It seems as though the main usage of unripe walnuts is for the maceration process, aiming for wine or liquor, as it is tradition in a number of European regions. A further use is for the Greek specialty glyko karydaki, a sweet fruit preserve, as opposed to the savory green walnut pickling.
For the drinks, green walnuts are quartered but nothing is discarded of. When used as fruit preserve, the walnut is not cut but the outer layer removed. And this is precisely the skin I did not wish to throw away. Hence, the skin will be used to add flavor and strength to my next maceration composition.