Deep soils store up to five times more carbon than first thought: study

“Deep soils store up to five times more carbon than is commonly reported, a new study by Murdoch University and Cranfield University in the UK has found.

Soil locks in greenhouse gases by storing carbon, making it a crucial player in the fight against global warming. Greenhouse gases are released when soils are exposed to air by farming, peat drainage and deforestation.

Current estimates of soil organic carbon are based largely on measurements to depths of 30 cm. This approach has evolved in North America and Europe, where soil is generally more shallow.” …

This is currently being discussed on the international biochar-policy group, latest comment here…

I found a nice back-ground document on soil carbon in NZ, Co/ Prof. Louis Schipper’s Waikato University page… scroll to…

“Soil Carbon and Nitrogen

If you are interested in learning about soil carbon or soil nitrogen, two non-technical articles published in the New Zealand Science Teacher can be found here – Soil carbon, Soil nitrogen.”

I’m not sure how old this article is… but it seems to imply that NZ soils under current farming practices are unlikely to become a useful carbon sink. Does this article need to be revisited with biochar application in mind?

TLUD Second burn

The Second burn of the TLUD was an attempt to increase the feedstock value by adding new material in through the secondary air gap during the process. WE started with a half barrel of chips as a way to test the process and it worked reasonable well, although possibly 20% of the material was untouched by the time the embers started to drop from the bottom of the barrel.

Some thoughts below the pics.

  • The supplementary feedstock did reasonably well in the time. Anything under about 10mm charred reasonably well, the pieces around 25mm had a solid, uncharred core.


Thoughts on the burn

  • Its possible that starting the burn with only half a barrel meant that any asymmetry in the lighting (with some diesel) was perpetuated because it had immediately to draw from below rather than getting a good, open, fire started before the process went anoxic.
  • Its also possible that the asymmetry of the air flow from below was wider spread than we thought and the unburned part of the barrel was completely starved of oxygen. I had assumed that the multiple pathways available through chip would tend to even things out, but apparently, once the burn pattern is established, you are stuck with it.
  • The initial temperature rise caused by the open fire front on the top may also have had something to do with the problem, if you can’t get the heat up to start with, the process can’t rectify that
  • Not sure about the amount of smoke produced. It wasn’t huge and it didn’t last long, but it was much more than the previous burn which used dried Sugu (cryptomeria japonica) foliage as kindling. Sugu burns very hot and immediately, that may be the key to smokeless startups.
  • I will not do partial burns in future and will make sure to get the widest possible fire front started above the feedstock charge before it depends on the up draft.
  • Getting the barrel further off the ground should improve the airflow and reduce any ground effect, plus give us more room to unblock inlets as needed.
  • I will also add a couple of steel bars across the top of the barrel to increase the air flow and improve combustion of the evolved gases, but that also demands building a retort to sit inside the afterburner, like this.
  • Supplementary feedstock needs to be reasonably dry and probably less than 15mm at its thickest point but I suspect can be of arbitrary shape and should be added as soon as possible once the top of the barrel is anoxic. A longer time in the barrel would have produced a better result and a more even burn below should create better charring conditions above.

Next task

Another burn. Add the steel bars which will also give room to add supplementary feedstock, probably put the failed feedstock from Thursday into the mix and give it another burn and try to find a 100-150 litre barrel to stand on top of the burn barrel as a retort.

I have 2 new WWOOFERS arriving Monday, guess what they will be doing.

Callaghan Innovation – biochar funding

Peter Kerr writes about technology funding in NZ from his StickNZ blog. He has had some harsh words to say about the process that has led to the development of the Callaghan Innovation (you can search his blog for this…

I note that his latest post discusses an important announcement that will be released today by CI. A quick look at the CI website reveals a “Fund Finder“. I’ve not explored this yet, but maybe a useful tool for biochar researchers, project, technology and product developers?

Your experiences with funding may have valuable lessons for others reading this post. Do consider sharing them.


AllBlackEarth – progress report

We have had 35 people sign up to date. That’s probably a 10% strike rate but early days yet. Plenty of names missing that should & probably will arrive in time. I hope we can circulate stats based on the signup form (interests, region) but I guess this can wait until our numbers stabilize and our structure / plans are agreed around a new management team.

NZBRC kindly provided a speaking slot for me, to announce the release of this website during this 4th edition of their annual workshop (4-5 July). I’m not sure of workshop numbers… looked to be about 50 participants. I’m not planning a synopsis on the workshop here (hoping others attending, more qualified than me, will step up for comment on this).

We hoped to gather those interested in the new group over lunch at the end of the workshop. My apologies for the poor organization of this – it failed to happen. But I think we may have identified at least 1 or 2 new potential organising committee members. I propose maintaining the G+ circle as the communication tool for the ABE management team. I will circulate a notice to the old team for each to put their hand up again, to see who is interest in continuing. If you are keen to help, then please let us know. Also interested in advice and suggestions on how to manage this process (I’m a novice at this).

Thoughts on the TLUD

About a year ago I asked an incinerator maker to build me a TLUD based on a design I’d seen on YouTube. Yesterday it worked properly for the first time.

300 litre TLUD burner

300 litre TLUD burner

The main burner barrel has 50 x 25mm holes in the bottom and stands on 3 bricks during the burn. The middle section is half a 300 litre barrel afterburner with a series of tabs cut in the lower edge. Tabs are alternately turned inwards and outwards. They both support and stabilise the afterburner and allow secondary air into the chamber. The flue is a 50 litre oil drum punched through; probably a bit too short and wide but it appears to do the job.

When I first tried it I used cryptomeria that had been through a mulcher and failed completely. Although cryptomeria is full of volatiles and should burn well, the chip size was too small and simply choked the fire. About a year ago we had a pile of old pine trees cut down and mostly chipped into pieces 10-25mm and now we have several large piles of chip awaiting use.

At the end of summer I had as much of the driest material as I could put into trays made of old freight pallets and stacked in the barn until the weather changed and the fire bans disappeared.

Pallet stacks with dried woodchip

Pallet stacks with dried woodchip

Yesterday, with the help of my mate Simon Coughlan, I filled the TLUD and set it off again. This time the burn was nearly perfect. It was smokeless from almost the first moment and 2 hours later the first of the embers started to fall through the air holes in the bottom so I doused it with about 50 litres of water.


  • The 300 litres of chip had almost all burned, about 5% uncharred material left at the end
  • Zero visible emissions from the moment we lit the top. After a long hot summer and another couple of months stacked in a breezy barn but out of the rain, moisture levels must have been pretty low, after comparison with known material at 25% I am going for under 20%.
  • The burn was silent so probably not a very strong draw but the product is very acceptable. Probably a better flue would shorten the burn time rather than improve the quality.
  • chip size and burn completeness

    chip size and burn completeness

    The char is mostly odourless and snaps/crushes readily, I’m pleased with it.

  • There was a very slight unevenness in the burn within the barrel, only visible at the very bottom with most of the unburned chip to one side, I’m guessing it was because that side was closest to a slight slope up from the concrete pad we were burning on and the air flow might have been slightly inhibited on that side.
  • There was very little smell of incomplete charring, again, guessing that it came only from the unfinished char at the margins.
  • The char is very hydrophilic, it soaked up the water really well and remains moist to the touch next morning.
  • Total product almost exactly 30% I put in 300 litres and carried away 5 x 20 litre trugs of material, including the incomplete char.

Next Time

  • Use taller bricks to support the barrel and possibly even out the air flow to reduce further the uneven burn. Its not critical but doing better is good.
  • Add fuel during the burn. As the charge in the barrel sank, I could see the twigs we used to start the fire sitting on the top, charred but complete so I could tell that the system was working and there was no air in the upper part of the barrel which was very hot.At that point I experimented with tossing in via the flue some random twigs lying about. Apart from one that caught on the top of the chimney, none of them produced any smoke so I am convinced that they dropped onto the top of the char bed and did not burn but rather pyrolised and all the off-gasses were then burned in the afterburner.I guess that since the upper part of the barrel is both very hot and oxygen free, we should be able to add an arbitrary amount of new material to the char bed as the process continues. The new material will not be able to cool the fire because that is going on well below the top of the char bed which itself will insulate the flame front and the flame is, in any case, being fed from below. As long as the new material does not significantly interfere with the gas flows (either by collapsing the char with extra weight so that the upper bed becomes impermeable to the gasses or by being too fine and acting as a blanket) we should be able to keep adding new material throughout the burn if we are prepared to accept that some might not be fully pyrolised at the end.

    Since the burn takes about 2 hours I’m thinking we can add new material from about 30 minutes in as the bed gets well below the top of the barrel and keep adding until about 90 minutes in and still expect to get it fully charred.

    The good thing is that size should not matter. If there are too many small pieces in the original charge they snuff out the air flow, if the pieces are too large they create uneven pathways that make the burn too assymetrical, but once the flame front is well buried in the charge, the size of the pieces being added should be irrelevant as long as they are not too heavy for the char bed or too thick to fully char in the available time.

    Another plus is that the extra fuel will have no production cost. All of the chipped fuel/charge has to be run through the chipper which has a cost, but picking up random rubbish fuel from anywhere that can be added later has a production cost close to zero;the rubbish needed picking up anyway and there are no extra processing steps. That should make the resource cost efficiency as high as possible with this system. I’ll be interested to see how high a moisture content we can get away with.

    I will make a stack of larger pieces and probably add them by removing the flue temporarily. Although a design with a sealable feeder chute would be better, if anyone has a design for one let me know in the comments.

The Future

  • I am unhappy with the amount of waste heat the system produces, If I had been able to capture the energy given to heating the air around the barrel I could have baked 20 loaves of bread or roasted a meal for 6, possibly while doing a stir fry on the top of the afterburner.From a sustainability and energy efficiency perspective, there is a crying need for an equivalent of a wood-fired pizza oven that will do some real work with the heat while producing the charcoal. I’m prepared to put some $$ into a real idea for that.

Carbonisation of biomass-derived chars and the thermal reduction of a graphene oxide sample studied using Raman spectroscopy

John McDonald-Wharry, PhD candidate from Waikato U. has kindly provided a link to a newly released paper on his work. He will be presenting related to this at the NZBRC workshop on 4 July with the title “Studying Carbonisation with Raman Spectroscopy”. Continue reading

Big Biochar Experiment

Cecile Girardin from Oxford Biochar presented results from the 1st year of the Big Biochar Experiment at the recent British Biochar Conference (I will post separately on this conference).

I’ve had a dialogue going with Oxford Biochar since early last year about expanding their project into NZ and SEA. They have had quite a few of these inquires and are keen to collaborate but have been hampered by a lack of resources. We plan to re-engage on the subject soon. I hope we can pull together a NZ version of this work. This could be as simple as local gardeners signing up to the UK site or a collaboration on a new local project. We need to sort out NZ biochar supply issues but that will be an exciting challenge for aspiring local producers.

The biomass used for biochar, its preparation, biochar production methods and process conditions, along with pre-application processing, create numerous variables even before you get your biochar in the garden. These variables could be reduced to some extent by providing the same biochar to all participants… but then we would only be testing one biochar.

I like the idea of opening the project up to all potential biochars with data gathered on their production. Maybe project funding could be sort to test each char as a science collaboration.

Biochar Education

The ABE site will have a lot of valuable research results. On the education page, I would like to see some interpretation of these results for gardeners and small farmers, as well as more conventional farmers, with practical help in implementing the information.

I’m not sure how to achieve it, but education usually works best when actually demonstrated in practice to interest groups – maybe someone able and willing to do presentations on biochar, as the practical extension of the website?