In a post-fossil fuel economy, what could natural gas pipelines be used for?

Question

The United States (as well as many other countries) is covered in a vast network of tubes:

These tubes vary greatly in diameter. Some could hardly fit a baseball, while others are large enough to comfortably fit a prone human.

In a future world of renewable energy, where this natural gas infrastructure is no longer needed for fuel transportation, how could these tubes be repurposed?

If your proposal requires pipelines to have a certain diameter, please take into consideration how prevalent that pipe size is when explaining the reach and impact it would have. I have used the United States as an example in this question, but if you are more familiar with the natural gas infrastructure of another country you should feel free to use that country as part of your answer instead. For bonus points*, include a consideration of contaminants that linger inside these pipes (likely not food-safe, for example), and how that might impact your proposal.

*Disclaimer: not actually worth extra stackexchange points.

Not enough for a full answer, but at least some of them could be repurposed to remove household waste, and also there is a theory i saw long ago, can't refind it now, where some researchers suggested the now big empty caverns previous filled with gas could be used to store excess household/industrial CO2, so the pipes could fairly easily be reversed to take the bad household gases back to the pumping stations and into these CO2 resevoirs. — Blade Wraith, Jun 07 '18 at 13:51
@BladeWraith: Carbon capture and sequestration is a scam, in my opinion. The total energy expended in capturing and storing 1 MT of $CO_2$, would be generated by power plants and engines that produce several times that amount of $CO_2$. Unless there are major carbon-neutral energy sources available, CCS is... well, even a dead duck is usable...so not even that — nzaman, Jun 07 '18 at 14:07
Reminder to close-voters: The problem cannot be fixed if the OP is not made aware of it. — Frostfyre, Jun 07 '18 at 16:09
Petroleum products can be used for more than just fuel - lubricants, plastics, etc. Are there parallel non-fuel uses for natural gas? — arp, Jun 07 '18 at 22:17
some of the mains could still be used to transport natural gas for use in the plastics industry. — John, Jun 07 '18 at 22:55
A bit too flip for an answer perhaps, but Belgium actually does has pipelines that deliver beer to pubs. Why not repurpose them to that end? — ohwilleke, Jun 08 '18 at 02:20
For certain pairs of end points, water could be shipped in them. Corrosion could/would be a big problem with this. Natural gas is reducing. You'd need to adjust the water pH so that it wasn't oxidizing (making it basic?). — Jim2B, Jun 08 '18 at 15:40
A thing I have not read is the problem that pipelines generally go where the product was required from where it was sourced. The same source and destination are not to be expected for an alternate product class. Moving energy would likely be a close match for most fuel pipelines but not necessarily a direct fit. — KalleMP, Jun 10 '18 at 15:16

score 70 · Accepted Answer · answered Jun 07 '18 at 14:21

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They can used for underground power and communication lines, as a replacement for overhead lines.

The reason why overhead lines are still prevalent in America is due to the initial cost of installing the lines underground and the sheer number of lines needed for the sparse rural areas covering most of the US. However, if the power companies had available pipes across the country to simply snake the power lines through then the installation costs should be significantly lower.

Having underground lines would lower the number of outages due to not being affected by strong wind, falling branches, or drunk drivers, so the power companies would likely support it. It would also improve the view of most areas due to no longer having interconnected monoliths cutting across the landscape, so environmental groups would likely back it as well.

answered Jun 07 '18 at 14:21

Giter

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This is excellent. It also makes intuitive sense that many (but of course not all) of the routes currently taken by natural gas pipelines might one day be useful for electrical transmission. Wind/solar/hydro isn't always produced in the same locations as natural gas, but sometimes they are, so there is definitely potential for network synergy. – Pink Sweetener Jun 07 '18 at 17:03
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This is/was already done NY Times Article, so it isn't a crazy idea. – hazzey Jun 07 '18 at 20:56
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Williams Oil and Gas out of Tulsa established Williams Communications on this basis. – pojo-guy Jun 07 '18 at 22:14
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Williams Co ran fiber in their pipes; they're not supplying electrical power through a retrofitted pipe as far as I can tell. Probably because "Whereas finding and repairing overhead wire breaks can be accomplished in hours, underground repairs can take days or weeks, and for this reason redundant lines are run." (Not to mention how much bigger the wires need to be if they're not in free air.) IMO, they weren't offered $2B because they have glass wires inside steel pipes; it's all about the right of way. – Mazura Jun 08 '18 at 00:45
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So what you're saying is: in this future, the internet is a series of tubes. – Pharap Jun 08 '18 at 01:33
Is this safe for pipes once filled with an explosive gas? Do the pipes meet current standards for containing fiber optics without modification? (My intuition says these probably aren't problems, but worth posing the question.) – jpmc26 Jun 08 '18 at 09:20
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@jpmc26 Fiber can be laid without any containment other than its own sheathing. Dropping it inside a steel pipe with 1/3rd inch wall thickness is so much overkill it's not even funny. From the fear of explosion perspective, fiber is one of the few ways it is safe to get a signal to devices that are in an explosive atmosphere environment. – pojo-guy Jun 08 '18 at 11:51
@Pharap I have it on good authority that when Verizon at up their network 20+ years ago, they buried conduits for fiber optic, knowing that current usage would take about 1/4 of 1 cable, with 4 cables fitting in a conduit. So they buried 4 conduits and rented out the excess capacity. What's an extra ten million (the materials) on a 2 billion dollar project (predominantly labor), anyway? So yes, the Internet is tubes. – Draco18s no longer trusts SE Jun 09 '18 at 16:54
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@Pharap Even in the present and recent past (e.g. when that comment was made), the “series of tubes” line was easily the most reasonable analogy the man made. It’s an entirely reasonable way to describe things. And the internet is certainly not a dump truck. The rest of that speech, on the other hand, went kind of off-the-rails and made far less sense. It’s always been kind of weird that the least objectionable part of the speech is the one that got harped on. – KRyan Jun 09 '18 at 18:50
@KRyan & Draco18s, my joke isn't a criticism of the late senator or Giter, it's just a play on the irony that a phrase associated with a lack of understanding of the internet would, in this hypothetical future, be correct in a very literal way. (In fact I agree that the tubes analogy was probably the most redeemable part of the speech.) Let's leave it at that though, otherwise we run the risk of clogging the tubes. – Pharap Jun 09 '18 at 19:19
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@Draco18s And then everybody did this. This led to a huge fiber glut in the early 2000's during the dot-com bust where communications companies couldn't recover their investments and went bankrupt. – user71659 Jun 09 '18 at 19:26
@user71659 Yep. I just happen to be two handshakes away from the guy at Verizon who was responsible for that maneuver. As well as (the plan? technology?) behind the antennas that provide cell coverage across the Sierra mountains where the freeways are. My dad was a lawyer for the company at the time and worked closely with that person (I do not know his name). This was probably back during the Air Touch days and I would have been 12-16. Got a good long "let me tell you about..." last December on a road trip. – Draco18s no longer trusts SE Jun 10 '18 at 00:03

score 43 · Answer 2 · edited Jun 08 '18 at 03:40

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It is actually a trick question, in a fully renewable energy economy natural gas pipelines will continue to transfer natural gas produced from renewable sources.

Natural gas normally comes from fossil fuel sources, but at its most basic it is methane which can be renewably generated from the decomposition of organic material (such as food wastes or other organic garbage).

There are a number of operating biogas producers using large scale digesters (often common for waste processing plants or dairies) which mostly use the gas on-site. In a post fossil fuel world it may make economic sense to have larger scale processing centers and use existing pipelines to distribute the gas for usage.

edited Jun 08 '18 at 03:40

Brythan

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answered Jun 07 '18 at 17:26

Josh King

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Yup, Fossil fuels continue to be widely used as they’re very effective for transporting energy, and it’s easy to build and maintain a device that’s uses them. But this isn’t because they’re fossil fuels, but because they’re hydrocarbons. There’s no reason a renewable fuel system wouldn’t use hydrocarbons. Our local buses use a renewably produced LPG equivalent. – Dan W Jun 07 '18 at 18:29
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I can't tell if you're being a pedant about the fact that I was careless in equating "renewable energy" with "GHG neutral", or if you really believe that bio-fuels are a promising solution to climate climate change. The idea that bio-fuels can be a renewable, net-carbon-neutral step in the carbon cycle is not really taken very seriously by most economists and environmental scientists anymore: feedstocks just require too much land and energy, and (depending on the waste product) there either isn't enough waste, or it's cheaper to reduce waste rather than to turn it into fuel. – Pink Sweetener Jun 08 '18 at 04:10
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@PinkSweetener If you're concerned about carbon, it's entirely possible that some other way of dealing with carbon emissions can be found. Maybe there's a way to absorb carbon out of the atmosphere, making the process net neutral, or maybe a way of capturing it before it was released is developed. There's no reason to assume that the only solution to carbon emissions is to stop using any substance that emits it when burned. Use your imagination. Or maybe anthropogenic global warming models were just wrong all along, or maybe the effects of warming aren't all that bad. – jpmc26 Jun 08 '18 at 09:28
@PinkSweetener where I live the new busses are powered by biogas: methane. I believe the methane is produced from human sewage at the moment (which is not going to reduce in quantity). I don’t know the numbers but I would be surprised if human sewage methane production isn’t a sizeable dent in our natural gas consumption - and as the population increases, the production can increase. – Tim Jun 08 '18 at 11:16
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@PinkSweetener You speak as if we can only sustainably produce methane from cows. Not true, in a clean energy future we could synthesize methane with the Sabatier process, with the perk that it feeds off atmospheric CO2. – Saiboogu Jun 08 '18 at 12:43
@jpmc26 As discussed in the comments to the original post, carbon capture is basically vaporware (pun intended). I'm interested in real solutions. Non-fossil fuel energy sources are far more economically and technologically proven than carbon sequestration, particularly carbon solidification which is very energy intensive. With such a high energy demand, you might as well use the power directly and skip the sequestration. No serious climate policy expert believes that hydrocarbons have a place in a climate-change mitigating future. – Pink Sweetener Jun 08 '18 at 13:52
@Tim Waste biofuels can play a small role in some circumstances, as they already do, but I believe waste biofuels are for small, local solutions. There isn't enough easily bio-fuelable waste to meet energy needs, and burning biofuel waste still releases GHG emissions into the atmosphere. In terms of mitigating climate change, it's much better to either recycle waste or dispose of it in a way that locks the carbon up so it cannot decompose and enter the atmosphere. – Pink Sweetener Jun 08 '18 at 13:57
@Saiboogu Its just so energy intensive. You might as well electrolyze hydrogen gas and burn that instead. Its also hard to imagine at this point how this could reduce emissions: you're taking CO2 from the air (very energy intensive) and adding it to electrolyzed hydrogen (very energy intensive) to create a fuel that is a more potent GHG than the CO2 you started with. It's a very unproven technology, and I don't understand why people feel so strongly about reaching for these scifi solutions in order to keep fossil fuels when a fossil fuel free future is already foreseeable with current tech – Pink Sweetener Jun 08 '18 at 14:01
In general, I do not think this is an acceptable answer to my question. You are fighting the question's premise, and you're doing it with speculative, fringe science that goes against conventional climate policy plans. This post should have been made as a comment, not an answer. – Pink Sweetener Jun 08 '18 at 16:52
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Perhaps the question needs some editing in that case. Synthetic methane could have a place in a "post fossil fuel economy," but it clearly has no place in a "post hydrocarbon economy." They are different things. Advances in energy production can reduce the costs of synthesizing methane. Establishing and following standards for fuel containment, transfer, etc can reduce it's impact as a GHG, and Sabatier produced methane (using solar/wind/hydropower) can be carbon neutral. As for why - – Saiboogu Jun 08 '18 at 18:23
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Methane is vastly easier to store and transport than hydrogen. And hydrocarbons overall offer ease of transport and storage unmatched by many other energy storage mediums available today or imagined in our near future. Plus chemical energy storage is the only viable option still for certain scenarios, such as space launch vehicles. – Saiboogu Jun 08 '18 at 18:24
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@PinkSweetener No serious physicist doubted Newtonian mechanics 300 years ago, either. Science and technology updates. "It's impossible," is the age old cry of people who were wrong. – jpmc26 Jun 08 '18 at 21:45
Our resident industry professional says we won't even get that far: "the question implies scenarios when we run out of natural gas [...] I do not think the Earth running out of natural gas anytime soon." – Mazura Jun 09 '18 at 05:17

Mark Olson · Answer 3 · 2018-06-07T17:14:29.037

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It's unlikely that they would be repurposed. Since natural gas is the least carbon-emitting of the fossil fuels, it's likely to continue to be used for longer than coal, and its use is likely to tail off over a period of fifty years or more.

The key thing here is that pipelines don't stay in good shape without maintenance and as natural gas usage ramps down (and remember it hasn't even peaked yet) it's likely that the system will be abandoned a bit at a time when the cost of operation and maintenance exceeds the value of using it.

The long-distance pipelines have significant redundancy and as production drops, the redundancy will decrease as specific pipelines can no longer earn their keep and are abandoned. The local distribution system has no redundancy, so as usage declines a section of pipes serving a part of a city will earn less and less and at some point it will be more economical to transition the last uses to whatever the new power sources are and stop maintaining the pipes.

(Paragraph added based on questions below) The process will be gradual. As usage of natural gas decreases and the cost of extraction increases, people will move to other power sources and the industry will become less and less profitable. The companies will react by cutting costs, including maintenance (which will suffer for years before a pipeline is abandoned.) Another way to cut costs is to cut off local delivery networks that are no longer profitable and to drop entirely redundant long-distance pipelines which are no longer needed. A section needing expensive maintenance or replacement will be an especial trigger to abandon it. The whole system will slowly shrink and in general, the parts which get abandoned will be older and in need of repair.

It's possible that the pipes will be dug up and recovered for raw materials. That's plausible enough, but depends on fiddly legal details (the gas company owns right-of-way access rights, but who has the right to dig across your property to pull up the pipes?) and on relative costs compared with other sources.

But the bottom line is that the pipeline system is likely to be in pretty rickety shape by the time it's all abandoned and not likely to be useful for very much.

edited Jun 07 '18 at 17:14

answered Jun 07 '18 at 13:48

Mark Olson

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I'm not sure I understand how a single pipeline would be incrementally abandoned rather than suddenly abandoned. One year it will economically feasible to maintain the pipeline, and then in the next it won't. ISOs bid for grid capacity three years ahead. I think it's entirely plausible that a pipeline could be suddenly abandoned if regional natural gas suppliers obtain an insufficient number of CSOs in the Forward Capacity Market to justify keeping everything running full speed. – Pink Sweetener Jun 07 '18 at 16:56
@Pink Sweetener: I don't understand what your point is, but I've added some more material to the answer which may help. – Mark Olson Jun 07 '18 at 17:15
Ah, I see. Well first of all, pipeline companies cannot cut maintenance gradually as you suggest. Upkeep of pipelines is heavily regulated: a natural gas supplier is either using and maintaining a pipeline, or it's not. There is no scenario where a natural gas supplier anticipates that a pipeline won't be needed in a few years, so they stop maintaining it and decide to just use it until it completely rusts out. Abandonment would have to be sudden, with the pipeline still intact after it stops moving gas. This means it can be used for something like what Giter suggests. – Pink Sweetener Jun 07 '18 at 17:48
+1. OP would have to tell us what in their world is now economically feasible to push through these pipes. Black gold or bust. – Mazura Jun 07 '18 at 18:23
@Mazura The main expense is putting the pipes in the ground. Are you suggesting that the cost of pumping something through a pipe is so prohibitively expensive as to be not worth it for anything other than oil (natural gas isn't black, I'm sure you know)? Long-distance pipes already exist that transport water, telecommunications, and electricity. In this scenario, the pipes are already in the ground. – Pink Sweetener Jun 07 '18 at 18:52
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@Pink Sweetener: They said that about railroads, also. And about the bridges and tunnels and subways of New York City. When a industry is failing and losing money, maintenance always suffers. (So does pretty much everything else, too, of course.) – Mark Olson Jun 07 '18 at 19:10
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@MarkOlson Yes, but to the extent that the pipelines couldn't be used for anything else? A pipe that was yesterday DOT-approved to transport explosive gas will probably be good enough to serve as a water slide tomorrow. Maintenance issues for these things typically relate to preventing gas leaks (a hard task that we often fail at) - I have trouble imagining a situation in which pipes are abandoned in such poor condition that they can't even keep some wires safe from tree roots. – Pink Sweetener Jun 07 '18 at 19:43
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Upstate New York has a really lovely network of bike paths built over repurposed railroad pathways and bridges, a great example of repurposed infrastructure. My beloved NYC Subway absolutely needs some work, but even if it became twice as decrepit and ended up shutting down, some of the tunnels could be used for other things. Subterranean subway station restaurants? Who knows. I just don't see your basis for declaring that no pipelines will be abandoned in a condition that will allow them to be reused for any purpose. – Pink Sweetener Jun 07 '18 at 19:47
This really should have been posted as a comment, not an answer. You are fighting, even rejecting the premise of my question. – Pink Sweetener Jun 08 '18 at 16:55
@PinkSweetener - That'd sure be one expensive waterside to maintain that no one has to pay for to use. It's not that they can't be used for anything else. It's that the company that has done this (Williams CO) prob won't be maintaining the pipe after they've pulled some fiber in it - at least not to the current degree. The real prize is the right of way; that's what's worth $2B. - Frame challenging is expressly permitted at WB. – Mazura Jun 09 '18 at 05:11

pyeR_biz · Answer 4 · 2018-06-09T14:25:50.463

Many misinformed Answers here

People should actually read the references they have quoted.

Not an answer, just a point of view from a Natural Gas / Petroleum Engineer

The answers about pipelines will still be used for 'biofuels', 'biogas', 'landfill gas', 'Hydrogern' storing CO2 etc are very misinformed. Those Wikipedia pages are misinformed as well, they are 'theoretically true' The truth is, compressing is expensive.

These pipelines have utility for Natural Gas since NG is extracted from deep, high pressure high temperature wells (HPHT wells), a natural high pressure is provided by the reservoir, which let's us humans to use/transport the gas at a reasonable cost. The cost of compressing increases exponentially as the difference between input and output pressure rises, compressors increase the pressure from 10-20bar (natural) to 30-100bar for long distance transmission only. These gaseous mixtures do not have the natural pressure that NG has, an oil company could compress a gas from 15bar to 30bar; for lower initial pressure than that, the owner would rather burn it (flaring), than find a use for it. In Fact, any gas is useless for commercial applications if it has no pressure. To think these pipelines can be used for used biofuels is naive, it's like traveling on an Autobahn with a bicycle. Answers here are talking about compressing any gas like it's free.

As someone who has been around pipelines and gases all my life, I would say the accepted answer is plausible.

This is from one of those studies that answerers here just saw the title of, read the conclusion.

EDIT

There is a lot of discussion on using alternate energy careers and fuels in these pipelines, ignoring the thermodynamics and mechanics of such operations. Hence, I am posting a few sentences from my favorite undergrad book (Mccabe-Smith-Harriot 5th Ed, Page 204) to make a few things clear about why these pipelines, are natural gas pipelines.

*The theoretical head developed by a centrifugal pump (context: any pressure head increasing device), depends on the impeller speed, the radius of impeller and the velocity of the fluid leaving the impeller. If these factors are constant, the developed head is same for fluids of all densities and is same for liquids and gases. The increase in pressure, however, is the product of the developed head and the fluid density. If a pump develops a head of 100 ft and is full of water, the increase in pressure is 100*62.3/144 = 2.9 atm. If the the pump is full of air at ordinary density the pressure increase is about 0.007atm.*

Natural gas is at a high pressure naturally, rising up due to its own pressure from thousands of feet under the earth. It also has a higher density due to high pressure (see here). Hence, the pressure difference created by a compressor on such an input is large. Once you lose pressure of Natural Gas, it is effectively wasted (because the cost of compressing is high), hence flared (unless the volume is very large).

So when the answers above discuss biogas, landfill gas, biofuels, hydrogen, CO2 to use in these magnificently long and large diameter pipelines; it's naive, because there are no known high pressure, significant volume sources of these gases. And unfortunately, it also exhibits an ignorance of the properties of these alternate fuels that are being promoted. These fuels are compressed to burn, and not transport at the scale at which a country requires. Compressed air is used in many industrial operations, but not as a primary energy carrier. You don't want to put in more energy, than you get to use later.

Using these pipelines for such purposes is not the way forward. These gases may be mixed with natural gas for transport, but that is also silly; because you manufactured the gas after investing in separation processes, and then you mix it back with another gas to transport. Plus, the question implies scenarios when we run out of natural gas.

On a side note, I do not think the Earth running out of natural gas anytime soon.

These are actual pressures in pipelines. In a gas distribution network, notice entry point is high, Those are big pipelines where most of the pipeline money went. The city is just the delivery point, a tiny part of the network.

What do you think about the below answer from @mart on Compressed Air Energy Storage? Not compressing gas for transport, but rather for use as energy storage seems to comply better with the information you provide above, and it's something already done at some renewable facilities so there's at least some evidence that it's cost effective. But are the pipes designed for this? Could air in long tubes double as storage and short-range transmission? — Pink Sweetener, Jun 08 '18 at 16:48
@Pink Sweetener as mart has mentioned 'headaches'. As an industry fellow, I would rather call them barriers that can't be overcome. This is not because oil and gas engineers are not ready to adopt new technologies. It's because the underlying reasons are based on the laws of thermodynamics. I will add a reference. — pyeR_biz, Jun 08 '18 at 17:26
Balderdash. One cubic meter of natural gas is about ten kWh. A typical small workshop compressor can deliver 30 m^3 per hour at six bars and takes 4 kWh. That's 13 percent. The numbers are a bit different for air, and we need a bit more than six bars, but this is surely not out of the world. Oil producers flare the gas because the investment for a gas pipeline can earn more money elsewhere. Legislation could force them, and it wouldn't make a big dent in anyones pocket. — Karl, Jun 09 '18 at 11:59
6bar pressure is residential areas. I have seen 30bar and 45bar long distance pipelines with my own eyes and even put an ear on it to hear it. The question is about natural gas pipeline network, not a 'small compressor network' and some tiny pipes at 6bar. 6bar pressure is for residential areas, kind of remember that from a course on City gas distribution I did. Did you read the screenshot from the Wikipedia reference that answerers have quoted? And your comment on flare actually just fits into what I said, it is not a separate point. — pyeR_biz, Jun 09 '18 at 14:04
@PinkSweetener You can add a bounty to the question to reward an existing answer if you want to. The option to start a bounty is available beginning 48 hours after you posted the question, which is about now... — user, Jun 09 '18 at 18:57
-1, this a̶n̶s̶w̶e̶r̶ rant is completely off the point. 1. as Karl commented, compressing is not that infeasible. Gas companies don't bother because because it's a big security risk not to flare the gas and they have plentiful access to higher-density energy. But security is much less problematic if compression happens at small decentralised sites. 2. Not all artificial sources of combustible gas start out at low pressure. E.g. the Sabatier reaction operates at ≈15 atm.. 3. when you don't have enough gas to use the pipelines at their rated pressure, just use them at lower pressure! — leftaroundabout, Jun 11 '18 at 11:22
@people ok, tha last comment just made me laugh. You guys should stop now. Lets call it a day. — pyeR_biz, Jun 11 '18 at 14:00
Well, you can call it a day whenever you like, but it doesn't make your post appropriate. It is mostly a lot of “argument by authority”. To get to the more technical side with one thing, that textbook quote is irrelevant here because there's no reason to compare pumps with the same head for different densities. A compressor that has to start at atmospheric pressure would obviously be designed much lighter/faster. (It might use an axial rather than centrifugal design.) Such compressors are already in use all over the world: in gas turbines, because those do also require compressing air. — leftaroundabout, Jun 11 '18 at 15:53
The only argument that's right here is that we would probably never have enough artificial gas to fully load the natural-gas network. But that doesn't mean we couldn't make use of part of it. To use your own analogy: it's perfectly possible and actually makes sense to drive on the Autobahn with a bicycle, if it happens to be there but there are no cars that use it. — leftaroundabout, Jun 11 '18 at 15:59
Ok, 1) Karl's comment is for pressures at around 6bar pressures, please apply the bernoulli's equation and figure out how far the gas can travel at that pressure. And let me know if a gas can traverse long distance pipelines at that pressure. I will then ask my boss to use your theory. Btw, You can buy a $ 500 compressor that will give you that output, we'll throw those $ 50k to $ 1mil compressors that we use. — pyeR_biz, Jun 11 '18 at 16:04

score 5 · Answer 5 · edited Jun 08 '18 at 03:41

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If you are going to use them, the only thing I can think of is a vacuüm train. Although it's likely not using a "full" vacuüm but a low-density air environment as the pipes wouldn't be able to handle full vacuüm in all likelihood.

What you do is place a small maglev train in them for transport of goods. The lowered air pressure means lower air resistance. The speed and relative silent operation allow you to unburden a portion of the normal tracks and roads.

edited Jun 08 '18 at 03:41

Brythan

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answered Jun 07 '18 at 14:49

Demigan

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I was going to post something like this. Basically as a kind of hyperloop, at least for the really big ones. This chart shows that most lines are 8" or less, which would not work well for any kind of transportation. – AndyD273 Jun 07 '18 at 17:44
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@AndyD273 Maybe a hyperloop transport for really small objects, aka one of those pneumatic tubes at the bank drive-through scaled up to cover inappropriately large distances. Depending on how seriously OP wants to take their economics, I could see a story in which these networks replace Amazon delivery drones. (If the tube diameter is large enough, you could get (cold, stale, nasty) pizza delivery from the other side of the country!) – Ti Strga Jun 07 '18 at 21:54
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It's the Alameda-Weehawken Burrito Tunnel! – Micah Jun 08 '18 at 04:45
@TiStrga You could actually use it like a train. Have several containers that are the width of the pipe, and a driver either pushing or pulling them through. The 8" pipe has something like 7.5" inner diameter, meaning you could have a 7" cylinder run through it easy, which is pulled (or pushed) by a little motorized engine. It could be a couple feet long probably meaning it would work for a lot of stuff that you'd want to ship. – AndyD273 Jun 08 '18 at 14:09
@Micah I was thinking more on these lines ;) https://what-if.xkcd.com/31/ – Demigan Jun 08 '18 at 17:43

score 5 · Answer 6 · answered Jun 08 '18 at 12:48

It's already been done. And its being done a LOT.

Williams Brothers was a pipeline company founded in 1908.
A lot of the nations natural gas pipelines in place had been placed by them. In the 1970's they diversified into several companies, one of them a communications division. This division would use pipelines that had been decommissioned to pull fiber optic cable through the unused lines. You can read in the Wikipedia article how they built a nationwide fiber optic network TWICE. They sold the first one to LDDS (which became Worldcom, then MCI). The second continued to be owned by Williams Communications until they went bankrupt in 2001, where it was acquired by Level 3 communications.

Technology has advanced for having both through the same line concurrently. It is now common practice to pull at least one fiber optic cable through natural gas pipelines that is used (at least) to monitor the pipeline.

score 4 · Answer 7 · edited Jun 16 '20 at 11:03

You would still use them.

It's a post-fossil economy but that doesn't mean that natural gas produced in factories -biogas- (like landfill gas from waste or some kind of algae process of biofuel that if you want I can explain more) wouldn't be used. Natural gas would still be a good energy source, and if it's produced from organic compound it won't increase the net value of CO₂ in the atmosphere.

Also, natural gas isn't the only energetic gas, you can still send hydrogen produced artificially with water electrolysis (break water in H₂ and O₂ that I can also explain) and send it with the pipelines (note that hydrogen made with electrolysis is only an energy vector/carrier because it doesn't have net energy gain, if you look that read biohydrogen).

Finally, I don't know if it's possible to send liquid on that pipelines, but you could send some biofuels.

Why the downvote? If you explain me I could improve my answer. — Ender Look, Jun 10 '18 at 18:25

score 4 · Answer 8 · answered Jun 07 '18 at 22:29

To add to Josh King's excellent answer -

We'll still need natural gas for plastics.

In the US, natural gas is one of the main feedstocks for plastics, beating out coal and oil as the primary source for carbon polymers.

https://www.alleghenyfront.org/this-is-exactly-how-natural-gas-gets-turned-into-plastics/

https://extension.psu.edu/how-plastic-is-made-from-natural-gas

Even if we get to the point where 100% of our plastics are recycled, continued population growth means the market for plastics will outpace the supply of recycled materials. In addition, replacing metals and woods with plastics as products made from those materials wear down will reduce the environmental impact of mining and forestry.

And plastics are used for a lot of things that people consider critical infrastructure. If you watch the videos below, you'll notice that the American Plastics Council focuses on biotech, but it's actually in many things that your day-to-day life depends on.

https://www.youtube.com/watch?v=rE70FAEOX-M

https://www.youtube.com/watch?v=l2Yh_y7Wlbk

https://www.youtube.com/watch?v=viTtllRFYsc

Gas will certainly continue to be needed for plastics, but it wouldn't require a very branched network of pipelines, would it? It's not like every producer of a plastic product actually starts out from the raw gas; rather the polymers are prepared at a few big chemical plants. The resulting dense resins / thermoplasts are then transported further by ship, rail or road. If you'd want to use the pipelines for these, you'd have to equip them with conveyor belts running inside, which would be cool but probably wouldn't pay off. — leftaroundabout, Jun 11 '18 at 11:32
@leftaroundabout "It's not like every producer of a plastic product actually starts out from the raw gas; rather the polymers are prepared at a few big chemical plants." That's actually what I'm talking about - the wells where the raw gas is piped up from and the chemical plants are in separate states, sometimes thousands of kilometers apart. We currently use the pipelines to transport the gas from the wells to the plants where it's refined into plastic, so there's no reason to assume we'd stop just because we no longer the gas as fuel. — KernelOfChaos, Jun 11 '18 at 23:31

score 3 · Answer 9 · answered Jun 08 '18 at 07:58

Compressed Air Energy Storage

You post fossile fuel economy would need some energy storage. One way to achieve this is compressed air energy storage: Compress air using solar or wind power, expand it through turbines at a later time to regain some of the energy. The pipelines not only connect points, they themselves also provide a certain volume to work with.

The system would look like this:

Places near large pipeline terminals that are well suited for wind or solar power generation compress air into the pipelines
This process also creates heat, which will either go to waste or be used in co-located industrial processes or even district heating (though I doubt many compressor sites will be situated in residential areas)
At gas terminals, generators with expanders supply electrical power as needed
This requires heat, this is could supplied by some renewable source (biogas?)
Alternatively, the cooling gases go through when expanding is used in a co-located industry
Gas storage tanks, caverns etc. can also be used

I think you can't give a roundtrip efficiency of such a CAES system without accounting for energy use at co-located industry. Something between 50% and 70% could be achievable. That's the thing about a post fossile economy: You have to treat energy (in any form - heat, cold, electricity ...) as if it's worth something. That means energy flows will be more closely coupled.

There are of course headaches:

Air needs to travel from compression sites to expander sites. Depending on air volume, there will be pressure losses (=energy losses) along the way. This will effectivly limit how much power can be transmitted like this.
Flushing the natural gas from the pipelines will be interesting: Normally you'd flush a pipe from one end with an inert gas like N$_2$ until the natural gas level on the escaping end is safe (Gas on this end will be used until to diluted, then flared, then vented). For flushing the whole pipeline system, cheaper inert gases would have to be used. CO$_2$ maybe (but from what source?) or sometimes water could be used. I'd expect the refurbishing of a gas pipe network to compressed energy storage to employ a generation of engineers & tecnicians.

score 3 · Answer 10 · answered Jun 08 '18 at 08:18

Use them as a minable resource.

The Romans built a quite extensive network of aquaeducts. After the fall of the Roman empire, they met all kinds of fates, from continued use to being dismanteled.

The is one Roman aquaeduct in present day Germany, the Eifel Aquaeduct, which was used as a stone quarry. Note, even the limestone deposit within the aqueduct was used.

Depending on the setting of your post fossil-fuel world, gas pipelines could make for a useful "natural" resource. Think, of modern day low background steel, which is a similarly artificial "natural" resource, which is mined for its special properties.

score 2 · Answer 11 · answered Jun 07 '18 at 21:46

For the larger pipes, I can see them being re-purposed for long distance shipping of time sensitive items, or just less than 1 day shipping across the country.

Shipping companies might use automated skate boards, luge, bobsleds, etc. to whip through these pipes carrying 1 or more packages. Packages that can be delivered without the need of long-haul semis, being thrown on an airplane, or couriers could reduce the time to cross mountains or areas with few roads.

Shipping this way probably wouldn't eliminate current shipping methods, but could act as a supplementary method for super fast delivery.

However, a break in a pipe, a mechanical failure on a delivery system, or a host of other things could cause massive problems, due to not being able to easily access the tubes for maintenance and clearing blockages. An accidental breakage due to someone digging in the wrong spot or an earthquake could cause all kinds of issues as well.

This idea would assume that the inside of the pipes are (for the most part) seamless, otherwise very smooth, and without quick dips or bumps.

This is very close to what I was going to answer, and although not quite, you can add this to your answer: Pneumatic parcel delivery, like a big version of the old school pneumatic tube. — Bohemian, Jun 11 '18 at 11:47

score 1 · Answer 12 · answered Jun 08 '18 at 03:13

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Compressed Hydrogen Gas

Electrical energy can be stored as chemical energy by electrolyzing water. The hydrogen can be transmitted in pipes the same way as natural gas.

The major problem is that hydrogen damages metals, and the mitigations add cost. It's conceivable that existing pipelines could be retrofitted with protective liners.

answered Jun 08 '18 at 03:13

Spencer Joplin

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Why the down-vote? – Spencer Joplin Jun 10 '18 at 20:43

score 1 · Answer 13 · answered Jun 09 '18 at 08:29

The obvious answer is a massive bagpipe, which the US military could use to globally coordinate ship and troop movements. Such nation-spanning pipes should be able to produce sound heard all the way across both flanking oceans.

If the military by then has better ways of communicating, then I believe storks could use the pipes as a more efficient way of delivering babies. Flying through the air carrying a squirming child has historically been error prone. If enough pipes are available, storks could just put the babies in pipes and then use air pressure to push babies to destinations. I think this might decrease the total number of storks required to do baby delivery, which is good since most bird species have been declining.

Final alternative, pipes could be used for secret storage. By capping one end, people could whisper secrets into the open end... the secrets would then be contained. Passwords, aliases, hideouts-- any secret a person doesn't want to accidentally share could be stored in a nationwide series of secret storage tunnels. By timing the echo length of the pipeline -- which could be days for really long pipes -- people would have timestamps for when to stop by to recover their secret, with an option to whisper it again. People could encrypt it by speaking in their preferred animal language, in case they miss their timestamp. As people outside the same family rarely speak the same animal tongue (no one outside my clan so far as I know speaks bottlenose dolphin, for example), that would protect from most accidental hearings.

This made me laugh - the storks are a bit far out, but I do love bagpipes! Obvious, indeed! — bytepusher, Dec 17 '19 at 22:52

score 0 · Answer 14 · answered Jun 08 '18 at 18:46

They could be converted to a renewable fuel source. Josh King mentioned renewable sources of natural gas, and Spencer Joplin mentioned hydrogen, although most natural-gas pipelines would need to be replaced to carry hydrogen anyway. Other strong possibilities are methanol, which replaces gasoline and can be synthesized by hydrogenation of captured carbon dioxide using hydrogen produced from renewable energy and water; dimethyl ether, a gas which can be produced through dehydration of methanol and can replace either propane or diesel (in redesigned engines); and ethanol, which is more dangerous to store and transport than methanol but can easily be produced from plants in a carbon-neutral, renewable way.

These would not use the last mile of pipe leading to people’s homes, but the accepted answer of running power lines and fiber through them could.