Biochar is a new word for an old thing. A special kind of charcoal that you add to soil, it’s made by burning wood and plant waste at low temperatures. It’s currently the focus of a great deal of scientific interest. Al Gore, NASA climate scientist Jim Hansen and Gaia Hypothesis originator James Lovelock have all cited it as one way of dealing with our environmental crisis. But it’s not some cutting-edge technology. Biochar dates back thousands of years.

In the 1950s Dutch soil scientist Wim Sombroek came across a kind of highly potent black soil in the Brazilian Amazon. Its rich nutritional profile and dark appearance were in great contrast to the typically poor, terracotta-coloured soils of the area. Contrary to what might be expected, the soils of tropical rainforests are usually acidic and low in minerals and nutrients. Their luxuriant plant and tree life exists because of something called ‘nutrient cycling’, which means that most of the jungle’s carbon and essential nutrients are locked up in its vegetation. As this organic matter decays, it’s recycled so quickly that few nutrients ever reach the soils, leaving them practically sterile.

Carbon dating has put the incredibly fertile super soils Sombroek discovered – known locally as ‘terra preta’ or ‘black soils’ – as at least 2,500 years-old. Some date as far back as 6,000 years. Evidence has since come to light that they were bio-engineered by the ancient indigenous people of the Amazon, to get around the problem of soil infertility and increase agricultural production. They added bones, manure and, crucially, charcoal to make the terra preta, which still cover ten per cent of the Amazon basin to this day.

Today, we are only just waking up to the potential of biochar. Here’s how scientists think it can help with our two greatest environmental threats:

Soil Infertility

People are concerned about melting Arctic ice caps and the deforestation of the Amazon basin, but not enough of us are aware that the very soil beneath our feet is in danger. Modern farming practices – intensive harvests, the planting of monocultures, as well as the use of pesticides and industrial fertilizers – have stripped it of much of its goodness.

Research from the United Nations shows that over a third of all soil on our planet is ‘severely degraded’ – meaning it lacks the nutrients, beneficial bacteria, fungi and micro-organisms essential for plants to grow. Globally, healthy soil is being lost at a rate of 24 billion tons a year. In the UK alone, we are only three or four decades away from our soil being rendered completely infertile. In just 30 years the green arable fields of England could become as barren as the sands of the Sahara Desert.

This is where biochar comes in. When dug into the soil, biochar has been scientifically proven to boost soil fertility. Due to its highly porous structure and large surface area, biochar is a great home for the beneficial micro-organisms that make soil fertile.

Greenhouse Gas Emissions

Some gases in the Earth’s atmosphere stop heat escaping into space. Known as the greenhouse gases, they are the primary drivers of global warming and climate change. The main greenhouse gas is carbon dioxide (CO2), while the others are methane, nitrous oxide, ozone and water vapour. The burning of fossil fuels, like oil, coal and gas, causes an increase of CO2 in the atmosphere.

The situation is made worse by deforestation. Trees and plants absorb CO2 from the air as they grow. Using energy from the sun, they turn the carbon captured from the CO2 molecules into building blocks for their trunks, branches and foliage. This is all part of the carbon cycle, meaning that mature forests are reservoirs of stored carbon. If they are razed to the ground down, then most of that carbon is released back into the atmosphere, increasing CO2 levels.

Biochar can help cool the planet by storing carbon. When biochar is dug into the soil, it fixes it there and stops it being released into the atmosphere. It has also been shown to reduce the amount of methane and nitrous oxide being released into the atmosphere.

Biochar is not a complicated technology. It can easily be made from leftover organic waste and only needs to be applied to soil once. And yet, its potential in terms of helping us regenerate our planet’s natural ecosystems is huge. It’s humbling to think that for this crucial knowledge, we have the ancient people of the Amazon to thank.