Terra Preta or dark soil is a unique form of soil that was created by human activity. This anthropogenic soil has some unique properties; in addition to being incredibly fertile and maintaining this fertility for hundreds of years, Terra Preta is also a form of carbon sequestration. Both characteristics have led to widespread interest in Terra Preta across the world, with some people even proposing that it could be used to create a carbon-negative fuel, using a power generation technique called gasification.
Before we delve into all of Terra Preta’s claims, it might help to understand what, exactly, it is. Dark soils were observed in the Amazon basin by many early explorers, and as early as the mid-1800s, people were wondering where these soils came from. They were notably richer than neighboring soils and clearly had distinct properties that were identifiable even in this age of science. The investigation revealed that Terra Preta was heavily mixed with bio-char, or coal, and some people theorized that it came from volcanoes.
In fact, a closer look at the components of Terra Preta indicates that it was made by people, possibly the same pre-Columbian civilization that shaped large tracts of rainforest. In addition to bio-charcoal, Terra Preta also contains plant remains, manure, pottery shards and fish remains. In a sense, Terra Preta is a glorified compound, but it is extremely rich in minerals and very deep in many parts of the Amazon.
To make Terra Preta, people used a technique called slash and char, in which patches of forest were felled and burned in low-intensity, partially smothered fires to generate charcoal. That coal, in turn, got trapped in the carbon rather than releasing it into the atmosphere, which explains why people are excited about the possibility of using Terra Preta as a carbon sequestration tool. In addition, the content of the Terra Preta mixture makes it very rich, stimulating the growth of beneficial bacteria and fungi.
In theory, Terra Preta could be produced anywhere and could end up being a valuable tool for correcting severely damaged soils. The widespread use of aggressive chemical fertilizers around the world could be replaced by Terra Preta, which would also help repair soils damaged by these chemicals. Additionally, Terra Preta could be burned in gasification engines, potentially sequestering carbon while creating energy. Gasification is an ancient technique for generating energy from the burning of biomass under controlled conditions that transforms it into gas; this gas can and has powered a variety of vehicles.