Help: How do I calculate greenhouse gas emissions from combustion? This Applicability tool includes a calculator for calculating the amount of annual GHG emissions from Stationary Fuel Combustion Sources at your facility. After using the calculator to arrive at the CO2e emissions for these combustion sources, you will be returned to this page, where that total for Stationary Fuel Combustion Sources will be prefilled in the table below for summing the amount of annual CO2e emissions from combined sources at our facility.