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:
1) How will it affect the natural process of returning plant waste to nature to feed the soil?
2) Is there a more efficient way to provide fuel?
3) Can conservation reduce fuel needs in the first place?
4) How much land and infrastructure is actually needed to grow and make ethanol?
5) How will it affect natural diversity in the local ecosystems?
6) Can the land, labor, and infrastructure be better devoted to growing food to feed hungry people?
The next notion is converting trash to fuel. This is unsound because it violates the first rule of conservation. If you convert trash to fuel then you will always need a supply of raw resources to create new materials. Secondly, when converting trash to fuel, one unit of trash would have to produce at least one unit of energy equal to the amount of energy required to produce the original unit of material just to break even.
Fossil fuels degrade the environment in both extraction and use. Natural gas has been promoted lately as a sound source, but the facts weigh heavily against it. The U.S. has only an estimated 1532 trillion cubic feet (tcf) of reserves that are technically recoverable. The U.S. uses about 23.1 tcf per year. At that rate it will only last 66 years while it pollutes the environment. However, if the option of being dependent on it to replace foreign use of oil then the reserves will only last about 25 years. Likewise, oil shale, domestic oil, and coal all have serious environmental hazards. They are all limited in reserves because they are finite resources. None of the fossil fuels are sound energy sources given our current state of technology and knowledge. Nuclear energy has too many downfalls (toxic waste and storage, nuclear weapons, security and safety risks). It should rightly be called "Toxic Energy." Toxic energy is not green.