1. Carbon dioxide (CO2): This is the primary greenhouse gas produced by combustion. It is formed when the carbon in the fuel combines with oxygen from the air.

2. Water (H2O): This is also produced during combustion, formed when the hydrogen in the fuel combines with oxygen from the air.

However, depending on the fuel and combustion conditions, other waste products can be formed as well, including:

* Nitrogen oxides (NOx): These are pollutants formed from the nitrogen in the air during combustion.

* Sulfur dioxide (SO2): This is a pollutant formed from the sulfur in the fuel during combustion.

* Particulate matter (PM): This is a mixture of solid particles and liquid droplets that can be harmful to human health.

* Unburned hydrocarbons: These are incompletely burned fuel molecules that can contribute to smog.

The specific waste products produced will vary depending on the fuel being burned, the efficiency of the combustion process, and the presence of other chemicals in the environment.