Understanding Methane and Its Sources
Methane (CH₄) is a significant greenhouse gas and a major component of various fuels. Its presence in different energy sources varies, making it essential to identify where it is predominantly found.
Methane in Biogas
- Biogas is primarily composed of methane and carbon dioxide, produced through the anaerobic digestion of organic materials such as agricultural waste, food waste, and sewage.
- The methane content in biogas typically ranges from 50% to 75%, making it a renewable energy source.
- Biogas can be harnessed for heating, electricity generation, and as a vehicle fuel, contributing to reduced greenhouse gas emissions.
Comparison with Other Options
- Coal Gas: While coal gas (town gas) contains methane, it is mainly a mixture of hydrogen, carbon monoxide, and other gases produced from the gasification of coal. Methane is not the primary component.
- Water Gas: Water gas is produced by passing steam over hot coal, primarily consisting of hydrogen and carbon monoxide, with only trace amounts of methane.
- Petroleum: Methane is present in natural gas associated with petroleum, but petroleum itself (crude oil) does not contain significant methane. It consists mainly of hydrocarbons in liquid form.
Conclusion
In conclusion, the correct answer is option 'D' (Biogas) because it is the source where methane is a major constituent, unlike coal gas, water gas, or petroleum, where methane is either absent or present in much smaller quantities. Understanding these distinctions is crucial for environmental studies and energy management.