Not an expert. Just a random guy thinking out loud.
To burn you have to dry out the fuel matter and warm it up to its combustion T.
If the air is -50, the fire has to give up enough enthalpy to not just dry up and warm up the wood, but also melt the water in the fuel. That energy cost is huge.
That cold air is dense won’t come close to overcoming the enthalpy of melting and having to dry the fuel.
Also that the air is “dry” is irrelevant at -50C. The air is dry because it can’t hold onto moisture so it won’t dry out the fuel. Also, the water in the fuel is frozen so even if the air was relatively dry there would still be a huge kinetic barrier to sublimation.
I’m not an expert either but I have experience with getting fires to burn. Starting a fire in the cold is quite a bit harder. Mostly because if it’s cold, then it’s the middle of winter, and that means the kindling is covered with ice and snow, which has to be melted and evaporated off. A dry log has a lot of potential energy in it. A frozen log full of water and snow has zero or even negative potential energy, as in, even if you get it to burn it might take more heat out of the fire because of the ice than it adds back by burning.
But, that might not apply to peat fires because 1) larger, hotter fires make more efficient use of fuel, especially if they are in some insulated space where all the heat is not going straight into the atmosphere and 2) the peat might be dry.
Scouts learn to start a fire in any weather - even cold rain. You split the log and use the dry wood inside for kindling. Wood takes a season to dry in the first place, and isn't going to get wet (inside) just because it's raining. FWIW
And peat is nowhere near as dense or insulating as wood. Wood doesn’t really want to change temperatures easily, which is partially why we make floors out of it.
To burn you have to dry out the fuel matter and warm it up to its combustion T.
If the air is -50, the fire has to give up enough enthalpy to not just dry up and warm up the wood, but also melt the water in the fuel. That energy cost is huge.
That cold air is dense won’t come close to overcoming the enthalpy of melting and having to dry the fuel.
Also that the air is “dry” is irrelevant at -50C. The air is dry because it can’t hold onto moisture so it won’t dry out the fuel. Also, the water in the fuel is frozen so even if the air was relatively dry there would still be a huge kinetic barrier to sublimation.