Doesn’t hydrogen seem like the perfect fuel of the future?
It’s everywhere! Literally 90% of the universe. A pound of hydrogen gas contains three times the energy of a pound of gasoline. When it burns it produces water, with zero carbon emissions! What’s the hold-up with saving the planet with hydrogen fuel?! Well, there are a few problems:
1. Pure hydrogen is almost non-existent on Earth;
2. Producing it requires a lot of energy;
3. Producing it cleanly costs a lot of money;
4. Transporting and storing it is difficult and expensive.
So first of all, there is virtually no plain hydrogen gas on Earth. Most of the hydrogen on Earth is in the form of water. And counter-intuitively, the hydrogen in water is “burned up.” It has already given up its heat just in the process of becoming water. In order to get energy out of it again, you have to break its bonds, which requires – wait for it – energy!
How much energy? In fact, more than you can get from burning the hydrogen, so there is a net energy loss in the process. This is especially a problem these days when we use fossil fuel-generated energy to split the chemical bonds to get hydrogen gas. A whole lot of CO2 is emitted in the process, thus defeating any “climate solution” purpose it had!
Most of Earth’s hydrogen is combined with other elements into molecules because – well, that’s what chemistry does. Many of the compounds are hydrocarbons that are in fact used as fuels – and when they’re burned they make carbon dioxide and water. At this point, more than 98% of the world’s hydrogen is produced by “stripping” it from natural gas in a process that produces more CO2 than simply burning the natural gas.
Less than 1% of currently produced hydrogen can be considered to be essentially carbon-free. This is the hydrogen produced by electrolysis, where renewable electricity is used to split the water into hydrogen and oxygen gas.
Commercial hydrogen is categorized based on its source, coded with colors. If it is made purely from renewable energy it is called “green” hydrogen. If it is made from natural gas or another CO2 emitting process it is called “gray.”
There is also “blue” hydrogen, which is made from natural gas along with a process of “carbon capture and sequestration” (CCS). Some other color names are used for other processes, most of which also produce CO2. At this point in time green hydrogen costs at least three times as much as gray.
Blue hydrogen depends on the ability of CCS to capture 95% of the CO2 in order to make it as clean as electricity from photovoltaics. There is at present no CCS technology that can capture that much CO2. In fact, while there is much hype about it, there is no CCS technology at all that is functioning economically today.
But let’s say we somehow figured out how to make a lot of green hydrogen – i.e., no carbon emissions, and at a low enough cost. Turns out, hydrogen is not so easy to store or transport. It can’t simply be dropped in as a substitute for natural gas or propane.
While its energy density per weight is high, its energy density per volume is low unless it is stored at very high pressure, or liquified, both of which take yet more energy to achieve. Additionally, hydrogen can cause metals to become brittle over time, making it problematic to use existing gas pipelines to transport it. Also, because the hydrogen molecule is small and light it tends to leak more readily than other gases, so will more easily be lost in transport.
Whatever happened to those fuel cell-powered cars that President G.W. Bush touted for developing hydrogen-based transportation? A tank of hydrogen powering a fuel cell using electric motors is much more efficient than an internal combustion engine (60% compared to about 15%). We understood this was the future of transport!
But lo and behold, it has never come to fruition for several reasons, but especially their cost and the difficulty of deploying hydrogen filling stations. Also, the net efficiency of the fuel cell vehicle is about 40% less than a battery electric car. While Toyota is actually still pushing the technology, most expert opinions are that it has already lost to batteries. Around 50,000 fuel cell cars exist worldwide, compared to around 20 million battery EVs. That’s a 1-to-400 ratio.
All that being said, most experts believe that, as the cost of green hydrogen comes down, it can play an important role in decarbonizing certain sectors of the economy, but only in the last 10% or so that is particularly hard to decarbonize.
These sectors include steelmaking, concrete, air travel, and peak electrical supply. For these applications, carbon-free hydrogen could indeed play an important role in the complex choreography of a carbon-free economy.
But as they say, it’s no silver bullet – just part of the silver buckshot needed to take down the atmospheric-warming enemy!
Paul Stancioff, PhD., is Professor emeritus of physics at UMF. Cynthia Stancioff is just a person trying to make sense of things. Email: pauls@maine.edu or cynthia.hoeh@gmail.com. Previous columns can be found at https://
Comments are not available on this story.
Send questions/comments to the editors.
