Currently, the entire world uses 400 quads of energy. One quad is equivalent to 2.93 trillion kilowatt hours. The United States uses the greatest amount at 100 quads of energy, yet it only has 5% of the world's population. This is important to understand because if the current world population of 6 billion people used the U.S. Standard then it would equal 2,000 quads of energy. That total means that with our current fossil fuel use the pollution would be five times greater than it is now. When the population grows to 9 billion people then the U.S. standard would require 3,000 quads of energy. The amount of pollution would be 7.5 times greater than now. Currently, the U.S. is the most inefficient place on Earth, because with proper conservation methods and appropriate technology the US can have a higher standard of living with only 15 quads of energy. The entire world can have the same high standard with only 300 quads of energy. All the while, pollution can be almost eliminated. This is all possible with today's technology. Eventually, breakthrough technologies may reduce energy needs to 30 quads for the entire world.
The true renewables energy sources are solar, wind and water. These renewable energy technologies are already advanced and sound economical investments. As for hydrogen, it is an energy carrier rather than an energy source, so both renewable and fossil fuels can be used for the energy source. However, if fossil fuels are used then it still is an ecologically degrading approach to energy. The true renewables are the best.
Ethanol and biomass fuels have been touted as a renewable energy source, but in reality, they are not sound choices for large scale infrastructure. In fact they waste space and interfere with ecological diversity. According to the Earth Policy Institute, 'The conversion of ethanol from corn is one ton of corn = 39.4 bushels(1379 liters) = 110 gallons (418 liters) of ethanol. The grain it takes to fill a 25 gallon tank (95 liters) with ethanol just once will feed one person for a whole year. Converting the entire U.S. grain harvest to ethanol would satisfy only 16% of U.S. auto fuel needs.'
A few points to consider before converting plants or plant wastes to ethanol: