The thermal generation refers to the heat energy generation cycle. There are four combustibles for thermal energy, oil, natural gas, wood, and geothermal waste.
The main disadvantage is that the thermal oxidation operates at 800-900 C compared with 250-350 C for the catalytic alternative. The high operating temperature also means that more energy must be added to the process as a supplemental fuel, compared to a comparable catalytic process. This contributes to a higher operating cost of the unit.
Another disadvantage of the high operating temperature is that NO2 can be formed in the flame, perhaps requiring additional emission controls. For catalytic oxidation, the cost of the catalyst and its replacement due to premature deactivation ass to the cost. If deactivation can be minimized, catalyst replacement costs can be minimized.