Blending hydrogen with methane gas is not a climate solution

Earlier this year, the utility company Pacific Gas & Electric (PG&E) notified its customers of a proposed rate increase to raise more than $90 million to finance a trial of “hydrogen blending,” in which hydrogen will be added to existing natural gas pipelines to help reduce climate pollution.

PG&E is doing this at the request of its regulator, the California Public Utilities Commission (CPUC), as part of the state’s efforts to reduce greenhouse gas emissions. However, everything we know about hydrogen blending tells us that this practice is not a meaningful solution for curbing emissions.

Blending hydrogen into methane yields limited pollution reductions

In December 2022, the CPUC instructed PG&E to propose “a pilot program to test hydrogen blending in natural gas,” asserting that “pilot projects and further study can help the development of the clean renewable hydrogen market, enable a variety of use cases, and contribute to achieving California’s climate goals.” The materials PG&E sent out to its customers echo the CPUC’s argument about hydrogen’s climate benefits, claiming that “using existing pipelines may be a cost-effective and timely way to transform California’s future energy system and achieve decarbonization at scale.”

But these claims are simply not supported by the evidence. Blending hydrogen into the methane gas supply does not reduce emissions by very much. If PG&E could create a blend of 20% hydrogen and 80% methane gas by volume, emissions from methane gas use would only drop by 6%, given the reduced energy density of hydrogen. But a recent study commissioned by the CPUC and conducted by researchers at UC Riverside found that more than 5% hydrogen in a hydrogen-methane blend becomes potentially problematic for infrastructure and appliances – an amount of hydrogen that would yield a mere 1.5% pollution reduction.

Many other technologies can deliver larger emission reductions than the 1.5% that is possible with hydrogen blending. For example, using wind, solar or geothermal capacity to generate electricity for California’s grid would deliver a 100% emission reduction for each kilowatt-hour of generation avoided at a methane gas plant, far more than using that electricity to produce hydrogen that will be burned along with gas. Each gas-powered home furnace replaced with an electric heat pump would deliver a 93% reduction in emissions from operating the equipment. Heat pump water heaters deliver similar savings: each gas water heater replaced with a heat pump water heater would cut operational emissions by 91%. If California is going to reach its goal of cutting climate pollution by 85% by 2045, these are the kinds of technologies it needs to invest in.

So why is the CPUC telling utilities to create pilot projects for hydrogen blending?

An outdated understanding of the role of hydrogen

The CPUC’s insistence on this project seems like a carryover from an earlier era when it appeared that hydrogen might play a more central role in cutting climate pollution.

The CPUC’s initial evaluation of hydrogen mixed with methane gas happened in the context of a 2012 law to facilitate and encourage the use of methane from biological sources such as dairies and landfills. The 2012 legislation prompted the CPUC to investigate potential contaminants in biomethane, including hydrogen, that might cause harm to public health, the environment or energy equipment. By 2019, the CPUC decided it should establish a limit on the amount of hydrogen that could contaminate biomethane added to gas pipelines.

The CPUC’s actions were further shaped by the passage, in 2018, of a law – supported by gas utilities and hydrogen business groups – that added green hydrogen to the state’s list of clean energy storage technologies targeted for increased use. The law defined green hydrogen as hydrogen produced from water using electricity. In contrast to its concern about the safety of incidental hydrogen in gas pipelines, in 2019 the CPUC began to evaluate how much renewable hydrogen could be added into pipelines “to reduce the carbon intensity of the gas used in the state.”

As the next step on this path, the CPUC commissioned a study on operational and safety questions regarding hydrogen blending. Centering on the question of how different metals and components of methane gas infrastructure may be degraded by exposure to hydrogen, this 2022 report from UC Riverside concluded that the injection of hydrogen into the gas network “becomes concerning as hydrogen blending approaches 5% by volume.” The concerns the research team raised include degradation of plastics and metals in the gas network, unsafe operation of end-use appliances and increased fire risks because of hydrogen’s greater flammability. The report called for real-world demonstrations of hydrogen blending to learn more, without questioning whether hydrogen blending is a valuable climate protection measure.

In fact, the report simply assumes that hydrogen is beneficial and makes the claim, without citing any evidence, that “[h]ydrogen blending into California’s natural gas pipeline infrastructure can help accelerate the transition towards the use of clean hydrogen as a fuel and energy storage medium, and help the state meet a number of climate and air quality goals.” This unsubstantiated assertion may be what the CPUC was referring to when it decided utilities should create hydrogen-blending pilot projects and wrote, “as the UC Riverside Study finds, clean renewable hydrogen can be a beneficial fuel and energy storage medium that can help California meet its climate goals.”

Pure hydrogen may have a role to play in cutting emissions from hard-to-electrify uses, such as some industrial processes, but blending hydrogen into gas pipelines is not a valid path for California to reduce its climate pollution. Policymakers should acknowledge the great strides made in clean electricity technologies over the past decade, invest in the pollution reduction potential they offer and end support for dead-end hydrogen projects.