I love to sing 
char char char from the hilltops to the valleys. But most people think I am crazy. Terra pretta was where I first read about it in the Amazon. By a fish collector in the 90s though, not a gardener. Ha.
Terra pretta, the original Mayan made biochar. It’s 1000-3000 years old and that soil is still to this day considered one of the best on earth. Mind you all the while sitting inside a rain soaked nutrient desert (aka Amazon basin). Every single atom of nutrients is recycled in that ecosystem. It’s the classic example of law of minimum. Anyway it will blow your mind.
Char is a complete waste of time if you don’t reuse your soil.
It is most effective in living soil. If you turn and burn the soil every run char is NOT for you practically or $$.
Char is great. It improves drainage like perlite, yet the pores (and microbes) in the char hold onto moisture. Most importantly it is a microbe sink. Like a battery. It keeps nutrients from running off by holding them in the soil. Microbes love it. It is like a swanky microbe hotel in the soil. They reside in the pore gaps close to all the nutrients. The char in your can filter is all you need if you dont have a place to burn or want to buy it. Commercial char is not the cheapest bag at the grow shop. Don’t chuck that filter carbon. It is some of the most porous char on earth. When your filter is spent all that activated charcoal makes a great biochar source. When I turn under freshly loaded up biochar, then check it in 2 weeks, the mycelium just entombs it. It’s hyphae just grow between the pores. It becomes a microbe transit hub for mycelium to catch the train. Or maybe a mycoboost hotel.
Where I am going is, long term, the char holds the nutrients: micros, macros, carbon (C0 & C02), amino & lipid chains. I find now days I worry less about weekly feed schedule routine. And more about generally loading up my char batteries in the winter. I would go into it, but that’s too long a tangent for your thread. But once things are growing I don’t adjust much unless the need arises. Sit back and watch things grow so to speak. My beds never gave me this luxury until I amended with the char. Pinch me type of difference.
I know my outdoor seasonal approach does not straight up work for an indoor set up. But I bet if one did a side by side with chared up reused super soil VS a scheduled feed no char sister clone grow off, you would roll with the char after.
Buying char depends on your point of view. It is so easy to make yourself in a wood stove or campfire. Burning wood on a hot summer day in an industrial zone for a few cups of char. Then shipping it to an amazon warehouse on a truck; then to your home. Pretty shitty way to make it. I make it with a high efficiency wood stove with pile of wood harvested within a few miles of my home. Rather than shipped. That not always practical but good if you can do it yourself. The char in your can filter is all you need if you dont have a place to burn. Campfires, pour water on the marshmallow coals. Don’t let it burn out to ash. You want the popcorn like squishy stuff. Not the harder brickets. Those hard ones will huegel down, but not real char.
Most important never put raw char on plants. You have to load it first. Otherwise it will load itself by robbing the garden of it nutrients. No joke. They’re a lot of ways, but I mix it with compost tumbler scoop, then float it in piss in a bucket. Forget about it for 2-3 weeks. Good to go. Best to add it for the soil mix. It’s not as good as a top dress. You want it homogenized like you would perlite. I would suggest 1/2 cup per gallon of media in a pot.
I have even read about towable retort ovens (pyrolysis, no oxygen present) that the syngas that is released from the wood can be captured, stored and used into tanks. Virtually zero emissions besides heat energy. The us forest service uses these regularly to char up pine beetle dead forests. The studies in Yellowstone show more moisture in the soil, more nutrients, more plant and animal species diversity after application of char. Rather than it becoming co2 and methane as it rots (thank you microbes).
Also scrap annuals crops like grass, corn, and sugarcane (usually open burns) and invasive weeds like kudzu, blackberries, j knotweed make excellent char. They can even char grassy manures.
Chemical fertilizers on crop land can be reduced. Think (trucks, sprayers, planes,) how much less co2 that would make from a renewable resource? With char batteries mixed in.
I even read here in Washington state they use it around holding lots and slaughter yards for cattle. To prevent nutrient runoff and waterway eutrophication. Char is piled up to make a nutrient sink. Then spread it on the crops when it’s loaded up. Brilliant. I also read they are mixing it into the feed to prevent methane farts from cattle at the source. No shit.
Now burning down the redwoods to make char for the pot growers is not good. But charing up scrap grass and down or dead trees just makes sense. Sorry if I got passionate about this one.
