President BidenJoe BidenUS tells Americans to leave Kabul airport ‘immediately,’ citing ‘credible’ threat Britain, France to propose Kabul safe zone for people trying to flee Afghanistan Pollsters confront tough survey landscape after 2020 flubs MORE has set an ambitious and a highly consequential goal for the United States — a net-zero emissions economy by 2050.
Achieving this climate goal will require a massive transformation of the U.S economy, building new infrastructure and an urgently needed improvement of our global competitiveness. So, how do we get there? We need a game plan.
Creating a zero-emissions electric grid with solar, wind, nuclear, hydro and storage is necessary, but far from sufficient. We also need a clean fuel to reduce emissions from industrial heat, long-haul heavy transportation and long-duration energy storage. Hydrogen, produced without greenhouse (GHG) gas emissions, is a prime candidate.
We applaud Secretary of Energy Jennifer M. Granholm for recently announcing the “Hydrogen Earthshot”, an innovation initiative with the goal of producing GHG-free hydrogen at $1 per kilogram by the end of the decade. That would be a global gamechanger. To accelerate the scale up of such breakthroughs for economy-wide deployment, the hydrogen game plan needs deep understanding of the complex interplay between research and development (R&D), infrastructure, economics, markets and policy.
Today, the U.S. produces 10 million tons of hydrogen annually, 95 percent of which comes from natural gas via steam methane reforming. Most of this hydrogen is used for ammonia production to make agricultural fertilizers and to make gasoline, diesel and plastics from crude oil. Each kilogram of this “gray” hydrogen costs about $1, and comes with 10 kilograms of carbon dioxide emissions.
Separating the carbon dioxide from hydrogen and permanently sequestering it underground turns gray into “blue” hydrogen — but raises the cost by at least 50 percent. To make blue hydrogen a viable option, we need R&D to reduce carbon dioxide separation costs as well as policies that impose a direct or an indirect charge on carbon emissions. Additionally, we need a pipeline infrastructure to move hundreds of millions of tons of captured carbon dioxide from the hydrogen plants to geologic sites for permanent storage. There is no free lunch.
Alternatively, devices called electrolyzers can be used to break down water using electricity and produce what is termed “green” hydrogen. Green hydrogen is genuinely green only when electricity generation has net-zero emissions. This is part of President Biden’s climate plan with a target date of 2035. But that is only part of the story. Today, green hydrogen costs $4 to $6 per kilogram — about three to four times more than gray or even blue hydrogen. To make green hydrogen competitive, the price of zero-carbon electricity must be reduced by 30 percent and the electrolyzer system costs must fall by 70 percent or more. Green hydrogen may need an upgraded grid, but it does not need a new infrastructure to be built.
If you are wondering why there are so many colors for a colorless gas, let us add one more — “turquoise” hydrogen. This is based on a promising approach called methane pyrolysis where natural gas is cracked to produce GHG-free hydrogen and pure solid carbon as a co-product. Solid carbon can be sold for a variety of market applications, which partly offsets the cost of hydrogen. Furthermore, it can be hauled away in trucks and does not require new infrastructure to be built. Turquoise hydrogen has the potential to reach the Earthshot target, but R&D is needed to develop cost-effective pyrolyzers and policies are needed to encourage solid carbon markets.
Policies that align technologies, supply chains, infrastructure and markets are essential for success and scale up. Creating new infrastructure, such as pipelines and transmission lines, is expensive, time consuming and comes with social acceptance challenges. This is particularly true for high-pressure hydrogen pipelines which are a safety risk because of hydrogen embrittlement of steel.
Therefore, green and turquoise hydrogen that can use thousands of miles of existing electricity transmission lines and natural gas pipelines to move the feedstock for on-site GHG-free hydrogen production have the potential for faster scale up.
If GHG-free hydrogen is to be used to fuel long-haul trucking and maritime shipping, $1 per kilogram target would make it cost competitive with diesel, underscoring the importance of achieving the Hydrogen Earthshot goal. Unlike diesel, hydrogen’s volumetric energy density is much lower even at high pressure. However, liquid ammonia may be an attractive carrier for hydrogen. Fortunately, liquid ammonia has a global infrastructure in place, since ammonia is used to produce fertilizers.
The difficult challenge for hydrogen is its use for industrial heat. Burning hydrogen has to compete with burning natural gas. Natural gas is so inexpensive (without a carbon emission charge) that hydrogen production costs would need to be 50 cents per kilogram, (one-half the Hydrogen Earthshot goal) to compete. This highlights the need for either a direct price on carbon emissions such as a carbon tax, or an indirect price on carbon emissions, such as a mandated clean energy standard, or a combination of the two.
Achieving President Biden’s goal will not be easy. As President Kennedy rightly summarized 59 years ago while launching the moonshot program, “we choose to do these things not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win….”
Arun Majumdar is a professor at Stanford University.
John Deutch is a professor at MIT.
Ravi Prasher is a professor at University of California, Berkeley.
Tom Griffin is a member of Breakthrough Energy Ventures.
Majumdar, Deutch and Prasher are members of the Breakthrough Energy Ventures Scientific Advisory Board.