This is a good video on how biochar was discovered in Central America.
The Secret of El Dorado – programme summary
In 1542, the Spanish Conquistador, Francisco de Orellana ventured along the Rio Negro, one of the Amazon Basin’s great rivers. Hunting a hidden city of gold, his expedition found a network of farms, villages and even huge walled cities. At least that is what he told an eager audience on his return to Spain. http://www.bbc.co.uk/science/horizon/…
The Intergovernmental Panel on Climate Change (IPCC) reported Biochar as a key technology for reaching low carbon dioxide atmospheric concentration targets. The negative emissions that can be produced by Bio-energy with carbon capture and storage (BECCS) has been estimated by the Royal Society to be equivalent to a 50 to 150 ppm decrease in global atmospheric carbon dioxide concentrations. Annual net emissions of carbon dioxide (CO2), methane and nitrous oxide could be reduced by a maximum of 1.8 Pg CO2-C equivalent (CO2-Ce) per year (12% of current anthropogenic CO2-Ce emissions; 1 Pg=1 Gt), and total net emissions over the course of a century by 130 Pg CO2-Ce, without endangering food security, habitat or soil conservation. Wikipedia http://en.wikipedia.org/wiki/Biochar