An ancient environmental technology is making a comeback. Five
centuries ago, Spanish explorer Francisco de Orellana reported
vast areas of indigenous settlement and cultivation along the
Amazon River. Surprisingly, the incredibly rich and productive
forests of this region were supported by poor soils. The ability
of these soils to sustain such large populations was, until
recently, a mystery. The discovery of terra preta — a fertile
black soil manufactured by these ancient civilizations — now
paints a picture of how these peoples were able to sustain
themselves. More importantly, the discovery teaches us much
about how we can sustainably support ourselves on this
increasingly crowded planet. Recent experiments with terra preta
have produced large increases in crop yields. And the primary
component of terra preta — the key to its fruitfulness — is
biochar. Biochar is the material remaining after biomass (in
this case, plant material) is burned through a special process
called pyrolysis. Pyrolysis differs from