Looking at ways to dry firewood faster and cheaper

[jason6586]

Hello,

I have a small scale firewood business going now and I have orders for about 70 cords this year so far. I know that it will be more next year because of a few different things that I do for my customers that the other guys don't and I have had my phone ringing already for next winter with new customers. I started doing bundles this spring and have sold about 300 bundles this summer already. My problem is I can only sell my wood within a 50 mile radius without USDA-DNR certification and a kiln to kill the bugs. I have a cement block building that is 12'x20' that i really don't use other than for storage of mainly junk so I am looking at converting into a kiln if i decide to go that route. Right now I season my wood outside under a lean to roof next to my shed, the lean to is 20'x120' with a concrete floor so i can store a good amount of 16" chunks in there and for now its working well but i'm seasoning my wood about 1 1/2 to 2 years to get it to 15-20%. I was doing some thinking over the past few weeks and thought if i enclosed the lean to and put a bunch of sliding doors on the side for easy access and a double door with adjustable louvers on the one end for loading and add two huge barn fans on the other end would that speed up the process and would it be worth the extra investment in the sheeting, fans and labor (I can get them cheap since the neighbor added on to his barn and bought new ones and would sell them to me). The fans are 48" belt driven fans 3 phase that spin at 750 RPM and create 32,500 CFM from what the tag says (If needed I could maybe bump that up by changing pulleys if the motor would handle it). I pile my wood all the same way and have about a foot between the rows so the fans would be blowing into the end grain of the wood. The reason I would have multiple access doors on the side is so I could remove the wood closest to the fan as I would anticipate it drying faster and then replace it with green wood. What does everyone think of this idea for my local (within 50 mile) customers verses kiln drying everything. One concern I have is how to maintain the humidity other than just not running the fans on humid days, it would be kind of the same concept of a grain bin with a fan. Maybe there is some sort of humidity control that would automatically kick the fans on and off when the humidity level reaches certain points. I'm not too concerned with the electricity usage as the fans are only 1 hp 3 phase and it says the amperage is 2.6 amps. I currently don't have 3 phase power but it's at the electric pole which is only about 75' from the building so I can't imagine it would cost a whole lot to get that hooked up. I look forward to everyone's thoughts on this idea and thank you very much in advance.

I almost forgot to mention the entire roof on my lean to is brand new transparent panels so i get a lot of sunlight and it is much warmer when you stand under it.

Thanks Again & Have a great day!

Jason

 

[dave_dj1]

I don't see your idea wouldn't work but I don't think it would work for what you need.
You will have to get the wood up to temperature to be considered bug free. I would suspect you would need to have the kiln certified in some way too.
You could always make a wood fired kiln, if that is an option.

 

[jason6586]

Thanks for your reply, I think you misunderstood my post or I didn't explain it good enough. That set up would be different from the kiln, which is a totally different building. The kiln would only be for if i decided to become certified and sell outside of the 50 mile radius. I was mainly thinking about enclosing this lean to, putting the doors and fans in for taking green wood and try to dry or season it quicker and at a much greater capacity than a kiln for my local customers that by law dont require kiln dried firewood. Even if I could get my dry time from green to 20% to under a year I would be happy and view it as a win. Also i believe that I could offer a lower cost quality product verses running everything through a kiln because all I would have is electricity expense (that i don't expect to be high being 3 phase) and I could use the lean to for other purposes as well.

 

[zogger]

As to the fans, with the broiler houses here, my boss found that changing the pulleys so that they spun a little slower increased electric motor longevity. Of course those start and stop a lot more often than what you would be doing, which is a lot closer to constant use.

Another thought is with you processing that much wood, you must get a certain large amount of "uglies" which might not be suitable for sale, but could be used as a heat source for that building to get the wood heated and dried to official kiln dried standards, enough to kill bugs, etc.

So..maybe a lot more heat inside and less airflow?

 

[haveawoody]

A cheap fast way to dry wood is a hoop house with a clear plastic cover and open ends.
A standard 1 year drying becomes 4 or 5 months in a clear plastic covered hoop house.
No need for fans, extra heat or any other drying other than good sunny days and well stacked wood not in contact with the ground inside it.
The differential of heat inside the hoop house and outside will draw moisture out of the wood at record speed.

You can make the hoop house yourself with 1" pvc pipe, pvc joiners and pvc glue and a bit of lumber or even pallets for he base support in a few hours.
Clear Plastic to cover the hoop house from tsc and pallets for the floor of the hoop house.

 

[jason6586]

As to the fans, with the broiler houses here, my boss found that changing the pulleys so that they spun a little slower increased electric motor longevity. Of course those start and stop a lot more often than what you would be doing, which is a lot closer to constant use.

Another thought is with you processing that much wood, you must get a certain large amount of "uglies" which might not be suitable for sale, but could be used as a heat source for that building to get the wood heated and dried to official kiln dried standards, enough to kill bugs, etc.

So..maybe a lot more heat inside and less airflow?

I do have the 12x20 foot brick building that I would make into a kiln if i decided to go that route. If I was to enclose that lean to it would be just standard steel siding and un insulated as I wouldn't want to invest in insulating that large of a building. If i was to sell wood outside of my 50 mile radius I can just put that into the 12x20 kiln. So eventually if it all would go as planned and I had the demand I would be using both buildings and drying methods. I'm just trying to figure out if that amount of air movement would drastically speed up drying or just make it a little quicker as long as I could control the humidity.

Thanks

 

[woodchuck357]

Drying fire wood is not like drying lumber, the humidity doesn't need controlled just reduced. If the shed gets sun, stretch plastic over the open side to heat the wood and let the fans run all day. Or use black plastic or painted tin to make a tunnel and use the fans to draw the heated air thru then blow it thru the stacks of wood.

 

[Jerryv88]

I think the heat will do more drying than a huge amount of air blowing on it. As has been suggested, you want to make a solar collector with the wood inside it so that it gets hot. Some air should be drawn out, but too much air exchange will cool it down. A small vent in the top is probably enough. The hoop houses would work well but probably even better with about 90% of the ends blocked to retain more heat.

Jerry

 

[haveawoody]

Jerryv88,

Hoop houses work real well with plastic on the ends with a decent size hole at the bottom of one end and the top of the other.
That setup makes for a natural ventilation and stops the plastic from starting to condensate with to much end closure.

Hard to say though if natural air movement with both ends open or as you say 90% ends closed to retain more heat is better at drying wood.
Each has it's plusses and minuses.

 

[Poindexter]

Jason, a couple questions. It seems to me if your clear roofed porch was south facing you ought to be getting splits down under 15-20%MC in one summer season. So... 1. Which way does your clear covered porch face and 2. what kinda wood and how big of splits are your putting in there?

As for the rest, it just doesn't make "sense" to me to use eletricity to dry firewood so other people can burn the wood so they don't have to use as much electricity to heat their homes. You may very well make a buck on the setup, it just seems ironic or bizarre or un-natural or something.

Rather than ongoing electric useage, have you got room to put up a greehouse or hoop house (same thing really - clear sides and roof, raintight, with air circulation)?

 

[GeeVee]

GREAT thread already. I think everyone has offered some great thoughts.

I recognize Jason will only kiln dry wood already reduced to a low MC, and be largely killing bugs, and really inspection and certification probably isn;t going to be too hard in agri- rich wisconsin. I'm only guessing thats is his locale. He ought to be able to use a concrete building and uglies to make some serious heat and production of kiln finished wood to order. His problem would packaging and storing for the demand. A week of wood fired production would be followed by three weeks of delivering inventory. I think he has some barn space or use for hoop houses.

His existing 20 by 120 lean-to is next to a big frickin barn and already has a good roof, and he's on the right track to enclose and ventilate and not care too much about exactly how fast, just knowing its faster- assisted, for a few bucks.

I was surprised at first that the fans at 3 phase were going to pull so few amps. But then it made sense.

You are definitely on the right track using some barn tech, and greenhouse tech, combined.

Temp, Humidity, you control them, you have it licked, but as someone mentioned. -At what cost do you reach a point of diminishing return?

 

[muddstopper]

I am just going to past along an observation I had last year. My buddy bought some green split wood and stacked it in his green house thinking it would dry it quicker. What really happened is the humitity shot way up in his green house and water was dripping from the plastic. Wood actually molded in just a couple of wks. I think if he had ran the fans in the green house, everything might have been alright, but stacking the wood under an enclosed plastic building/hoop house,/green house etc. doesnt work.

 

[zogger]

I am just going to past along an observation I had last year. My buddy bought some green split wood and stacked it in his green house thinking it would dry it quicker. What really happened is the humitity shot way up in his green house and water was dripping from the plastic. Wood actually molded in just a couple of wks. I think if he had ran the fans in the green house, everything might have been alright, but stacking the wood under an enclosed plastic building/hoop house,/green house etc. doesnt work.

Ya, you for sure have to ventilate it. They get hot in there and the humidity is unreal, and that is with a big fan running and shade cloth! It will max out a 120 degree thermometer easy by 10-11 AM in good sun without a fan. Ours does anyway in the summer. We leave the control set at 100 even and the fan is mostly on all afternoon.

If you were to make a hoophouse on a slight slope, and leave the ends open, with loose stacked splits, heat builds up and it would be self ventilating. I think that would be the easiest and no electricity required.

 

[cantoo]

muddstopper, air flow is usually the issue with wood under plastic.

 

[haveawoody]

I've tried open ended clear plastic hoop houses with about 1/2 the time for properly dried firewood stacks compared to right outside the hoop house.
They self ventilate, don't build up condensation, any amount of sunlight makes the inside of even an open end hoop house quite a bit warmer than the outside air.
I think as long as you make the wood warmer than the natural outdoor air it begins to shed water fast, having open ends to remove it just as fast makes it a simple system.

Some % of end closure has got to be a perfect amount for ventilation, heat build up and no condensation.
For me I didn't mess with what already worked very well to let the air flow full force as it wanted and indoors it was always warmer with any amount of sunlight.
Downside here in snow land is winter snow loads require a very hefty structure so making a year round one is not cost effective.

 

[blades]

A frame - construction could be similar to hoop house- no snow load that way, wind shear is a concern but not much different than the hoop or other garage in a box rigs- Ventilation could be handled by a solar powered attic fan or similar if forced air is really needed. Do need to block ground based moisture -repurposed billboard tarps or old roofing rubber membrane can take care of that at very reasonable cost or free if ya get lucky. Could actually use those items for the whole thing- harking back to camping days, man the inside of a tent with no vents would get hot.
Jason - you could just use the tarps to enclose the sides the fans would just be for circulation really do not need to have a forced are flow as there would be enough exchange in that type of loose construction. Access would not be a problem just roll up the area/side you wish to transit through.

 

[kingOFgEEEks]

Just jumping in with some math here:

If your drying room is 12' x 20' x let's say 10' high, that means that to fully exchange all of the air in the room, a fan needs to displace 2,400 cubic feet of air. (that's assuming an empty room).

I wouldn't think you would need to exchange the air more than 1 or 2 times an hour, so 2 x 2,400 / 60 = 80. That means an 80 CFM fan would fully exchange the volume of air in an empty room twice in an hour.

Heck, a solar powered attic fan, or maybe two, can do more than that. You might even get that much flow from passive venting, with a vent down low on one end, and another up high on the opposite end.

Remember, if you exchange the air too fast, you lose any heat built up from solar gains or your kiln, so I wouldn't go crazy on the fans.


/Just my $0.02

 

[blades]

Most of the solar kilns plans and pictures/descriptions I have looked at were just that - passive ventilation.

 

[jwade]

tha

A cheap fast way to dry wood is a hoop house with a clear plastic cover and open ends.
A standard 1 year drying becomes 4 or 5 months in a clear plastic covered hoop house.
No need for fans, extra heat or any other drying other than good sunny days and well stacked wood not in contact with the ground inside it.
The differential of heat inside the hoop house and outside will draw moisture out of the wood at record speed.

You can make the hoop house yourself with 1" pvc pipe, pvc joiners and pvc glue and a bit of lumber or even pallets for he base support in a few hours.
Clear Plastic to cover the hoop house from tsc and pallets for the floor of the hoop house.

thats an ingenious idea. how many cords do you process that way a year

 

[woodchuck357]

Most of the solar kilns plans and pictures/descriptions I have looked at were just that - passive ventilation.

Those were designed for drying boards.
Lower air movement is fine for drying lumber but for drying firewood more air movement is needed. wood dries because the air around it has lower moisture content and the moisture moves toward the drier. Heating air lowers it's relative humidity but without enough movement the air quickly becomes loaded with moisture and the wood doesn't dry any more. When drying lumber lowering the humidity of the air drastically causes cracking and warping. Cracks and warps are of no concern with firewood.
Fast drying requires sufficient movement of dry air thru the wood stacks.
Think of how good a clothes drier would work without forced air blowing thru it.