is a special type of charcoal
made from select biocarbon sources
by controlled combustion processes
for a special purpose: to add to soil.
Biochar is made from plant biomass burned or baked at 500–1000 degrees-C in low or no oxygen. We expect charcoal to be made from woody tree debris, but to use in soil, weedy biomass may be more useful.
Biochar is lightweight because it's mostly carbon – 60-85% – one of the lightest, smallest atoms. And biochar made from plant biomatter is mostly empty – a micropore sponge left after boiling out sap and cells. Charcoal is the hollow skeletons and plumbing of plants.
Carbon creates structure. Biochar's micropores opens, loosens and aerates soil,to allow roots and microbes to penetrate and breathe.
Biocarbon's micropore sponge absorbs water into its vast inner empty spaces. Each gram of biochar in soil can hold 8 grams of water to keep soil wetter, longer.
Biochar stores charge. It attracts and captures both electron and ions. Biochar's inner spaces fill with nutrients loosely held in solution, ready to feed microbes and plants.