Potassium hydroxide

 So, I read this interesting article(1) about applying KOH(potassium chloride) to biochar making more micropores and WSOC (water soluble organic carbon) available. This is what they did, using different biochars from different feedstock:
"5 g of each biochar was heated with 200 ml of 1 M of either H3PO4 or 0.1 M KOH for 1 h at 90 C, then cooled down to room temperature. The solid (treated biochar) was separate from the solution by filtration. The treated biochar, once isolated, was dried at 60 C for 24 h."

They sell this stuff (Niagara-450) which consists of 98-99% KOH, as pipe cleaner for about 6 euros. I plan starting some pot trials as soon as the weather turns a bit warmer.

(1) Y. Lin et al. / Chemosphere 87 (2012) 151–157