When thrown into landfills and dumps, ordinarily biodegradable things such as food scraps may end up taking much longer to decompose because they lack enough oxygen for microorganisms to do their job, which is to convert waste to nutrient-rich soil.

One needn't grow a compost pile in the backyard to help out. In 2003, San Francisco became one of the only large cities to pick up compostables along with trash and recyclables. Now, with those green, wheeled bins homeowners and renters have, everybody can easily do the responsible thing yet have someone else do all the dirty work.

What's compostable

• Food (bread, fruits, vegetables and meat, including bones and eggshells)
• Food-soiled paper products (pizza boxes, napkins and paper towels, paper plates, milk cartons, tea bags, coffee filters and grounds)
• Plants and wood (leaves, grass, weeds, wood crates and sawdust)

Common plastic grocery bags aren't allowed in the green bins, but biodegradable bags are available to purchase. Norcal Waste Systems' composting website provides a list (PDF) of stores that sell these bio-bags.