Hydrogen in a nutshell

Hydrogen (H2), a versatile energy carrier, is a chemical element discovered in 1766 by Henry Canvendish. It can be produced from several primary sources and used in numerous applications.

Depending on the volume of CO2 emissions during production process, hydrogen is classified into different colour categories: 

• Grey hydrogen - produced from steam methane reforming (SMR) or coal gasification. These methods of hydrogen production are among the most popular and the cheapest. However, their main disadvantage are high carbon dioxide emissions.
• Green (renewable) hydrogen - produced from electrolysis of water using electricity from renewable sources. Its main advantage is zero carbon emissions. 
• Low-carbon hydrogen - produced from renewable or non-renewable energy sources with reduced emissivity below 5.8 kg CO2 eq/kg H2.
• Blue hydrogen - produced from fossil fuel process using carbon capture and storage (CCS) system. 
• Purple hydrogen - obtained in the process of electrolysis using nuclear power. 
• Turquoise hydrogen - obtained in the process of methane pyrolysis. Although no CO2 is emitted in the production process, the by-product is solid carbon which must be stored or disposed of, ultimately resulting in a risk of carbon emissions. 
• White hydrogen - derived from natural geological sources.

Depending on the volume, supply distance and local conditions, hydrogen may be transported in different states of matter and by different means. The methods of transporting hydrogen with highest technological potential are pipeline transport, road transport and sea transport. Depending on the end users’ needs, hydrogen can be transported in compressed or liquid form, or as hydrogen derivatives like ammonia or methanol. 

Pipeline transport is the most economical method of transporting large quantities of hydrogen in gaseous form under high pressure. The challenge with this solution is the relatively high cost of the pipelines which must be properly adapted to prevent so-called hydrogen embrittlement. The transport of hydrogen via a dedicated network already takes place in Europe (e.g. Belgium). 

Road transport of hydrogen, either in compressed (CGH2) or liquid (LH2) form, is the standard solution used for short and medium distances. 

Maritime transport of hydrogen is the most economically viable over long distances. Hydrogen can be shipped in Liquid Organic Hydrogen Carriers (LOHC) in liquid form (LH2), or in ammonia or methanol. 
 
Hydrogen can be stored in both underground and aboveground tanks. Underground it is stored in salt caverns, rock caverns or depleted natural gas and oil fields. Currently, the most common method of hydrogen storage is in pressurised tanks, mainly at industrial plants. Such tanks are also available in mobile form. Likewise in transport, hydrogen can also be stored in ammonia or in LOHC. 

Hydrogen has a wide range of applications in various industries. The key sectors of economy where hydrogen can be used include:

• refining industry (e.g. as a feedstock in crude oil processing);
• chemical industry (e.g. for ammonia production);
• petrochemical industry (e.g. for the production of organic chemicals and polymers);
• metallurgy (e.g. for direct reduction of iron);
• transport (as fuel for road, maritime and air transport);
• energy storage (storing energy during surplus production periods).

Poland is the third largest producer of grey hydrogen in Europe, with annual production volume of approx. 1 million tonnes. The largest quantities of hydrogen in Poland are used in gas generating sectors: in the refining industry - in crude oil processing, and in the chemical industry - mainly for ammonia production. The main field of application of green hydrogen as Renewable Fuel of Non-Biological Origin (RFNBO) is the replacement of grey hydrogen.

Green hydrogen is a valuable component in the energy transition, with great potential in shifting to a zero-carbon economy and ensuring diversification and security of energy supply. It is likely to become an important factor in fossil fuels phase-out, without distorting production processes. Due to its properties as an energy carrier, new areas of green hydrogen application are constantly identified. It can be used for the production of other renewable fuels such as ammonia or methanol, thus enabling the development of new ‘green economy’. Hydrogen derivatives are also utilised as zero-emission marine fuels. In addition, hydrogen can provide a solution to the problem of interruptions in renewable energy supply by storing excess energy during surplus periods and releasing it when RES are insufficient. Another hydrogen application currently considered is the potential of this gas in district heating.