Some bartenders are using lacto-fermentation as a way to create ingredients for the bar, use up leftover produce, reduce purchasing (by reusing containers instead of buying new products), and even fermenting leftover citrus and garnishes.
Jennifer Colliau is the creator/owner of Small Hand Foods syrups, former owner of Here's How, and a bar sustainability consultant who worked on The Perennial and The Interval at Long Now. She has shared her base recipe and tips on lacto-fermentation below.
For lacto-fermentation, you want a 5% brine. Dissolve 50g of salt into 950g water.
Put your veg and aromatics into a jar, Cambro, kimchi press, or whatever you have that's not metal, and pour enough brine to cover them completely.
Use something to push the veg down under the level of the liquid if you have to. Cover loosely and let sit until cloudy and it smells tangy, about 5 days. Taste, and when it's to your liking, keep it in the fridge.
Some combos I like:
Persian cucumbers, fresh dill (flowering if you can get it), garlic, black peppercorns, chile flake
Carrots, fennel bulb, coriander seed, bay leaf, garlic, black peppercorns
Cauliflower, cumin seed, mustard seed, black peppercorns, chile flake
Edamame in shell, garlic, Szechuan peppercorns, chile flake
Any mix of hot and sweet peppers, fermented a little extra (about a week), then puréed with enough of the brine to make it pourable is my go-to hot sauce. If you want add sugar, lemon zest, a little black garlic when you purée it, but I like it straight.