Biochar is a kind of charcoal made on purpose from plants and other once-living waste — wood chips, straw, husks, even some manures — by heating them with very little air. That slow, low-air burning is called charring, the same idea as char in charcoal. What you get is black, light, and full of tiny holes. People mix it into soil to help the earth hold water and plant food, and to give tiny soil life a place to sit. Others talk about it as a way to lock carbon in the ground for a long time, so that carbon does not go back into the air as gas and warm the planet. It is a fairly new word, at home in farming, climate, and environment talk, not in old novels. It is cousin to barbecue charcoal, but not the same thing: barbecue charcoal is made to burn again, and biochar is often made to stay in the soil. It is also not compost. Compost is rotten plant matter, still breaking down. Biochar has already been burned in that special way, so it changes much more slowly. Some farmers like it; some scientists say the results depend on the soil, the crop, and how the biochar was made. So it is a real thing, not a fantasy — but not magic powder either.

生物炭