Combustion energy (gross calorific value) and total CO2 emissions from 11 model rubber compounds, polyurethane, and other materials related to rubber products during a one-time complete combustion were measured sequentially using methods in accordance with ISO 20463 using a bomb calorimeter. Eleven model rubber compounds and biobased polyurethane were prepared for these measurements. The combustion energies of the model rubber compounds were found to be 27 900 to 40 700 J/g. These measured combustion energies, after subtraction of the combustion energy of carbon black (CBK), were related linearly to the carbon content of these samples without CBK. A difference in the combustion energy of rubber products and that of CBK was observed. From these results, an estimation via the calculation of the combustion energy of the rubber products was developed from the formulation of the rubber product. Total CO2 emissions could be calculated by the results of total volume and the CO2 concentration of combustion gas collected from a bomb used for the measurement of combustion energies. The total CO2 emissions of these samples were 1.83 to 3.02 g/g. The relationship between total CO2 emission from model rubber compounds and the theoretical CO2 emission calculated from the carbon content of these samples was linear. It was found that these methods had high precision. High reproducibility of the methods for such measurement was confirmed by the use of a round-robin test, which was carried out by six Japanese chemical laboratories.