Biochar may seem like a modern innovation in climate science and sustainable agriculture, but its roots extend deep into human history. The concept originates from ancient soil management practices using Terra Preta, a highly fertile soil created by Indigenous peoples of the Amazon Basin over 1,000 years ago, long before European colonisation of the Americas.
The term Terra Preta, meaning “dark earth” in Portuguese, describes soils containing unusually high concentrations of low‑temperature charcoal residues mixed with animal bones, fish remains, broken pottery fragments, manure, organic residues, food scraps and compost. This deliberate blending of waste and carbon created something far more valuable than the sum of its parts.
Scientists first identified these soils because of their unusually dark colour and extraordinary fertility compared with the surrounding tropical soils. Typically, soils in this region are highly weathered, acidic and nutrient-poor due to heavy rainfall that leaches nutrients from the ground. Patches of Terra Preta stand out as deep, dark and nutrient-rich, capable of sustaining agriculture for centuries without significant loss of fertility.
Although European explorers and naturalists recorded these unusual soils as early as the 19th century, they were not fully understood at the time. Many scientists initially assumed the soils were natural geological anomalies, with one theory suggesting that they formed from volcanic ash deposited from the Andes.
It wasn’t until the mid-20th century that researchers began recognising Terra Preta as anthropogenic soil - created by human activity. Following this shift in understanding, it became clear that indigenous Amazonian communities used Terra Preta as a land management tool, transforming poor tropical soils into long-lasting, productive agricultural land.
Unlike most agricultural soils that degrade over time, Terra Preta soils continue to remain fertile today, even centuries after the societies that created them declined. One of the key figures in bringing international attention to Terra Preta was Dutch soil scientist Wim Sombroek, whose work in the 1960s documented the remarkable fertility of these soils and suggested that charcoal additions were responsible for their unique properties. Subsequent research confirmed that Terra Preta contained large amounts of stable carbon, much of it derived from ancient charcoal. This discovery suggested that the soils are not only fertile but also capable of storing carbon for hundreds to thousands of years.
By the late 20th century, scientists began to ask whether similar carbon-rich materials could be intentionally produced and applied to soils elsewhere and play the same role in modern soil systems. This question led to the development of the modern concept of biochar. Biochar is a similar carbon‑rich material produced through pyrolysis, a process in which organic biomass, such as crop residues, wood chips or manure, is heated in a low-oxygen environment.
Interest in biochar grew rapidly in the early 2000s, alongside rising concerns about climate change and widespread agricultural soil degradation. Today, it is studied and applied not only for improving soil health and nutrient retention, but also as a promising method of carbon sequestration and climate change mitigation.