BioChar With Craig Sams


This episode, I’m talking BioChar with Craig Sams, the co-founder of Carbon Gold, a company that produces a range of BioChar products for the garden but also for agricultural use. I interviewed Craig in his beautiful garden in Hastings, so please excuse the cries of the seagulls who tried to get in on the act around halfway through the interview.


We discuss:

– What is biochar?

– Why did people start to produce biochar? What are its origins?

– How is it produced?

– Does it matter what kind of biomass goes into the kiln to make the biochar? Do the end results vary depending on the input?

– What is the difference between biochar and simple BBQ charcoal? Won’t BBQ charcoal be almost as good?

– What does it actually ‘do’ – how does it help plants?

– Is there a rule of thumb regarding which soils and which types of crops it works best on?

– How is it best to apply?

– Can you apply too much?

– Is it for application on new plantings only – or is it also good for mature specimens?


About Craig: Before this interview, I probably knew more about Craig than about his product, because he’s a legend in many fields, not least in food and growing. He founded the first macrobiotic restaurant in London in 1967 and went on to start Harmony Foods, which later became Whole Earth Foods. He and his friends provided the food for the first ever Glastonbury Festival in 1972. In 1991, he and his wife Josephine Fairley founded Green and Black’s. He was Chair of the Soil Association from 2001-2007 and is the author of four books, including the seminal text ‘About Macrobiotics’.


Craig’s website is


To read more about/buy BioChar products, go to


To read more about the CarbonGold Tree Rescue and to nominate a tree, visit


Follow CarbonGold on Twitter: @carbongold

Like on Facebook:


Further Resources


The Greenhouse Gas Removal Report 


Episode Transcription




{SFX: Intro music plays}


[00:01] INTRO: I’m Sarah Wilson and you’re listening to the Roots and All podcast. I’m here to help you get growing. Join me as I explore everything plant-related, both indoors and out, and provide the information you need to create your perfect green environment.


[00:17] {SFX: Intro music fades out}


[00:21] SARAH: This episode I’m talking BioChar with Craig Sams, the cofounder of Carbon Gold, a company that produces a range of BioChar products for the garden, but also for agricultural use. Before this interview I think it’s fair to say that I knew more about Craig than about his product because he is a legend in many fields, not least in food and growing. He founded the first macrobiotic restaurant in London in 1967 , and went on to start Harmony Foods which later became Whole Earth Foods. He and his friends provided the food for the first Glastonbury festival in 1972 and in 1991 he and his wife, Josephine Fairley, founded Green & Blacks. He was chair of the Soil Association from 2001 to 2007, and is the author of four books including the seminal text about macrobiotics. First off I asked Craig to explain what BioChar is.




[01:11] CRAIG: BioChar is charcoal. The difference is that it, it’s what you do with it. BioChar is charcoal that you put in the ground and that you don’t use to barbeque your sausages or whatever. The term “BioChar” defines that in practise BioChar is, when it’s made specifically to be used as BioChar, is processed in very slightly different ways, and people are still experimenting with different heat levels and different particle sizes and all the rest, but basically BioChar is charcoal.


[01:53] SARAH: So you couldn’t get your barbeque charcoal and put that in your soil? It presumably-


[01:57] CRAIG: You could.


[01:57] Sarah: You could?


[01:58] CRAIG: You could take lump wood charcoal, not the briquettes, because they’re- you have to grind it up and you have to grind it up to, to make it effective you really want the particle size to be under ten millimetres, and really you want it to be almost dust because everything is happening at a microscopic level.


[02:22] SARAH: Right, okay. So when you say it’s to do with the process of making it does it matter what you put in to make the BioChar, and do you use the same thing time and again when you make Carbon Gold?


[02:36] CRAIG: We use hardwood charcoal. The difference is, you’ve got- the Japanese use bamboo charcoal a lot because they have a lot of bamboo. Bamboo has very large cells. Hardwood has very small cells, and conifers are somewhere in between. The cell size is slightly important because part of the function, an important part of the function of BioChar, is that it is what is called a “refugia”, so in the soil you’ve got mycorrhizal fungi, you’ve got actinomyces bacteria, I could go on and name all ten thousand but I never remember them all {laughs}, and they all are working together with the plant to keep the plant healthy, to supply it with nutrients and defend it against pathogens, the fungi that normally would only attack a dead plant. The plant is making sugar in its leaves with photosynthesis, so it’s sending it down to feed this bacterial community, that’s fine. If you imagine gazelles grazing on grass that’s fine too, but then along come the lions and tigers to pick off the surplus population. In the soil the lions and tigers are protozoamites, nematodes, ameobi. They’re little tiny organisms that we can’t actually see but they’re a lot bigger than a bacterium or a fungal cell – a protozoa, one protozoa, needs to eat fifty thousand bacteria a day to keep going. If you are a bacterium you divide every twenty minutes, so actually if you do the maths, after seven hours you are fifty thousand bacteria if there aren’t any protozoa to keep your population down. When you have BioChar in the soil the bacteria and fungi go into the pores, the original cell structure of the wood that made the BioChar and they hide there, just as your ancestors- our ancestors would go into caves to keep the sabre toothed tigers out. So there is an argument that the smaller pore sizes- bacteria, even with the smallest pore sizes, they don’t have any problem getting in and out but that keeps out predators, and that’s also the argument for having lots of tiny pieces of BioChar ‘cause then that’s lots of little fortresses that the beneficial bacteria and fungi can hide in.


[05:19] SARAH: How did people start making BioChar?


[05:22] CRAIG: People have been making charcoal going back to the beginning of time kohl, eyeshadow, the root of that word is in the Egyptian word for charcoal, and we still use the word kohl to describe carbon, in German or Dutch “kohlenhydrat” means “carbohydrate”, “kohl” just means “carbon”. We’ve always been making charcoal, there are a few examples in West Africa and a few examples in parts of Europe, Swabia in particular, where people used charcoal as an agricultural amendment and even allotmenteers in this country, they would have deliveries of soot from local chimney sweeps that they would use to enhance their soil. It wasn’t quite BioChar but it was on the way. What we discovered about eighty or ninety years ago was, as the Amazon Rainforest was being cleared there were certain areas that has what the Brazilians call “terra preta” which means “black earth”, “dark earth”, and those areas were incredibly fertile so that farmers who had land on that terra preta would actually sell it by bags at garden centres and by the truckload to fellow farmers because it went down ten or twelve feet, so they could just hoover up a couple of feet off the surface and sell the land rather than the produce of the land. The people then sort of looked at “where did this all come from?”, and the answer actually goes right back to the early Spanish invasions of Latin America and South America, and Pizarro, who was busy looting the Inca cities up in the Andes mountains was told by somebody “you know, if you think the Incas are rich you should go down this river, there are cities down there, populations, who are insanely rich and they have gold” and of course being Spanish he got excited, they built a boat up in the mountains or up in the Andes, and Pizarro’s brother and a guy called Francisco de Orellana sailed down the Amazon and sure enough they came to this area which Francisco de Orellana described as “more rich and fertile than the finest lands of Castile and Aragon” back in Spain, and populated with busy farms – really wealthy – we went ashore and we were repelled by people with spears and arrows; our boat looked like a porcupine as we retreated, and they were lead by women with hair down to their knees and gold around their necks who would club to death any man who showed signs of cowardice. He then sailed down the river, he couldn’t get back up, and noted wherever there were these rich population centres but he never went ashore again, and when he came out in the Atlantic, having discovered the Amazon which was named after these Amazonian women, these very powerful matriarchal civilisations, he went back and the King of Spain had him in court and said, you know, let’s get an expedition together, and eventually they went back up the Amazon to get their hands on the gold and there wasn’t anything there because everybody had died. The reason they repelled them wasn’t because they didn’t want them to have their gold but because they knew that if a white man breathed around you, within a few days you would be dead of a cold or measles or smallpox because they had no natural immunity. So that whole civilisation collapsed, and it wasn’t really until the last few decades that we discovered that the foundation of the civilisation was this incredibly fertile soil. The way they did it was every year, or regularly, they would dig pits, fill it up with their food waste, their forest waste, their animal waste, their own waste, and then cover it up with clay and make it into BioChar – or charcoal – in exactly the same process that a English charcoal burner would use putting turfs of grass over the top of their charcoal burn – they used clay because they didn’t have turfs of grass – and they would then spread that on their land and that’s what kept their land rich and productive year after year after year.


[10:19] SARAH: So we took that principle and brought it back to – well, the UK and other places obviously. Does that work better on one type of soil or is it just as good across the board?



[10:31] CRAIG: If you have sandy soil it’s almost miraculous because- well the problems with sandy soil are legendary but, you know, fine for growing carrots but anything else, you know just to stop them forking, but all your nutrients run through, it doesn’t matter if you’re using organic fertilisers or chemical fertilisers, they wash through. Your soil structure, it’s very hard to build a good soil structure, so putting BioChar into sandy soil immediately stimulates the growth of the fungi and bacteria that glue soil particles together. If you have clay soil, probably the other extreme, depending on how degraded that soil is, BioChar makes a difference but it’s not as spectacular. So it really depends, so then you’ve got your loams and silty soils in between. Um, it always seems to do something; the main things are it has cation exchange capacity, so a teaspoon of BioChar has the surface area of two tennis courts which means there are lots of little points that magnetically stick, so there are positive and negative points that stick to the negative points in minerals. So your nitrates or your manganese or boron, or whatever your nutrients are don’t wash through the soil when it rains, they stick to that. Also BioChar is porous so it helps to hold moisture. When the soil is drying out the bits of BioChar have a much higher moisture level. And then the main reason is they’re full of the bacteria and fungi that typify healthy soil and if you have BioChar in the soil, even if you’re using nitrates which tend to cause a collapse in population of beneficial fungi and bacteria, you still keep a good strong resilient population of those fungi and bacteria so that when the disease-causing fungi – which have a place in the world, if we didn’t have them eating plants, dead leaves and dead trees we’d be up to our ears in biomass, you know, they’re what break dead biomass down into smaller particles, but you don’t want them attacking living biomass but that’s what they do when the living biomass haven’t got their protections in place.


[13:04] SARAH: And so does it work with mature plants as well as younger plants, and does it work on all plants?


[13:11] CRAIG: There is a yew tree in Totteridge that is estimated to be three thousand years old. It was dying, and one BioChar treatment – just one treatment – that was three years ago, it’s thriving now. There’s a tree called the Charter Oak in Bexley that was planted to celebrate the royal charter that established Bexley as a town, so it’s an ancient oak, it was dying so it got the BioChar Air Spade treatment eighteen months ago; it’s thriving. And there are many more examples of it, in fact at Carbon Gold we now have a promotion called Tree Rescue where people can nominate a veteran tree that needs help and we’ll do it for free, up to a limit.


[14:06] SARAH: Yeah. I saw that on your website, I think that’s brilliant. And how is it best applied? I see you’ve got sort of various different-


[14:16] CRAIG: If you’re starting from scratch you just mix it into the soil. And you really want sort of five percent by volume. If you’re potting, you know, potting compost that sort of thing, we make a potting compost using coir, it’s frustrating to me that there are people who are buying our BioChar and mixing it with peat, but it makes a big difference to the quality of plants that you propagate. And, you know, our aim is to get people off peat completely, we can’t stop people doing that when they’ve paid good money for the product. So it’s really good for the propagation, it accelerates the root formation that’s so important in a young plant. And then when you’re planting it, sprinkling a little bit in the planting hole also just helps the plant connect to the surrounding biology in the soil. When you’re dealing with something like a tree, a full-sized tree, then the methodology is either fork it in – not so good – air spade which is like high pressure air, you blow the soil away from the roots, put the soil back in on top, maybe add some compost, and what we’re really excited about is something called “vogt” {he spells it} geo-injector and that actually, and I’ve used it myself, it’s quite amazing because you stick these tubes into the ground and they blow a mixture of air and BioChar into the soil without disturbing the surface of the soil. So you actually look and you can see the earth just heaving every so slightly as this BioChar is whipping in. And then you move a couple of feet on and you do it again, and that way you’ve put the BioChar in with minimal disturbance of that network of mycorrhizae and bacteria that are so important to soil structure.


[16:26] SARAH: Yeah. So presumably they are using it in places where they have, as you say, elderly and very important trees. Somebody recommended your product to me who I value their opinion scientifically; what kind of institutes are using the product, who’s trialing it scientifically?


[16:44] CRAIG: The University of Reading have done an ash dieback trial, the RRSL; Reading Scientific Services, it’s like a university research spinoff, did a trial in Braintree with ash trees when ash dieback was at the height of awareness – in fact I’m going up there in a couple of weeks – but we know that the trees that were treated with BioChar, and they were already had been planted so they were about four years old, the ones that were treated with BioChar are all thriving, the ones that were not are all dead or dying because the whole forest has ash dieback as a problem. And we’re now doing trials with mature ash trees to confirm that. We’re nine months away from a royal warrant. Honey fungus is another disease that we’ve very successfully cured on some very beautiful mature trees. And then there’s plants, you know, we supply tomato growers all over Europe, both organic and non-organic because it makes such a difference to tomato plant health, you don’t get blight which is the nightmare, you don’t get root-matt disease which is a terrible disease where the plant spends all its energy growing roots instead of fruits, so these are commercial trials. The University of Reading now want to do a major research project with us, and we’re helping them to put together their grant applications. Overall, just very roughly, in 2010 there were about 900 research papers published on BioChar and that’s pretty much doubling every year, so now everybody’s doing it, and in fact the people at Reading said to me “we need an angle because so many people now are putting in research applications to do something with BioChar and we need to have something that pushes the buttons of the people who make the decisions about those grants.”


[16:59] SARAH: I saw probably the worst piece of research possible – I was Googling – and I saw mention of the fact that sometimes BioChar might have free radicals in it. You mentioned that you’ve done some research on that.


[19:13] CRAIG: Anything that burns has free radicals in it. Anything that you get up to those temperatures you generate free radicals. The way that BioChar is made burns off most of those in the process. Every batch that we sell we analyse for various things including free radicals, polyaromatic hydrocarbons and we’re always way, way below the levels of nothing to worry about and the tend to evaporate off after- whatever is left after- but there’s far less in it than a couple of lungfuls of London air.


[19:52] SARAH: Right. Okay {laughing}. And does the product have a shelf life after you’ve bought it, do you need to use it by a certain time?


[19:56] CRAIG: The biology does. So the BioChar lasts forever, and that’s what makes it such an attractive product to farmers and growers is once you’ve put it in the ground you don’t really need to add it every year. We do something called Biology Blend that just boosts the biology when you’ve already got the BioChar in the ground but normally it’s, it just goes on and on.


[20:25] SARAH: And could you put too much into your soil potentially?


[20:26] CRAIG: Yes, you really, you know, it’s just, it’s a waste of money but if you get up to, you know I’m talking per hectare now, five to twenty tonnes per hectare is optimal, and different people find – again, it depends on the soil type, if you’ve got a sandy soil you might want to put even more than twenty, if you’ve got a clay soil you’re probably happy with five to ten – but when you get up to fifty then it’s overkill really, and it’s counterproductive because BioChar is getting in the way of the soil itself.


[21:05] SARAH: Is it vegan?


[21:06] CRAIG: Oh that’s a good question actually because- well, BioChar itself is vegan. The product we make has worm casts so worms get fed waste and their poo is then dehydrated and that’s a very rich source of all the beneficial soil bacteria that you want, and mycorrhizal fungi we add and uh, trichoderma, so we are putting microorganisms in, but you know if you’re a vegan you inhale and kill thousands of microorganisms all the time. At least we’re giving the microorganisms a fighting chance once they’re in the soil and increasing their chances of survival. When a worm eats a mouthful of soil, for every actinomyces bacterium in the soil six come out of the worm’s bottom, so worms in the soil are constantly increasing the fungal and bacterial population. Then the protozoa and the mites and the predators come along and gobble them up and, um, so that’s where the BioChar helps in that it gives them protection from the predators.


[22:21] SARAH: And I suppose lastly could you just explain to me, in probably layman’s terms, why is the process such a good thing not just for your soil but for the environment in general?


[22:31] CRAIG: We have a global warming crisis on our hands and for reasons that are more to do with the power of lobbyists and decision makers about agriculture in Brussels and Washington who don’t actually understand about climate change, we’re doing all the wrong things. So we burn wood – we should be turning it into BioChar, we should be turning it into compost, or ideally we should be using it into buildings. We shouldn’t be burning any wood, ever. That’s part of the problem. Then we burn food. We hear people bleating about palm oil in food; more palm oil, three times more palm oil, is burnt as biodiesel than is used in the food industry. I developed the original peanut butter recipe that used palm oil instead of hydrogenated fat to make a healthier peanut butter that didn’t have oil separation, so I’m particularly frustrated at seeing this. When everybody’s saying “oh I won’t buy that biscuit because it’s got palm oil in it” and then they fill their tank with diesel thats ten or twenty percent palm oil. And the same applies to ethanol; I have a cousin in Iowa who grows corn on three thousand acres, it all gets turned into alcohol to be mixed with petrol. And we could be planting trees on all that land, we wouldn’t be deforesting these peat forests of Indonesia if we just stopped burning food. So that’s really frustrating too. What really makes me grumpy is the fact that Greenpeace and Friends of the Earth, charities I’ve supported and been involved with actively since the 1970s, oppose the idea that carbon credits from forestry or organic farming, and organic farm can increase soil carbon by seven or eights tonnes per hectare per year, a forest by eleven tonnes per hectare per year, and yet the NGOs opposed paying the same price for foresting soil carbon or BioChar for that matter as for wind and solar. So we pay a hundred and sixty pounds a tonne for every tonne of carbon dioxide we avoid with wind and yet we won’t pay ten pounds a tonne to a farmer who’s farming organically or biodynamically and building up soil carbon, sucking it out of the atmosphere. The good news is the Royal Society published a report about three weeks ago called GGR: Greenhouse Gas Removal and that’s where we have to go. It’s crazy to have to tell people in China, who’ve never had a car, “you can’t have a car because we’ve screwed up the atmosphere”, but what you can do, and what the Chinese are doing God bless them, is you plant trees. And then you suck the carbon out of the atmosphere and keep it out. You know, at the moment the sea is taking nine or ten billion tonnes of carbon dioxide a year out of the atmosphere, and the land and the forest that we have is taking about the same amount, but then were growing food and burning it, we’re growing- chopping forests down and saying “oh, I’ve put it in my woodburning stove, aren’t I good?” and it’s just not the, it’s the wrong approach. There are buildings now, there’s an eighteen story student housing centre at the University of British Columbia in Vancouver that’s made of wood. In Japan they’re building a seventy story skyscraper that’s going to be made of wood, and it will be earthquake proof because wood flexes in those sorts of situations. Steel and concrete are responsible for ten percent of our greenhouse gas emissions. Every time you replace steel or concrete with wood you’re taking something that’s making the climate worse and replacing it with something that is locking up carbon that was in the atmosphere. The house that we’re in was built in 1770. The wood in that house was taking carbon out of the atmosphere in 1066, or certainly probably something like that. So we just need to rethink the whole issue of climate change and pay the people who are taking carbon out of the atmosphere the value of the carbon, and then tax carbon on the oil companies and the steel companies and the concrete companies, and then the money will be transformative.


[27:23] SARAH: Do you think there will be a subsidy for BioChar production in the future?


[27:25] CRAIG: Well if you had a carbon price you wouldn’t need a subsidy because every tonne of BioChar that goes in the soil is three tonnes of carbon dioxide locked away forever. So the more BioChar we put in the soil the more we are keeping out of the atmosphere. And if you take the wood that made that BioChar and burn it, you know a tree takes fifty years taking carbon dioxide out of the atmosphere, somebody spends fifty minutes burning it in a power station, and then you wait fifty years for the tree that replaced that tree to grow, and you call that carbon neutral. It ain’t carbon neutral, no, we need to start to reward the farmers and the forresters who are taking carbon out of the atmosphere and anything that they do that keeps it out, whether it goes to BioChar or to a building it doesn’t matter. It’s keeping it out of that cycle of return.




[28:16] SARAH: Well, if you weren’t already familiar with BioChar I hope that’s shed some light on it; I know it did for me. It’s well worth having a look at the website,, I just purchased some of the normal and some of the tree fertiliser which I’m going to trial in a client’s garden where they have honey fungus. I’ve also purchased the seed compost and the multipurpose compost which I’m going to run trials with in my own greenhouse next spring. I’d really like to extend thanks to Craig for agreeing to the interview. It was a pleasure to listen to him, he is a great storyteller and I could have asked him questions all day. You’ll notice that he casually mentions in the interview that he invented the original peanut butter recipe that replaced hydrogenated fat with palm oil, i.e. the recipe that the biggest global producers of peanut butter have used for decades, and many people would probably dine out on that as an accomplishment for the rest of their lives but for Craig it’s just another in a long line of achievements. If you search online you’ll find far more eloquent people than I have written about Craig and what an interesting and knowledgeable person he is. And I’m not going to try and compete with him here but I will say I think what sets apart truly awesome people is the desire to share their knowledge and I used to honestly believe the saying that those who can do, those who can’t teach, but now I’ve realised that it should be “those who can, do and teach”. Thanks for listening and I will catch you next Tuesday.


[29:47] OUTRO: {SFX: Roots and All theme music begins to play as Sarah speaks} You can download or listen to the podcast direct from the website, you’ll also find my blog and a sign-up form for the newsletter which gives you a weekly round up of content plus the inside scoop on upcoming guests. Or you can subscribe wherever you normally get your podcasts. Email me with comments and feedback at, follow me on Twitter @rootsandall, Facebook /rootsandalluk and Instagram at @rootsandallpod, but please also check out my patreon where you can make a one-off donation or take out a monthly subscription to help support my work, because if you like what I do please help me to continue doing it. Even if you make a one-off donation of a pound, trust me, it all helps and I will be immensely grateful.


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