The global economy is currently reliant upon fossil fuels but their use produces colossal amounts of chemical pollutants, especially greenhouse gases. The use of fossil fuels is unsustainable and must be reduced; a number of solutions have been considered.
Attention has centred upon the renewable electrification of previously greenhouse gas-emitting activities, particularly for transportation. However for most industrial applications chemical-based fuels are favoured, due to their higher energy densities. Synthetic fuels and biofuels have potential however they currently suffer from similar problems as fossil fuels, since they result in the emission of pollutants or put pressure on available land also used for food production.
An alternative approach is to move from fossil fuel reliance to a hydrogen-based economy. Hydrogen is not a greenhouse gas and when it is used in fuel cells only water is produced. Also, the low oxidation temperature prevents the formation of nitrous oxides; a significant pollutant associated with conventional fossil fuels.
The global chemical industry is reportedly responsible for 2 x109 tonnes of greenhouse gases per year. In order to decarbonise this industry, it must shift its focus to sustainable hydrogen production. Hydrogen can be created using multiple methods, which have been categorised using a colour-based system.
Green hydrogen, produced via electrolysis with renewable electricity, has the lowest environmental impact. However the most common type of hydrogen produced currently within the UK is grey hydrogen and it is created by an industrial process called Steam Methane Reforming. This process produces a large amount of carbon dioxide which is released into the atmosphere. However if this is captured and stored or reutilised it is classified as blue. The UK is targeting 5GW of hydrogen production capacity by 2030; Blue hydrogen is the most viable option since currently the technology required for green hydrogen is not economically viable on a large enough scale.
Globally hydrogen production and utilisation programmes are gaining significant traction. Therefore, having an understanding of the hydrogen economy and associated reaction processes is becoming essential for future engineers.
Written by James Eyers – MEng, Prototype Design Engineer