Hydrogen is in the news these days as a potential clean-burning fuel that could help decarbonize the energy sector. Proponents say hydrogen fuel can solve the intermittency problems associated with …
Hydrogen is in the news these days as a potential clean-burning fuel that could help decarbonize the energy sector. Proponents say hydrogen fuel can solve the intermittency problems associated with solar and wind and address difficult fuel challenges in specific sectors like long-haul trucking, maritime shipping, aviation, and the manufacturing of steel and cement. But we should separate the hope from the hype by understanding the difference between zero-carbon “green” hydrogen and the “blue” hydrogen promoted by the fossil fuel industry.
Pure hydrogen does not occur naturally on earth. It is found in compound forms with other elements, most abundantly in combination with oxygen as water (H2O), and with carbon in methane (CH4). These compounds must be broken apart to obtain pure hydrogen, and that takes enormous amounts of energy. How it’s done makes a tremendous difference in whether the end result is environmentally friendly or climate-destroying.
“Green” hydrogen is produced from water using electrolysis, and when this is achieved using electricity from renewable energy sources, such as solar or wind power, the resulting hydrogen is the only type that can be considered truly CO2-free or green. Advocates for the development of green hydrogen technologies point out that as solar and wind production scale up and become cheaper, it makes sense to use those energy sources to manufacture hydrogen for specific parts of the economy, and to balance the grid.
Green hydrogen projects are being developed in Europe, Asia and the Middle East to explore those possibilities, and California is funding a green-hydrogen-fueled power plant and developing hydrogen fuel cells for trucks, buses, locomotives and aircraft.
By contrast, the most commonly used method derives hydrogen from methane gas (fossil gas or so-called “natural” gas) through steam methane reformation or SMR, which uses steam at high pressure and extremely high temperatures (750 to 1,000 degrees F). This is “gray” hydrogen, which has an extraordinarily high carbon footprint: about 9-12 kg of CO2 for every kg of hydrogen.
Roughly 96-98 percent of hydrogen production around the world is produced from fossil gas, and most of it uses the SMR process, with methane gas as both the feedstock and as the source of power to achieve the required levels of heat and pressure. Much of the resulting hydrogen is used in additional petroleum processing, to make synthetic nitrogen fertilizers from methane, and in other industrial processes.
Methane gas proponents claim that carbon capture technology can significantly reduce the carbon footprint of SMR. They’ve invented a new marketing term, “blue” hydrogen, for their reduced-carbon product, which they are touting as a climate-responsible alternative for natural gas in every application, from electricity generation to home heating. The problem with their claims is that even if such a huge portion of the carbon associated with SMR could be captured and stored safely—and that technology does not yet exist—the lifecycle carbon and methane footprint of the natural gas used as feedstock and to power the process remains decidedly damaging to the environment.
Just how damaging was illuminated this past July with the publication of a new research paper by Robert W. Howarth of Cornell University and Mark Z. Jacobson of Stanford University. Published by the Society of Chemical Industry and John Wiley & Sons Ltd. in Energy Science & Engineering, “How green is blue hydrogen?” is the first peer-reviewed analysis of the lifecycle of carbon dioxide and methane emissions from blue hydrogen. Using established metrics of the life cycle emission rate and the 20-year warming potential of methane gas, the authors found that the greenhouse gas footprint of blue hydrogen was in fact “more than 20 percent greater than burning natural gas or coal for heat and some 60 percent greater than burning diesel oil for heat,” even assuming that the promised capture and safe storage of carbon dioxide could actually be achieved.
The infrastructure bill approved by the Senate in August contains generous funding for what it calls “clean” hydrogen, but unfortunately, it does not adequately differentiate between genuinely green hydrogen and the fossil fuel-intensive blue variety. Jim Walsh, senior policy analyst at the non-profit environmental organization Food & Water Watch, has written that the bill includes at least $25 billion in new fossil fuel incentives and supports, mainly for blue hydrogen and carbon capture technologies, over and above the annual $15 billion in existing taxpayer-funded oil and gas subsidies. Blue hydrogen gives the fossil fuel industry the illusion of “clean energy” climate action while perpetuating methane gas production for energy, petrochemicals and plastics, and diverting investment from more beneficial and proven technologies. That’s classic greenwashing, on an unprecedented scale.
Reclaiming Hydrogen for a Renewable Future — Earthjustice
Howarth RW, Jacobson MZ. How green is blue hydrogen? Energy Sci Eng., 2021; 00: 1-12