July 2025 edit:
Fellow Captains!
Update 3 brought us many new things, along with some numbers changing in this setup!
I will not adjust the rest of the guide, since P.O.O.P still works out and everybody has to do their own math for their island anyway.

Here are the key numbers for your calculation:

Anaerobic digester:
Slight increase from 7,5 FG -> 8 FG / 60, so a minor buff here. Compost output doubled though, so keep that in mind.

Sludge-to-Fuel Gas Ratio:
2,25 Sludge -> 1 Fuel Gas
1 Sludge -> 0,44 Fuel Gas

Sulfur-to-Fuel Gas Ratio:
A major nerf here:
1 Sulfur -> 1,32 Fuel Gas (compare to Update 2's 1->1,84)

Contract:
1500 Sulfur -> 4500 Sludge on 8 modules, so a 1:3 ratio.

Fuel Gas-per-Shipload (8 modules):
A thicc buff here:
4500 Sludge -> 2000 Fuel Gas (previously 2160 -> 885,6)

Sulfur Mine:
Maintenace cost increased from 10 to 16, so 60% increase
Sulfur per workshift increased from 36 to 54, so 50% increase
Overall, I would argue for a buff here, despite the 10% maintenance extra.
Maintenance output can be improved via offices now, but Sulfur is hardcapped to this 1 mine.
Storage seems to be nerfed? Not much of an issue, in my opinion.

Offices:
You can let your citizen shuffle some excel sheets (just like Captains do IRL when calculating...) and increase the world mine efficiency! This affects the output of the mine.
I think the maximum is 20% extra output.
Let me know in the comments if you had some tests with that!

Conclusion:
Sulfur per Fuel Gas as a key number got a heavy nerf by roughly 28,26 % and it looked bad at first to me, however, overall I think P.O.O.P got even better!
The main reason for that is both the increase in cargo ship storage as well as the sulfur mine output increase:
To off-set the loss 28,26%, we would need an increase of 39.38%, and what Sulfur lost in value, it gained in mass: The mine got a 50% increase per shift. So less worth per Sulfur, but way more of that.

The buff on the ship should positively affect the amount of workers used. I haven't done the math on fuel per cargo unit, since I lack the old numbers, but maybe some of you guys have done the calculations here. The cargo almost doubled though, and that alone is a heavy buff for this setup. I think Unity cost stays roughly the same for the contract. It looks like it scaled from 2,2 to 4,5, which is close to the almost doubled capacity of ship storage.

Does this look familiar to You?



Once you start cleaning sour water and scrub your exhaust, your island will slowly but steadily drown in sulfur. Even more so if you had a shortage earlier on and thought
"Man, I would love to use the better rubber recipe, but damn, there is not enough sulfur. Oh what is that? A mine? Perfect, let's build it and import like 1k or so."
Yerp, I did that. Not only did I regret using the construction parts on it, but also that I filled up my storage early on even more after I realised that my production is getting out of hand.

But, alas, as a captain you are not worth your salt if you are not fixing problems. So, after I quickly checked the pollution levels on dumping mixed acid into the ocean or burn the yellow powder straight into the atmosphere, I checked the trades. Slag for sourwater. Mhm. I don't want to use limestone for that.

And then I found a way better solution:




480 Sulfur exported straight off my island for... 2160 Sludge?! Awesome!

So, what's so good about sludge? It is a sh!tload of energy. Literally.
The sludge of your settlement yields some nice little extra fuel gas here and there, but importing that from outside and throwing that stuff into an Anaerobic Digester for the bacterias to feast on cracks up the scale to some noteworthy degree:



18 to 7,5 Fuel Gas + some compost for fertilizer or landfill is a nice number if you import in cargoship loads. Lucky for you, I did some number crunching so you don't have to.

Alright, let's talk numbers!



From that trade we can deduct that 1 Sulfur = 4,5 Sludge

If 18 Sludge = 7,5 Fuel Gas,
we can calculate that roughly
1 Sludge = 0,41 Fuel Gas

That means that 1 Sulfur = 1,84 Fuel Gas

A big Cargoship with 8 modules can import up to 2160 Sludge per trip.
2160 Sludge * 0,41 Fuel Gas = 885,6 Fuel Gas

A gas boiler needs 72 Fuel Gas / 60 for 48 Steam

885,6 Fuel Gas / 72 = 12,3 minutes

So, on a maxed out turbine/generator setup, you can get 15 MW of electricity for 12,3 minutes per shipload. Which is something I used that fuel gas for on my last island. You can pump the Co² into limestone or recycle it into graphite, but anyways, it is easening up the pollution on your island as well as saving coal for your furnaces.

But there is more to it:



A cracking unit can easily turn that into Diesel and some water (which is always nice). Just add oxygen!
The ratio here is 1,5 Fuel Gas = 1 Diesel
Our 885,6 Fuel can be cracked into roughly 590,4 Diesel. There is no noteable waste produced in that process and it only requires an Air Seperator which needs 6 workers / 250kw and some maintenance. That's almost free. Even if you deduct the Diesel usage of your import/export setup, you will end up net-positive on Diesel.

Remember, 1 Sulfur = 1,84 Fuel Gas. That means that you can turn 1 Sulfur into 1 Diesel and have 0,34 Fuel Gas left for other usage. Think about that ratio again when you raise your fist angrily into the air, lamenting about the golden powder which is oozing out of all your storages.

Which leads me to my final food for thought: The Sulfur Mine.

If you want to maximize the concept of P.O.O.P, you need to think big. Sulfur as a byproduct is not enough, you have to import it. Which is also a big caveat on this setup:

You need unity to run the mine, you need another cargo ship (which will need Diesel and workforce as well) and that turns it to the more advanced side of usage of cargo depots.

But the mine is unlimited with vanilla settings!

But anyways, it is worth it if you want to play more with fuel gas outside of petrochem or farming.

See for yourself:





You have the numbers at hand, so feel free to calculate around. We can see here that, if you were to go all in, you would have roughly 397,44 Fuel Gas / 60 from that sulfur mine. You will have to decide for yourself if it's worth it or not. (And if you can manage to export these amounts of sulfur at all)

I had 1 Cargo Depot 6 running the contract on my last island and 20 Digesters running at the shoreline. That sounds like a lot but the good thing about Anaerobic Digesters is that they do not require that much. 1 Digester needs 4 workers and 50kw.
1 Gas Boiler was constantly running from the imported gas alone, another one was managed manually every 30ish minutes or so.

The Sulphur Mine was running on some "set and forget" setup. The cargo next to the import dock was actually taking all the islands sulfur production with a balancer prioritized and filling up as well. I was too lazy to tune down the shift/production on the mine accordingly and might have saved some unity and workers. All I wanted to do was making sure that the importing ship is constantly on the run, bringing more of the free energy to my island, as well as making sure that my island is not drowning in sulfur. Goal achieved.

The gas was lead into my petrochem tank, which in turn had alerts for being too full/too empty and I was switching on/off the second gas boiler accordingly. But that really depends on Your setup and Your situation. I also had two cracking units close by which allowed me to supplement my Diesel production as well and saved me the hazzle of expanding my Distillery rows (which I was too lazy for and wanted to avoid).

I would say that this setup is a valid bridge between burning Coal and going Nuclear.On my testrun, I did not even get a reactor running at all, because the solar panel production was taking over and I barely had to run any coal at all in the end. The imported Fuel Gas was enough to fire up my base load on the grid.

Fuel Gas is a nice energy source, since the transport in pipes beats coal on conveyors, and it is more flexible and cleaner as well in certain regards.

So, I hope this guide was helpful to you and I finish with a picture of my statue of Poopmetheus Prometheus, holding the eternal flame and watching over my Digester setup.