Agriculture

"Terra Preta", or "dark earth", is an Amazonian Indian technology which can vastly improve soil fertility and pull carbon dioxide out of the atmosphere, potentially keeping it out for thousands of years. Biomass - plant and animal waste such as manure, waste wood, and crop leftovers - can be turned into charcoal (or "biochar") and then buried in agricultural soil, making rich black earth that plants grow very, very well in. Charcoal is extremely porous, and provides a perfect environment for beneficial soil microorganisms that help plants grow. It also holds water, and can greatly help crops to survive drought conditions.