Hydrogen is an energy carrier that can store and deliver usable energy, and a crucial feedstock for various industrial sectors.

While its combustion produces no greenhouse gases, the production of hydrogen can have varying degrees of associated greenhouse gas emissions. 

• Electrolytic hydrogen should only be produced from additional renewable electricity, linked to when and where it is being generated.

• The amount of greenhouse gasses emitted to produce hydrogen, regardless of technology or feedstock, must be central to assessing the climate impact of hydrogen. 

Currently, the vast majority of hydrogen produced worldwide is “grey” hydrogen, produced using fossil gas and generating large amounts of greenhouse gas emissions. Renewable hydrogen, or “green” hydrogen, has the potential for very low associated carbon emissions but requires large amounts of renewable electricity to be produced. This renewable electricity demand must be met with additional renewable capacity, and must be produced and consumed simultaneously, and in the same areas. If not, “green” hydrogen production cannibalises existing renewable electricity needed to decarbonise the power grid and support the phase-out of coal and gas through direct electrification. It therefore shifts emissions to a different place in the wider system instead of reducing them. 

“Blue” hydrogen is produced through the same process as grey hydrogen (i.e., by reforming natural gas), but it is paired with carbon capture and storage (CCS) and has the potential to be low-carbon. Whether this potential is realised depends on the amount of upstream methane emissions resulting from natural gas extraction and transportation, as well as the share of CO₂ emissions resulting from hydrogen production that cannot be captured and permanently stored. To be considered low-carbon, these emission sources, as well as other potential points of emissions along the entire value chain, must be kept to an absolute minimum, strictly monitored, and regulated. 

Substituting “grey” hydrogen and unabated fossil fuels with low-emission hydrogen has great potential for reducing emissions if done right. However, the production of low-emission hydrogen must be paired with renewable energy sources and careful management of greenhouse gas emissions throughout the entire value chain. 

Figure 1: Producing Hydrogen from Electricity