The answer is yes. We cannot fully abandon synthetic fertilizers and still feed the world’s 8.2 billion inhabitants. But biochar-based fertilizers—that is, biochar mixed with compost, manure, or synthetic fertilizers or biochar made from nutrient-rich residue—offer a middle ground.

Normally, crops use less than 60% of the nitrogen and potassium and less than 20% of the phosphorus in chemical fertilizers. What remains ends up in streams or in the atmosphere as N2O or a stinky ammonia gas. This isn't just bad for the farmer, who's paying top dollar for fertilizers, but the environment.

Mixing biochar with synthetic or organic fertilizers keeps the nitrogen and other nutrients in the soil for longer, increasing “nutrient use efficiency.” This means that farm fields can use less fertilizer while producing the same amount of food.