ELI5 Burping - how loud was the world loudest burp?

What exactly causes a burp, and why does it happen? How do cows and their burps play a role in greenhouse gas emissions? When they say  “livestock are responsible for burping the methane equivalent of 3.1 gigatonnes of carbon dioxide into the atmosphere annually" what does the methane equivalent of CO2 mean? Where was the world’s loudest burp recorded?

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