The question seems to have a repetition in the responses. Natural gas is primarily used for powering steam turbines, producing electricity, and energy production. However, if you are looking for what natural gas is typically not used for, you might consider applications such as:
- Transportation fuels (though it can be used in compressed natural gas vehicles, it is not the primary fuel source for most transportation).
- Residential heating (while it is often used for heating, it's not exclusive to natural gas as other heating methods also exist, e.g., electric).
In the provided responses, all options seem to relate to energy production. If you meant to ask which option does not fit or is the least common application of natural gas, it may require clarification on the context of "not used for."
Feel free to provide more context or specify what you're looking for!