For many energy analysts who focus on reducing carbon dioxide emissions, hydrogen as a fuel is intriguing. Plentiful (the most plentiful element in the universe), odorless, colorless, tasteless, and very combustible. But H2 does not live alone. It is bound up with other elements, including with another plentiful element, oxygen, to form water, H2O.
Hydrogen has dazzled energy mavens for decades, as it has potential to become a substitute for conventional fossil fuels in gas turbines, internal combustion engines, and industrial heat applications. Also, fuel cells. The product of using pure H2 as an energy source is often claimed be environmentally benign. But that claim has doubters.
The most recent critique of hydrogen enthusiasm comes in the peer-reviewed journal Atmospheric Chemistry and Physics, published by the European Geosciences Union. Analysts Ilissa B. Ocko and Steven P. Hamburg, both from the U.S. environmental group Environmental Defense Fund, in an article titled “Climate consequences of hydrogen emissions,” write, “While zero- and low-carbon hydrogen hold great promise to help solve some of the world’s most pressing energy challenges, hydrogen is also an indirect greenhouse gas whose warming impact is both widely overlooked and underestimated. This is largely because hydrogen’s atmospheric warming effects are short-lived – lasting only a couple decades – but standard methods for characterizing climate impacts of gases consider only the long-term effect from a one-time pulse of emissions.”
For short-lived greenhouse gases, they say, “this long-term framing masks a much stronger warming potency in the near to medium term. This is of concern because hydrogen is a small molecule known to easily leak into the atmosphere, and the total amount of emissions (e.g., leakage, venting, and purging) from existing hydrogen systems is unknown.”
Ocko holds a PhD in atmospheric and oceanic sciences from Princeton and works in EDF’s Washington office. Hamburg, working out of the Boston office, has a PhD from Yale in forest ecology and has done extensive research on methane emissions. He has been a lead author for the United Nation’s Intergovernmental Panel on Climate Change.
Ocko and Hamburg conclude, “While more work is needed to evaluate the warming impact of hydrogen emissions for specific end-use cases and value-chain pathways, it is clear that hydrogen emissions matter for the climate and warrant further attention from scientists, industry, and governments. This is critical to informing where and how to deploy hydrogen effectively in the emerging decarbonized global economy.”
Another take on hydrogen’s problems comes from energy journalist Irina Slav, writing in Oilprice.com, with a story headlined “The Green Hydrogen Problem That No One Is Talking About.” Most H2 today comes from using natural gas to break the strong bonds between hydrogen and oxygen in water. But because of the natural gas connection, many hydrogen enthusiasts call this “grey hydrogen” at it produces CO2. Capturing the CO2 and burying it, earns the sobriquet “blue hydrogen,” from the ranks of the hydrogen colorists. But the most enthusiastic hydrogen advocates are focused on “green hydrogen,” where electricity produced from renewables breaks the H-N bond.
But the fly in the hydrogen energy ointment, writes Slav, is basic: “Water.” She notes, “There is much talk about the falling costs of solar and wind and how they will make green hydrogen viable very soon. What nobody seems to want to talk about is water….When hydrogen advocates talk about the bright future of the technology, they focus on the costs associated with the electricity needed for the electrolysis. But electrolysis, besides electricity, needs water. Tons of water – literally.”
An industry source told her “that the production of one ton of hydrogen through electrolysis required an average of nine tons of water. But to get these nine tons of water, it would not be enough to just divert a nearby river. The water that the electrolyzer breaks down into constituent elements needs to be purified.”
And purifying water, Slav reports, “is rather wasteful. According to the same source, water treatment systems typically require some two tons of impure water to produce one ton of purified water. In other words, one ton of hydrogen actually needs not nine but 18 tons of water. Accounting for losses, the ratio is closer to 20 tons of water for every 1 ton of hydrogen.”
That translates into heretofore hidden costs. Distillation is the simplest was to purify water with electricity, cheap but slow. Using non-household costs for electricity in Germany, a leader in green hydrogen plans, $0.19/ KWh, “At a power consumption rate of 0.717 kWh, the distillation of a liter of water, then, would cost $0.14 (0.1147 euro). For a ton of water, that would be $135.14 (114.72 euro).
But the purification costs are steep, some $2,432 per ton. “This is based on the assumption that the water would be purified using the cheapest method available. There are other – much faster – methods, but they are also costlier, involving ion exchange resins or molecular sieves.
–Kennedy Maize
Twitter (@kennedymaize)