I would strongly suggest heating with propane for the first week or so - then switch to wood. If it's -60 degrees - within a week anyone without wood or propane will be dead.
One fairly easily obtained fuel is Coal. Search the web for “bulk coal”. A pallet of bagged anthracite is not crazy expensive and burns hotter than most other fuels. It won't degrade as quickly as wood and takes up a lot less space.
If wood is available in your area you are lucky but it is a lot of work to store up a large enough supply for a long winter.