On some of my previous ‘Renature’ story adventures, I kept hearing about what sounded like a quite magical and game changing substance known as ‘biochar’. Indeed, both Julia (The grass is greener with goats) and Sebastian (The pig poop plant plan) told me of its wonders and Julia said she even hosts workshops at her Terra Robinia homestead (near Messines) about how to make it.

The person who comes to teach these classes is a Dutch/Portuguese chap called Martijn and I started to get the feeling that he was just the man I needed to see. He lives near São Brás and now that summer is over (and the season for making biochar has started again) he very kindly invited me round to visit him at what he calls his ‘Permaculture Playground’.

Now, before we go on, maybe I should try and answer what we might call ‘the burning question’:

What is biochar?

Well… I admit I didn’t really know either and after Martijn had greeted me warmly and invited me into his really quite tiny little house, he tried very patiently to explain (and to show me) the answer to that question.

Martijn really knows his stuff and the scientific processes, temperatures and mathematics behind it. There’s just no way that I was going to be able to keep up with all that. I’m afraid the best I’m going to be able to offer you is the gist. A sort of ‘biochar for dummies’, if you will.

With that in mind, the very simple answer is that biochar is: charcoal, but buried underground.

For the slightly more complex answer, maybe we should start by talking about plants and how they perform what could be thought of as the ultimate magic trick, namely: photosynthesis. As we all know, they ‘breathe’ in carbon dioxide and (to our eternal gratitude) expel oxygen. They then use that carbon (along with a little sunshine and water) to ‘build themselves’ (a pretty neat trick you have to admit).

However, when a plant dies it slowly starts to decompose and that carbon is released back into the atmosphere. Indeed, we quite often speed up the process by setting fire to it - either to warm our homes, or as frequently is the case here, have bonfires to clear the land and get all our branches and whatnot out of the way.

Now, biochar is produced when we still burn it, but in a place with limited oxygen - a process known as ‘pyrolysis’.

How to make it?

Martijn came to live in Portugal 8 years ago and was interested in learning more about permaculture and this led him to get more and more interested in biochar. However, in order to make it he needed the right equipment and this, in a strange twist of fate, has meant that he has had to learn to become quite an adept welder as well.

Using a combo of metal that he buys, as well as bits and pieces he finds around, he has been experimenting with creating all kinds of different biochar burners. The basic principle with all of them though, is to limit the oxygen by burning from the top (the secret to a smoke-free fire) and to stop the process at just the right moment with the use of water or sand.

Carbon negative inventions

Through trial and error, he’s really been refining his technique and his latest burner that he showed me in his house was particularly neat. It's his ‘carbon negative biochar indoor cookstove’. Using what's called a ‘gasifier’ (that looked to me like a thermos), he filled it with wood pellets and, with strategic holes in the bottom to let in just enough air, he lit it from the top and the flames started shooting up (like an upside-down rocket) into the stove where he cooks soups and stews and even pizza (with his homemade pizza oven).

While we're on the subject (but please don’t ask me how), he also manages to have a bath from the heat produced by his burners.

He just has to remember when the flame turns blue, to stop the process by placing it in a sandbox. And, once he’s bathed and fed, instead of the fuel literally 'going up in smoke', he’s left with this very high quality biochar.

Now, the process does release some carbon back into the atmosphere (that's why he also has a chimney) but it’s much less than what would happen if the material was left to decompose naturally and it actually ends up being what's known as ‘carbon negative’.

You see, now that the organic material has been turned into biochar, it will take a lot longer to break down. Indeed, it will prevent that carbon from escaping back into the atmosphere for hundreds (if not thousands) of years. Which is great, but it gets better…

The Benefits - everything AND the kitchen sink

There’s a long list of benefits and reasons why ‘Renature people’ are so excited about this stuff. Martijn calls it a ‘force multiplier’ and says that just about every aspect of a farm or homestead can be improved by the addition of biochar.

I’ll keep it simple, but once dried and broken up (the most labour intensive part - and also the reason why you might really need a bath afterwards), the main benefit is that it does wonders for your soil. It is highly porous and thus able to attract and retain water and nutrients, which in turn increases soil fertility and biodiversity. This means more plants grow and start doing their thing, capturing more carbon and creating more ‘biochar fuel’, thus neatly completing the circle.

You can even feed it to your livestock as it improves their digestion and even, apparently, Martijn told me, experiments have shown that it makes cows produce less methane (although I don’t quite know how they measure such things).

It's even useful in the kitchen too. It works super well for washing dishes, even in cold water and without the need for soap. Martijn says, if you put a piece in the fridge it will absorb bad odours and keep food fresh and you can even brush your teeth with it. I’ll leave it there but the list goes on and on...

What materials can you use?

You can make biochar with almost any organic material and Martijn is up for trying anything. He showed me both a carbonized goat horn and a dog skull he made for a friend.

The Permaculture Playground

I don’t have space to tell you everything but Martijn showed me around the rest of the Permaculture Playground and it turned out he was really quite a wizard when it comes to the whole garden thing as well. His particular specialities were a ‘super’ plant called vetiver, as well as white sage (the special kind of sage witches burn to chase away the bad spirits).


Martijn is pretty carbon negative in other areas of his life too. For instance, he doesn’t have a car and gets around by bicycle. If you visit Permaculture Playground (Jager Biochar) on Facebook or jager.biochar on Instagram you will be quite impressed, not only by pictures of his flaming biochar burns and other ongoing projects, but also how he manages to carry back all the tools and metal needed to make his burners.

Indeed, he seemed quite unconcerned about how he was going to get all the way to Messines for the next workshop at the Terra Robinia that weekend. To be honest, I wouldn’t be surprised if the next thing he invents is a biochar jetpack. I see him as a mix between Iron Man and Captain Planet.