Kiln operations: Any restrictions or EPA regulations?

[Curlywoods]

I was told that if I am going to install a dry kiln, there might be EPA or restrictions/regulations dealing with waste water.  Does anyone know what issues might come up before I take a serious plunge?  I hate to go to the county and ask a bunch of questions that might open up Pandora's box, but I also want to be honest.  County offices might blow this whole thing out of proportion or maybe I am missing something about waste water issues that I should be made aware of too.  Just looking for info before I get too deep into researching a kiln system.

[Frank_Pender]

Mike, my policy has been, don't ask, don't tell.  Most of them do not even know that ther might be a bit of waste water.  I put mine on the blackberries when they are producing to help keep them sweeter.

[Gary_C]

My understanding is there are some trace amounts of various compounds in the condensate water like tannic acid from the oaks that cannot be discharged into sewer systems or streams. The EPA or city would not permit you to put it in any storm drain or sewer system.

I agree with Frank. Don't ask and use it to water your grass.

[shopteacher]

I wouldn't want to swear this to be fact, but my thought would be that the water doesn't caintain any impurities other than what dust might be pulled into the evaporator by the fan.  The system works by condensing water vapor on a cold coil just like a dehumidifier.  Water vapor doesn't contain impurities so I would guess this would be similar to to distilled water.

[Den Socling]

There is a long list of organic chemicals that come out with the water. I have heard talk about EPA involvement in conventional kilns but I haven't seen anything anywhere between Ontario and Hawaii. California is probably the place to worry. 

With vacuum kilns, all of the water and it's chemicals are easily contained. With one installation which dried a lot of oak, sodium hydroxide had to be added to neutralize the acids before it went into city sewer. With another installation that dries a lot of hard maple, we hope to get ethanol conversion from the sugar water.

[Frank_Pender]

Den you would have some awful sweet running motors?

[ellmoe]

   An "oldtimer" once told me. "sometimes it is better to beg forgiveness, than ask permission".

Mark

[Fla._Deadheader]

  If Tannic acid is forbidden, then Florida will need to dry up a LOT of rivers and swamps. 

[Brian_Bailey]

If'n your drying oak, don't water your elderberries with it. Believe me, they don't like it.

I was told to just add a little lime to neutralize the acid, then just dump it in an out of the way spot.

That's for a Nyle L-150 kiln,  those big hi temp DH kilns might be another story.

Don Lewis will surely have an answer on this.

[Don_Lewis]

There is never any tannic acid the the water from a DH kiln or the moisture vented in a conventional kiln. Tannic acid can only be removed from wood by having it stand in water. It does not leave by evaporation. Same goes for sugars in Maple kilns. The Thujic Acid in Cedar or Juniper does evaporate at lower temperatures than water and when drying these species, there are steps that should be taken. It isn't difficult and you can make great hunters dope with it.

The water will be slightly acidic because the water that moves up and down in trees comes from the forest floor which is quite acidic in a healthy forest. But the water from even a kiln drying Oak is less acid than rain water. Whoever supplies your dehumidification system has been down this road countless times and can provide you with information that you need for permitting.  With good information, you can get permits but I would not bring it up unless asked specifically.

[Brian_Bailey]

On page 59 of  the Forest Products Laboratory's General Technical Report #118, "Drying Hardwood Lumber" it states that,

"When oak is dried in a dehumidification kiln, the condensed water used to heat the dehumidified air has a pH of around 3.4. The characteristics of this condensed water are described in detail by Solliday and others (1999). For new dehumidification installations, check with State water control officials for up-to-date requirements for water diposal and treatment."

I was unable to find this detailed report on the web.

I do know that when I'm drying oak in my DH kiln that the water in my collection bucket is slightly bluish in color and has a slight acidic smell to it and it kills elderberries  .



 

[Don_Lewis]

The bluish cast may be copper corroding and should be checked. It is not from the wood.  I have never seen that on any of the hundreds of Oak drying condensate tests we have done. If it is a Nyle DH unit, please call as soon as you can.

The pH of 3.4 is on the low end. It will run 3.3 to 4.5 when drying Oak. Rain is usually about that (the lower the number, the more acidic). If you go into the forest and check the surface, it will usually be 2.7 or so. The soil neutralizes it somewhat and thus in the tree, is less acid. The drain water from a DH kiln is normally much less acid within 3' of the drain due to action of the soil. You can push it further by having the drain drip on to garden limestone. This is not usually required but a few people do it or promise to do it when they get the permit.

[Brian_Bailey]

Thanks Don.

My kiln is a Nyle L-150 I bought in 1989.

I haven't dried any oak in 2 years, been drying mostly cherry, maple, and walnut.

Currently drying a load of the same and the water is clear.

I did have the system checked and recharged 2 years ago after I left the compressor running when I took the temp. up to 140 degrees. The pressure blew the gas out of the compressor thru one of the fittings.

Been running fine ever since. The kiln doesn't owe me any money so when it finally konks, I'll just up-grade to a L-200  .