An activity creating a tiny “landfill in a jar” to discover what happens when food breaks down without air. When food scraps are sealed away, they start to rot anaerobically and create biogas, including methane, a powerful greenhouse gas.

To help us see this invisible gas, we stretch a small balloon over the jar — and as the food breaks down, the balloon slowly inflates, becoming the head of our silly Methane Monster. Over the next three weeks, we’ll watch our monsters “burp” more and more gas, decorate them, name them, and measure their methane with a gas sensor.

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