Let's consider an automobile. The waste heat goes to the radiator, but the rest of the energy winds up heating the brakes and tires and so forth. You may as well consider all the heat in a gallon of gas as waste heat.

You heat your home but eventually all the heat escapes to the environment so once again all the energy in the wood, gas, or oil burnt becomes waste heat.

In fact it would be only a fraction of any fuel consumed that would not be wasted. For example a fraction of the energy of the diesel fuel that is used in construction is stored as potential energy when materials are lifted to upper floors. Other examples are processes where heat is used to make chemicals and metals etc.

The vast majority of the energy in the fuels consumed is contributing to the waste heat you ask about. The calculation could be based on the total energy of the fuels consumed. I can't calculate it. I don't have enough information.

Still, the earth is a big object and I believe this waste heat is a drop in the bucket in terms of global warming.

The CO2 is more significant because the greenhouse effect has all the heat from the sun shining on the planet, and all the heat trying to re-radiate into space, in the equation.  Even a small change in the CO2 results in an enormous amount of trapped heat.