What other energy sources could replace the use of petroleum?

Answer 1

There aren't many energy sources that can replace petroleum. Petroleum - gasoline and natural gas - is both energy-rich _and_ easily portable; very few energy sources meet both criteria. In most applications, you would need to combine two or more power sources to replace the petroleum.

Electrical: In order to be portable, you'll need to store the electricity. Batteries are heavy and not particularly efficient. Charging the battery can take considerable time, and the batteries themselves can undergo a finite number of recharge cycles before they need to be replaced, and batteries can be expensive. The electric energy used to recharge the battery has to come from someplace, and that's generally a power plant that uses hydroelectric, nuclear, coal, oil, or natural gas.

Wind: Wind power isn't constant, and varies too much over the course of a day. We can't use wind power for vehicles, although sailing ships using solely wind power crossed the oceans for hundreds of years.

Nuclear: Nuclear power plants are massive. They're "portable" in ships, but not in land vehicles. Nuclear powered ships can sail for a couple of years before needing to be refuelled.

Hydroelectric; Hydro-electric power is generated by using running water to spin turbines to generate electricity. At its simplest, this can be something as simple as a water wheel, but to generate substantial amounts of energy, we'll need a large volume of water falling quite a distance. That means a high dam, with lots of water behind it. That's not at all portable, of course, but it's generally pretty reliable and constant. The flooded valley behind the dam can have its own costs; however, the water storage, flood control and recreational resource aspects make hydroelectric dams an attractive option.

Solar: Solar power works as long as the Sun is shining. You'll need batteries (see above) for night time or periods of bad weather.

Alcohol-based fuels; We can convert plant matter into alcohol and use the alcohol as our portable fuel. However, alcohol contains less energy (fewer BTUs per gallon) than gasoline, and the plant materials aren't easily fermented to produce alcohol. In current alcohol production, it takes gasoline and natural gas to make the alcohol, so we often get less energy from the alcohol than we spent in fossil fuels to make it. Also, current alcohol production is almost totally dependent on corn, so we're using food to create fuel. The price of corn has recently risen high enough that some people are struggling to afford the food that we're turning into alcohol. And if we devote acreage to grow some other plant, we're decreasing the amount of edible crops we can grow. It's sometimes an uncomfortable tradeoff.