# Pollution Control

#### theRUFFIAN

##### Chieftain
I am trying to do some cost/benefit analysis for the late game. I am usually in Republic, with 1/3/4 unit support and 2 gpt for each unit above that. Let’s assume I have more units than can be supported, so I am paying the 1 gpt for additional units. By the modern era, I have railed everything and my workers are mostly just used for pollution control. So when I discover ecology and recycling, I am wondering if I should be building mass transit and recycling centers in certain cities. They each cost 2 gpt for maintenance.

Does anyone know the probability that a certain city will produce pollution on any given turn? I know certain improvements like factories affect this, but I don’t know by exactly how much. This will allow me to compute the cost of these improvements vs the cost of the workers needed to clean the average amount of pollution.

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So when I discover ecology and recycling, I am wondering if I should be building mass transit and recycling centers in certain cities. They each cost 2 gpt for maintenance.

recycling centers reduce pollution by buildings to one.
mass transit reduces pollution by population to one.

Each population point above 12 causes one pollution, hence with a population below 14 mass transit has no benefit at all.

The great iron work causes 4 pollution.
Factories, coal plants, offshore platforms and manufactoring plants cause 2 pollution.
Research labs, airports and commercial docks cause 1 pollution.

So pullution by buildings can reach up to 15 and 11 without the iron works and 9 without coal plant.

How does one point of pollution translate into probabilities? Is it 1% per point?

I am usually in Republic, with 1/3/4 unit support and 2 gpt for each unit above that. Let’s assume I have more units than can be supported, so I am paying the 1 gpt for additional units. By the modern era, I have railed everything and my workers are mostly just used for pollution control.
Mine too. But late-game Worker-maintenance is never an issue for me, since most of my late-game Workers are Foreign, whether captured directly or built/chopped out of captured cities.

If I build Hospitals at all, I usually only do so in my capital, my FP-town, and then first-ring towns which still have enough free tiles to reach Pop13+ while harvesting a per-worked-tile average of (just under) 2 FPT -- so usually only on Large/Huge maps (which I play less often). But if a town can get big enough to need/use a Hospital, then it will usually (eventually) get a Mass Transit as well, in between building advanced military units (if I'm going for Domination) or spaceship parts (if Space).

Recycling Centers, not so much. Recycling is not needed to build Spaceship parts or military units, so may well represent a research-distraction I can do without (at Emperor). I tend to only build Factories, some kind of power-plant (ideally Hydros -- ideally from Hoovers!), and maybe Commercial Docks (coastal by definition, and pollution doesn't affect water-tiles), and only in the core towns (under Republic) so I won't have much (building) pollution to worry about in the first place.

So when it appears, I just set an appropriately sized stack of Workers to (auto-)mop it.
How does one point of pollution translate into probabilities? Is it 1% per point?
I think so, yes.

Like @tjs282 , I have a mix of captured workers and native workers. The unit upkeep on workers is not usually a factor for me. If I've done a good job at keeping my trade rep clean, I always sell extra copies of my luxuries for gold-per-turn, which usually covers my unit support costs.

If I have several productive core cities and plan to take a pause in warring in the late Middle Ages, I will sometimes try to pre-build for Smith's to pay for maintenance on all my Marketplaces. I've also lost Smith's in a wonder cascade, or when playing a continents map with an advanced AI on the other big land mass.

Imagine though if that gold revenue from trading your luxes didn’t have to go to unit support. I know it’s not a huge factor, but if you didn’t need half of those workers, that golf could be used for other stuff like unit rushing or spy missions. Or could even be traded for some other resource you are in need of. Just because the system is good doesn’t mean it can’t get better

Imagine though if that gold revenue from trading your luxes didn’t have to go to unit support.
But Foreign Workers require no maintenance, so unit-support costs for my Pollution-moppers are near-zero.

And at my usual settings (Emperor, Standard Continents), if I'm not going for Domination, I don't need a huge military in the Industrial Age, either: all I need is a complete internal rail-network, and enough forces to defend myself from AI-invasions. (Unless the map-generator has given me useful chokepoints, I will also generally avoid signing RoPs with neighbours after building my rail-net)

Republic gives no military police-induced Contentment, so there's no point in garrisoning landlocked internal towns: instead, I'll keep a skeleton-crew of defenders along my borders, with the majority of my bombardment-units and attackers ready to move to deal with any incursions on the same turn they arrive. Even in the unlikely event that I still share a land-border with one or more AI-Civs that late in the game, I still do not need large garrisons in every town, only in those towns which could be reached and sneak-attacked by my neighbours' fastest units, within a single interturn.

Let's say I own 40 towns, all of which will likely be Pop7+. Under Republic, that's 120 free units to play with. With, say, 30 Artillery, 60 Cavalry/Tanks and 30 Infantry (e.g. 25 spread across my most vulnerable towns, 5 in reserve), I have almost nothing to fear from any potentially adventurous AI-Civ until they start fielding Bombers and/or Marines in quantity (at which point, some of my unit-roster might need to be swapped out for Flak/Fighters, and/or my coastal towns might need 2 Inf-defenders instead of only one, or zero).
Just because the system is good doesn’t mean it can’t get better
And that is what the Editor is for...

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Imagine though if that gold revenue from trading your luxes didn’t have to go to unit support.

Most likely it will go into maintenance of buildings. After the industrial age maintenance can easily rise to 20 to 30 gpt. So for 40 metropolises it is 800 to 1200 gpt. Try to fund that with only selling luxuries and resources. You may need to spend production into wealth just to avoid a fiscal deficit at 100% research.

ancient times: barracks 1 gpt, granary 1 gpt, temple 1 gpt, marketplace 1 gpt, library 1 gpt, courthouse 1 gpt, aqueduct 1 gpt, collosseum 2 gpt, harbor 1 gpt.

middle age: bank 1 gpt, cathedral 2 gpt, university 2 gpt.

industrial age: factory 3 gpt, hydro plant 3 gpt, hospital 2 gpt, airport 2 gpt, policestation 2 gpt, civil defence 1 gpt, stock exchange 3 gpt, commercial docks 2 gpt.

modern times: manufacturing plant 3 gpt, recycling center 2 gpt, research lab 2 gpt, mass transit system 2 gpt, SAM missile battery 2 gpt, offshore plattform 3 gpt.

That is up to 10 gpt for the ancient age, up to 5 gpt for the middle ages, up to 18 gpt for the industrial age and up to 14 gpt for the modern age. That is total of up to 47 gpt.

Now for the sake of convenience i assume that only every second city has coastal buildings and also every second city has an aqueduct. Then it is down to 43.5 gpt.

If temples, cathedrals and colloseums are skipped, then it is down by 6 gpt to 37.5 gtp.

If you have adam smith, then it is down by further 8.5 gpt to 29 gtp.

If you have Sun Tzu and the pyramids, then it is down by further 2 gpt to 27 gtp.

If SAM missile battery and civil defence are skipped, then it is down by 3 gpt to 24 gtp.

If you have the Hoover Dam, then it is down by further 3 gpt to 21 gpt, but only if you have no other power plant left.

Nuclear power is preferable to hydro because it adds as much as two factories instead of just one as the other power plants do. I guess there must be some incentive to risk a nuclear meltdown.

I'm interested in the math behind the comparison between hydro power and nuclear power.

For nuclear power, I have to spend 240 hammers to build nuke plants in every city that will get a factory, on top of the 240 hammers to build the factory.

For hydro power, I usually have a 2nd prebuild going in a riverside city as I am teching towards Scientific Method; the main prebuild is for Theory of Evolution. When I get ToE, I usually take Electronics as one of the free techs and build Hoovers from that riverside prebuild. I spend 800 hammers but I get free Hydro plants in *every* city. I don't have to spend 240 hammers in each potential factory city for the Hydro plants.
Yes, I understand that Nuke plants boost factory production more than Hydro plants. I'm not sure yet if it's a better fit for my game.

If you already have the Hooverdam, then the math is similar to the manufacturing plant. You have to pay 3 gtp and get the same net increase in production as with the manufacturing plant, which however is more costly at 320 shields and is available a bit later in the tech tree.

Say you have a base production of 40, then it is 60 with a factory, 80 with factory and hydroplant, 100 with the nuclear plant and 120 with nuclear power plant and manufacturing plant. 120 shields per turn would be rather convenient for building modern armour. So clearly it can be worth it.

In terms of mere production the costs are in within 240/20=12 turns. But maintenance also matters. If we interpret 3 gpt as 6 shields per turn on wealth, then it takes 240/(20-6)=17.14 turns to get even.

Apologies for going on a tangent, but you tweaked the settings to increase the presence of pollution (e.g. by increasing the worker turns to remove it), do we think the AI has the intelligence to prioritise production of workers?

I tend to use the hydro power from Hoover to assist in the production of nuclear plants in the core. A nuke plant can be built in just 5 or 6 turns in general if you already have a hydro plant, so you’re only missing out on a couple of units being produced. It pays for itself in the same amount of time though if you can get a 3 turn MA down to 2. And without nuke plants, the free hydro plants really help in the other cities just outside your core.

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