Carbon footprint for wood firers.

One of the reasons I went to visit Morioka Shigeyoshi is to ask him some questions about wood firing for an upcoming panel I am on. I am one of the “and some others” on the panel. I will also be presenting a talk on firing Nanban.  I am unsure what the tilt  of the conference will be but looking at the presentations of the other speakers it looks like ecology as it applies to wood firing is one of the main topics.

I asked Morioka a couple of questions relating to ecology and wood firing. I should say I don’t believe it is possible to put a green veneer on wood fired kilns. In fact I think that should be acknowledged and put out in front by wood firers. It isn’t green in the sense the word is used these days. There are variables that mitigate the carbon foot print of wood firers compared to people who work a more conventional job. Things  such as wood firers tend to stay home more making work and some, like Morioka, grow their own vegetables so there is an offsetting effect in not having to go to the store as much but all in all it is a pretty un-green way to fire. My point is that when I put the questions to Morioka I had to preface them with a “These are from a Western/European perspective” and then ask the questions. I wouldn’t ask them because they  stem from my own interest. I got the expected smirk from him. Having said all this these are the questions I asked him.

Question. What  is the state of wood firing in Japan? That is to say, what would a young person just getting into wood firing see as his future?

Morioka answered that question with a confused laugh and said something to the effect that isn’t it fun to have a job that you can play with fire. He went on to say the number of wood firers is decreasing, mainly because the work is so difficult. At the same time he has a steady stream of youngers that want to apprentice under him.

My next question.  What do you think about firing with wood as the question relates to putting so much carbon into the air?

This question obviously took him by surprise. It isn’t something he has thought a lot about. He then answered that it is renewing the forest by taking the old wood out so new wood can grow.

I had a couple of more questions for him but the whole exercise was getting so stilted and uncomfortable I didn’t ask them.

This is very interesting to me for a number of reasons. The fact that firing with wood is a very dirty way to fire is obvious to even the most casual observer. I think there is a want among wood firers to  minimize or obfuscate that fact by talking about green ways to look at the process. I don’t think this is a good tactic. People aren’t so enamored by wood fired pottery that they are ready to give a pass to those who fire in this way when it comes to dirtying the air. I am very interested in how much carbon actually is produced by wood firing a kiln. I did a calculation on how much wood it took to fire my teachers rifle kiln. We threw in about 300 bundles of wood. Each bundle weighed about 17 kilograms. So 5100 kilograms of wood, 5.1 tons of wood. This amount of wood fired enough work to keep my teacher and a couple of apprentices in work to sell for one year. That is to say that is  the total carbon output for 3 people for one year. My guess it is less output than one airplane trip to Germany to present a talk on ecological ways to fire. Just a guess. I think there are firers that will argue there are ways to get the desired effects by firing with a cleaner burn, i.e., less smoke coming out of the chimney. My opinion is the amount of wood consumed in reduction, that is “wasted” in reduction,  is minimal as the calculation of how many calories it takes to take large kilns up to temperature is in effect a set number.

Hard Data.

I listened to a podcast today that happened to have some information in it I have been been interested in for a long time. It gives the carbon output of wood in relation to putting out  a single atom of hydrogen from the same wood.

The podcast can be found here.

The part I am talking about happens at minute = 30:50  It was sponsored by the American Enterprise Institute. AEI isn’t going to give the most sympathetic ear to the environmental movement but I think the data in the podcast should be given a serious audience. The presenter of the talk sees natural gas and nuclear as the absolutes if one wants to seriously get away from hydrocarbons. I think he has presented some of the data in a way that is more supportive of his position than might be the case but I don’t doubt his numbers.

The following data relates the density of the power source. Density is important since it gives a measure of output of energy per defined unit.  An example would be how many solar panels would it take to give the same power to equal a barrel of oil. To get the correct definitions it is best to listen to the  podcast.

Here are some numbers for the density of wood compared to natural gas.

wood =10 carbon atoms for every hydrogen atom.

natural gas =1 carbon atom for every  4 hydrogen atoms

Natural gas gives a  40 fold reduction in carbon relative to the amount of hydrogen in the fuel.

I don’t have enough knowledge to know more about the topic but it looks like wood is 40 times less efficient than gas. I am sure there are a host of variables but that is the simple formula. How can you paint that green?

Work fron the father of the guy firing the kiln.


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15 Responses to “Carbon footprint for wood firers.”

  1. Dorion Says:

    I would say that your friend Morioka is partly right–the fact that wood is a renewable resource isn’t trivial. Gas and oil, and by extension electricity (of which a large portion is produced by coal power plants) may produce less carbon but it’s carbon that has been safely sequestered for millions of years. It would be nice to have a formula to figure out exactly how much carbon is being release though.

  2. Eric Says:

    Hi Dave,
    interesting question : why firing with wood ? Is it for aesthetic reason ? Can gas provides same effects ? I know that rotted wood gives so much carbon than fired.
    Some informations on
    Pleased to read u.

    • togeii Says:

      Hello Eric,
      Thanks for your comment and questions. The paper you linked to is very interesting. Reading the paper I don’t accept that releasing carbon into the air through burning is the same as what happens to carbon that is released through decay.

  3. John Dorsey Says:

    You should check out Masakazu Kusakabe – I fire his smokeless kiln and it is a marvel:

    All my wood is coming from downed trees on campus and we have no smoke!

    Also, at NCECA this year, Nancy Utterback presented a paper on green ceramics. Here is her discussion about carbon emissions/ carbon neutral firing.

    • togeii Says:

      Hello John,
      Thank you for your comment. I will take a closer look at your site.
      I don’t think smoke is the problem. I think the release of carbon is. It would be a very easy answer to the excess carbon problem if smoke was the problem. As I understand things the release of carbon to get to the hydrogen is the process. Smoke is just a different problem of large particulates. It is very difficult to get around the “tyranny of large numbers” to use the language of the guy in the podcast I linked to.
      Downed trees release their carbon if left to decay very slowly but it is done through a very ecologically positive process. My guess would be burning wood would have the same carbon release as letting it decay but it greatly speeds the process. The decaying wood would have a much more carbon sink plus profile is my guess. It provides nutrients to the next generation of trees along with some other benefits to animals.
      I will read the paper you linked to and either leave a detailed comment here or at your blog. The paper linked to in the comment by Eric above doesn’t actually make any claims other than decaying wood releases carbon. There isn’t any data to back that up in relation to the the time variable.
      My point is that wood firers shouldn’t try to paint wood firing green with elaborate justifications. A carbon neutral firing that relies on wealthy firers to achieve isn’t a good justification. I mean that in the way that most carbon offset programs are based in having wealth to deploy to purchase the tree seedlings or what not.

  4. Page not found « Togeii's Weblog Says:

    […] content of wood firing. New blog post. […]

  5. Carbon footprint of wood firers part 2. « Togeii's Weblog Says:

    […] firers part 2. By togeii I recently wrote a blog post on the carbon footprint of wood, see here for part 1. Through a comment my attention was drawn to a presentation and a pdf file on the carbon […]

  6. John Dorsey Says:

    Dave – great response! Really good discussion! Glad you brought up HOW downed wood would be rendered back into carbon through long term decay.

    My thoughts would be that woodfirers should try and be as green as possible while firing – not that woodfiring is the most green firing method possible. It is such a complex mathematical formula to try and calculate all the different methods of energy release and get to a point of actually being able to compare apples with apples. Ultimately, electric v. gas v. wood might be engaged only on an aesthetic level.

    The particulates matter IS important, however, as nuisance will keep us from firing as much as anything else – especially in close quarters. Kusakabe-san’s design allows us to fire in the middle of our campus – so great!

    My guess would be that it would also be interesting to look at the number of woodfirerers world wide (and the quantity of firings) to look at ourselves as an industry to compare us to other forms of firings (or other industries, for that matter). An impossible task, I know, but are we worrying about something insignificant or contributing in a large way to a big problem?

  7. togeii Says:

    It is a very interesting discussion. I think much more data is necessary.

  8. Markus Boehm Says:

    Am 07.06.2010 um 04:00 schrieb

    Dave, you wrote: It looks like the smallest carbon footprints aren’t going to be found in wood firing.

    My first question: really?
    Because if we want to have ceramic we have to consider that firing clay is an extremely energy consuming process and indeed an important question is: what kind of firing does the least damage? So wouldn’t it be better to compare the different ways to fire – instead of looking at woodfiring separately?
    For me English is a foreign language and I’m asking myself if the discussion might be based on
    unclear words: carbon is a solid, energy rich matter. If it is oxidised then (usually) Carbon dioxide is the result. Carbon dioxide is aerially and a normal part of the air that we are breathing. If sun radiation goes through air with a high amount of carbon dioxide this air heats up more than if the air has less carbon dioxide. This effect is used in greenhouses to save energy and it contributes to the climate change. In German language the term “carbon footprint” doesn’t exist, we speak of CO2-emmissions.
    So what does woodfiring in this way with our atmosphere – compared with other firing methods? The common point of view is that a tree takes CO2 from the atmosphere, releases oxygen and stores the carbon in the wood. When a tree dies the wood is decomposed and the carbon is oxidised, the resulting CO2 goes back into the atmosphere. In contradiction to that process the use of fossil fuels like coal, gas or oil adds ADDITIONAL CO2 to the atmosphere, contributing to the global warming, because the process of forming coal, oil or natural gas (and that way taking CO2 PERMANENTLY out of the atmosphere) is finished on our earth because that process requires large rain forests , where the trees fall under water and are covered with sediments, so that the wood cannot be decomposed and CO2 is not emitted into the atmosphere.
    At that point David brings the term “time frame” into the discussion, saying that wood firing would only be carbon neutral if it happens in the time frame of natural decomposing – and as far as I understand it he is saying that this time frame would be 30 to 100 years. So if the forested area is kept at the same size (which is not true for my region, more than 100 square kilometer of forests were planted additionally during the last 20 years), then the CO2 that I release with my wood kiln would be compensated in 30-100 years by the growth of the new trees. So if I would follow this line of reasoning then still the smallest carbon footprint comes from woodfiring (compared with fossil fuels) because with gas, oil or coal the ADDITIONAL CO2 is NEVER reduced from our atmosphere again – according to the current level of our economy or science.
    The next questions are about the process of decomposing wood.
    First: the time frame
    For woodfiring I store the wood for at least 2 years to become dry. Then it is used and totally decomposed in the fire.
    If I would let the wood lie at the ground like a dead tree in the forest (which is a silly assumption as all the wood is used here in middle Europe) the appearance after those two years depends much on the kind of wood: willow would be nearly fully decomposed as well as most of the soft needle wood like pine, oak would last the longest.
    So doesn’t it look like the time frame between firing and rotting differs not too much?
    Second: carbon sink
    David wrote: “There is the additional problem of what seems to be the 50% or so of carbon that goes into the soil for longer sequestration in natural decay of wood. This sequestration in itself isn’t carbon neutral but seems to be a carbon sink.”
    So how exactly should this process of “50% or so of carbon going into the soil” work?
    If I look at such nearly decomposed wood then the result is very light (if dried) and will give up nearly no energy if I try to light it. There is certainly not 50% of carbon left, and if some years more have passed then you will find hardly any carbon where the wood was laying on the ground. I would be very happy if that would be the case: My wife uses for her gardening bark to cover the earth between her plants. This wood is decomposed much too quick as I have to by new bags every year. But if she digs up the soil she doesn’t find any carbon…
    So David: Where are the “hard data” for this process?

    David: In your blog you wrote:
    “Natural gas gives a 40 fold reduction in carbon relative to the amount of hydrogen in the fuel.
    I don’t have enough knowledge to know more about the topic but it looks like wood is 40 times less efficient than gas. I am sure there are a host of variables but that is the simple formula. How can you paint that green?”
    Isn’t that a completely different discussion – the discussion of fuel efficiency? And is the way you are discussing blind on one eye? The amount of natural gas (as well as oil, coal or uranium) on our planet is limited – and it’s use contributes a lot more to the global warming then the use of wood (as pointed out before) so it has a totally different environmental QUALITY as fuel – how can you compare it without looking at the point that every cubic meter of gas that you are using will be gone as CO2 and H2O into the atmosphere and that the CO2 WILL NEVER RETURN? How can you paint that more green?

    And indeed: suicide isn’t a solution – as after that some CO2 emissions will occure…


    European Woodfire Conference
    Markus Boehm

    web :
    fon : +49 (0)39833 22219
    fax : +49 (0)39833 22252
    mob : +49 (0)171 1710799
    snail : Alt Gaarz 6, D-17248 Laerz, Germany


    • togeii Says:

      Hello Markus,
      I can understand why the idea that wood firing is a carbon additive process creates a lot of hostility. I have been fielding very hostile responses from both Australia and the U.S. For that reason I have checked out of the discussion on line. I am still researching the questions I am attaching at the bottom. My preliminary research suggests the stance taken in these two papers is not correct. The two papers I am talking about can be found here,
      The easiest papers I have found to understand can be found here,


      There are many more papers but they are far more technical and I will cite them in my research.

      I would like to send you a link since you asked for some hard data on long term soil sequestration. My wording was a little sloppy in my blog post. I would change it from

      There is the additional problem of what seems to be the 50% or so of carbon that goes into the soil for longer sequestration in natural decay of wood. This sequestration in itself isn’t carbon neutral but seems to be a carbon sink.


      There is the additional problem of what seems to be the 30-40% or so of carbon that goes into the soil and the forest floor for longer sequestration in natural decay of wood. This sequestration in itself isn’t carbon neutral but seems to be a carbon sink.

      I would point you to this study,
      Please don’t read this as the final word. It is part of my preliminary research. It states clearly that there are many more studies on different variables that need to be carried out in order to come to conclusions.
      Please feel free to post to the Australian list. Thank you too for asking for hard data. You were the only one to ask for such data.

      The main questions I am trying to answer for myself are

      What is the efficiency of wood in relation to other types of fuel. That is to say how much of the power is lost in side effects, i.e., boiling off of water, etc.

      What is the carbon differential between standing and cut lumber? What is the total carbon for “waste” wood.

      · What amount of total carbon in a tree is returned to the air through regular decay processes?

      · What amount of carbon is retained in the soil or otherwise not released back in to the air?

      · What amount of carbon is converted to other compounds through either being digested or other trans-formative processes?

      · What is the time line for the decay and release of carbon from all processes in a decay scenario?

      · Can the natural decay cycle be seen as a carbon neutral, carbon additive or carbon “sink” event with regards to the environment?

      What is the area needed if you grow your own wood in order to stay carbon neutral?

      What is the use/replace ratio expressed in a plant-able area figure? This question is closely related to the one above.

      What is the carbon input needed for oven-drying lumber. This will affect the waste wood input.

      I am sure I will have more questions. I should stress the blog post you are reading is an initial statement of what I thought. I am also a wood firer and am researching these questions for my own interest. I am not trying to get anyone to quit wood firing. It is ridiculous the reaction I have gotten. The questions haven’t been researched and should be. The over reaction of people is stunning. You are the second person who has used the word suicide.

      For those who aren’t subscribed to the Clayart list these are two posts I have put there.

      There are a lot of very helpful and interesting papers on the topic of wood acting as a carbon “holding company” . which is a pdf file. There are two tables at the bottom that are well worth a look. is another. Take a look at figure 1.
      These are two easy to understand studies. There are tens more I am looking at and none of them suggest that burning of wood is carbon neutral. The studies are done by researchers looking into questions that differ by study but none of them see cutting wood as an exercise in putting a little in the bank and being able to take it out later. This is the basic model being offered by most wood firers.
      The question of if “waste” wood is carbon free is addressed in the Carbon and Forests paper I linked to above. It clearly states there is about a 20% long time carbon sequestration gain in converting litter to chips and then making products out of them.
      The idea that oil derived fuels or coal should be kept in a carbon sequestered state, not burned, but that somehow since wood is renewable it is OK to burn isn’t supported by any data. The 2 papers linked to, 2 of many, stress the time factor in determining the effectiveness of wood as a carbon sink.
      Here is something from another paper.
      This is taken from a report compiled by a forest products company. One would expect them to give a sympathetic ear to cutting.
      Begin cut and paste.

      It may take 150 years for regenerating trees on each

      coupe to recapture carbon removed during timber


      End cut.

      From a different source. This is from an environmental impact report.


      It is impossible for a biomass power plant that burns existing forests to be carbon neutral since any increase

      in forest cutting negatively affects the current baseline condition of forest growth versus cutting and

      mortality. Furthermore, it is the overall carbon emission input rate into the atmosphere from an energy

      source that matters, because overall carbon sequestration rates can not be expected to increase to make up for

      increased carbon inputs. With biomass burning of existing trees, the overall sequestration rate may even

      decrease because of the impacts on the forest, creating a double whammy.

      End cut.

      The total carbon sequestered in a tree isn’t equal to the carbon it takes to plant the tree and grow. The tree sequesters more carbon as time passes, peaking at about 75-120 years depending on the tree. The carbon content of a tree is roughly 50% of weight. That is a lot of carbon to throw out into the atmosphere in one go. It is especially important to note that the baseline rate isn’t going to magically increase just because trees were planted to “offset” cut trees. Take a look at Figure 1 in the second paper I linked to.

      It seems the logic of wood firers is that since oil and coal are final units in the carbon cycle it isn’t OK to burn them but since wood isn’t a final stage unit is is OK to do what one wants with it. Wood has to be seen as a carbon sequestering medium to understand its function. It is sticks of carbon. There is a balance that is maintained in nature that can’t be sped up or slowed down depending on the needs that are at hand.

      My original post to the list was for data on wood, electricity and other fuel amounts. I have gotten data from a couple of people off line for gas and electrical. I have found a simple way of figuring the carbon footprint for wood if the wood was prepared without producing any other carbon inputs. The carbon output would be .5 of the input weight. The output for gas and other fuels is in some sense easier to figure as a lot of work has gone into those calculations.

      Back to preparing for my next firing.


      Claudia wrote,
      the forest burns NATURALLY every 50 or so years

      My reply,
      That is exactly my point. Thank you.

      We just finished a wood firing last night and I don’t feel the least bit of guilt.

      My reply,
      Good, me neither.

      Robert Harris wrote,
      However some of your points are a little skewed.

      My reply,
      You and my wife agree on at least one point.

      He also wrote,
      For starters I am
      going to assume that when we talk of a carbon footprint we are really
      talking about a method of measuring our impact on global warming through the
      “Greenhouse Effect”

      My reply,
      No, I am talking about the amount of carbon wood firing puts into the air.

      He also wrote,
      In burning at a higher temperature you are certainly burning more cleanly –
      that is more of your wood is being turned into Carbon Dioxide (the main
      greenhouse gas) and water. However this actually means that when you burn a
      piece of wood you get closer to the theoretical amount of CO2 that can be
      produced – instead of producing a large amount unburnt (or not quite burnt)
      material. Which of course is more likely to cause respiratory problems but
      adds less to the greenhouse effect.

      My reply.
      Clean burning doesn’t matter.
      All the studies I have read say all the carbon from a tree eventually goes back into the air.The efficiency of the burning doesn’t matter for what I am talking about. The inefficiently burned wood is in effect being rendered to a state that facilitates decomposition, that is to say it will return to the air faster. I would like to see some writing that says that efficient burning of wood somehow reduces the carbon content. It doesn’t. It only reduces other more visible byproducts such as large and small particulates. I haven’t read a single mention of methane byproduct from natural decomposition. Can you provide any studies that mention methane production in the time frame of natural decomposition please. This link, talks about active production of methane as an energy source. I don’t know enough about it to say anything.

      He also wrote,
      If the wood is added to a compost heap then far more of the carbon will be
      trapped (as organic material) than if the wood were burnt. Of course
      depending on how it is decomposed some of it might be turned into methane
      which is a far far more potent greenhouse gas than CO2.

      My reply,
      I can’t find any data to suggest natural decomposition in situspan> causes methane production. I am not talking about disposal of wood in compost heaps. I am talking about how much carbon wood firing puts into the air.
      Carbon trapped in the soil will eventually return to the air but at a much slower rate. This is in keeping with the natural carbon cycle. Burning it speeds up the cycle. This seems to be the crux of the problem. In my last message I had a couple of extracts from studies that unequivocally say burning wood isn’t carbon neutral. I would like to see some studies that say it is neutral, or that it somehow reduces the amount of carbon in a piece of wood. Does anyone have links to these types of studies? All studies state without question that the time frame is important. Speeding up the time frame renders the tree carbon negative.



  9. John Dorsey Says:

    Dave – I really appreciate your research and being the vessel for this discussion. I am so intrigued and will keep up reading and inputting when I find something relative…

    Best – John

    • togeii Says:

      Hello John,
      Thank you.
      It really is a topic that is interesting and should be researched. I hope you can participate in a webinar I hope to hold when I am ready to present the data.

  10. How did my carbon credit end up in your kiln? « Togeii's Weblog Says:

    […] blog post of about a week ago has provoked a lot of discussion on a couple of ceramics lists in the U.S. […]

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