How many tons of greenhouse gases does an average cow emit per year?

Answer 1

Depends on the breed, it's diet and where it lives - anywhere between 400 and 1800kg per annum, typically about 800kg.

The majority from burps, some from farts. The exhaled gas is 90% nitrogen, the greenhouse gas constituent is methane.

By mass you're looking at approx 100kg of methane per annum, the equivalent of approx 2 tons of CO2.

All figures approx and from memory, allow a 50% margin of error.