Conversion

• One of the biggest problems with using hydrogen as a source of energy is the cost and time it would take to convert to hydrogen as a fuel source. Dependence of oil-burning fuels is so high that the Central Intelligence Agency estimates that America consumes over 18 million barrels of oil each day. By switching over to another energy source, all of the oil-burning equipment used in America would have to be converted to use hydrogen. It would take decades to break even on the conversion from gasoline to hydrogen as a fuel source.
  
  

Storage

• Hydrogen in its natural state is a gas, making it extremely hard to store. Special containers would have to be developed just to store hydrogen fuel. Also, using hydrogen in its gas state poses as problem to the average consumer. Of course, hydrogen can be converted to a liquid and then used; however, this alternative also has its problems. Hydrogen is extremely corrosive to steel, so storing it in a vehicle can cause safety issues. The best way to store hydrogen is in pressurized hydrogen tanks. As of March 2011, companies are still trying to develop hydrogen tanks that are small enough for the average citizen to handle.
  
  

Reactivity

• Hydrogen is extremely reactive. Hydrogen will react to almost any element it comes in contact with. It is also very flammable and has the potential to spontaneously combust. In a transport vehicle, such as a car, ship or plane, this causes huge concerns. In a realistic scenario, a simple fender-bender can easily turn into an explosion if the hydrogen-filled fuel tank is disrupted. Hydrogen fuel tanks will need better protection than the gasoline fuel tanks used in automobiles now.
  
  

Fuel Production

• While there are several benefits to hydrogen fuel, the production of hydrogen is costly and complicated. Hydrogen is only considered economical because it is renewable and abundant. Hydrogen atoms are so light that elemental hydrogen atoms escape from Earth's gravity and into the atmosphere. Most of the hydrogen on Earth exist in chemical compounds like water and hydrocarbons. Therefore, hydrogen must be extracted from these compounds. There are several methods for extracting hydrogen so it can be used as a fuel source; however, each of these methods is more complicated than the gasoline production process.