Blending hydrogen into U.S. natural gas pipelines presents significant safety risks and is likely not viable in most systems, according to a report commissioned by the Pipeline Safety Trust, a group that represents the American public in policymaking and regulatory venues.

Policymakers should not permit hydrogen blending in gas distribution systems and the long-haul transmission lines that feed these local gas grids, according to a report by pipeline investigation and auditing firm Accufacts Inc. Hydrogen blending may be suitable in transmission lines that exclusively serve industrial customers, though additional research is needed, Accufacts concluded.

"We call on policymakers and other decision-makers to be diligent and cautious in considering hydrogen pipeline projects," Pipeline Safety Trust Executive Director Bill Caram said in a Jan. 17 press release.

The federal government's plan to invest billions of dollars to develop a low-carbon hydrogen economy lends urgency to the issue, the Pipeline Safety Trust and Accufacts said. The U.S. Energy Department's draft clean hydrogen strategy proposes developing injection standards for hydrogen blending into gas pipelines, as well as assessing the potential to repurpose gas lines to carry hydrogen, the report noted.

The gas industry has also advocated for hydrogen blending, pitching it as a way to decarbonize various end uses, make use of long-lived infrastructure, and support energy system resiliency by complementing the electrification of heating.

In a letter responding to the Accufacts report prior to its publication, the American Gas Association and American Public Gas Association said: "The report contains many inaccurate statements, misinformation, and ignores research, past experience, and current projects on hydrogen blended natural gas transported by pipelines."

An 'unforgiving gas'

In December 2022, California regulators directed the state's investor-owned utilities to conduct hydrogen pilot projects. The order was part of a proceeding that also produced a hydrogen blending report by the University of California at Riverside.

The report found that blending hydrogen in volumes approaching 5% of the gas stream raises a number of concerns for public safety, the environment and end-use applications. The authors recommended large-scale demonstration projects and research and development to assess hydrogen's impacts on gas distribution systems.

The many information gaps identified in the UC Riverside report are just one factor that may make hydrogen blending unviable, Accufacts concluded. Additionally, hydrogen has several properties that make it more likely than methane to leak, ignite and explode. Those properties make hydrogen transportation in both distribution and transmission lines "substantially more dangerous than conventional natural gas pipeline operations," Accufacts said.

Hydrogen's potential volatility also raises concerns about transporting the gas through the densely populated communities where distribution lines run, Accufacts said. Currently, three pipelines chiefly located in low-density areas of the Gulf Coast account for 85% of the nation's 1,500 miles of hydrogen transmission lines, according to the report. The report said operators should focus on building dedicated, small-diameter hydrogen pipelines sited in low-density areas.

Accufacts identified customer-owned gas piping inside homes as "the weakest link" in the delivery system. Introducing hydrogen into the wide range of this piping presents serious public safety concerns, the firm said.

"Hydrogen is a very unforgiving gas, that can easily explode in the open, but is especially destructive when explosion occurs in the confinement of buildings, such as residences," the report said. "It is this final factor that leads Accufacts to conclude that hydrogen, even as blends, should never be allowed in gas distribution systems."