Making sense of hydrogen

The potentially beneficial application of truly clean hydrogen has attracted much attention but it has only a limited role to play in reducing climate pollution in the U.S. Most hydrogen made today – and many forms of hydrogen production proposed for the future – are not truly clean. Producing hydrogen from fossil fuels or diverting clean energy away from more beneficial uses toward hydrogen production can slow America’s progress in reducing our impact on the climate. It can even move us in the wrong direction.

To prevent the worst outcomes, the United States must ensure that public policy support for hydrogen is limited to near-zero-emission production methods and to those applications for which other decarbonization solutions (such as electrification) are not options now and will not be in the future.

What is “clean” hydrogen and what is not?

Clean hydrogen is hydrogen made from water using electrolysis powered by electricity from renewable energy sources such as wind, solar or geothermal power that is specifically dedicated to hydrogen production (that is, not diverted from other uses). Clean hydrogen must also be produced, stored and distributed through systems that minimize leaks. Because hydrogen is an indirect climate pollutant (increasing the lifespan of climate-warming methane in the atmosphere, among other effects), even hydrogen from electrolysis can be harmful for the climate if significant amounts of it leak into the atmosphere.

Hydrogen made from methane gas (typically called “natural gas”) is not clean. It creates significant global warming pollution. The most common process for creating hydrogen today, known as steam methane reforming, extracts hydrogen from methane gas molecules. This process creates carbon dioxide as a waste product, and generates pollution from the production of the methane gas used to create the hydrogen, the fuels burned to power the process, and leaks of methane and hydrogen to the atmosphere.

Adding carbon capture and storage (CCS) to steam methane reforming does not solve its climate problems. While carbon capture could cut emissions from the process by more than half, those emission reductions depend on capturing a higher portion of carbon than commercial facilities have demonstrated the ability to do.

Using grid electricity to create hydrogen through electrolysis is also not “clean.” At worst, it can create even more climate pollution than creating hydrogen directly from methane gas. That’s because increased electricity demand for hydrogen production may prompt the operators of coal- and methane gas-fired plants to increase the amount of power (and pollution) they produce.

Table ES-1. Climate impact of different methods of producing hydrogen

When is clean hydrogen not a climate solution?

Clean hydrogen is not an effective climate solution when better options are available. Spending money and developing infrastructure to use hydrogen when electrification would have been possible will slow the nation’s efforts to cut climate pollution.

Hydrogen, including clean hydrogen, has many drawbacks. Hydrogen:

• Is inefficient to produce;
• Readily leaks into the atmosphere, exacerbating global warming;
• Is energy-intensive to store;
• Is difficult to transport; and
• Is potentially unsafe.

The inefficiency of producing hydrogen and the global warming consequences of hydrogen leaks mean that the benefits or harms of hydrogen are highly contingent on how it is produced and handled.

What is clean hydrogen good for?

The major value of clean hydrogen is that it can provide an energy source for uses that would otherwise be difficult to decarbonize.

• Clean hydrogen can enable industrial processes that require high heat, such as steelmaking, which are difficult to electrify with current technology.
• Clean hydrogen is critical for applications that require hydrogen as an input, such as fertilizer production, and that currently use dirty forms of hydrogen.
• Clean hydrogen may be useful for some long-distance trucking, maritime shipping and aviation, which are difficult to electrify because current batteries are heavy and bulky and reduce available cargo space.

What is clean hydrogen not good for?

Hydrogen is not the climate-friendly choice in any application where electricity can be used directly.

Using clean electricity to produce hydrogen instead of using clean electricity directly is inefficient and wasteful. Some of the energy that goes into producing hydrogen is lost in the process of producing hydrogen, storing and transporting it, and burning it or using it in a fuel cell. For example, if hydrogen is produced through electrolysis and then used in a fuel cell to generate electricity, only 40% of the initial electricity used to make hydrogen is ultimately available to be turned back into electricity. In contrast, storing electricity directly in lithium-ion batteries is 70% to 90% percent efficient.

Greater decarbonization can be achieved by avoiding the use of “dirty” hydrogen and limiting the use of clean hydrogen to those applications where electrification is not possible.

• Electricity is a more efficient and cost-effective option than hydrogen for light-duty vehicles and for medium- and short-range trucking. Electricity is also a better choice than hydrogen for heating buildings and providing hot water.
• Blending hydrogen into the methane gas supply is not only an inferior climate solution to electrification of homes and businesses, but it produces (at best) only modest climate benefits compared with burning methane gas. Any benefits are unlikely to be worth the additional cost of hydrogen blending.

 How can the nation get the greatest climate benefit from hydrogen?

For the nation to obtain the greatest climate protection benefit from hydrogen, public policies should only support the production of truly clean hydrogen and only encourage its use where better options are not available.

• Federal and state policies should not reward the production of hydrogen from methane gas.
• Public policy should not support the use of hydrogen where electrification is more efficient, such as heating buildings.
• Because hydrogen is an indirect climate pollutant, it is important to limit deliberate or accidental releases into the atmosphere from any facility that handles hydrogen. Federal and state governments should set standards that limit acceptable hydrogen leakage to a very low level.