Addressing climate change requires not only a clean electrical grid, but also a clean fuel to reduce emissions from industrial heat, long-haul heavy transportation, and long-duration energy storage. Hydrogen and its derivatives could be that fuel, argues a commentary by four energy researchers in the journal Joule. However, they note, a clean US hydrogen economy will require a comprehensive strategy and a 10-year plan.

The commentary suggests that careful consideration of future hydrogen infrastructure, including production, transport, storage, use, and economic viability, will be critical to the success of efforts aimed at making clean hydrogen viable on a societal scale.

The authors are:

• Arun Majumdar, a Jay Precourt Professor and Co-Director of the Precourt Institute for Energy at Stanford University and lead author of the commentary. He served in the Obama administration as the Founding Director of the US Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) (2009–2012), as the Acting Undersecretary for Energy (2011–2012), and as the Vice Chair of the Secretary of Energy Advisory Board (2014–2017).

• John Deutch, an emeritus Institute Professor at MIT. He has served as Chairman of the Department of Chemistry, Dean of Science, and Provost. In the Carter administration, he served as Director of Energy Research (1977–1979), Acting Assistant Secretary for Energy Technology (1979), and Undersecretary (1979–1980) in the US Depart- ment of Energy.

• Ravi Prasher is an Adjunct Professor at the University of California, Berkeley. He has more than 20 years of experience in working in R&D in large industry, startup, government, and academia. He was one of the first program directors at ARPA-E. Prasher has published more than 100 papers on thermal energy science and technology and holds more than 30 patents.

• Tom Griffin specializes in identifying high-impact technology investment opportunities in the manufacturing sector for Breakthrough Energy Ventures. He has more than 25 years of industrial experience in applied technology development and deployment, including contributions over a wide range of energy and environmental sectors. He served as CTO at both Edeniq and Pennsylvania Sustainable Technologies (where was also co-founder), pursuing capabilities and applications in biofuels and catalytic fuel upgrading.

We applaud the US Secretary of Energy, Jennifer Granholm, for launching the ambitious Hydrogen Earthshot program with a technology-agnostic stretch goal of greenhouse gas-free H₂ production at $1/kg before the end of this decade. Similar R&D programs with techno-economic stretch goals are needed for H₂ storage, use, and transport as well. The Hydrogen Earthshot is necessary to create a hydrogen economy, but it is not sufficient.

—Arun Majumdar

About 70 million metric tons of hydrogen are produced around the world each year, with the US contributing about one-seventh of the global output. Much of this is used to produce fertilizer and petrochemicals, and nearly all of it is considered “gray H2,” which costs only about $1 per kilogram to produce but comes with roughly 10 kilograms of CO₂ baggage per kilogram H₂.

An H₂ economy already exists, but it involves lots of greenhouse gas emissions. Almost all of it is based on H₂ from methane. A clean H₂ economy does not exist today.

—Arun Majumdar

Researchers have plenty of colorful visions as to what a clean H₂ economy might look like. “Blue H2,” for example, involves capturing CO₂ and reducing emissions, resulting in H2 with less greenhouse gas output. However, it currently costs about 50% more than gray H₂, not including the cost of developing the pipelines and sequestration systems needed to transport and store unwanted CO₂.

To make blue hydrogen a viable option, research and development is needed to reduce CO₂ capture costs and further improve capture completeness, say Majumdar and colleagues in the commentary.

“Green H2” has also captured scientists’ attention. Green H₂ involves the use of electricity and electrolyzers to split water, without any greenhouse gas byproducts. However, it costs $4 to $6 per kilogram, a price that Majumdar and colleagues suggest could be reduced to under $2 per kilogram with a reduction in carbon-free electricity and electrolyzer costs.

“Turquoise H2,” which is achieved through methane pyrolysis, when methane is cracked to generate greenhouse gas-free H₂, is also creating a buzz in the research world. The solid carbon co-product generated in this process could be sold to help offset costs, although Majumdar and colleagues point out that the quantity of solid carbon produced at the necessary scale would exceed current demand, resulting in a need for R&D efforts to develop new markets for its use.

Whether blue, green, or turquoise, greenhouse gas-free hydrogen or its derivatives could be used in transportation; the chemical reduction of captured CO₂; long-duration energy storage in a highly renewable energy-dependent grid; chemical reductants for steel and metallurgy; and as high-temperature industrial heat for glass and cement production. But for these applications to become a reality, H₂ production will have to hit certain cost benchmarks—$1 per kilogram for the production of ammonia and petrochemicals or for use as a transportation fuel or fuel cells.

The researchers also emphasize that the US will need to consider how H₂ pipelines will be developed and deployed in order to transport it, as well as how to store H₂ cost-effectively at a large scale.

Developing and siting new pipeline infrastructure is generally expensive and involves challenges of social acceptance. Hence, it is important to explore alternative approaches for a hydrogen economy that does not require a new H₂ pipeline infrastructure. Instead, it is worth using existing infrastructure to transport the feedstock for H₂—electric grid for transporting electricity for water splitting; natural gas pipelines to transport methane for pyrolysis.

… While there has been some systematic study of geological storage, the United States Geological Survey should be charged with undertaking a national survey to identify the many locations where underground storage of hydrogen is possible while also considering the infrastructure costs needed to use these caverns.

—Majumdar et al.

Other recommendations from the authors include:

• Hydrogen R&D should be integrated with a private-public partnership for technology demonstration program to address economic, regulatory, supply chain, and policy considerations and thereby establish a credible de-risking approach to attract private investors.

• federal and/or state authorities must adopt policies to support a hydrogen market either by a charge on GHG emissions or via clean energy standards that involve GHG-free H₂ as an option, or a combination of the two. These policies should also include the enabling market creating policies for solid carbon produced via methane pyrolysis. Furthermore, governments should use their purchasing power to create a demand for GHG-free H₂ and, most importantly, use a reverse auction to foster a globally competitive supply chain in the private sector.

• Despite the strong interest in green hydrogen from electrolysis, the economic reality suggests that there could be a significant fraction of the hydrogen originating from natural gas. Therefore, a holistic hydrogen strategy should also be aligned with a national carbon management plan, which should include an infrastructure for carbon capture, transport, and sequestration derived from processes yielding either gaseous (SMR) or solid (pyrolysis) carbon co-production.

Resources

• Majumdar et al. (2021)“ A framework for a hydrogen economy,” Joule doi: 10.1016/ j.joule.2021.07.007