the village idiot

We had agg221 (arbtalk member) over with a rig he made up specially to measure the constituents of the off gas. I'll see if I can dig out the results.

That's interesting. I hadn't heard of converting chip to biochar in ring kilns before. Would certainly bring the cost of production down. I'd be worried that the emissions from the ring kilns (methane in particular) might counteract the environmental gains from the biochar? I wonder if he can 'flare off' the gasses from his ring kiln chimneys, cutting his emissions and maybe harness that heat too? You can link retort kilns together too and use the excess wood gas to fire the next kiln in line.

Blimey! Thanks Bolt. My main focus was to try not to initiate a climate change argument. We've got other threads for those!

SHIPPING LANES. Summer 2018 saw the return to the Wood of our good friend John Shipp. His task this time was to thin a large stand of predominantly Sycamore which had started to monopolise the 'classic' ancient woodland species in a portion of the South of the main Wood. Sycamore is not considered a true native species of the UK. It made the mistake of arriving onto our shores a little too late to appease the boffins who came up with the classification. A lot of woodland managers cannot abide Sycamore and will pull out any saplings that dare to poke their head above the humus. Personally I don't have any particular grudge against it. Sycamore has been around long enough for many species to have become adapted to make use of it, including us humans. Sycamore is a good firewood, a nice carving wood and is highly sought after as a veneer. Rippled Sycamore is used to make violin and cello backs and commands an extremely premium price. Sycamore does tend to get a little dominant if not kept in check. It seeds prodigiously and casts a dark shade which inhibits the growth of other species. Managed well though it can form a welcome part of your woodland mix, and we might well be very glad of it once our Ash populations are decimated. John got going with the thinning, taking out about 30% of the stems which we had marked up in advance. The ground conditions were a little soft so John used his grab digger to construct brash mats with the branches of the felled trees. These formed 'highway routes' for the extraction, the branches cushioning the considerable weight of the tractor and fully loaded timber trailer. These brash mats break down pretty quickly and there is no sign of them after a few years. Once the felling was complete and all the timber extracted we were left with a lovely open stand with lots more light getting through to encourage the understorey. John stacked all the timber roadside ready for the timber lorries to come and take it to the firewood merchants. On this occasion no monies changed hands. We did a good old fashioned barter. John received the revenue from the sale of the felled Sycamore and in return did a good few days forwarding timber for our own firewood operation. This was from the ride widening work Steve and I had been busy with the previous winter. There was far too much timber and far too long an extraction route for us to manage alone with the limited kit we have. It felt nice to do a barter and I will always consider it as a potential option into the future when other jobs come up.

BIOCHAR. Whatever your personal take on the role played by our species in the alarming rise in global temperatures, what cannot be disputed is that global warming and levels of carbon in the atmosphere are intrinsically linked. If we are going to halt the increase in global temperature and prevent an unprecedented amount of future suffering we are going to have to find ways to remove carbon from the atmosphere. Trees and Woodland can be a huge help here. As you all know trees contain a large amount of temporarily stored carbon removed from the air as carbon dioxide. This carbon is released back to the atmosphere when the tree decomposes or is burned to ash, making trees effectively 'carbon neutral'. If more of the Earth's surface is planted up with trees or left to naturally regenerate and is kept as tree cover into the future the size of this 'carbon bank' will increase. If carbon is in trees it is not in the atmosphere. What would be even better is if the carbon stored in trees was not released back to the atmosphere when the tree dies. This is where Biochar comes in. Biochar is essentially just charcoal broken down into smaller pieces and sometimes 'charged' with nutrients. Charcoal is a very stable form of almost pure carbon. If it is incorporated into the soil it does not break down for hundreds, even thousands of years. Organic material converted into charcoal and buried will not release it's carbon back to the atmosphere for a very long time indeed, giving the atmosphere some much needed breathing space and us humans a chance to get our act together regarding our choice of fuel sources. Biochar incorporated into soils also has the additional very important benefit of improving soil quality, especially where soil fertility is poor. Under a microscope you can see that charcoal is composed of a multitude of tightly packed tubes (the tree's water and nutrient channels, the xylem and phloem, are preserved in the charcoaling process). Once in the soil these tubes attract water and micro-organisms that benefit plant growth. The tubes also hold onto fertiliser, stopping it leaching down to regions below where the plant's root systems can access it. This means that less fertiliser needs to be used to achieve good crop yields, another huge carbon saving. Trials with biochar are still ongoing, and at present it is only really marketed to gardeners and hobby growers. If scientists do prove that charcoal/biochar can live up to it's promise then production could be scaled up massively, improving crop yields, reducing fertiliser use and just maybe saving the planet. Not bad going for the boring old black stuff that burns your burgers on the BBQ. That concludes this thread's delve into the world of charcoal. It's high time we headed back into the trees!

That's not the Hay Wain Paul. Not that it really matters, it's still a nice painting.

CHARCOAL. THE VERDICT. I had a lot of fun making charcoal for a few years. It can be quite a good option for a woodland worker as it uses up resource that you haven't got another use for and you can be doing other jobs such as splitting logs whilst the charcoal kiln is running, as long as you stay in the vicinity. I stopped making charcoal in 2016 (although I still have the retort kiln). There were a couple of reasons for stopping. When young Steve came on board I had to get a bit more business minded to ensure that we could both earn a living. It became very apparent that in our circumstances our time was much more profitably spent producing firewood rather than charcoal. In the time it takes one person to complete a full burn cycle producing £150 worth of charcoal this same person could have processed somewhere in the region of £800 worth of firewood. The other main factor involved in the decision to stop was the fact that the kiln had started to take on a rather different shape and was becoming harder to operate. This is a problem, to a greater or lesser extent, with all metal kilns on the market. When mild steel continually heats up and cools down you get warping. I had nearly exhausted my second inner chamber before the kiln had paid back it's initial capital cost. It is only fair to point out that my retort kiln was one of the first produced and it may be the case that newer incarnations are built more robustly. It is also the case that the first Exeter retort ever produced is still in working order and must have paid for itself several times over by now. I'm not sure how the owner has managed to achieve this, I always abided by the manufacturer's usage guidelines. It is my personal view that the Exeter I purchased in 2012 is not strong enough to be the backbone of a successful commercial operation. Other owners may disagree.The Pressvess retort kiln is more solidly built (using thick boiler plate for the charge chambers). The fact that it is not portable (the Exeter retort can be mounted on a trailer) will though be a deal breaker for some. Treewood Harvesting (remember Jake Fish taking out the conifers) had a Pressvess retort and that too was showing signs of warping fairly early on in it's life. The Pressvess retort: Ring kilns also warp over time but they are very significantly cheaper and cost effective to replace. There are people out there who have managed to maintain a viable business on the back of charcoal production. I was not able to but evidently it can be done. There is an additional product line which, if it takes off, could tip the scales significantly towards viable profitability. This product is Biochar and it has a few nifty tricks up it's sleeve. A lot of you will be familiar with Biochar already, but I will outline it's nature and it's promise in the next post for those that haven't heard of it.

That's the spirit Stubby, you've tackled far worse in the past.

Absolutely. And I'm sure you'll be full back to health in no time.

That must be very trying for you Stubby.

It would be very quick to do with a chainsaw and 'too deep' presumably wouldn't matter for firewood. I have an issue with Birch going soft in the round (5 mtr lengths), extracted after 3 months down, and then in the stack for two months.

Titty height? Encouraging to see you are already adopting officially recognised forestry terminology.

Do you happen to know how deep they make the cut? I tried this method once without much success, but I only skimmed the surface.

Cor! What a beautiful spot. I foresee a very fulfilling retirement. Presumably those are your spruce in the background? I look forward to reading your updates. My personal knowledge is fairly specific to the type of woodland we manage, but there is a huge resource of tree knowledge on this forum. You certainly won't need a gym membership, not with those slopes!

CHARCOAL II, OR MAYBE IT'S III ? I'M AFRAID I'VE LOST TRACK, I'LL GO BACK AND CHECK. NO, THAT WOULD BE SILLY. BUT THESE THINGS MATTER TO SOME PEOPLE. BARE WITH ME A MINUTE. OH JUST GET ON WITH IT! I THINK I'LL JUST GET ON WITH IT. In the previous main post I described the mechanics of a charcoal burn with the Exeter Retort. There is a little further work involved before you have nicely bulging bags of finished product. The kiln takes quite a few hours to cool down. I always left it overnight. by the time you come back to it the next morning it is almost always down to ambient temperature. You can check the temperature on the digital thermometer, if it tallies with the atmospheric temperature outside you know it is safe to open up. The Exeter retort makes fantastic charcoal. I never had any unconverted wood in the whole time I was using the retort. Upon opening the outer and inner door on one end you are greeted with a kiln just over half full of gently tinkling charcoal. The volume drop is due to the fact that most of the constituents of the wood (primarily water) have been driven off, leaving behind surprisingly pure carbon. The wood looks exactly the same as when you loaded the kiln only it has shrunk and is jet black. The bark and all of it's texture is perfectly preserved. You can actually convert any organic matter into a pure carbon form in a retort. For a while I was sticking all kinds of things in to see what would happen including flowers, skulls and bananas?. Even a feather comes out in pristine carbon form, although it disintegrates as soon as you touch it. Of course at this point any normal person's brain turns to dead bodies, my brain was no exception. It would be perfectly possible to convert Granny into charcoal and then use her (literally) to cook the sausages for her wake. If anyone has ever had a better idea for a business model, I am yet to hear it. One of the many benefits of a retort over a ring kiln is that you don't have to climb in to empty it. The charcoal can all be scraped out into a receptacle using a modified long pole. The process only takes a few minutes. You can then re-load the kiln and do another firing the same day. In theory you can do a burn a day with a retort kiln, although I found that a burn every other day was more realistic. With a ring kiln, this quick a turn around would be nigh on impossible. Before the charcoal can be bagged up it needs to be graded. This is a simple process of passing the product over a mesh screen. The small chunks (fines) fall through and the lumpwood charcoal makes it's way to the end and drops into a waiting bag. The bags are then stapled or stitched up, and you are done. The Exeter Retort has in internal volume of 1.7 cubic mtrs and returns on average around £150 worth of charcoal per burn. This does not compare very favourably to firewood so it is best to convert wood that you have no particular other market for. Overstood Hazel is ideal as although it is fantastic firewood it is relatively difficult to sell as customers have been conditioned into expecting split logs. There is more to report on the retort kilns (including an intriguing scientific experiment we were party to) but be warned it is not all totally positive. In the next post I will give you my personal opinion on whether I think they are unilaterally a good investment. Also some info on biochar, a very interesting by product of charcoal manufacture.

WOW! That's a fair old stroke of luck. What a fabulous looking place. You've already got some fantastic habitat there by the looks of things but there'll be lots you can do to improve it further. Where abouts are you? And thanks for the kind words!

arf arf!

It's not, but it could actually be used for this. The problem would be the batch size. You would only get 1.5 cubic mtrs of firewood per run, and even with the high price that kiln dried can fetch, the numbers would not get close to adding up.

Thanks sandspider, it's not too shabby is it.

Nice one Ti. Is this at home or at Betel, or are they one and the same?

Hmmm, that's a shame. I wonder if they have considered the fact that once the Ash dies and topples over they are going to have a fair bit of trouble shooting and riding? Scrub is good, and other trees will colonise in time to take the place of the Ash. It would be good though, as you say, if the Ash was used for something. I'm going to a Woodland Communication day in a couple of weeks. One of the speakers is talking about managing woodland with Ash Dieback. I'll report back on what the latest advice is.

Thanks Lucan, You raise a very valid point. Ash stools of this size sometimes don't regenerate after being cut. We will take the risk as if we don't coppice it will not be too many more years before these stems fall anyway under their own weight. This cleaves the stool open and often kills the tree. We are also in the epicentre of the Ash dieback outbreak. I have not seen an Ash in this Wood in the last two years that isn't on it's way out, and we have a lot of Ash! We will leave a certain percentage of stools as standing dead wood for habitat but the vast majority will be coppiced assuming we can get to them in time. We are not certain that we will lose pretty much all of our Ash but the omens are not good. The firewood that the felling generates will help to fund our activities to keep the Woodland thriving in the wake of Chalara.

Just a quick flash forward to a couple of pictures from today. It was a lovely morning when we first got to the Wood: We are coppicing Ash in a compartment at the moment. This picture will give you an idea of the sort of size a lapsed coppice Ash can get to. Steve is not a small chap.

Quite a high percentage of unmanaged woodland is used by their owners for shooting. Management works like the ones I have been describing make fantastic habitat for game birds and vastly improve the lines of sight for gun stands. One way to get an 'in' might be to pitch the benefits to their favourite sport. I would think that a marvellous day's shooting is as good as money in the bank for a lot of land owners.

RETORT KILNS. Retort kilns differ from ring kilns in two fundamental respects. Firstly, in a retort kiln the fire used to fuel the process doesn't come into direct contact with the wood you are trying to convert. Secondly, a retort kiln 'recycles' the flammable wood gas released by the converting wood, feeding it back into the fire to produce a self sustaining loop. This 'gas capture' system results in a retort kiln being not only significantly more efficient but also dramatically less polluting. Un-burned wood gas, which can billow for hours out of a ring kiln is not nice stuff. There are a few different designs of retort kiln, though really only two or three serious manufacturers in the UK that I know of. The two types that I am most familiar with are the Exeter Retort which has a long firebox underneath the charge chamber but isolated from it, and the Pressvess Retort which often has two charge chambers side by side with a separate firebox between the two. They essentially work in a very similar way. I'll describe the process involved with the Exeter as this is the kiln that I have. I purchased Puffing Billy in 2012. It was the second machine off the production line. Stubby's mate Alan Walters has the first. For those of you paying far too close attention you will have noted that this was before I had started in the Wood. My first forays into retort charcoal production took place at the farm where I was working on the ice cream. Ice cream and charcoal are not easy bedfellows and I was continually having to go for a scrub up. These pictures of Billy were taken at the farm: As you can see from the picture above, the Exeter Retort is composed of an inner 'charge chamber' where you put the wood you want to convert, and an outer chamber that surrounds all the gubbins. The outer chamber has a double skinned wall filled with insulation. The ash at the bottom shows the front end of the firebox, this is accessible when the kiln is closed up through a hatch in the outer doors. The eagle eyed among you will be able to make out three structures on the top of the kiln in the top picture. All three are chimneys. The tall one in the middle is the flue for the firebox. The two either side are plumbed directly into the inner charge chamber and allow the water vapour from the charge wood to escape. To operate the kiln you fill the inner chamber with as much wood as you can fit into it, preferably much more efficiently than I have managed in the photo example! The Exeter retort can be loaded from both ends. The charge chamber is then bolted shut. The doors are sealed with large diameter fire rope. The outer doors are then also bolted shut and the chimney caps removed from the two short chimneys. You are now ready to start the burn. The process begins by lighting a fire at both ends of the firebox. There are hatches each end of the insulated outer doors to enable access. You keep feeding the fires with very dry wood (I used free pallet tops from a local office supplies firm). After a few minutes the fire extends the full length of the kiln. The fire feeding continues for about 2 hours, at this stage in the burn the two small chimneys are belching out copious amounts of very white and cloud like water vapour, even with very seasoned charge wood. After about 2 hours the water vapour starts to take on a yellow tinge. This is a sign that the charge wood is running out of moisture and starting to emit wood gas. Wood gas is highly flammable stuff and not to be wasted, so when the emissions become predominantly yellow the two chimneys from the charge chamber are capped. This diverts the wood gas via two tubes directly to the firebox underneath. From this point on the conversion process is entirely self sustaining. The kiln runs off it's own juices. The amount of energy stored in wood is phenomenal. The two gas pipes literally roar with intense flame sometimes for up to 8 hours. Left alone during this phase the internal temperature of the kiln would sky rocket and melt the retort. It is the charcoal maker's job to keep the internal temperature at around 550 degrees C. This is achieved very easily by tweaking a butterfly valve in the main chimney leading from the firebox, or opening and closing the firebox doors. There is a digital thermometer mounted on the side of the retort for monitoring the temperature of the flue gasses from the charge chamber. This gives a good approximation of the temperature of your converting wood. When the gas peters out the conversion is complete. The kiln is shut down by closing the outer doors and the butterfly valve, and all you can do then is wait for it to cool down and eat your beautifully toasted savoury snack which has been warming on the thoughtfully included pasty shelf. (No extra charge) To be continued...