Hydrogen has the potential to be an important industrial feedstock and fuel. There are, however, various ways to produce and use it, leading to diverse supply chains with different environmental implications. Two considerations for the role of hydrogen in a low carbon economy stand out – ensuring that hydrogen production and supply has sufficiently low impact on the climate and using hydrogen in an optimal way. In this article, Dr Christopher Jones considers whether our low carbon hydrogen standards are good enough, how they can be improved, and how the use of hydrogen might be prioritised to have the greatest impact on sustainability.

• Low carbon hydrogen standards in the UK measure emissions from ‘well-to-gate’ on government funded projects – downstream emissions from the transport and storage of hydrogen are not encompassed.
• This means the UK standard can allow for more greenhouse gas emissions over the life cycle of hydrogen and does not sufficiently prioritise the lowest carbon option.
• Policymakers should make our low carbon hydrogen standards tighter and mandatory for all new hydrogen producers, to incentivise only the lowest carbon options for hydrogen.

Hydrogen production

Hydrogen has multiple production means. It can be produced via electrolysis or stripping hydrogen from natural gas or a biomass feedstock, but there are several variations within these processes.

Thermal treatments of natural gas (grey hydrogen) account for 99% of current production and have high carbon emissions.

Capturing and storing the carbon released through this process (blue hydrogen) should lower most of these emissions but with elevated ‘fugitive’ greenhouse gas (GHG) emissions from sourcing more natural gas.

Electrolysis separates hydrogen from water, so no carbon is realised by the reaction – its environmental impact is largely determined by the source of electricity, whether renewables (green hydrogen) or the grid average. Gasification processes with biomass inputs are also in development for hydrogen supply.

Low carbon hydrogen standards

The UK, US, EU and others have set low carbon hydrogen standards. In the UK’s case, this means for government funded projects where GHG emissions are measured ‘well-to-gate’, (i.e. across the production process but not including hydrogen transportation and storage), emissions should not exceed 2.4 kgCO₂e/kg of hydrogen.

This is particularly important for blue hydrogen, where there is significant uncertainty about the overall GHG impact for production. It takes more natural gas to provide a Megajoule (MJ) of blue hydrogen than a MJ of natural gas used directly. Emissions from natural gas extraction and processing have an important climate impact that the industry has so far not managed to curtail.

How far blue is from grey hydrogen rests largely on how much CO₂ is captured in production. The UK Environment Agency guidance requires capture rates of 95% or more, but there is little data on actual capture rates for blue hydrogen, with projects not yet meeting these requirements consistently.

These standards are important for ensuring future hydrogen does what we need it to, but currently they only apply to government supported schemes and minimum capture rates are guidance as opposed to law. Current UK standards also do not encompass downstream emissions from the transport and storage of hydrogen or the role of hydrogen as an indirect GHG.

Comparing standards internationally

The EU definition for low carbon hydrogen (3.4 kgCO₂e/kg) includes downstream emissions. For context, one study for the UK government puts potential downstream emissions (for the period up to 2030) at 0.7 to 2.3kg. While there are monitoring and evaluation benefits of limiting to well-to-gate, it does mean that the UK standard can allow for more GHG emissions over the life cycle of hydrogen and does not sufficiently prioritise the lowest carbon option. The US standard sets a maximum well-to-gate emissions value of 4 kgCO₂e/kg of hydrogen, but also offers progressively larger tax credits from 3 to <1kgCO₂e/kg_.

None of these current standards account for hydrogen as an indirect GHG when leaking into the environment, and its effect on the abundances of methane, ozone, stratospheric water vapour and aerosols. Quantifying the impact of leaked hydrogen emissions is challenging but the effect may be significant, therefore it is crucial to minimise leakage.

More data is needed to fully quantify leakage potential, particularly over large distribution networks, as proposed for hydrogen home heating. Improvements in sensor equipment and more studies on losses in different pipe configuration, storage and handling processes would allow for more informed judgement of hydrogen’s full climate change impact potential.

Prioritisation

Around 95 Mt of hydrogen is produced annually and is predominantly used for making fertiliser and petrochemicals. Future demand is expected to grow for these traditional uses and for new energy sector applications, like industrial processes and transport. The gap between production capability and foreseen demand makes it important to consider where hydrogen is best used. There are several ways to do this, for example through the use of the Hydrogen Ladder. But there must also be consideration of alternatives and the suitability of hydrogen for the role. Decision makers must therefore prioritise where new hydrogen production will have the greatest impact on sustainability – for instance, replacing high carbon hydrogen industry feedstocks or home heating, where more effective alternatives already exist for the latter.

If blue hydrogen cannot meet environmental criteria on production emissions when standards are enforced, then green hydrogen will be the predominate form of production. In this case, production may follow where renewable electricity is available at lowest cost. This may introduce new international trade between countries looking to become green hydrogen exporters (e.g. Australia, Chile and Morocco) and regions with growing markets for hydrogen such as Europe and Japan.

Stronger regulations and better standards

Strong and aligned regulation that considers hydrogen transport, storage emissions, as well as hydrogen leakage over the supply chain is needed for environmental safety, but also to provide investor confidence. The majority of planned low carbon hydrogen production capacity is stuck at the final investor decision stage awaiting clearer policies on regulations and incentives from future consumers like the UK. Policymakers can ensure that the UK is well placed to attract investment and provide such confidence by having comprehensive regulations that are reviewed regularly to incentivise only the lowest carbon options for hydrogen. This would take into account technological advances, new research and evidence, and allow for stakeholder feedback.

Governments are already taking positive steps to ensure new hydrogen production is suitable for the low carbon future, but these standards should be tighter, mandatory for all new hydrogen producers, and should account for hydrogen leakage.

Tightening standards would mean expanding the scope of UK, US and Japanese definitions for low carbon hydrogen to include transportation and storage, and for the UK, EU and Japan, enhancing incentives for very low GHG emission H₂ as proposed in the US.  Mandatory standards set by the Department for Energy Security and Net Zero could be applied in a similar way to the Renewable Transport Fuel Obligation, as is the approach for renewable hydrogen in the EU. Tighter standards would also include a commitment to monitor hydrogen leakage and then develop a robust standard which minimises it.

The issues around whether sources of hydrogen are low carbon enough, and available to meet demand beyond existing crucial uses such as fertiliser, have implications for policymakers planning for a low carbon transition. While markets may adjust themselves to prioritising the allocation of low carbon hydrogen to sectors with fewer alternatives, policymakers should take the approach of routinely reviewing the hydrogen sector and plan ahead to ensure priority sectors can source hydrogen safely and effectively. This needs to happen in a timely manner to avoid further delays to investment in low carbon hydrogen and in alternatives to hydrogen where decision makers are unsure whether to electrify or await hydrogen options.