"Dairy farms produce large amounts of two things: milk and poop. Milk finds its way into delicacies like hot cocoa and grilled cheese sandwiches but the poop just piles up.
Dairy farmers bulldoze the mess into artificial ponds called manure lagoons, where anaerobic microbes break it down into methane, a powerful greenhouse gas. Methane traps 80% more heat in the atmosphere than carbon dioxide, contributing to around one fourth of climate change to date. The cow digestive tract also produces methane and releases it when the cow burps.
About 50% of the methane that California emits comes from dairy farms. In order to meet strict climate goals, the state has proposed ways to regulate dairy methane emissions. But these efforts run up against a big problem: There isn’t currently a reliable way for dairy farmers to measure the amount of methane produced on their farm."