Firewood and Kindling Drying Kiln

timfromtang

Greetings All,
I am fairly new here (although not to the forest) so please be gentle.

Can anyone offer me advice concerning kiln drying firewood and kindling. I need a capacity to dry about 40 pallets a week.

I would prefer a diy/low capital solution

I would plan to use wood as a fuel for the heat

I am also open to commercial solutions

Are there any irish firewood kiln manufacturers?

Anyone got a kiln for sale or swop?

Sláinte

timfromtang

bogman_bass

is it economically viable to kiln dry firewood?

TomOnBoard

bogman_bass wrote: »

is it economically viable to kiln dry firewood?

Good question that will no doubt elicit differing opinions.

To my mind, much depends on the moisture content that you want the end-product to contain. As a generalisation, anything much less that 20% m.c. will not be maintained in Irish conditions for more than a few days in Autumn/Winter. If its below that coming out of the kiln, timber will take in moisture from the air and end up at/around 20% anyway.

The energy needed to expel moisture to any desired m.c. (using heat and/or air circulation) needs to be costed in along with any investment in sheds/drying stores/equipment etc to answer the question. If you have low cost energy, and facilities that can be easily converted to suit the drying process, AND you end up with a quality product that produces a good NET return, then it may be very economic. However, if you end up burning a metre of wet wood to dry another metre of wet wood, you may be better off just selling the 2 metres of wood off as just that- wet wood. Economies of scale would be very important here.

ford2600

In a country where people don't understand mc for most part, probably not.

If you have a decent quality stove and a decent quality installation I'd be spending on good wood or drying it well.

I've got super dry bagged firewood, @ slightly less than 20% but have started burning myself rather than competing with lads selling sh1te to same market.

A friend of mine has such a business, no idea how profitable it is or not.

TomOnBoard

ford2600 wrote: »

In a country where people don't understand mc for most part, probably not.

If you have a decent quality stove and a decent quality installation I'd be spending on good wood or drying it well.

This is true.

I'm constantly amazed by the number of people I come across who have spent maybe 1,200 to 2,000 on a thundering big water heating stove in their living rooms and can't understand why the manufacturers' claim of being able to heat 10 or 15 or some huge number of radiators can never be fulfilled and there they are burning (smouldering really) chunks of wet ould spruce that they bought "at a great price" and blame the stove, the plumber, the chimney and Uncle Tom Cobbley an'all, but can't see that if you feed sh!te into the stove, you'll get a sh!te response from it.

Most stove owners simply don't understand the fundamentals of wood-burning. As a result, they can never maximise the heating value of this resource which is one of the only true renewable sources of energy for heating that exist in an easily usable form today. Also as a result, people who try to provide a quality product in the form of well- seasoned firewood find it hard to compete with cheaper stuff that has not had the required care and attention to turn it into good fuel.

OK... Rant over!!

wayoutwest

OP -Apparently you can build your own log drying kiln using a shipping container, a sawdust boiler burner and lots of old radiators......if you've got the space and sawdust(it sounds like you have, if you are going to process 40 cube per week) - then it could be worth looking in to.

timfromtang

Hi all,
thank you for the replies, helpful and unhelpful

On whether it is economic or not to kiln dry......

well in my opinion the most economic way to produce wood fit for burning is of course air drying provided you are not renting expensive space or such,

In irish conditions air drying down to circa 25% mc is relatively easy

however from the point of view of selling the produce there is a premium for kiln dried stock

I am hoping to air dry down to at least below 25% (as low as i can go of course), and then finish with a kiln to 19%mc

So, on kiln suppliers???? any info?
anyone got a kiln to sell??
and indeed

has anyone built their own and prepared to share their experience with me?

Sláinte
timfromtang

TomOnBoard

timfromtang wrote: »

I am hoping to air dry down to at least below 25% (as low as i can go of course), and then finish with a kiln to 19%mc

I reckon we probably went a good bit off topic by going down the economics route as the O.P. seems to have really wanted answers relating to the kiln-drying plant.

However, that last message flummoxed me. Sorry, I can't leave it:

Whatever about using such an economically marginal technology as kiln-drying to get m.c. from 65% to 20%; using it to get m.c. from 25% to 19% seems wrong on soooo many levels...

timfromtang

TomOnBoard wrote: »

I reckon we probably went a good bit off topic by going down the economics route as the O.P. seems to have really wanted answers relating to the kiln-drying plant.

However, that last message flummoxed me. Sorry, I can't leave it:

Whatever about using such an economically marginal technology as kiln-drying to get m.c. from 65% to 20%; using it to get m.c. from 25% to 19% seems wrong on soooo many levels...

Many Thanks Tom constructive criticism is always welcome
Please can you elaborate.....


It may be naive to think that drying from 25 to 19% would use considerably less energy and time than from 65 to 19????, that i can build a cheap and effective kiln enclosure from plastered straw bales (live in a straw bale home so have the expertise required here), that i can supply heat from on site woody waste, that i can perhaps use some spare mechanical capacity of the tractor running the wood processing machinery to run some fans too........... That Genuinely kiln dried and neatly presented logs and kindling command premium prices?????

I would welcome to opportunity to talk with you or any other with expertise in this area, I am open minded and friendly and will not bite.

I am open and always happy to be corrected, i do not percieve being told i am wrong as an attack, but as being "helped"

i am contactable as timfromtang on skype or gmail

If it were not for the my perception that the market "requires" or "would prefer" kiln dried i would of course prefer to air dry my produce.

tim

wayoutwest

Timfromtang -Are you planning on kiln drying 40 cubic metres of logs per week? If you were going to process spruce, which needs air drying for upto two years (to achieve your desired 25% mc),then you are going to need a LOT of covered, well ventilated space to dry a couple of thousand tonnes of chopped logs....have you considered this?
I would imagine that such a large operation would require some sort of planning permission.....a kiln made of straw might make that hard to get.

timfromtang

wayoutwest wrote: »

Timfromtang -Are you planning on kiln drying 40 cubic metres of logs per week? If you were going to process spruce, which needs air drying for upto two years (to achieve your desired 25% mc),then you are going to need a LOT of covered, well ventilated space to dry a couple of thousand tonnes of chopped logs....have you considered this?
I would imagine that such a large operation would require some sort of planning permission.....a kiln made of straw might make that hard to get.

Howdy,
I have access to space
I have access to forest
I have considered the air drying

40 M^3 per week would seem a small enough volume of a low value item like firewood, rough planks and posts and kindling for 2 men to make a living and pay for a machine or two wouldn't you say?

Quality Quality Quality

I have robust and effective air drying procedures in place for my already established firewood customers (much smaller volume we are currently expanding). These should scale nicely to my planned output.

wayoutwest If you had read my post carefully you would have noted this
"
that i can build a cheap and effective kiln enclosure from plastered straw bales (live in a straw bale home so have the expertise required here),"

I'll build one for you too after my own if it works out, and expect a kiln enclosure made from bales of straw to be CHEAP CHEAP CHEAP

keep em coming
tim

TomOnBoard

timfromtang wrote: »

Many Thanks Tom constructive criticism is always welcome
Please can you elaborate.....


It may be naive to think that drying from 25 to 19% would use considerably less energy and time than from 65 to 19????, that i can build a cheap and effective kiln enclosure from plastered straw bales (live in a straw bale home so have the expertise required here), that i can supply heat from on site woody waste, that i can perhaps use some spare mechanical capacity of the tractor running the wood processing machinery to run some fans too........... That Genuinely kiln dried and neatly presented logs and kindling command premium prices?????

I would welcome to opportunity to talk with you or any other with expertise in this area, I am open minded and friendly and will not bite.

I am open and always happy to be corrected, i do not percieve being told i am wrong as an attack, but as being "helped"

i am contactable as timfromtang on skype or gmail

If it were not for the my perception that the market "requires" or "would prefer" kiln dried i would of course prefer to air dry my produce.

tim

Tim,

I'll take you at your word that you don't bite LOL!

Ok, Here's a bit of elaboration, and if it is too techie, remember you asked for it...

The first issue is the science of the thing. Green wood is comprised of fluids and solids with some vapours, although the latter are negligible for the purposes of this discussion. The wood is the substance that contains all those fabulous chemicals that are the real fuel; the fluids are predominantly good old H2O.

The H20 is held in the wood as free water (FH2O) and bound water (BH2O). Over time, the FH20 will leave the wood by capillary action until the MC in the wood is equal to the Relati9ve Humidity of the air immediately around the piece of wood. Now, we're at the Fibre Saturation point (FSP) and you basically have air-dried wood with a MC between 25% and 30%, although some species like Birch have an FSP as high as 35%.

A kiln could be used to arrive at the FSP and obviously it will get to the FSP much more quickly than air drying alone. Circulating air around the stack also speeds up the process. But what about drying even further, i.e. getting MC lower than the FSP??? Well, that's the nub of the problem.

Remember that BH2O? Well, its more or less still there in the wood and is much more difficult to shift that the FH2O. It is bound to the wood cells by the Hydrogen component of the H2O molecule and needs considerably more energy to release that water.

In your scenario, the air-drying will get your wood to the FSP before it goes near the kiln. As Relative Humidity fluctuates in the air, it will also fluctuate in the wood. Therefore, if you dry the wood (using a kiln) to say 5% MC, it will absorb moisture from the air until it reaches equilibrium with the MC of the air.

So, in summary, the science of the process will mean that:

1. It will cost significantly more to kiln dry from 25%MC to 19%MC than it would to achieve the same 6% result above the FSP;
2. Once the wood has been kiln-dried, it will need to be sold and/or used quickly, before it absorbs moisture; otherwise large, expensive, humidity controlled storage areas will be needed.
3. You will be using large amounts of energy to achieve the objective, and regardless of the source of that energy, it will create higher costs and levels of waste by-product (including pollutants).

The second issue deal with the perception that kiln-dried is better, and therefore will attract a price premium. Well, I would defy anyone to show me a better result from say 1-week Kiln-dried Ash at 19%MC than from 2-year Air-dried Ash at 25%MC, except in the smallest and most sophisticated Gasification boilers/stoves. I do accept that the presence of a label that says "kiln-dried" will sway some potential buyers, although over the medium-long term, if you're providing a quality product to your consumers, they will return again and again, regardless of that label.

A related issue is that of the price you can achieve. Staying with Ash, I can get a loose Cubic Metre delivered for €85 from a lovely local man who is just making a few bob on the side of his farming activity. If I want Kiln Dried Ash delivered, it'll cost me €180 per loose metre from a local hardware store. Would I pay such a premium? Not on your nelly!! I'll take 2 metres from the nice man any day of the week. Why?

Because he is a nice man, has a good reputation passed by word of mouth and provides good customer service.

The third main issue with your scenario is the environmental footprint. As someone involved in Forestry and related activities, I take the environment very seriously (as I'm sure a straw-bale man like yourself does equally, if not more so). Your scenario seems to me to be unduly industrial in its orientation all to achieve what is, in my view, a negligible benefit.

I'll leave it there for now. I hope this elaboration helps…..

I'll come back to the Straw Bale building... (after my fingers recover from typing this)...

wayoutwest

Tim -I have read your post carefully, and ..er no...please don't come and build me a straw bale kiln enclosure - my O.H already thinks that I have an unatural obsession with piles of wood....another fuel producing structure in the garden could be the ..ahem...'last straw'.:)

timfromtang

wayoutwest wrote: »

Tim -I have read your post carefully, and ..er no...please don't come and build me a straw bale kiln enclosure - my O.H already thinks that I have an unatural obsession with piles of wood....another fuel producing structure in the garden could be the ..ahem...'last straw'.:)

I too obsess about piles of wood, lovely saved up sunlight that it represents, and magically releases that saved up sunlight in our fireplaces too WOOHOOO!
tim

timfromtang

Tom,
Thank you for the explanation Very helpful indeed

I am one of those local farmers (selling air dried hardwood by the trailer load)
and looking to upscale a bit (100 acres of trees we have converted to forestry on our small farm)

We did our first thinning and tending operation on 16Ha summer 2013 and removed some 48,000 stems. Of this only the Larch remains the rest being sold or spoken for. The butts of the larch are suitable for fencing post and rough exterior plank manufacture (1998 planted and some are 30cm dia at breat height) and the remainder for kindling.


I dream of being able to make a living for my family and that of my sister from these 100 acres.
We planted in 1998, 2001, 2003, and 2011 and now the whole farm is Forest.
the long term plan:
to produce firewood, kindling, planks, Larch and Oak fence posts (square sawn and round) and to add value to these sufficiently to enable us to make a living from such a small area of forest. i.e. using diversity of products to realise new yields from the forest to increase income.
We have just also begun to explore the amenity and food yields that are possible from our forest too. Potentially each new yield can also include at least one new man or woman in the operation to help realise that yield.

I will take your advice and concentrate on using quality air dried stock for the kindling and firewood side of things. Buying in wood to feed the kindling and firewood operations at times we do not have timber from our own forest operations.

Knowledgeable and helpful you are.

Many thanks again
tim

jerryg

I dry my timber in a polythene tunnel and I find it very useful. It keeps the timber nice and dry and even on a sunny winters day you are still getting a drying effect.I still think that you need to let your timber mature for at least a year to two years to get it down to below 20% moisture content.

timfromtang

jerryg wrote: »

I dry my timber in a polythene tunnel and I find it very useful. It keeps the timber nice and dry and even on a sunny winters day you are still getting a drying effect.I still think that you need to let your timber mature for at least a year to two years to get it down to below 20% moisture content.

Thank you Jerry,
How do you manage ventilation of your tunnel? (the humidity can get really high in there) and do you grow in there at the same time as drying your wood?
I'd be concerned about tearing the plastic with stray blocks of wood, have you had problems like this and if so how have you managed them?

many thanks
tim

jerryg

My polthhene tunnel is 25 feet wide by 40 ft long and roof ht is 10 foot to the centre ,it is in a sheltered location and I deliberately left the doors about 8 ft by 8 ft I will try to get a photo up if I can.I do all the work so I am careful not to pierce the side,but you could put pallets up along the side if you wanted.I have just this August started to use it and I think I will continue to do so .I have 50 cm long larch and older timber in there at the moment to dry out .You might be able to get a second hand tunnel on Done deal or Farmers Journal but remember the higher the better as a large tunnel always has a much more pleasant atmosphere.IMO.
Regards,
Jerry

jerryg

I should have mentioned in my previous posts that if you are using a chainsaw in a tunnel that both doors need to be open as there is a danger of a build up of noxious fumes otherwise (carbon monoxide) so beware.

TomOnBoard

The polythene tunnel idea for air drying timber is a good one IMHO. Such use of solar heating at a relatively low cost has much to commend it.

I wonder would a mushroom tunnel be even better? Because the covering is black, it ought to capture even more heat than can be captured by clear plastic. Of course, in either scenario, adequate ventilation would be crucial in order to move moisture-laden air away from the drying wood.

I'd install ventilation that maximises natural airflow and thermal characteristics as much as possible, such as using air inlets low down on the sides and extractor fan (s) high up on the structure.

wayoutwest

I looked into using a polytunnel as a 'solar kiln some time ago.These are some key points that I can remember.
☆Straight sided tunnels can hold lots more pallets/crates than curved sided ones.Enough height for forklift.
☆Position length of tunnel on 1:20 slope(rising away from prevailing wind direction.This will encourage the natural rise and ejection of humid, warm air.
☆Use clear plastic, rather than the opaque stuff that growers use (more heat)
☆Sliding doors either end will provide easy access and make it easier to control the air flow rate.Additional (controllable)vents set into the doors so air flow can be maintained when doors are shut during periods of high winds
☆The plastic cover has a short (5 or 6 years?) lifespan.so it's replacement has to be seen as a running cost of the tunnel.

jerryg

This paper may also be of help
http://www.coford.ie/media/coford/content/publications/projectreports/cofordconnects/Drying%20of%20firewood..pdf

I would agree that a straight sided tunnel is of more benefit as it allows more airflow.I had the previous cover on my tunnel for more than ten years if you buy a cheap cover they will only last 5 years.I have no doors on my tunnel to get max air flow and being honest just never got around to making them!

timfromtang

Great stuff,
A really helpful thread this has turned out to be.
Lots of food for thought, a secondhand tunnel may make a very good soalr drier.
The question now is.....
Do we need one in tang or not??
I have a garden polytunnel
and a hayshed
I shall stack and store some outside under cover too
and test all three systems
time and a weighing scales will tell.....

Many thanks to all for helping me clear my thinking on this subject.

tim

timfromtang

Well,
Thanks all for the helpful posts.
We have got our tunnel, i have sawn 18 1 metre long legs to make a timber wall and raise the height of the tunnel. I have cut and welded up and drilled 80 metal brackets to bolt it down to our silage slab, we are in the process of sawing the extra timber we will need to affix the cover (secondhand tunnel).
Our tunnel is 19 M long and 5.8 wide, and with the walls will be 3.9 metres high. Hopefully this will work out as a good drying solution for our firewood and kindling.
Plans are to put it up sometime over the next month or so (shame to waste this lovely dry spring weather) so we are rushin around clearin yards and sellin scrap metal etc gettin ready for construction day.
When i get up to my 50 posts i shall post pictures of the construction here.

Any tips or subtleties anyone can think of before we begin construction? i was thinking to slope the roof slightly to aid air movement (warm air rises)
the orientation is fixed by our slab and will be roughly north/south on the long axis.
tim

TomOnBoard

timfromtang wrote: »

Well,
Any tips or subtleties anyone can think of before we begin construction? i was thinking to slope the roof slightly to aid air movement (warm air rises)
the orientation is fixed by our slab and will be roughly north/south on the long axis.


tim

Hi Tim

I would consider making a kind of chimney (preferably using scrap metal tubing painted matt black) on the end, as high as you can get away with. The heat of the sun will heat that up and create a chimney/airflow effect resulting in a much faster airflow in the tunnel that will occur naturally. Your objective will be to get as much air as possible flowing through the tunnel and touching the timber, thereby drying it out- you then need to expel that moisture laden air.

I would put an air inlet low down on the North end, and build the chimney on the South end with the tunnel vented high up. This ought to give you more surface area to catch the sun's heat from ground level upwards. Try to keep the east and west sides as airtight as possible to ensure that air flows throughout the length of the tunnel.

As you say yourself, a slight rise is a good idea. If you follow my scenario, you will want the rise to go from North to South.

I really must drop up one of the days to see your setup.

Good luck

Tom

wayoutwest

I think I would position it on a S.W/N.E axis, in order to channel the airflow from the average wind direction, yet still allowing sunlight onto both sides.
This looks like a neat ser-up.Note the net sides that let in more air -however, if your site is exposed to the wind I would reduce or omit this feature.

timfromtang

thank you Tom and wayoutwest, I will look into the chimney idea as it will save buying fans and pv panels to drive them in the short term. We hope to start bolting the posts down to the slab mid to late next week.
visitors are always welcome
just pm me for my phone number, and drop me a line
tim

timfromtang

I have thought about the solar chimney, I have some plastic coated corrugated metal roofing i can use to build it with. I imagine its dimensions could be optimised, either by calculation and practical testing or by testing alone.

I would plan to use timber framing on the outside of the chimney box structure as i fear that an internal frame may cause turbulence and be less efficient??

Does anyone here have any expertise to offer??
the tunnel will be 5.8 meters wide, 3.9 meters high (1 meter walls + the semicircle tunnel) and 19 meters long, giving an internal cross sectional area of about 19 meters squared and volume of 361 meters cubed.

Chimney cross sectional area?? and suggestions for a starting point?
I can probably go higher more easily with a skinny chimney, than i could with a fatter one, tall and thin and fast draught, or shorter and fatter with a slower draught? with the tin the latter would be easier. which would be better i wonder?
The tin i have is 750mm wide, a 0.75x0.75 box chimney would be relatively easy to construct, 0.56 meters squared cross sectional area, any opinions on this for a starting point?

guy ropes for the chimney perhaps???

I shall leave an extra 1.5 meters of space outside one end of the tunnel when i position it so that the chimney can be constructed on the end over the door.

The current plan for the side walls is to cover then with plastic on the outside, and with planks (to protect the plastic) on the inside of the 150mm sq timber wall posts.

a further call for suggestions
how much slope to put on the tunnel roof to aid draught? since it is a fluid flow situation I'd imagine that a small rise will be enought to have a significant effect, but how much? 1/2 a bubble in a 1 metre level?? more?
less? opinions welcome?

tim

Oldtree

I think this is a great idea and had planned to use the polytunnel to get the drying started in the winter (but just didnt get there this year), after blocks have been made as even this early in the year i can get 100 degrees on a sunny day (with both doors closed.

accidental forester

The polytunnel looks great. The mesh around the bottom is the business for plenty of air circulation. IMO air movement is the most important aspect of seasoning timber. Clear or black plastic is a good question; sunlight versus heat? Teagasc should set up a test.

We finish our split timber in tree crates (the Euro pallet sized crates garden centres import trees in) in a SE facing barn lean-to. I've been very surprised at how quickly the sitka is ready. The batch we brought over to the house last week was cut in July, put into short rounds in mid-Sept. split towards the end of Nov.. It was down to <20%. The prevailing wind is SW but enough moves through to do the job. We're only processing for our own and extended family use. We go through about 15 crates per year to heat our small, rather poorly insulated farmhouse using a 20 kw Boru central heating stove.

zetecescort

on the picture above in wayoutwest's post, would the timber dry better in the bags or stacked in rows?