"Biochar" is another name for charcoal (burned wood). It has some nutritional value for plants, but is mainly added to soil mixes to darken them, making them appear to be higher quality than they are, as darker soil is perceived by growers as more nutritious. You can create your own for free if you have a fireplace, barbecue, patio grill, etc.
"Post to earn Hive"
Promise? : P
Nice plants. Very green!