Even though hydrogen is the abundant element in the universe, it is hard to produce in large quantities on Earth. It can be produced by the electrolysis of water,
steam reforming of natural gas, coal gasification, thermochemical production, and biological gasification.
Eletrolysis is a process whereby water is split into its chemical components - hydrogen and oxygen. In this case, electricity is applied to water and it results in the following chemical reaction:
2H2O + energy ® 2H2 + O2
Research is being done to study the feasibility of using renewable electricity from sources like wind and solar to conduct electrolysis and generate hydrogen. Nuclear power is another method that can provide long standing electrical supply to generate hydrogen. High temperature electrolysis is being studied as a is more efficient way to split water than the traditional room-temperature electrolysis.
Steam Reforming of Natural Gas
Steam reforming of natural gas is currently the cheapest and most used way to produce hydrogen. By some estimates, it accounts for about half of the world’s hydrogen production. In this process, steam is fed methane gas at a temperature of 700-1000°C in a reactor with a metal based catalyst. The steam reacts with methane to yield carbon monoxide and hydrogen.
CH4 + H2O ® CO + 3H2
Apart from using natural gas as a feedstock, the process also requires an additional 10-30% natural gas that is used as energy to power the reaction.
Coal can be converted from its solid state into a gas using a process known as coal gasification. Gasification breaks down coal into its basic chemical constituents which includes methane gas. In this process, coal is exposed to hot steam and oxygen under high temperatures and pressure.
Gasification of Biomass
Hydrogen can also be produced through thermal gasification of biomass like cultivated feedstock, forestry by-products, straw, municipal solid waste and sewage. Under high temperatures the biomass breaks down to gas, yielding hydrogen, carbon monoxide and ethane. Steam is then introduced to reform the methane gas into hydrogen in a reaction similar to steam reforming of natural gas. The carbon monoxide is put through an additional process to attain higher levels of hydrogen.
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