Green hydrogen produced via electrolysis will facilitate conversion of some sectors with a moderate demand for hydrogen, such as rail transport and HGV road transport to zero-carbon hydrogen fuel, and facilitates the production of the hydrogen fuel at the point of demand at the depot. However, if hydrogen is to play a major role in the decarbonisation of heat and industry, electrolysis alone will not be able to provide the quantities of hydrogen required due to the massive increase in the installed power generation capacity that would be required to supply power to the electrolysis plants – potentially doubling or trebling the size of the power generating sector purely to produce hydrogen, since the demand for gas exceeds the demand for electricity in the UK.
Traditional sources of hydrogen, from the reforming of natural gas or gasification of coal and other solid feedstocks, will be required to produce hydrogen in bulk. These processes are commercially proven, and in safe and reliable operation in facilities around the world, including several natural gas reforming plants located in the UK. However, with these technologies hydrogen is produced with associated production of CO2, which would traditionally be emitted to the atmosphere. Utilising hydrogen from such a source in place of natural gas, for example for domestic heating or to supply energy-intensive industry, would actually result in higher CO2 emissions than those associated with using natural gas directly. However, it is possible to mitigate these CO2 emissions by employing carbon capture, utilisation and storage (CCUS). Advanced natural gas reforming and coal gasification technologies lend themselves to CCUS, since the CO2 can be removed from the ‘syngas’ (synthesis gas) stream as part of the normal hydrogen purification process and then exported for utilisation or permanent storage. Indeed, this is already happening in the fertiliser industry; in ammonia/urea fertiliser complexes, the CO2 ‘captured’ from the hydrogen production unit is utilised as feedstock for urea synthesis.
Adding CCUS will increase the cost of hydrogen production via reforming or gasification, and therefore one challenge is for governments to develop a mechanism to ‘reward’ the decarbonisation of hydrogen production.
Through CCUS, the CO2 emissions of hydrogen produced from fossil fuel sources can be reduced by around 90%. The so-called ‘blue’ hydrogen, hydrogen produced from fossil fuels in combination with carbon capture, therefore has a significantly lower carbon footprint if used to displace natural gas for heating. However, it is not zero carbon as there are still some residual CO2 emissions associated with the hydrogen production plant that cannot be directly eliminated – is there anything more that can be done?