CompostGlobal Warming/Climate ChangeSoil BiologySoil ConservationSoil Rehabilitation

Biochar – Potential or Pitfall? Carbon Storage vs. Soil Quality

We’ve been having a pretty lively discussion on biochar in a recent post. One of the commenters, Rhamis Kent, found the video below which I thought I’d put up for all to consider.

In it the Woods End Laboratories people question whether biomass should be turned into biologically inactive biochar, when it could instead be turned into biologically active compost — particularly when many find it necessary to pre-soak biochar in urine, compost or manure anyway, so as to reduce its yield-stunting effects (like binding nutrients so plants can’t use them, and the high pH of biochar).

My thoughts on the issue are to trial it at home by all means, and let us know about your well-documented results, but I’d hate to see people supporting large scale, energy intensive, profit-centric implementations of this.


  1. Three rooted fig starts two with about 25% charcoal were fertilized
    with a strong urine solution they all survived and are doing ok.
    The fig without charcoal lost its leaves after the urine application.
    but put new leaves out later.
    I planted sweat potato potted slips into charcoal rich soil had heard that fungi increases the sweat potato disease resistance and that charcoal is a base medium that encourages fungi growth.
    The resulting poatoes were small diseased and black. Those without the char were large clean but many had been eaten on by toothed critters.
    I think that the store bought slips had been in their little pots to long and this encouraged disease would like to know more about the charcoal in this regard.

    1. The carbon was too acidic for root crops such as sweet and regular potato as well as beets all require a slightly alkaline soil environment to avoid certain diseases and growth problems. Perhaps adding lime to your soil would be a sure way to bring your ph into a more suitible range.

  2. While I am a big fan of composting, I don’t think it prudent to write off the potential benefits of using biochar. There may be a benefit to using it to balance the PH of acidic soils, or may prove useful for growing plants that prefer higher PH. Yes we should be cautious before proceeding with massive applications of this prior to fully understanding the implications of our actions.

    I am very interested in the potential for biochar to be able to increase the biomas of soil microbes and I am curious to know if Terra Preta soils have issues with high PH.

    There are also concerns about Carbon reducing the cation exchange capacity of soils, thereby locking up nutrients and making them unavailable to plants. I think it would be a great topic of debate to explore the pros and cons on this site.

    Has anybody been able to source an analysis of Terra Preta? If so, please share it here.

  3. Great post, it is always good to mention constructive criticism and bringing debate on the methods we use in our ecosystems. It could be a benefit on a large scale if planned properly, but I can see how industrializing this can be a detriment. It reminds me of recycling these days. Some of it is shipped to China from the states defeating the entire premise of re-purposing materials and giving BIG industries an alibi to continue making these materials while overproducing and creating pollution.

  4. There’s something about biochar that horrifies me and leaves my mouth agape on an intuitive level. It’s like a new trend and everyone wants to jump on the bandwagon of this cool new thing. But what the hell is wrong with regular old composting, turning our scraps back into lovely jubbley, rich and healthy earth? I’ve been composting and loving it for 10 years. It feels natural and just right to me somehow. My instincts say that burning up biomass is increasing our dangerous imbalance in relation to the planet – red flags go up for me.

    Something George Monbiot said in an interview one time made sense to me. The gist was that it’s okay to use up whatever resources we wish to, ***so long as they replenish at an equal rate to being used.*** That would be the simple definition of sustainability. But that isn’t the case with biochar, is it? Or am I somehow mistaken?

  5. Personally I strongly advocate blending biochar into compost. It gives you the best of both worlds.

    The inconvenient truth about composting is that roughly 98% of the carbon in compost is back in the atmosphere within 5 years (depending on the soil and climate conditions). In contrast the carbon in biochar provides excellent “housing” for soil microbes, but they do not consume like they do with compost.

  6. The article goes “… should be turned into biologically inactive biochar…”. Far from inactive, biochar has powerful effects on the microbiology of the soil.

  7. 1) Here is a program aired in Australia discussing terra preta, biochar and pyrolysis:

    2) The merits of compost are undoubtable. Only problem is its relative instability and short life-span in the soil.
    3) Biochar too, as evidenced by Terra Preta, has also been shown to build the soil.
    4) This program will reaffirm what many have said; that biochar must be pre-saturated in a nutrient solution to reduce drawing nutrients out of the soil.
    5) Biochar alone is a not a panacea. Neither is compost alone. If we are to be called advanced, we need to use all logical and sustainable means available.

    In most of the cases presented, the fear is that biochar and pyrolysis is produced with fossil fuels. This fear is justified. The only reason why we need to sequester carbon in the first place is because we rely on too much fossil fuels. Its therefore illogical to try to reduce the impact of fossil fuels, by growing reliant on it for production of biochar.
    The win-win situation is when we reduce the number of functions reliant on fossil fuels AND when we manage to create biochar with renewable energy (solar or wind). Making biochar is not to mitigate the use of fossil fuels. It should be to rectify the past wrongs and to draw up all those tonnes of carbon we have put in the atmosphere in the first place.
    Rather than be so focussed on fossil fuels we need to use resources that are readily available like wind and shine.Its very frustrating for an Australian to see all the research that has been put into solar research, only to see its merits rejected by the government. One of those researchers, a Chinese national, returned home with this technology and has become one of China’s richest men. Obviously the technology had its benefits.
    The trouble with developed nations is that we are too comfortable with what we have, to accept neccessary change. China for all its polluting has the fastest growing green energy sector. Why? Because its a developing nation that knows it needs all the new technology obtainable to become truly developed.

    *We may call China a big polluter, but divide their carbon output by their population. Per person, we should still hang our heads in shame. Europe, the US, Australia are still the worst polluters per head.

    1. The wood gas produced is more than sufficient fuel for pyrolysis. Therefore we need no fossil fuels to produce biochar.

  8. I did some bio-char research around 3 years ago, the impression I got is that the reported growth benefits are more common in tropical/subtropical zones, so it is interesting to see the views expressed here.

    I made some charcoal (willow), crushed it, cycled it through the kitchen compost (4 months), then forked it into one raised bed at about =<10% of volume.

    I have a control bed right next to it same soil, I split both beds (16'x5') into two, and did a 'standard' 4 crop rotation for two seasons (so far) I can't say I've noticed any positive, or negative results, both beds seem to behave the same, though another two or 3 seasons are required for full comparison. Char is still visible in the soil mix.

    Some details: heavy clay soil with organic material added, both beds well mulched throughout the seasons. Cool temperate zone (east mids UK).

    It would be helpful if people reporting results (good or bad) with bio-char could include some zone, and soil info.

    James Joyce: Don't tell them that, the buggers will be taxing compost heaps next! (j/k)

  9. I am no scientist nor a farmer, but Pete’s comment seems right on.

    Perhaps the blogger could do a post with a challenge, everybody using similar methods etc, although the soil differences vary worldwide, perhaps the experts here have some way of taking that into account?

    Just throwing it out there.

    Biochar, from my reading, seems to prove that sometimes great ideas, have already been thought of, by the ancients.

  10. In my view, the problem is much more about “magical thinking” than it is about biochar.

    I consider the latter to just be another nice thing in the toolbox. It seems to have some quite useful applications. I’d love to play with it a bit in small scale trials in some regions of Germany that have acidic bedrock, acid rain problems, and nevertheless have been planted to soil acidifying trees.

    The point is just: it’s only one tool. The problem is one of: “If all you have is a hammer, everything looks like a nail to you”. There is a widespread mentality of “to deal with Problem X, I have to buy/use Product/Technique Y”. When working with Nature, one cannot do just one isolated thing. And that’s what biochar is not – a silver bullet.

  11. The most promising biochar technology I’ve seen is in distributing small inexpensive cookstoves that solve multiple problems together: replacing the open pot-on-three-rocks open fires that waste fuel and breed smoky pollution all over the Third World, make efficient use of agricultural wastes, and leave behind charcoal that gives soils the ability to retain nutrients and reduce nitrous oxide emissions. It’s at least a win-win-win; maybe even better!
    Large scale plantations and massive plants will be portrayed as dangerous and as abusing the land, even if they are done with the best safeguards; these ideas are just too new to be rushed to market! But putting mass support behind the small scale applications could conceivably be just as effective.

  12. What will really keep permaculture a fringe movement is people that have all the time in the world to negatively comment all over this site instead of using that time to write an article with practical on the ground results that others could actually learn from.

  13. IIn Sweden we have done filed trails with very good result. Bio char is a good solution for soil amendment to increase the harvest in pore soil. It is big difference to char from different bio material and the way it is produced.
    This is not just a simple process (burning biomaterial to char) it need to be controlled very exactly to get right quality. We have tried it on chicken manure with good result and high carbon surface. In the spring we going to perform bigger field trials in both north and south Sweden.

  14. Well this is all very interesting, nice to see Dr. James Joyce here.

    I’m quite proud to say that I have one of the most advanced Biochar enhanced Permaculture set ups anywhere, I have my own personal pyrolysis batch reactor (soon to be open source). I have been applying Biochar to my organic soil since roughly 2004 in a wide scale project which is open to anyone who wants to see Biochar enhanced soils in action, my blog can be seen here

    I now co-own an Australian company which sells agricultural waste stream nutrient bonded Biochar (BlackEarth Products) and if my company is doing something wrong please tell me what? Our pot and field trials are positive and we are working with two major Australian universities to confirm our trails. We are one of only a few small companies world wide who are offering Biochar for sale and I’m excited by the fact that we have an extremely low emission product that can be used directly into most soils with generally positive results with in the first 12 months.

    If you are making charcoal or using fire coals and ash this should never be used directly into soils, always compost it or soak for a month in a nutrient rich tea, by adding them to your compost the intense action by all the bugs can break the strong hydroxyl bonds and nutrient to nutrient bonds. The released hydroxyl ions get absorbed, neutralised, by all the organic acids the bugs make.

    While I have read over the text about large scale Biochar projects. I just don’t see it happening, the suggested carbon price is not going to make it worth while converting forests into Biochar, the technology is not there to do this in the scale talked about, the largest 200+ tons a day pyrolysis systems have been created to produce Bio-oils not Biochar, Biochar out of these system is often just a slight low grade by-product. Systems like Dr. James Joyce’s up draft gasification system or my companies continuous flow pyrolysis system are designed for small scale agricultural waste streams and have been developed to create agricultural grade Biochar.

    I’m in this business to help improve organic soils, reduce fertiliser use, reduce water consumption, increase soil based micro life, reduce 3rd degree burns on people trying to make their own Biochar (like myself) and maybe one day make a slight living out of it.

    If you bother to read my blog you will see that I always add home made Biochar to my compost systems, I have 4x300lt 2x400lt 1x1000lt compost bins going and a 44 gallon drum liquid tea. I use rock dust, biodynamics, worm casting, chop and drop, green manures, keylining, swales, mulches, VAM, chicken tractors, legumes and all of these processes are just part of my system, no single process including composting is the answer, Biochar in my system is just another part of my process.

    I have found Biochar takes time to work just like compost or rock dust, it’s not a quick fix, but I now have black productive food growing soils here, the Biochar has moved down into the soil profile, worms can always be found in areas of high Biochar use and I have often found large worm numbers in high Biochar composts.

    Please don’t blanket all Biochar as evil as this is just silly scaremongering. I’m extremely green thinking and I’m happy to answer any questions you have either here on the fourm or directed via my blog.

    Kind regards

    Barry Batchelor (Bazman – joined PRI 04-07-2005)

  15. How to keep permaculture a fringe movement and scare away curious people: malign the idea of profits. – JBob

    The problem I’m trying to address, as Thomas neatly put it, is that if all you have is a hammer, everything looks like a nail to you. At the moment the world is looking for solutions, but they’re doing it with a ‘magical-market mindset’ — believing that pouring otherwise good ideas (in certain situations) into market mechanisms that encourage silver bullet large scale implementation will give positive results. My beef with biochar is that it’s not the one-size fits all solution (what is?) some make it out to be. As we’ve seen in these discussions, it’s not as simple as that. There are factors to take into account (pH, nutrient binding, etc. etc.), but despite this there are organisations seeking to roll out large scaled implementations through financing provided by industrial polluting industries via CDMs (Clean Development Mechanisms). You can be sure if it’s profit-centric, then it won’t be objective, and if scientific studies for a particlar region and context show that it’s not in the interests of people to use biochar (due to adverse effects in specific climates/soil types, etc.), then that science will get obscured or binned. We see this time and time again.

    Permaculturists generally have their heads screwed on in this regard – that you can’t expect one technique to work in every place. Would you not agree with this? Getting megacorps or governments to bankroll biochar is not a good idea. I’d rather see them financing permaculture research stations, and paying for advertising to help make people aware of where we are in history and how to get where we need to go (more self-reliance, community, etc.).

  16. Here in the Philippines, I mix carbonized rice hull (CRH) with compost/vermicast. So I get a soil conditioner and fertilizer mix especially useful in cities where good garden soil is hard to find.
    Rice hull used to be a waste product. But local scientists discovered that CRH is perfect as a “carrier” of the beneficial microorganisms in compost. One time I used it to save a wormbin that had gone sour.It worked! That was when I discovered for myself the great vermicast-rice hull combo.

  17. Hi Jalynne, they do the same in Indonesia:

    Sorry the article is in Norwegian! Hope you know about the new Permaculture demonstration sites opening in the Philippines next year:

    “In addition, Permaculture Action Asia manages 8 Permaculture demonstration sites (opening Jan 2011) located around Cebu province, where you will be able to:

    – see Permaculture in action,
    – learn Permaculture,
    – buy organic produce (fruit, vegetables, meat and aquaculture produce)
    – support our work by buying from the on site nursery, where we will sell and distribute template Permaculture plans, seeds and plants.

    Our flagship demo site, Cebu Eco-Culture Club, is a 64 hectare timberland lease from DENR in the hills of Cebu City (Pardo), a showcase of the 5 zones of Permaculture from the home to farm to forest. The site also has 40 squatter families, who will become our first program benificiaries who will remain on the land and implement Permaculture in family home gardens and small plots, and serve as a model eco-village community. Cebu Eco-Culture Club has been tentatively marked as the site of the future Asian Permaculture Institute.”

    1. Much of china’s moderate and poorer soils would benefit from biochar applications. I Imagine deserts having the most to gain from biochar applications. Dry sands do not hold moisture well so it would benefit from the addition of a water holding amendment.

  18. I tried to comment on the video from woods end but did not get through.

    Their video, although looking very “serious” an scientific, has for me some serious lacks. Example are

    -pure biochar pH is measured and is high. OK. But what the effect on soid when mixed at <= 10% ? And is it true for any biochar made from any wood or biomass?

    -moreover, acidic soils is a major issuer over large areas of the world… In Africa some governement are ubsidizing lime producer and truck transportation and storage to improve soil qualities`

    -With the plant grown and shown on the video, roots "seem to avoid the biochar" : biochar pption seem to 25% – is it the same with 10% ? was it soaked in nutrients? What is the plant? what was the pH of the ground? Etc…

    Also Woods end lab does not adress the fact that many similar video/experiment show significant gain in growth. That is strange, as a scientist if you get a result against other experiments, you should try to investigate, not just show your result…

    -comparison with compost: compost is made from cyclic carbon, and not a gram of C is removed from the cycle as plants use it to grow, therefore returning it to atmosphere in a "short" time (few years). Effect on the C in the atmosphere is therefore nil, except for the reviving of the ground, which can then host more C in form of biomass… but that is a side effect, even if very interesting.

    On the other and, if biochar is used by bacteria, fungi and plant in relation mainly to its microporous strucure, and remains so for thousand of years, then it is removed for the atmospheric carbon cycle for that duration… wich is pretty good.

    – finally, biochar can be produced with most of the energy coming from the wood being pyrolised itself, in biochar stoves, as underligned by Brian above. Then it provides 1-a source of heat for cooking 2-a clean flame solving open fire health-related issues 3-A fire that runs on many more fuels than wood (eg nuts, biomass leftover, dried leaves, dried dung, etc) and 4-a small daily production of fertilizer…

    -Of course burning fossil fuels to produce biochar would be absolutely stupid. But as soon as you produce biochar as a final product of a fire which is mostly burning the gasses of the pyrolisis process, and taht the fire is used for another already existing purpose, that is totally different.

    -SO, we already have biochar stove for the part of the world cooking on open fires. There are biochar BBQ. Il someone come up with biochar heating systems, then even heatin your house could be carbon-negative and contribute to fertilzing soils…

    1. The soil in the video was already acidic so the addition of carbon made it worse. Biochar is not a cure all, nothing is. Biochar is excellent in certain senarios but in a soil already struggling with acidity it makes it worse. Acidic soil needs lime to balance its ph. But alkiline soils can benefit from biochar. The reason for biochar being praised for increasing yields by 880 percent is because the soil it was applied to was extremely alkaline and the plants planted in it were weakened so much by the extreme soil condition that they barely yielded anything 880 percent of hardly anything still isn’t much. I am happy to see that the whole world became all a flutter over this acid (carbon) biochar based on hearing the 880 percent increase in yield. Yes biochar can be a miracle amendment for alkiline soils but if your soil is acidic I would avoid it.

  19. I would like to know where he got his suggested sample rate of 25% from? my positive pot trials so far are using 600g of growing medium and a maximum 8g of Biochar, their test would be putting 150g into this test… that’s way to high. I get the funny feeling his tests are focused on discrediting Biochar or they do not fully understand the product. It works best as a structure for holding nutrients and microlife, I would also be interested to know how his source Biochar was made? Was it made in a controlled system as this can greatly effect the quality. His claim that it uses lot of energy to make is total BS too, it’s a self fuelling process, just like industrial compost.

    I think we should stop talking about Biochar as a magic climate change saving system and look at it as a positive product for improving suitable organic soils.

    I don’t think biomass to biochar will not happen on a massive industrial scale. Why? You can make bio-oil or bio-plastic or many other high value products from bio-mass, they are worth much more and the market will follow this direction, some small amounts of low grade Biochar will be produced from these bio-oil systems but not in the amounts that have been suggested.

    Once again biochar, compost, worm castings and rockdust etc.. should be used together to benefit growing systems, but biochar needs to be mixed to get shorter term benefits, if you add it straight you may get a negative effect or a very small positive effect in the short term, but better effects in the long term as biochar settles into the soil profile and as nutrients bond to it’s surface and microlife and soil fungus bind to it’s super porous structure.

  20. On a US National Forest we have applied Biochar to some Big Game Forage plots. Early results did not show huge gains in biomass growth, but did show promise in droughty soils. I help manage some very primitive soils in Oregon; the Biochar plots we put in had sustained green foliage into the summer. However, control plots had started to cure and dry on the stem. These results are by no means definitive and bear further observation, but they do show promise in an area where we go from winter to drought on some soils. Biochar used was created from Wildland fuel reduction effort, so this is a very sustainable application. As we are reducing wildfire risk, we can also improving the soil. This concept also could have positive implications to restoration of Old Growth trees in Late Seral Reserves (LSR) for the Northern Spotted Owl (i.e. biochar might mitigate droughty effects of climate change), as trees encounter more stress.

  21. Greetings from Finland!

    I am going to perform a small scale experiment on charcoals effect on plant yield and quality this spring (it is mid-winter with almost half-a-meter of snow in Finland now). I will set up small new kitchen garden plot with low raised bed. (I am going buy compost-made dark soil (in Finnish language we have a great word “multa” which means the dark, soft humus-rich soil) from garden store, so as a whole the experiment won’t be very “permaculture”.) The reason for this is that I don’t have enough of my own compost and because I want it to have uniform quality to have more reliable results.

    The garden patch will be a square-form low raised bed and divided into two columns which will both be further divided into two squares. As result the patch is divided into four squares. The whole big square will be made from uniform-quality soil material and will be planted with at least cale and beans. Two of the smaller squares will receive mix of fine charcoal and chicken manure as a fertilizer (column A.) The two other squares (column B) will receive the same amount of chicken manure as column A but no charcoal. Half of the both columns will be mulched and another half pale. So in the end there are square 1 with charcoal and mulch, square 2 with charcoal and no mulch, square 3 with mulch but without charcoal and square 4 without neither charcoal nor mulch.
    After plot is build and charcoal, chicken manure and mulch added, it won’t receive any additional fertilizer. Possible weeds will be wound up, dried and dropped on to the square of which they grew. Site will be watered if necessary.
    Plant growth will be documented by photographing and weighing the yield.

    There in short is my plan. If you have any comments, critique or ideas, please let me know.

    If charcoal is found to beneficial for plant growth and soil quality, it might be useful, especially for poor people: if cheap charcoal could reduce the need of expensive fertilizers it would help farmers economically. They could make charcoal themselves from agricultural and garden waste. I’m not meaning that you carbonize all your agricultural waste. But how about, for example, while doing chop’n drop in a food forest garden one would collect e.g. five percent of the chopped material and turn it into charcoal via pyrolysis (of course using the produced heat for cooking or such), mince it and spread it around the garden? Charcoal would be slowly buried under falling (or chop’n dropped) leaves and sticks. The growth of forest would replace the used biomass and nutritients wouldn’t be lost since al the charcoal would be returned to where it came from. This just speculation, I haven’t done experiments on this.
    I think it would be foolish to carbonize all your organic material. But it sounds a bit akward to me claim that small amounts of charcoal in the soil would be disastrous. I have understood that the finer the cahracoal is, the less of it is needed to get the positive effects. Might it be that the all ad up surface area of the charcoal particles is what matters in according to the growth increasing effects? The smaller the particle size, the greater the surface area/ weight ratio.

    There is some thoughts on the issue, not all of my own origin.

    – Aapo L

  22. Ok so you all talk about biochar like it is a bad thing, its not soil…. its a soil amendment… the surface area of char is vast and won’t break down, it will hold more beneficial bacteria and nutrients. Keeping them from draining and available for the plant when needed… we can use it to fillter runoff from feilds, then on the compost…. ther are lots of ways to charge your char… how about composting toilets. The floors of your animals pen. keeping a supply available for livestock to eat looks like it can help absorb methane and ammonia from the cows stomach…. making them less gassy and there soil will start holding the fertilizer so eventually the field’s won’t have to be sprayed with chemicals. These seem like environmentally responsible things to do

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