Lemmitor @A_norny_mousse@feddit.org in this community tipped that if the process serves and luck is on one's side, fermented birch sap can be better than champagne. Right now is the time when sap can be collected, so I'm giving it a shot!
The tree isn't terribly bothered, the tap hole is only a few millimeters deep. I only do one tap per tree.
Plan is to empty these tap bottles off several trees once a day into an intermediate container, use a Campden tablet per container and keep the intermediates in the fridge until I have enough, five liters maybe? Then one liter yeast starter, possibly with some cane sugar to lend a little extra aroma and colour (the sap is clear). Ferment fingers crossed. Serve force carbonated. Wish mi luck :D
If you inoculate it with vigorous yeast and add a bit sugar, you can just pour new bottles into active fermenter with minimal spoilage risk, certainly safer than storing non inoculated medium.
Great idea, thanks!