Besides a clean electrical grid, climate change mitigation requires clean fuel to reduce emissions from industrial heat, long-duration energy storage, and long-haul heavy transportation.
Image Credit: Verticalarray/Shutterstock.com
A new study proposes that hydrogen (H2) and its derivatives could be the potential fuel. However, a clean U.S. H2 economy needs a detailed approach and a decade’s plan. The study also comments that keen considerations of future H2 infrastructure, such as production, transport, storage, use, and economic viability, will be crucial to achieving the objectives of making clean H2 feasible on a societal scale.
The study was published recently in the journal Joule.
We applaud the U.S. 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.
Arun Majumdar, Study Lead Author, Jay Precourt Professor, and Co-Director, Precourt Institute for Energy, Stanford University
“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,” added Majumdar. The collaborators of the study also reiterated this.
Almost 70 million metric tons of H2 are generated globally every year. Among this, the United States contributes one-seventh of the total volume. A considerable amount of this H2 goes into manufacturing petrochemicals and fertilizers. Almost all of this is considered “gray H2,” which costs merely $1 per kilogram to manufacture but comes with approximately 10 kg of CO2 baggage for every kilogram of 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, Study Lead Author, Jay Precourt Professor, and Co-Director, Precourt Institute for Energy, Stanford University
Scientists hold numerous colorful visions related to the properties of a clean H2 economy. For instance, the so-called “Blue H2” attempts to capture CO2 and decrease emissions, producing H2 with lower greenhouse gas emissions. At present, this costs around 50% more compared to the gray H2, excluding the cost of developing the pipelines and sequestration systems required to store and transport unnecessary CO2.
According to Majumdar and his team, “To make blue H2 a viable option, research and development are needed to reduce CO2 capture costs and further improve capture completeness.”
One more form of clean H2, known as “green H2,” has also attracted researchers. Green H2 needs electricity and electrolyzers to slip water without generating greenhouse gas byproducts. But the process costs between $4 and $6 for every kilogram. However, the researchers say this price could be minimized to less than $2 per kilogram by decreasing the costs of carbon-free electricity and electrolyzers.
“Turquoise H2” is obtained through methane pyrolysis while cracking methane to produce greenhouse gas-free H2. This has also gained attention from the research community. The solid carbon co-product synthesized in this process could be marketed to tally the offset charges.
However, the research team highlights that the amount of solid carbon generated may exceed the existing demand, thus necessitating further R&D to develop new markets for its usage.
H2 or its derivatives, including green, blue, turquoise, or greenhouse gas-free (and, in actuality, colorless), could be employed in transportation, chemical reduction of captured CO2, as chemical reductants for metallurgy and steel, long-duration storage in a highly renewable energy-dependent grid, as well as high-temperature industrial heat for producing glass and cement.
However, to realize these applications, H2 production must meet specific cost benchmarks, like $1 per kilogram for the production of petrochemicals and ammonia or usage as a fuel cell or transportation fuel.
Furthermore, the scientists stress that the United States will have to plan how the H2 pipelines will the built and deployed for transportation. The storage and large-scale cost-effectiveness should also be accounted for.
The researchers commented, “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.”
The researchers continued, “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,” concluded the researchers.
Journal Reference:
Majumdar, A., et al. (2021) A framework for a hydrogen economy. Joule. doi.org/10.1016/j.joule.2021.07.007.