The different methods for hydrogen generation are numerous, depending on the source matter, whether the final product is to be pure hydrogen or some sort of hydrogen compound, and what its intended uses are. Producing hydrogen fuel for rockets or compressed liquid fuel cell cars can be done by the relatively simple and well-known process of electrolysis, splitting water into charged oxygen and hydrogen atoms by running an electrical current through it. Other forms of hydrogen generation with a water-based medium include hydrolysis using ammonia borane, and modified thermochemical thermolysis, where sulfur-iodine is introduced to produce hydrogen in a nuclear reactor and the sulfur-iodine compound is retained afterward for further use.
Solid oxide fuel cells (SOFC) that produce electricity are another alternative-energy option that both uses and produces hydrogen compounds in the process, without requiring liquid water. They operate like a battery, except their input can be natural gas and output carbon dioxide and electricity. Many variations on solid fuel cells exist, most involving the use of high temperatures and some sort of expensive heavy metal like platinum. A new form of hydrogen fuel cell uses water and substitutes a much less expensive molybdenum compound metal for the platinum, and is 70 times cheaper than using platinum while capable of operating using sea water.
Much slower methods of generating hydrogen in bulk include using biological processes such as fermentation, and dark fermentation, which does not require the presence of light to operate. Microbial reactions, termed electrohydrogenesis, can generate hydrogen from waste water. The use of plants such as algae for hydrogen generation are also in development. In 2005, algae researchers at the National Renewable Energy Laboratory (NREL) in the US project their hydrogen generation project will bring the cost down to $2.80 US Dollars (USD) per kilogram, making it competitive with gasoline.
Another novel method for generating hydrogen is to use solar cell electrical power. Solar concentrator cells channel electrical energy to a solid oxide that operates at high temperature, in excess of 2,012° Fahrenheit (1,100° Celsius). The expectation is that 50% of the solar energy would be converted to an equivalent value in hydrogen energy. This is being researched for hydrogen generation as the costs could be as low as $0.85 US Dollars (USD) per watt, which is comparable to the efficiency of wind generated power systems. Hydrogen generation can be done by many low-cost, low-tech, or high-cost, high-tech means, with current research making it a practical alternative energy today, not in the distant future.