric would be unitless: units of energy used in transport per calorie of food delivered. A horrible number if you drive an SUV to the store, which is often the largest part of the energy cost. Just another way of noting that most food, even stuff transported from afar, has a relatively low energy cost before you buy it. The bad ones are clear in the price: in winter in Europe we see cherries flown in from Chile, and they run around 35-60 euros/kg at the start of the season. About $0.50 per cherry.

You do have to do a mental adjustment for things that are heavily subsidized or have large negative externalities, as they can have large costs that don't show up in the sticker price.

The price isn't all energy, though, a lot of things come down more to labour cost. I don't think that's to be avoided or adjusted...though there are abuses in the world, that is far from the majority situation. On average I'd rather buy something made by somebody not paid a lot, because on average those low wages probably do more for them where they live than high wages do for an alternative worker in the developed world.

Jim