Sterilize THEN air dry?

[Wal Nut]

Would it work to sterilize hardwood slabs to remove the threat of unwelcome pests in them and then move the slabs into my A/C workshop to air dry in that environment? 

I understand from a time perspective this isn't ideal but if one has the time to let them dry on their own is there a downside to this approach? 

[customsawyer]

In short no.
Spray them to kill the insects, then dry, then sterilize. Heating up hardwood while it is green will cause lots of problems.

[doc henderson]

It would take a lot of heat (BTUs).  think of sterilizing dry wood, and the heat it takes.  If the wood was at 100 MC like our cottonwood, then you can think of numerous 5-gallon buckets of water in the chamber equal oin weight to the lumber, that you also have to raise the temperature of.  there are 30 cc per ounce.  A BTU is the heat it takes to raise the temperature of 1 g of water 1 degree Celsius.  

a gallon is 128 ounces or 3,840grams or CCs MLs.  
to go from 63° to 133° is a raise of 70°F or  17.2° -56°= 38.8°C
so 1 gallon of water takes 38.8°C x 3,840g = 148,992 BTUs of heat just to bring 1 gallon of water up to 133°F .
Acord of oak firewood contains about 25 million BTUs, so it could raise the temp of 25,000,000 / 148,992 = 167.8 gallons of water.
it would be the equivalent of 8.34 #/G x 167.8 G = 1400 pounds of dry wood.
that just brings up the water alone not the wood.  If there is some evaporation, then that water took the BTUs to get to 212° plus the extra for the phase change to gas/vapor from liquid.  

compared to sterilizing air-dried lumber, it takes a lot more heat.

[Wal Nut]

In FL there is a never ending stream of grubs. Some as big as my index finger. We don't have a freeze here. Leaving them to air dry for a year or two is giving them an open-ended dinner invite and they'll eat more than Joey Chestnut can in a year. 

I can't risk moving them inside to dry before sterilizing as then I'm risking contaminating my entire inventory. 

The power is a non-issue as far south as I am. No heat required to bring the temps up in fact the issue would be regulating the temps from getting too hot.

I've run small pieces (less than 20") of hardwoods through an oven to sterilize, then stickered and left inside my shop in the A/C to dry. 

I've not had any issues doing this over the years but this is just a larger scale version of it. 

[doc henderson]

after milled and dried, most pests will not tolerate the dry lumber.  where in Fl?  i.e. what is you EMC.  so you plan to air dry in an AC building?  That is better but will need fans.  I assume it is hot and humid.  My version of "air dry" is outside.  how do you plan to sterilize?  do you have a hot box? 

[Wal Nut]

Yes, lumber would be stickered and stacked inside my A/C workshop with fans and humidity control. EMC will stabilize ~8.5-9.5, same as our homes here. 

The issue is I can't bring anything inside the shop that isn't sterilized or I risk contaminating everything that's why I'm wanting to heat before moving it inside to dry. 

I have more wood than I can use short term so I have time on my side. Trying to continue building future inventory. 

[Southside]

Like Customsawyer said, it's a train wreck waiting to happen. Boreate treat the lumber, keep it off the ground, dry, HT, then move it inside. Unless you want Walnut firewood, then just HT it off the mill. 

[YellowHammer]

Most all green wood bugs and borers will not tolerate or transfer to dry wood, and the converse to that is most dry wood bugs won't migrate to green wood.

If you were to sterilize by keeping the moist very high, right at the saturation line, then you could do it.  Basically, you would build a walnut steam chamber, just is used for steaming green walnut.  The steam must come out superheated, and the moisture must stay at 100% so the wood neither absorbs nor loses moisture.  Any steamed wood is also sterilized.

However, as mentioned, there are many things that can go wrong and it takes a tremendous amount of BTU's.  It also very dangerous, and I know of one guy who got accidentally exposed in a walnut steamer, and the skin melted off his leg.  

Getting to those temps and enthalpies using electric heat would not be cost effective, however, direct steam via a wood or otherwise fired boiler where there is energy to burn, would work. 

Steam is used because it is injecting moisture into the air so preventing the wood from drying at all, it must be done in a saturated environment.  The wood must undergo no stress, just as the others have mentioned, or it will be ruined.  I personally have tried what you are contemplating with a conventional DH, electric strip kiln and it was a disaster, just as Southside, Customsawyer, and Doc have said would happen.  Been there, done that.  I did not have enough BTUs and could maintain a saturated environment.      

However, the easiest, would be to simply run the wood through a dip tank filled with an insecticide and all the little tunnels get filled with water and most of the bugs would be exposed and killed.

[Stephen1]

I think the boys have a good point about trying to sterilze with heat 1st. If you have a problem with bugs getting in your wood, I would think about yard outdoors, It might need a good sterilzation, get the dunnage off the ground, sterilze your blocks and or timbers you store your wood on. The Dr talks about sterilizing your blocking and stickers on a regular basis.  I have been looking at doing that this year, replacing my 8x8 that I stack my lumber piles on. I just cut 100 48" x 3x3 blocking and will kiln dry and sterilze them. use my old blocking for customers to load wood onto thier trailers.

[newhollandnut]

Just thinking out loud here...... if you had access to an iDry you could put it in and draw a vacuum for a few days. No heat, maybe run the fans. That would kill any bugs and not degrade the lumber. 

[Crusarius]

I did that with some spalted maple cookies It is amazing how much water came out of them under vacuum. I did not see any degradation to them but they were only in there for 8 hours.

[YellowHammer]

I do not believe the Idry pulls low enough vacuum to kill all insects, certainly not mold or bacteria.  The Dry pulls to a pressure of only approximately 30,000 feet, which is still pretty high, from a vacuum point of view. 

[rastis]

How much vacuum do you need to sterilize and for how long? I have a couple of good size vacuum pumps for my maple operation that could be repurposed in the off season. The main production pump pulls a consistent 25 inches

[doc henderson]

Killing them with vacuum is easy, the hard part is getting them to drink the soda!   :D  

[GeneWengert-WoodDoc]

There are three classes of insects...those that are in the tree before it is cut (mostly grubs), those that are casually flying by and think that wet wood offers them a nice meal (like the ambrosia beetle), and those that like only dry wood (termites and lyctid powderpost beetle)

Sterilizing in a kiln with heat,  or coating green lumber with spray, will not protect from the dry wood termites.  All the others will not survive drying due to heat and the lack of moisture.

Bottom line is that it is typically hard to economically and practically justify treatment of lumber before drying.

Note that in a kiln with 150 F and 100% RH, so can heat wood without damage for 12 hours.  A small amount of darkening means we would not do this with white woods like maple and ash.  In fact, there is a patent given for heating lumber at 100% RH, so I cannot recommend doing this process without a risk of getting sued.  The patent holder did sue several companies.

[Stephen1]

Just thinking out loud here...... if you had access to an iDry you could put it in and draw a vacuum for a few days. No heat, maybe run the fans. That would kill any bugs and not degrade the lumber.

From what I understand the vacuum does not sterilze your wood only heat will do that.