Welcome to engineering with Rosie. Today, I am going to be talking with chemical engineer Paul Martin about how easy it
is to simply replace natural gas with hydrogen in the future. So this is something that I have heard a lot of
people talk about. And I've seen several government programs that plan to do that to swap from natural gas to hydrogen in
the existing natural gas pipe network. Paul recently wrote an article about this topic about some of the challenges
that will face if we try to simply replace natural gas with hydrogen. So I'll put a link to that article in the
description. So check it out, if you are looking to see all the maths and the assumptions behind his analysis. I
recently had a zoom call with him, so, let's check that out. Now.
Our values tell us that the atmosphere is what we depend on to live, our economics tell us that the atmosphere is a free
public sewer. That's the problem we have to solve. And the rest of it, engineers will sort it out.
I'm a chemical engineer by training and background. And for 25 years, I've been helping people scale up processes that
are working in the lab. And back in the late 90s, we had a big project where they were trying to make hydrogen for use
for initially in vehicles, and then later it was going to be for combined heat and power in homes using fuel cells. And
the problem with this process, which we would all joke about over beers after work is that you're basically taking a fuel
and you're turning it into another fuel with losses. And the losses are not small, they're very substantial, you lose at
least at bare minimum 30% of the energy that you're feeding as fuel, there was a good intention, the intention was to
reduce emissions to reduce co2 emissions, because at least in theory, if you make hydrogen first you can bury the co2
if you capture it.
Okay, so that's blue hydrogen that Paul's talking about hydrogen made from fossil fuels with some sort of carbon
dioxide capture and storage. So in theory, this is cleaner than burning gas, even if there aren't a lot of projects
around yet where they are actually achieving this theoretical clean benefit. Of course, there's also the
option of green hydrogen, hydrogen made using electricity to split water. And as long as the electricity is renewable,
then that is a much cleaner alternative to replace natural gas, although it's currently really expensive. Alright, so
hydrogen sounds really appealing as a natural gas substitute? But why do we even need to replace natural gas
with anything? What's so special about gas that it needs to be specifically replaced?
The answers are pretty clear. Number one, it's really cheap. The other benefit is it's quite clean in the sense that when
you burn it, you don't get a lot of toxic emissions, you don't get a lot of particulate matter there. Sulfur is easy
to remove, it's also very easy to move, it's inexpensive to move, you can just build a pipeline, and the energy cost to
So let's just start blending hydrogen into our natural gas pipelines. Why not?
move a Joule of heat or BTU of heat is very low. So it's got a lot of advantages. But what are the disadvantages? The
massive disadvantage is obviously the fossil carbon dioxide that's emitted when you burn it. But the hidden
disadvantage, and I say hidden, because that implies that someone's hiding it. And they are. The hidden disadvantage
is the leakage. So about half of the leakage comes fro production. And the other half of the leakage happens fro
distribution. I mean, we can fix the leakage, maybe, but th co2, boy that's a tough on
absolutely
why, why not what's not to like. So why not blend it with natural gas, and gradually slowly decarbonize natural gas by
transitioning everybody from methane, from natural gas to hydrogen? and it sounds great. And in fact, you can do it
like it's feasible, it's possible to do it to about 20% by volume. And that's how we measure gas mixtures by volume.
Here's the problem. Here's the problem, there's always a problem. When you add 20% hydrogen to natural gas, you
actually reduce the energy content of the gas mixture by 14%. we decrease the 100 joules to 80 joules, right? And by
adding hydrogen, which at least burns, we've reduced it to 86 joules. So six out of the 86 joules are from hydrogen,
and six over 86 is the amount that we've reduced the co2 emissions. It's kind of like adding water to gasoline.
[laughing] if you can get away with it, and your customers are dumb, right? If they don't care about the energy content
of your gas and you sell gas by the cubic meter or by the cubic foot, then it's great. It's probably great business
[laughing] but it's Just not the best idea from the point of view of the environment, because you're really adding a
diluent. And the problem is that you can't just keep going, you can't go from 20% to 30, to 40, to 50, to 70%. The
hydrogen proponents, you know, they like to talk about the truth with their head nodding this way, but never the truth
with their head nodding this way, right. And the truth with their head nodding this way, about hydrogen's energy
content, is that although its energy content per unit mass is really good. Its energy content per unit volume is
really, really bad. When you take into account the two factors, right, the mass energy content going up and the
volume energy content going down. Okay, without boring people with that stuff. It's 3.2 to 3.6 times less energy
per unit volume of gas that's going by, or another way to look at it is that you have to move 3.2 to 3.6 times as much
volume of gas in order to get the same amount of heat. So we've got to stuff three times as much gas 3.2 to 3.6 times
as much gas through the pipes. In order to move a gas around, you have to do two things, one of them is you have
to compress it. So you have to put mechanical potential energy into it to squish it to give it a reason to move. And
the other thing that you have to do is you have to resist friction as it's moving down the pipe. So it's going to be
rubbing in a sense along the inside walls of the pipe as it's traveling. So mass and volume both matter and they
matter in a complicated way. And so here's where it gets interesting. When we talk about moving that 100 joules or
that 100 BTU of energy, the pipe itself isn't the problem, the frictional loss in the pipe, as it turns out, with the
mass energy content going up and the volume energy content going down. The result is that it's almost a breakeven, it's
pretty close, a pipe can handle round numbers, about 90% as much energy in the form of hydrogen as it could in a typical
natural gas. So that's not too far off. But here's the kicker, you have to compress it. And the problem is you've
got to compress three times as much volume, almost four times as much volume of gas in order to put in that energy
that's going to then be lost in your pipe. And so that means you have to put in three times as much energy per unit of
energy that you're delivering. So that's why you end up with this problem of 20%. It's the compressors. But it's also the
burners at the other end because the burners are all jetted to draw in a certain amount of air to make a nice flame. And
that depends on the energy content of the gas turbines. If anybody's got a turbine to make electricity downstream, they
really care about BTU content. In fact, at 20%, they're already screaming at you. Like Stop, stop it, this is bad.
This is gonna wreck my machine. Don't do any more of that. So you really, you're really in trouble there.
Yeah. Okay, so we're not going to be able to run existing boilers and existing gas turbines off pure hydrogen. I know,
I've seen a few manufacturers who are developing special hydrogen turbines for electricity generation, and where I've
seen pilot trials of hydrogen for home heating, they're, they're using special hydrogen boilers. But all of these
projects that I've seen, do plan to take advantage of existing natural gas pipelines to transport hydrogen
instead. Okay, so it sounds like we'll need a larger compressor to do that. But I mean, that's doable, it cost a
bit of money, but we can replace the compressors. So what else? Are there any other issues we're going to have using
our existing gas pipelines for hydrogen Instead?
Hydrogen is a tiny molecule, it's it's the smallest one, it's smaller than helium. So it leaks out of everything.
leakage is a problem for hydrogen, for sure. I guess, safety as well. Everybody's got pictures of the Hindenburg in their
mind, right? Because that was such a dramatic thing. And actually, we handle between 70 and 120 million tonnes of
hydrogen a year already in the world. And we do it almost without incident. I mean, there are incidents, but they're
rare, because we understand how to do it. But that's in an industrial context, you know, in chemical plants and
refineries where you have highly skilled people to maintain the equipment. And in fact, where we make a whole bunch of
compromises in working with hydrogen, in order to make it safer. The idea of storing hydrogen in your house is
fraught, like that's a very difficult problem to imagine. The idea that, you know, ordinary people with, you know,
toolboxes with wrenches in them are going to be allowed to have 700 bar hydrogen tanks in their house is mad. It'll
never happen. No, no fire marshal anywhere, who isn't, you know, asleep with his feet up on the dash of his diesel
firetruck is ever going to permit that to happen because they know what will happen. There'll be devastating
explosions in houses every once in a while, that'll take out the neighbor's house. That's just not a good idea.
Okay, so there are a bunch of challenges associated with hydrogen, I mean, if we're going to use it to as a
replacement for natural gas, but hey, we are in the middle of a climate crisis here. It is very easy to think of
problems with new technologies. I mean, I'm great at that. So yeah, easy to think of problems, but what we need is
solutions for the climate crisis, even if they're not perfect. Now, Paul mentioned at the start, how appealing
natural gas is all except for the issue of emissions. But that is a big issue. If hydrogen doesn't make sense as a
replacement, then what does and what are we going to use all of those natural gas pipelines for, if not for hydrogen?
So what we have to do we engineers, we're all stuck in this real world where we have to choose among real, real
alternatives, right? realistic ones, we, we don't get the choice of the perfect one. Fossil co2 and fossil methane
going into the atmosphere are bad, like really bad, devastatingly bad, and are going to be terribly expensive
for my kids generation and their kids. And everyone, every human afterwards. Those emissions should be really
expensive, right? And methane emissions cost nothing. They're free. And they're devastating, but they're free.
There's nobody's taxing them anywhere in the world, as far as I know. And co2 emissions are taxed in some places and
not taxed in others, but everywhere with the exception, I think of Norway, they're really cheap. So the atmosphere,
our values tell us that the atmosphere is what we depend on to live. And yet our economics tell us that the atmosphere
is a free public sewer, or a really, really cheap one. And so there's the fundamental problem we have to solve. That's
the problem we have to solve. And the rest of it, we engineers will sort it out. like, we'll look at what makes
the most sense. Do we store electricity? Do we store heat? Do we overbuild renewables and use them just when we need
them and let them spin on their own or you know turn off the solar panels when we don't need them. So my suggestion is
going to as an engineer, is use the energy that you made in the form that you made it in, figure out the cheapest way to
store it. And I do see a role for hydrogen, but its role is to replace the hydrogen that we depend on for our very
lives. And by that I mean, we depend on nitrogen that's fixed by virtue of the Haber-Bosch process by which we we
make ammonia from hydrogen and nitrogen. And that's all made from fossils, right? Now, we have to fix that. that's
massive, massive problem. It's something like 2% o greenhouse gas emissions in the world, by itself. And w
have made no progress solving that at all, because we don t have the carbon tax to make it happen. So that's what
I would do, I would focus, you know, practical, pragmat c solutions, lowest hanging fruit first, most important thin
s first, like eating is really important. So let's fix th t thing that would prevent us from eating in a post foss
l world. that should have a high priority, and worry ab ut transport, transport hydrogen marginal cases, or heat
ng hydrogen for high temperature industrial processes wo ry about those last, you know, let's burn fossils there fo
a bit longer, until we know we've got the right solutions in place. But comfort heating is gonna it's going electric,
nd there really isn't an alternative and the pipes in he ground, we're just gonna not use th
Thanks for that informative conversation, Paul. So if I can just try to summarize, subbinghydrogen for natural gas
sounds great at first, but the devil is in the details. And I think the most tricky details along with the equipment
upgrades that we'll need to go beyond 20% hydrogen, there's issues with leakage and safety when used in homes. Plus, the
emissions reduction is maybe not as large as you might think at first. In addition to these issues, there were other ones
we talked about that I had to cut like line pack and pipe embrittlement and challenges related to hydrogen storage. So
if those sounds really exciting to you, then head on over to some of Paul's articles that are linked in the description,
and you can read all about those issues. All of these challenges could be solved if enough effort and money is
spent on them. So whether that is the most pragmatic way to use the limited resources we have to develop clean energy
technologies? Well, that's a topic for another day. But I will note that there are several projects underway now to
look at some of these these challenges in more details. If you're interested in hydrogen technologies, then check out
some of the other videos that I've made on the topic. And if you've got any questions, or there's a technology you'd like
to see me cover, then write that in a comment.
Oh, and by the way, I just recently set up a Patreon page and I'm hoping to build the Engineering with Rosie community
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Thanks a lot for watching and I'll see you in the next video.