Those spoiled Norwegians living inland, where farms usually have quite some forest on their property, uses mostly birch for firewood. It has a high calorimetric value, and burns cleanly.
But, many other broadleaved trees are used as well.
I`m from a small island on the west coast, however. Pretty much like Shetland, but not THAT windy, so trees grow here, albeit slowly.
We are not as spoiled
and uses pretty much everything for firewood. I have much pine on my property, it was planted in the 50s because it grows rather fast.
It does "sputter" when burned, however. But this is really not a problem, as I burn it in a closed wood-burning stove, from traditional Norwegian company Jtul: http://jotulflame.com/3cb.html
http://jotulflame.com/jotulwood.html
When burning pine, the glass gets much dirtier than with broadleaves, but it is not that much of a problem.
As for the valve, it is a fast valve setup for wood-chippers, yes.