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Chapter 24 ‐ Pollution
Previous page: Chapter 23 - Death and enemies
Pollution in Factorio comes mainly in the form of air pollution. It is a byproduct of your machines and its production is inevitable, but it can be reduced greatly if you follow certain strategies. Pollution is measured on a per-chunk basis, with a chunk being a 32 by 32 tile square. Pollution accumulates in the chunks with working machines and spreads outward. Usually this spread results in a big pollution cloud surrounding your factory area, with decreasing levels of intensity towards the outer edges.
Individual buildings do not pollute very much but their combined effects tend to build up over time and even after you turn off all your machines the pollution takes some time to disperse and get absorbed by the environment. Polluting buildings and areas tend to become targets for enemy attacks, although buildings found on the way to a polluted area can also be attacked.
This feature is not yet supported directly, but enemy spawners that are being polluted get identified as such in the entity scanner.
Most factory machines produce at least a little pollution, but some machines stand out as big polluters. A machine pollutes only while it is actively working, and for electrical machines the amount of pollution generated is directly proportional with the power consumption. Therefore you can change the pollution output using modules or by stopping and activating machines.
For each individual machine, pollution is rated in terms of units produced per minute at full operation. Here is the full list:
- Burner mining drills are big polluters, producing 12 units per minute. The effect really adds up when you need a lot of them side by side.
- Electric mining drills are also big polluters that produce 10 units per minute, but they produce twice as much ore at the same time, and they can be improved greatly using efficiency modules.
- Pumpjacks produce 10 units per minute and have the same situation as electric mining drills.
- Boilers produce 30 units per minute, and once again the effect really adds up if you have a large factory that relies on several boilers for power.
- Stone furnaces produce 2 units per minute.
- Steel furnaces produce 4 units per minute but there is no disadvantage because they also smelt twice as fast.
- Electric furnaces produce 1 unit per minute, offering a major advantage if you are using clean energy sources.
- Oil refineries produce 6 units per minute.
- Chemical plants produce 4 units per minute.
- Centrifuges produce 4 units per minute.
- Assembling machines produce 4 units per minute at tier 1, 3 units per minute at tier 2, and only 2 units per minute at tier 3, meaning that higher tiers pollute less while also working faster.
- All other machines, such as vehicles, inserters, belts, or nuclear reactors, none of them produce any air pollution.
Most natural ground tiles absorb pollution slowly over time. Grass performs the best, but it is only 50% more effective than water or sand. Meanwhile, paved ground such as stone bricks or concrete, does not absorb any pollution at all.
Trees are particularly good at absorbing pollution over time, but if they encounter intense pollution, they will get permanently damaged. When a tree is damaged, it removes a significant amount of pollution in one go but its ability to absorb is reduced. Completely damaged trees completely lose their absorption ability. Dead trees and fallen trees that are not additionally damaged can also absorb some pollution.
The biggest pollution sinks are enemy spawners, which also keep track of how much they absorb and mobilize enemy attack waves accordingly. They do not do this at all in peaceful mode.
Vanilla Factorio offers no machines that can suck pollution out of the air, but pollution can be controlled using strategies. Meanwhile some mods do offer such machines.
Efficiency modules (also known as effectivity modules) reduce the power consumption of machines, and the effects of multiple modules can add up until the limit of 80% reduction. The pollution benefits of this are both due to the machines themselves polluting less and due to the decreased demand from boilers to power the machines.
Efficiency 1 modules are cheap and they offer 30 percent reduction each, and most machines have 2 or 3 module slots. Therefore you can get 60% reduction with 2 modules, which is already great, or get the upper limit of 80% reduction using 3 modules. Therefore filling your machines with efficiency 1 modules can decrease your overall pollution massively.
Despite the modules being cheap, you need a lot them if you are going to fill every machine, and some machines pollute more than others. Therefore some machines can be prioritized and others can be skipped entirely. Generally, electric mining drills are excellent candidates for filling up with efficiency modules, because your mines tend to be at the edges of your bases and so they are furthest from your power plants and closest to the enemy bases. When you fill the mining drills with efficiency modules, it becomes a lot easier to defend the mines and to independently power them.
Other machines that strongly benefit from efficiency modules are oil refineries, because they consume a lot of power and pollute a fair amount as well. You also do not build too many of them, so it is easy to keep track of which ones you have not put modules into. The same can be said for chemical plants to a lesser extent.
For other machines, the direct pollution reduction from efficiency modules is not that much because they do not pollute as much, or you tend to build very many of them, and so adding efficiency modules becomes mostly about decreasing your power demand.
Trees absorb pollution very effectively, so if you do not chop them down or damage them from heavy pollution, then forests tend to prevent your pollution cloud from passing over them and reaching enemy bases.
Solar panels are relatively expensive to produce and they do not have the best yield, but they are free and every kilowatt they produce is one kilowatt that a boiler does not produce. You need 15 solar panels to replace one boiler during peak hours. This is a good goal to aim for because when you do this, your boilers turn off during the day and your coal mining drills turn off as well. The boilers and coal drills only work at night, and due to the day night cycle of the planet, this reduces your overall boiler power pollution by more than two thirds.
This strategy is extra effective when you put efficiency 1 modules in your mining drills and oil processing buildings, so that producing coal or solid fuel costs less power and the overall power demand is lower.
If you want to completely rely on solar power, then you need at least 22 solar panels and 18 accumulators per boiler replaced. However, the precise ratio used by the community is 25 solar panels and 21 accumulators to get 1 megawatt. This ratio makes the accumulators be exactly sufficient for distributing the collected solar energy into an average output of 1.050 megawatts.
Nuclear power is not easy to set up but it produces almost no pollution when compared to boilers. The only pollution in nuclear power comes from centrifuges and uranium mining drills, both of which can be improved with efficiency modules. One single nuclear reactor produces more energy than 40 boilers and it only needs 1 or 2 centrifuges and 4 to 8 electric mining drills. Multiple reactors are even more effective because of the neighbor bonus. Usually after setting up nuclear power, you do not have to worry so much about consuming less power, meaning that you can relax your efficiency module strategy.
By themselves, productivity modules make a machine pollute a lot more. On the other hand, they decrease the amount of resources that need to be mined and processed overall, meaning that your factory needs to work and pollute less overall to get the same amount of products. The difference made by productivity modules is the greatest for labs, rocket silos, and assembling machines making expensive science packs. If you also use beacons to increase the speed and efficiency of your high-productivity assembling machines, then you can further reduce the amount of pollution produced per unit of science.