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So, the world has come down to a crashing halt. Nukes rain down from the sky, after the Cold War finally became a Hot War. Now, humanity is left with a wasteland.

After the big one, cities have been mostly abandoned to the dying and the (soon to be) mutants. Lets say you have a man living near a large city, named Bob. Bob decides that in order to get by, he’ll brave the muties and crazies to get any loot the city holds. Bob sells these scraps of to others, and starts a small company “Bob’s Scavenging Co.”. Bob eventually dies, and his son, Bob Jr., takes over the company.

How long would scavenging be economically feasible, considering that not much of what’s scavenged an be remade, and that over time things will break down?

  • Bobs Co. mostly Scavs off (Post apocalyptic slang for scavenging) metal scrap and stuff like that.

  • My story has a time frame of about 150 years.

  • The City they scavenge from is reasonably large, about San Francisco size.

  • Bob Co. supplies mostly locals, about 1,500 nearby folks

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  • $\begingroup$ "Economically feasible" will require some more details about the post-apocalyptic economy. How many people is he supplying? Are you trying to figure out how long goods will remain useful for (e.g.gasoline will go bad in a couple of years), or how quickly the consumers will use it (e.g. all the toilet paper will be gone in 2 months)? Also complicating matters is the fact that most of this stuff is priceless, since there's no way for anyone to make it themselves. $\endgroup$ – Nuclear Wang Nov 12 '18 at 20:44
  • $\begingroup$ @Nuclear Wang: No, I’m asking about how long it will be before scavenging all this stuff becomes to difficult to be profitable $\endgroup$ – DT Cooper Nov 12 '18 at 20:51
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    $\begingroup$ @Nuclear Wang is right that it will depend on demand. Are they using the metals just to make hand tools? Or (electric) railways? Is there competition, i.e. other scavengers? How likely are they to develop blacksmithing, so they can reuse metals they already have? Is population growing? Or they are barely surviving? But generally, a large city contains thousands of tons of metal (building frames, bridges, cars, pipes, fences, HVAC, etc.) $\endgroup$ – Bald Bear Nov 12 '18 at 20:56
  • $\begingroup$ @Bald Bear: Hand tools, armor, weapons. No, mutants scare away competition. They have blacksmithing, but its not good work. $\endgroup$ – DT Cooper Nov 12 '18 at 20:58
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    $\begingroup$ Economically feasible depends on the rest of the economy. Is there plentiful food? If you scavenge this stuff, what can you trade it for? If everyone is starving and farming has failed or whatever, then scavenging isn't economically feasible at all, since you can't trade it for food to live on. If everyone who survives becomes Amish and rejects technology, your scavenged car parts aren't worth anything. Not enough information here. $\endgroup$ – kingledion Nov 12 '18 at 22:22
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The one man supplying 1,500 people with metals for medieval-level technology will probably get everybody a basic set of gear in ~10 years.

But the thing is, they will not stop at medieval technology. They will want solar panels and wind turbines, batteries and electric devices. They will want metal vehicles, pulled by horses if they cannot generate enough electric power. They will want firearms, with black powder once the modern powder runs out or expires.

Moroever, there might be trade with more distant lands. SF is on the water, so travel is easy. They can get fruit from the south, timber from the North, chemicals from up the in the mountains. All in exchange for metal and high tech from SF.

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Easy answer: forever

We recycle scrap today. It's been going on for decades and decades and shows no end. A sizeable city (oh, let's say San Fransisco, population 884,363, since you're interested in it) would provide recyclable stuff for 1,500 people for centuries.

Why do I say this?

  • The population ratio is 590:1, meaning for everyone Bob's supplying, there's 590 people worth of stuff to recover.

  • The industrial base in San Fransisco is massive. There'd be enough reasonably easily recoverable metal (buildings, cars, factory equip, etc.) to last far into the future. And this isn't counting the possibility of a big freighter ship or military vessel that would supply metal forever.

  • Just the local metal scrapyard would supply you for years, if not a decade. And there's a lot more than just one in SF.

I could go on, but there's no need. Mutants are a problem, but resources are not. For all practical purposes for your story, if the major city is major like San Fransisco, the recyclables would go on forever.

What would a practical limit be?

Saturating your market. Like Bald Bear said. Eventually everyone has what they need. So, infinite supply, limited demand. Economic feasibility is in the black until you max the demand curve. Then it's in the red.

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  • $\begingroup$ The issue with a massive ship, etc. or even the golden gate bridge is having the equipment needed to turn large structures into pieces that can be handled by a couple of folks with whatever mechanical help still exist or can be rigged (engine lift, block & tackle, etc) as well as the tools needed to make a big thing turn into a bunch of smaller things - TIG/MIG/Oxy/etc isn't gonna be common 150 years post-event $\endgroup$ – ivanivan Nov 13 '18 at 3:48
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    $\begingroup$ @ivanivan, not at first, but how long would it take to scrounge a cutting torch and acetylene tank? The OP didn't specify how long after the apocalypse his story is taking place. Too long, and you're very right. Right after? Not that hard to find. $\endgroup$ – JBH Nov 13 '18 at 5:56
  • $\begingroup$ I disagree on forever--much of that metal will in time oxidize away. $\endgroup$ – Loren Pechtel Oct 1 at 14:41
  • $\begingroup$ @LorenPechtel it doesn't oxidize away, it simply oxidizes. The metal came out of the ground in the first place. It's merely a chemical process to convert the rusted metal to unrusted metal. Heck, you can buy the chemical at your local hardware store, but you can also use the time-honored method - smelting. $\endgroup$ – JBH Oct 1 at 19:08
  • $\begingroup$ @JBH But when it oxidizes it comes apart--much of the oxide will be removed by wind and water and lost for practical purposes. $\endgroup$ – Loren Pechtel Oct 2 at 2:32
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About the topic that appeared in the comments before, that a society would try to advance technologically...


I guess keeping things real is an important thing, to ask what would probably happen. The other question is what do you want your world to be like? If there are things you want to write about, there are ways to lay out a historic backstory or scientific base to justify your world as you want it. Is it probable, that future warriors ride on dinosaurs? No. But if you want to write a story about people who live with dinosaurs, they could have been cloned from prehistoric DNA (like in Jurassic Park) or survived under the earth crust or on a remote island or somehow be biologically backcrossed chickens. Is it probable that in a world some people have magic powers? ...


What does this mean for post apocalyptic societies?
If you want a highly (re)developed society, people rediscovered a lot of technology, found many old engineering texts, maybe the "right" people survived and were clever enough to found companies and universities... in that case they might have built own primitive factories and laboratories to produce materials and technology on their own, like in "Mortal Engines", although in that novel/movie they had over 1,5 thousand years to dig out technology.
If you want your world to rely mostly on scavenging and farming because you want that Mad Max feeling (but you also don't want to be first generation posties like The Walking Dead) you could argue that development is exponential:
It's much easier to make groundbreaking inventions, when you have many academically tought experts who are able to communicate with other scientists all over the world, read texts on the internet or send books with a steamer over the ocean...
However, let's assume after the apocalypse there were some groups of survivors who fought each other and concentrated on farming and securing their settlements and education (maybe even literacy) dropped massively in the next generation (because why learn mathemathics if you can use that time to shoot fresh meat or built a secure home for your family). In a world where everyone fights everyone, how could you even think of founding a university until some warlord has become mighty enough to force peace over the whole territory... In that case I tend to compare the post apocalyptic world to countries of the developing world: The rich and powerful are able to afford comfortable living conditions, technology and weapons (and even many people have some access to basic cheap technology while, except for that, living under quite primitive conditions), but the country is not developed or rich enough to produce those things on their own (or there is no interest in the ruling class to invest into the poor's education or living standards). While those upperclass people in our world can buy weapons from industrialized countries, there is no such in the post apocalyptic world and the "hightech" is the stuff that gets scavenged and is sold for a high price. Maybe technology was even destroyed/forbidden for some time in the past - after the apocalypse which might have been a war with highly effective weapons, or a scientific accident, maybe some religious fanatics saw the problem in man having too much power and knowledge and demonized and destroyed it...

All those things could influence the meaning that scavenging has in society and how profitable it would be - how much will people pay for a dug out machine gun or its ammunition in a world of crossbows and sabors... or think of the collections of ancient Roman art the popes collected during renaissance...

However, all those intellectual pastimes are just own ideas/inventions, not based on some theory about human nature or society or technical development.

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First, this is a highly speculative answer, but it pretty much has to be, given the subject involves predicting the future. So consider this my best guess, but not at all authoritative.

You will start to run out of gasoline in just a few years. Once that's gone, you might be able to keep motorized things running for a few more years on biofuels and such, but then you will also start to run out of consumables like motor oil, because they also break down after a few years. Within at most a decade or two you will no longer have fossil fuel powered vehicles and tools. That's devastating. And once the people move out to the country to get away from the disease and danger of the city, the lack of motorization will make it very hard and expensive to bring scavenged goods from the city to the people.

Wind and solar power will start to fail after 20 years or so, and eventually the composites in fan blades and bearings in motors will fail, and solar cells will degrade. You might be able to find enough spares to keep some solar power going for few decades or maybe even 100-200 years, but not at industrial scales. You won't be driving solar cars or running solar powered factories.

Coal will make a big comeback. It's an easy fuel to use with low tech, it can power steam boilers and home heaters, and there's a very nearly unlimited supply available. You could be a coal scavenger for a long time.

So the biggest problem your society will face in the medium term will be energy. Energy is the lifeblood of a modern society, and enables our standard of living. If you go back to water wheels or manual labor, your standard of living will crash back to pre-industrial levels.

Most foods will be spoiled within a few years to a decade. Now you will have to grow your own. Without mechanized farm machinery, you won't be quite back to subsistence farming, because there will still be available fertilizers and knowledge of scientific farming practices, but it will be close. The standard of living of the people will plummet. There won't be enough people to maintain old infrastructure, or enough free time to invent better ways to do things. And if there are a lot of people, they will probably starve. The carrying capacity of North America is greatly dependent on mechanization, high energy farming, and the ability to transport food long distances from fertile regions to the cities. All of that will be lost.

In the longer term, bearings will corrode, electronics will fail, medicines will all be extinct, concentrated fertilizer will be used up or unusable, and you will be utterly unable to replace it. Within a couple of generations you will be back to a small subsistence farming population, too busy growing food and staying alive to maintain old infrastructure. Flora and fauna will take over cities, roads will break down and become impassable, and eventually you'll have a world of small groups of subsistence farmers living out on the land and the cities will be largely abandoned.

Once this state is achieved, a technological society would have to be rebuilt from scratch, and to do that will require hundreds of millions of people. So your future recovery back to today's standard of living will take as long as required to grow the population back to pre-apocalypse levels. Hundreds to thousands of years, depending on the birth and death rate.

None of this includes the very real possibility of conflict. Getting people to peacefully cooperate while their standard of living craters is not easy. One possible scenario is a return to hunting and gathering because farming communities become rich targets for attack.

Things like steel will be available for a long time, but without concentrated energy you won't be able to smelt it very well - at least in quantity. You will be able to re-melt it into swords and hand tools and such using ancient techniques, but you won't be building new metal buildings or anything like that.

Your eventual society will probably look a lot like what the first settlers in America had, although the remnants of society will give you a permanent collection of better hand tools, and you might be able to keep interior LED lighting going with small scavenged solar panels. You might also have better housing, and there will always be enough steel and old wood beams and such to enable it.

As for scavenging being economically feasible... What economy? You will be back to bartering immediately, and money will be worthless. Barter makes it harder, because you have to find the person who has exactly what you need, and you have to hope that he needs what you have. I would suspect that there will be scavengers going far into the future, but the impact of scavenging on the overall standard of living of the people will diminish rapidly over time as old stuff degrades and the people lose the free time needed to scavenge as they work most of their waking hours growing enough food to survive.

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