Cows (and all ranch animals) produce bodily gases as part of their process of digestion. It all adds up. Also, agriculture contributes to Global Warming in several other ways, read more here. The production of cement, as we now do it, creates considerable greenhouse gases. Cars create a carbon load through their manufacture, and their use. Even the solar panels on your roof generated some carbon when they were manufactured.
You need to look at every aspect of your life to see your total carbon footprint. Cows are a big source of CO2 it takes a lot of feed to raise just one cow; reducing your beef helps the planet.
If the electricity for your electric car was produced in a coal-fired plant, your car is not as green as you were hoping. So you have to look at all phases of the lifecycle of each product or service in your life, to really understand your carbon footprint. It is generally true that in any advanced economy in our world, people are producing considerable CO2 just carrying out their daily lives - and certainly more than they realize.