We made flowerbeds that go all around our front deck with railroad ties. I used the chainsaw to cut them to langth and the corner angles, you almost have to sharpen after every cut, it wipes the sharpness out right quick!
Cutting them dulls chain. Burning them is health hazard. Just handling them is a mess. Not just no but f××k no. LOL
I have 4 cord of RR ties that are ready for the boiler. They are NOT TREATED, with anything. I got them from the sawmill as end cuts and rejects. If you can find a similar deal go get literally all of them. If they are treated, do not burn them. Don't burn them inside....don't burn them outside. Don't even touch them unless you are wearing gloves and you are OK throwing the gloves away.
There is a mill next town over that cuts RR ties , I know people who have done just that , getting the UNTREATED cut-off , rejects and slabs from the milling. I do know that they sell them for firewood but never personally have I used them myself. I did cut some of the slab-wood from a bundle for a friend a couple years back but that's my only personal experience with any of it.
My husband brought home some for me to make tiers on steep slope we had. No cutting, but same thing on the smell, especially when they were hot in the sun the smell was awful.
It's in the works now I hear... Eventually we'll get to the point where the simple mentioning of Dr. Seuss will get you pummeled with an entire gymnasium's worth of participation trophies.