As I write this piece, we’re in the midst of a (biodiesel) road trip to Washington, D.C., towing behind us an unwieldy piece of history: a solar panel off the roof of the Carter White House. It’s decades old, though it still makes hot water just fine. In a sense, we’re traveling backward—which in another sense is what I think we’re going to have to do for a while in the U.S. climate movement.

Are you one of those people who pour the milk down the drain on the expiration date?

Expiration dates on food products can protect consumer health, but those dates are really more about quality than safety, and if not properly understood, they can also encourage consumers to discard food that is perfectly safe to eat.

A recent poll of more than 2,000 adults showed that most of us discard food we believe is unsafe to eat, which is a good thing, of course, but it is important that we understand what food expiration dates mean before we dump our food -- and our money -- down the drain or into the garbage. On average, in the U.S. we waste about 14% of the...