Non-renewable energy sources are not effective, and cost far more than they offer in benefits. Fossil fuels formation is a very long process that occurs over thousands of years, and the reserves left in the earth are running out. Developing countries, including China and India, are requiring more energy and oil, and this means what fossil fuel reserves are left will soon be gone. Because of the time fossil fuel formation takes in the earth, it can not be renewed for thousands of years.
There are many hot discussions about pros and cons of nuclear power, and there are many critics and proponents for this form of energy. No matter how safe these operations are handled and barring any nuclear accident, which is almost impossible to do, radioactive waste is created which will be dangerous for hundreds or even thousands of years. This leaves a toxic legacy for future generations to clean up. Nuclear power is very risky, and can have disastrous consequences when something goes wrong. Incidents like Chernobyl and Three Mile Island have made many wary of allowing a nuclear power plant anywhere near their city. When all pros and cons are taken into consideration anything as deadly as nuclear energy should probably not be used. This energy is not renewable either, because there is a limited amount of Uranium in the earth, so when this is depleted then it is gone completely.
Fossil fuels are slowly being used up, and alternative energy sources that are renewable will have to be found to avert an energy crisis and supply the energy needed. Crude oil is full of hydrocarbons, and both the crude and refined forms of this substance contribute greatly to pollution and global warming increases. This energy source is not renewable, which means gasoline and diesel will not be fuel sources much longer. Because fossil fuels are not renewable, they can not be replaced. Removing these resources damages the earth, and new oil fields are getting harder to find every year. Anyone who understands how petroleum engineers find new oil fields knows the extended amount of time and large amounts of money this process requires.
Anyone who knows about the coal mining industry also knows why coal is also not the answer to future energy needs. Just like crude oil and natural gas, coal is a fossil fuel which is not renewable and harms the environment significantly. Mining for coal has changed a lot over the years, but recovering this resource still does great damage to the earth through mining methods, as well as greenhouse emissions. Coal is not unlimited, and eventually this fossil fuel will also run out as well. Since coal is a nonrenewable energy source, it is not a viable solution to any future energy crisis.
Without alternative energy sources, a severe energy crisis could occur globally. Fossil fuel reserves will not last long, especially at the rate oil and gas are consumed around the world.