The Secret of El Dorado (The discovery of Biochar)

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/2002/eldorado.shtml…