Originally Posted by Gr33nSanta
how about can filters, when they are 2 years old, is not the carbon in them charged? I always throw spent carbon in the outside garden but I want to start keeping it aside to experiment with a sub irrigated plantar full of carbon pellets in the reservoir. Not sure how effective, but I know someone who keeps his homemade biochar in 5 gallon buckets and uses pee to charge it.
I don't use it but pee does work.
Activated charcoal would need to be "charged". Using the word loosely.
Char tends to rob nitrogen and generally needs a food source and/or some microbial activity to give it a JumpStart.
Another avenue is to use 50% marine char for a mineral boost.