By Hannah Saulters

Spoiler alert: As much as 40 percent of the food produced in America ends up at the dump, off-gassing methane and contributing to climate change. And we consumers bear a great deal of the blame.

Become part of the solution with these free apps. Three of the four require a critical mass of users to create a sharing economy, so even if an app isn't yet functional in your community, go ahead, sign up and encourage other locals to do the same.