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- Methods of making hydrogen The main processes for making hydrogen use natural gas, coal, or electricity with water
- Other options for hydrogen production Biomass, solar power and nuclear power could all be used to make hydrogen in the future
- The different ‘colours’ of hydrogen The environmental impact of making hydrogen depends on how it is made, and what it is made from
Although it is a very common element, there are no large reserves of hydrogen gas on Earth. This is because it bonds with other elements, so the hydrogen we need is locked up in other substances. By using energy (heat, electricity etc) it is possible to separate out the hydrogen from feedstocks A raw material needed to fuel a machine or industrial process such as water and methaneA compound made of carbon and hydrogen that forms the main component of natural gas. Chemical formula CH4 .
Today, over 95% of dedicated hydrogen production is from natural gas or coal, which produces greenhouse gasA gas that traps heat and re-emits it into the Earth's atmosphere, raising global temperatures emissions. If we want to use hydrogen to help reduce greenhouse gas emissions, switching to a low-carbon method of production is required. The environmental impact of making hydrogen depends on what it is made out of (the
Current methods of making hydrogen
Hydrogen from fossil fuels
The most common method of making hydrogen today is called steam methane reformation (SMR), which combines methane (from natural gas) and water at very high temperatures (approximately 900°C) to produce a mix of carbon monoxide, carbon dioxide (CO2) and hydrogen. By controlling the amount of air, water and methane in the reaction, engineers can alter the SMR process and change the amount of energy required and waste gases produced.
Hydrogen can also be made from coal in a process called gasificationA process that converts materials directly into a gas, using heat, pressure and steam. A syngasA fuel gas mixture consisting mainly of hydrogen and carbon monoxide. Usually made as a product of gasification is created using coal and water at high temperatures. Above 750°C, the carbon in coal reacts with water to form a mix of gases, including hydrogen and carbon dioxide. The coal is used to provide the heat that the reaction needs to work.
Using fossil fuels to make hydrogen produces waste greenhouse gases. To make the process environmentally friendly, waste gases must be prevented from reaching the atmosphere by using carbon capture usage and storageThe process of trapping carbon dioxide from waste gases or the atmosphere, and then utilising it or storing it safely and permanently (CCUS) technology, which can remove and store up to 97% of the CO2 emissions that are produced. However, CCUS is not widely commercially available at present.
Hydrogen from electricity
Electrolysis is a process which uses electricity to split water into hydrogen and oxygen, using an electrolyserA device which converts electrical energy into chemical energy.
The electricity can come from a range of sources, such as wind power, solar power, nuclear power or fossil fuels. Any hydrogen produced is low carbon as long as the electricity used in the process is from low-carbon energy sources. Today, less than 5% of dedicated hydrogen production uses electrolysis; the process is expensive due to the cost of electricity (especially from low-carbon sources) and equipment. Production costs are expected to decrease as the cost and size of electrolysers improve.
Unlike other methods, electrolysis works at low temperatures, typically 20-100°C, and is capable of producing hydrogen at a range of scales. For example, ITM Power has built eight hydrogen refuelling stations in the UK, each supplied by an on-site electrolyser powered by renewable energy. There are large-scale electrolysis projects too; ENGIE plans to install electrolysers on an offshore platform in the North Sea, powered by electricity from offshore wind power. The hydrogen produced can be brought onshore using existing gas pipelines.
Other options for hydrogen production
Another energy carrier from which hydrogen is made is biomassPlant or animal matter that can be used to generate energy . Using gasificationA process that converts materials directly into a gas, using heat, pressure and steam, biomass is heated and mixed with steam and oxygen to produce hydrogen without combustion (burning). Scientists and engineers are always on the hunt for new methods of making hydrogen, such as novel ways of using solar power or nuclear power to break apart water at a range of temperatures to get hydrogen and oxygen.
The different ‘colours’ of hydrogen
Hydrogen is often described by a colour. This does not describe what it looks like, but how environmentally friendly the process of making it is.
The CCUS technology needed to safely remove greenhouse gas emissions and store them is not yet widespread. As of the start of 2020 there are just 19 ‘large-scale’ projects in operation worldwide; it is likely that blue hydrogen will become more common as CCUS becomes cheaper and more widely used.
Nevertheless, blue hydrogen is currently estimated to be the cheapest option for producing hydrogen gas in a low-carbon way. As the availability and price of renewable electricity improves, coupled with a fall in the costs of electrolysis equipment , green hydrogen could potentially become the dominant type in use over the next 30 years. See What's next for hydrogen? for more.