From Henry Brighouse our sustainable blog writer –

In the film ‘The Martian’, an astronaut (Matt Damon), stranded on Mars has to stay alive until another space mission from Earth can rescue him. His only option is to create soil, a biological medium in which he can grow food. All he has at his disposal are a few potatoes going to seed, a climate controlled tent, the discarded toilet bags of his departed comrades (definitely
biological), Martian dust and water. The story, naturally, has a happy ending.

Here on planet Earth, the thin layer of topsoil that sustains our lives and the ecosystem on which we depend took millions of years to build. Through the relentless action of the sun, wind and
rain on the planet’s rocky surface and the process of natural biological decay, life evolved. Yet, in the past 100 years, due almost entirely to unsustainable farming methods, we have managed to deplete this fragile life-support system to an alarming degree. As of yet there is no coherent rescue plan.


When we talk of ‘food security’, we are basically talking about fertile soil and its availability for the long term. The politics of land usually put short term gains first. This invariably means squandering environmental ‘capital’ to make those gains. Fortunately, running parallel to this self-destructive ethic, there is a growing awareness in our collective consciousness of our place in nature and our relationship to the Earth, including the earth beneath our feet, or ‘dirt’ as it is known in America (see ‘Dirt, the Movie’- exploring the relationship between humans and soil). If we look at ways in which we could restore the soil to its full vitality, a revealing approach might be to look at ‘biochar’.

The story of biochar is very old. In fact it was very old when Francisco De Orellana and his Conquistadors sailed up the Amazon in 1542. He recorded seeing a thriving civilization stretching for hundreds of miles along the banks of the Amazon. There were villages, towns, even cities, connected by orderly networks of roads. One city stretched for 15 miles with continuous and dense habitation. The people had moved great quantities of earth in order to create a hospitable landscape, yet they lived simply,using earth, wood and grass for their dwellings. They wore white woven cotton garments and made fine earthenware pottery.

If this account were true, then such a stable civilization must have been supported by an abundant agriculture. This is not the Amazon we know today, where, apart from the scattered indigenous tribal communities, poor soils support a mobile population of farmers continuously slashing and burning swathes of pristine jungle in return for two or three years of fertile soil before moving on. After this, the exposed and exhausted soil does not recover its jungle clothing but begins to erode under the heavy rains; an entirely man-made environmental disaster. There are also foreign companies clearing square kilometers of jungle habitat for GM soya or pastures for livestock to supply the meat industry.


So was Orellana’s account true, or was it a figment of his imagination, conjured up to impress the Spanish court? Orellana fell out with the king of Spain on his return and his report was forgotten. Half a century later, the elusive search for El Dorado and the greed for gold brought Orellana’s account back to light and a new Spanish expedition ventured up the Amazon. But this time the Conquistadors found nothing but the jungle we know today, with a few scattered native settlements, largely supported by fishing and hunting.

Almost half a millennium later, archaeologists flying over the high savanna plains of the Beni region of the Bolivian Amazon, noticed unnatural looking straight lines criss-crossing the ground. These lines connected large forested mounds and between them were imprinted everywhere shadowy dark strips of land. Investigations on the ground revealed evidence of ancient, man-made causeways linking large raised earth settlements of an ancient civilization, long-since vanished. But the defining character of this civilization was its agriculture, with a system so simply ingenious that not only did it enrich the poor and unstable soils of the Amazon, but actually created soil by its very nature.

Where it is discovered, this soil is known to local people as ‘Terra Preta’, or black earth. It is often two or more metres deep and is considered to have almost magical properties with the ability to grow anything. Some are even mining it and selling it by the lorry load. Terra Preta has been found all the way down the Amazon to its basin, and although archaeologists tend to disagree with one another, there is evidence of a once thriving civilization of millions of people, as sophisticated as any in the Americas.

But what happened to these people in the brief window of time between Oriana’s first visit and a second Spanish expedition 50 years later? The only explanation has been their lack of immunity to diseases such as influenza and smallpox that came with the Spaniards. These people trod lightly upon the earth for their sudden exit from the world stage left behind them no toxic wastelands for future generations to deal with, but instead, magical earth with a message for the future.

This same earth might also explain why the jungle reclaimed this land so quickly. So what is the Terra Preta and what is its relevance to today’s world? Upon analysis it was found in many samples to contain an abundance of broken pottery, probably to raise and stabilize strips of agricultural land above the flood plains. But more significantly it contained high concentrations of organic matter in the special form of charcoal, or ‘biochar’ as it has been named.

This has given rise to a fascination for biochar as a valuable soil amendment capable of improving soil biology and fertility. It can also be considered as a strategy for reducing our carbon footprint because when we make biochar we are locking up carbon and putting it back into the soil where it belongs, not into the air.

In my next blog we will take a look at what biochar does, and why there is so much excitement about it. And in the one after that, how to use biochar in the garden, how to make it, which way might be the easiest and the most practical and best for the environment.