CONCLUSION
Hydrogen as an energy source is an important current topic. It is referred to as the fuel of the 21st century. Hydrogen production is a crucial process coming from various resources. Currently, 48% of hydrogen is produced from natural gas, 30% from oil, 18 % from coal, and 4% from electrolysis. It is evident that fossil fuels dominate hydrogen production, and only a small fraction is produced by electrolysis. Thermochemical, biochemical, and photochemical production processes are still at the beginning and without industry use. In the automotive industry, only hydrogen produced by alternative methods makes sense as fossil fuels can be used as a fuel directly. That is the main reason to search for alternatives.
Water electrolysis recently cannot challenge traditional methods due to its high energy demand. Its use is suitable for countries with an abundancy of water and inexpensive electricity. Island is such country, sourcing its energy from geothermal springs. Another interesting method for hydrogen production is generators of the fourth generation. A heated cooling medium has a high enough temperature to conduct chemical cycles or high-temperature electrolysis. The most relevant method that could challenge fossil fuels in near future is hydrogen production using biomass. Biomass belongs to promising renewable sources of energy. Except for hydrogen production, it also holds large-scale energy use. The remaining issue of hydrogen use lies in its storage. Storage capacity needs to be improved for the global spread of hydrogen use due to its high weight and large volume. The cost of hydrogen still over-exceeds the cost of fossil fuels. The energetic efficiency (high energetic demand on compression, liquifying or reprocessing of chemical compounds) is another aspect needing to be increased.