Final answer:
Petroleum engineers specialize in the production of natural gas and petroleum, which are crucial energy sources for transportation and varied applications. They employ different methods to extract and refine these fossil fuels, but are not typically involved with coal or solar energy production.
Step-by-step explanation:
Petroleum engineers work in subsurface engineering activities related to the production of several types of energy sources, including natural gas and petroleum. These professionals are instrumental in the extraction and processing of petroleum, which is a naturally occurring nonrenewable liquid fossil fuel. Petroleum extraction is usually found in conjunction with natural gas, as they often coexist in reservoirs beneath the Earth's surface. Notably, petroleum oil is a crucial fuel source for transportation, and through refining processes such as distillation, cracking, and reforming, it can be converted into valuable products like gasoline.
Among the fossil fuels, they can be categorized as solid (coal), liquid (petroleum), and gas (natural gas). While coal is mainly used for electricity generation, petroleum's primary use is in transportation. As we move forward, the industry also explores alternative fuels like ethanol, biodiesel, and hydrogen fuel cells to reduce the impact of greenhouse gases and dependency on traditional fossil fuels.