3. Fossil Fuels Fossil fuels have been a widely used source of energy ever since the Industrial Revolution which was right before the 20th century. Fossils fuels are generally easy to use to generate energy because they only require a simple direct combustion. However, a problem with fossil fuels is they have a very negative effect on the environment. Not only does their excavation from the ground significantly alter the environment, but their combustion causes a great deal of air pollution.
![Hydroelectric ,[object Object]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)