Firewood kiln- anyone made one?

[openspaceman]

Here's mine, its cheeper to set up, free to run, greener, and much bigger!

 

Can you get a year's logs in it?

 

To my mind this looks a very good use of solar energy to season wood. Would it be worth erecting one of these on piers to increase capacity or would the wind loading be too great?

 

How many years use out of the covering?

 

Can you reckon a cost per M3 of solid wood seasoned?

 

The thing about seasoning a luxury good like firewood logs is the increased value can easily exceed the change in fuel value.

 

On the industrial scale the plant design allows for clean burning and the energy cost of venting steam up the chimney is a small proportion of the whole. As far as I can see there is little incentive to supply dry woodchip to the big users, who pay about £30/tonne as long as the wood is <45%mc wwb. So little incentive to dry this now. When NFFOs were first announced a large wood burning power station did commission a gas oil powered converted grain dryer because the premium on electricity generated from wood was great and gasoil relatively cheap.

 

How much it's worth spending per M3 solid wood for a luxury market is the interesting question. At the small scale the polytunnel looks appealing, get larger and the logistics all change. The physics stays the same though and the simple fact is 0.7kWh of energy leaves the system with every kg of moisture that leaves the logs. If you want big scale then you need an accelerated process to get the water out and match your throughput. A big business wants to keep output up to meet demand whatever the vagaries of the weather for drying. At this end of the business we decided the capital cost of the containment meant the drying cycle had to be less than 24 hours, the only quick way of meeting this was high temperatures because the limit wasn't the ability to move the water vapour away from the logs but the rate of migration of the moisture from the logs and the ability to deliver the necessary energy into the log.

 

Having a client that was adept with the grant system was the crux.

[gensetsteve]

18 stoner, out of interest, what dimensions have you gone for there, and how do you find it for vehicular access? Forklift, tractor or telehandler?

 

worth looking out for one of these. Brinkman britruk made mid 90's kubota diesel watercooled engine and comes with side shift. low mast and lifts 1000kg.

[ThrustSSC]

They are 27foot hoops, spaced at 8 feet, 12 bays long. I think its around 12 feet high.

 

We usually split outside(unless its raining) straight into bags on pallets and put in the tunnel with a small tractor with forks on the rear. When it comes to delivery we pick them up with front end loader tractor straight into truck/trailer. The hoops/doorway is high enough for access with a medium sized tractor with a cab on.

 

Although its nearly 100foot long, circulation is good with no doors on, and acheives 16% M.C. in one summer on hardwoods.

 

Thank you, sir!

[18 stoner]

Can you get a year's logs in it?

 

Yes. I usally sell over 100 cube a year. In some eyes that maybe classed as playing at firewood, but Im a tree surgeon that does firewood as a secondary basis for wet days etc, and to turn arb waste into product. I do intend to supply a high end product though, so charge accordingly for the premium quality. In 900mm bags laid out singly, I can get 150 bags in easily. I dare say if I stacked 2 high 250 would be easy to acheive.

 

To my mind this looks a very good use of solar energy to season wood. Would it be worth erecting one of these on piers to increase capacity or would the wind loading be too great?

 

Not sure what you mean by tiers?

 

How many years use out of the covering?

 

Its guaranteed for 5 years, upto 10 is possible but I will be happy with 7.

 

Can you reckon a cost per M3 of solid wood seasoned?

 

If you mean for the poly tunnel, it cost a total of £620. This was for new plastic and second hand steelwork. Labour costs of £600 to erect. If on a lifespan of only 5 years(plastic only of course) say £250 per annum. If there were only 100 cube per year, at £2.50 per cube I can accept that considering the benifits associated with solar kilning.

 

I have not worked out costs for producing the product recently.

 

The thing about seasoning a luxury good like firewood logs is the increased value can easily exceed the change in fuel value.

 

Totally agree, thats why its working for me and possibly will do even if I did say 500 cube a year, but doubling the cost of investment doesnt mean doubling of profit.

 

On the industrial scale the plant design allows for clean burning and the energy cost of venting steam up the chimney is a small proportion of the whole. As far as I can see there is little incentive to supply dry woodchip to the big users, who pay about £30/tonne as long as the wood is <45%mc wwb. So little incentive to dry this now. When NFFOs were first announced a large wood burning power station did commission a gas oil powered converted grain dryer because the premium on electricity generated from wood was great and gasoil relatively cheap.

 

How much it's worth spending per M3 solid wood for a luxury market is the interesting question. At the small scale the polytunnel looks appealing, get larger and the logistics all change. The physics stays the same though and the simple fact is 0.7kWh of energy leaves the system with every kg of moisture that leaves the logs. If you want big scale then you need an accelerated process to get the water out and match your throughput. A big business wants to keep output up to meet demand whatever the vagaries of the weather for drying. At this end of the business we decided the capital cost of the containment meant the drying cycle had to be less than 24 hours, the only quick way of meeting this was high temperatures because the limit wasn't the ability to move the water vapour away from the logs but the rate of migration of the moisture from the logs and the ability to deliver the necessary energy into the log.

 

Having a client that was adept with the grant system was the crux.

 

Sorry mate, got a bit burned out by this point, and I have had wine! Lol!

[renewablejohn]

I dont know what is classified as small scale but my 2 x 20mtr tunnels have a capacity of 200 m3 but annual production through the tunnels is approx 400 m3 per annum as your rotating the stock all the time. The critical sales period is June to Sept as restocking at this time allows the processing to be sold in the current firewood season.

I cannot really see any scale issues in using polytunnels and will be adding another 20 mtr tunnel later this year specifically for drying arb waste for power production.

[Billy68]

nice forklift handy tool

[farmerguido]

Cat weazel is talking piers, not tiers; they are concrete blocks with stainless threaded bar on them that buildings inspectors insist timber framers use to prevent the building blowing away.

 

Five Degree Piers - Cast concrete foundation piers

[18 stoner]

Cheers for that, we call them Dollies:thumbup:

 

Used them on dutch light houses but never on tunnels.

[openspaceman]

 

If you mean for the poly tunnel, it cost a total of £620. This was for new plastic and second hand steelwork. Labour costs of £600 to erect. If on a lifespan of only 5 years(plastic only of course) say £250 per annum. If there were only 100 cube per year, at £2.50 per cube I can accept that considering the benifits associated with solar kilning.

 

That would be a good benchmark for comparing drying costs, we can assume the full capacity and a single use (as the poly tunnel is probably cheaper than other covered storage before the customer puts it in their storage).

 

Correct me where I am wrong

 

So:

 

£1220 amortised over 5 years and 250 bulked m^3 which is 125 solid m^3 and 50 tonne of oven dry wood per annum.

 

In UK under cover the best equilibrium moisture content we can expect is 10% and in the winter 20% is probably realistic in an unheated store. Let's say we end up with 62.5 tonnes of firewood On a simple rate of return calculation ignoring interest that's £3.9 per tonne of product and represents a cost of £6.50 per tonne of moisture removed. In 2000 my target cost for the fast dryer was £10/tonne moisture removed on a 24 hour cycle.

 

 

 

I have not worked out costs for producing the product recently.

 

 

The production cost is a bit irrelevant to the drying equation unless you have to either borrow or allow for the cash flow, i.e. how much do you charge for the labour and wood cost which you may not see a return on for 6 months. If it's waste wood and wet weather working when wages have to be paid anyway you may ignore it. On the other hand if you buy in wood at £50/tonne wet and process it using staff employed for the purpose then it is significant.

 

The real question is how much more is a 1m^3 bag of seasoned wood worth to you than the same unseasoned and then what is a 1m^3 bag of seasoned firewood worth to you on the day before Christmas eve when you only have unseasoned cordwood left in stock.

[18 stoner]

Very interesting costings, and possibly a different way of looking at it.

 

I think there are possibly two ways of justifying the majority of firewood production. There are those who depend on it as a main income and those who run firewood as a sideline because "they might aswell".

 

I guess I fall into the latter one, as we are primerily tree surgeons and have the opportunity to use arisings from treework and turn them into a job when its quiet, wet etc.

 

Those however who depend on firewood as a main income need to sharpen the pencil more I guess. Im in the fortunate position to make firewood pay and be worthwhile doing without over complicating things.

 

Having said that, although our timber is "free", the costings are very different and production is more labour intensive than say someone buying in nice straight cordwood putting 20+ cube per day through a processor with one man.

Edited May 26, 2012 by 18 stoner