Though you may not see a compost bin next to the trash and recycling bins where you live, in California’s Bay Area, a green bin is the norm. From those green bins, food scraps, yard waste, and the like can be transformed into a dark, nutrient-rich material for farms near and far. KQED’s Bay Curious series answers the question: How Does Oakland Turn Food Scraps to Soil? An excerpt:

Magic (and chemistry!) really start at the landfill, which despite its name is primarily a composting facility. When the transfer trucks arrive, they dump all the green waste onto an asphalt pad that’s larger than a football field. Asphalt doesn’t absorb water, which is critical, because compost piles need a lot of water to effectively decompose.

Next the green waste is passed through a machine that grinds the materials into smaller bits. Now the green waste is starting to look more like dirt or soil, and less like a heaping pile of leaves, Christmas trees, melon rinds, coffee cups and mysterious lumps of someone’s unfinished dinner.

But this is where the plastic bags come back to haunt us. When a plastic bag is mixed with green waste, the grinder spits out tiny pieces of plastic that can pollute the air, be accidentally eaten by birds, and otherwise wreak havoc on the environment. So if you take one thing away from this article, remember: No plastic bags in the green bin.

To learn more about composting, watch Inside the Compost Cycle: Turning waste to nutrient-rich soil. Bonus: The Surprising Places We Waste Energy and Rescuing NYC’s Leftover Cuisine.

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