Shipping by rail and sea is incredibly efficient. Some googling tells me rail is 471 ton-miles per gallon. The average American produces 1600 lbs of trash per year, so you can ship one person's trash for a year almost 600 miles with one gallon of fuel. Even long-distance trash transportation is a negligible contributor to someone's oil use.

Could you not extract the methane, and run the train on it, and transport it for free?

Poopetual motion? (sorry for the shit jokes)

Sure, if you can invent a methane extraction process that needs no expensive equipment, has no maintenance, and is safe, then it would be "free".

> There's even a poop train to Alabama

An NYC poop train bound for other parts played a big role in season 4 of the television show Billions.

https://uproxx.com/tv/billions-stock-watch-poop-train/

Poop != sludge

Poop and sewer sludge are not the same thing.

It is almost the last step in the treatment process, using a centrifuge to remove the majority of liquid.

Some municipalities will sell the sludge, and it is spread on agriculture fields.

Dry composting toilets are not remotely practical for high density areas like NYC.

Hmm, that's probably a good point. NYC residents likely have little use for compost. And having to wheel bales (?) of dried poop out of your flat could get a bit annoying. Then again, presumably they already take out their trash, so maybe it's not totally unfeasible?

It's difficult to fully sterilize the compost, and it's very easy to end up with compost that is full of pathogens and parasites. With millions of people in a small area, I think that alone makes this idea infeasible.

The toilets also don't produce bales of dried poop, the composting only partially completes in the toilet itself--it has to be completed outside in a compost heap.

Also dry composting toilets tend to produce more odors than the average person wants to deal with in their small living space.