The correct answer is option 2: Methane and carbon dioxide. Biogas is a type of gas that is produced by the decomposition of organic matter in the absence of oxygen, a process called anaerobic digestion. It is commonly generated from sources such as agricultural waste, food waste, and sewage.

Methane (CH4) is the main component of biogas, typically making up around 50-70% of its composition. Methane is a potent greenhouse gas that is produced by the anaerobic bacteria during the decomposition process.

Carbon Dioxide (CO2) is also present in biogas, usually accounting for about 30-50% of its composition. Carbon dioxide is produced alongside methane during anaerobic digestion and is another greenhouse gas.

While Methane and carbon dioxide are the main constituents of biogas, it is important to note that biogas can also contain trace amounts of other gases such as hydrogen sulfide (H2S), ammonia (NH3), and water vapor (H2O). These additional gases can have an impact on the composition and quality of the biogas produced.

Alert - correct answer should be option 2: Methane and carbon dioxide