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using wood chips from construction

 
Posts: 36
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I have a question about using wood chips from a nearby materials recycler.

I understand that small diameter hardwood would be ideal for wood chip mulch, though as of yet I haven't found a good source for this. I want tons and tons...organic, no funny schtuff...

So, I found a source that sells bulk wood chips for pretty cheap. The wood ships are from construction lumber. I like to be a part of a recycling operation.

Here's the description of the wood chips that they take:
"Any clean wood, nails OK. Wood that is not recyclable includes but not limited to, painted wood, any kind of treated wood, particle board, etc"

That sounds to me like douglas fir 2x4s and perhaps plywood sheets for the most part. Plywood doesn't sound that appealing due to the use of whatever glue is used.

Would plywood glue break down into anything harmless over the course of a few years?

I'm OK with using 2x4s and stuff even though that's not small-diameter lumber, and would be lignin rich. I'm not tilling this into the soil. I just want thick blankets of mulch to keep in the moisture. The more the better. We're in northern California. Hot dry summers.



 
gardener
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Location: NE Oklahoma zone 7a
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From what i gather the glue in plywoods are various forms of formaldehyde.

Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, so it does not accumulate, converting it to formic acid in the body.[citation needed]

-wiki

Some people think its a problem and avoid it while others think it is quickly broken down once it enters the environment.

As with importing any organic material onto a site, there are some risks that could affect your crops more imedietely. There is never any way to know the full history of organic material that ends up on your land. In the longterm nature will breakdown any nasty, its just a matter of deciding if you want that risk right under your fruit trees.
If you were waiting for the toxic stuff to dissipate for too long then it might have been faster to grow a living mulch.
 
pollinator
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Location: Derbyshire, UK
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Hmm.. could 'painted wood' include old stuff with lead paint on? And I consider particle board (like mdf) to be pretty nasty stuff- though its more important to not burn it than anything else. I haven't tried composting it, but I have used it in outside structures- it usually disintegrates when it gets wet. Treated wood could be anything- creosote isn't very pleasant, and people here used to treat wood with use engine oil!

--------Edit
Hmm.. actually I think I have read it wrong.. that is saying the wood chip is clean wood only, not painted or treated wood?

I have composted plywood before- its takes forever but it gets there and you don't end up with big lumps of glue like you do with mdf or osb board.
 
gardener
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Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
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"Any clean wood, nails OK. Wood that is not recyclable includes but not limited to, painted wood, any kind of treated wood, particle board, etc"


The first thing to make sure of is that they are truly following the above statement and not making exceptions.
I wouldn't worry a lot about "painted wood or particle board, especially if you plan to compost it first .
For mulching, it sounds like the end product would be acceptable even if it did contain plywood.
If you have a concern, a permeable membrane under the mulch (landscape cloth or cardboard) will go a long way in preventing contact leaching.
It would also prevent unwanted sprouting of seeds, help keep your moisture in place longer and so on.

Treated wood will mostly contain copper compounds that will not go away without hot composting and mycoremediation.
This is wood that has been treated to keep fungi and molds from gaining a foot hold in a house, some are even "contact" types which are designed to be laid on soil and not rot.
You should ask yourself "Is this something I would put in my garden beds?" If your answer is yes, then go right ahead. If your answer is no, then you may need to rethink or devise a method of dealing with the contaminates prior to use in your soil.

formaldehyde goes away, copper and other metals do not, sulfides/ sulfates, bromides/ bromines, "salts" and other compounds can reside in soil almost indefinitely if no fungi can attack and decompose them.
In certain instances this is not a bad thing, for instance you want to make a permanent path way and keep "weeds" from showing up.
There is also the possibility of soil improvement (mineral defects for instance could be helped as long as the compound isn't inert, it will eventually break down).

This is more of a judgment call you have to make for your situation.
I would find out all I could about the possible chemical content, do the research on those components and then you can make an educated decision.
 
Vlad Alba
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Cool. Very good info.
I have seen the piles of stuff these guys take and it looks like they are true to their word. Lumber, no weird junk. They pile it and let it kind of compost for awhile so the time I receive it it's a nice kind of dusty musty dark brown rather than light brown fresh wood look. Honestly it looks like the wood component in most organic potting soils I have seen.

I get that formaldehyde is in plywood, and copper from the green treated lumber. But what about bromide and sulfates? Where do those come from?

It's not an ideal source but I believe it's a good one for the price 20$/ton

My goal is to feed the fungi and provide a thick moisture conserving mulch. And weed barrier.
 
Bryant RedHawk
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cupric bromide or cupric bromine are some of the older wood treatments, the bromine and bromides are normally used in wood rated for ground contact, it is a nice poison (if you like poisons, I don't) for keeping molds, fungi, termites, borers and other nasty things out of the wood.

The newer "yella wood" and others now use sulfates or sulfites since these break down and are far less danger to the environment. It is also why most "treated" wood now is not approved for ground contact.

It sounds like those guys are doing a good job and service with their business.
 
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Location: Lafayette, California
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for those still following this thread,
Exterior grade plywood, at least in the US, uses phenyl formaldehyde, interior grade uses urea formaldehyde
Interior grade will quickly delaminate and eventually decompose as the binder is water soluble.  Exterior grade will eventually degrade after exposure to water, sun, microbes and the like.  

Formaldehyde in it self is a huge family of chemicals and not necessarily "bad" chemicals.  The smell of fresh cut grass has formaldehyde compounds in it.  The smell of hay/straw bales too.

The use of sawdust and chipped plywood needs some caution.  I would not be using it among crops I plan to consume, though as sheet mulch component to choke out weeds, I would use it.  

Never burn it!

Other treated wood products have no business in compost or mulching operations. Avoid those at all costs.  You cannot determine, easily, if the lead content is at dangerous threshold, same for other preservatives with copper or arsenic.

again NEVER BURN IT!

Boric acid compounds are water soluble, purported to be non-toxic to higher order animals and not for use in ground contact lumber.  In a chipper/compost operation, I expect this would compost more slowly and have minimal, if any, measurable impacts.  If you are working on certifying your operations as ORGANIC, keep this out of your piles/mulch.


I am working on protocols to address debris from construction projects.  Wood in particular is an issue in CA as we no longer have biomass electrical generation as an option. On site composting is the avenue I am pursuing right now.
 
Bryant RedHawk
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Good post Patrick, really good post.

treated wood has in the past ten or so years changed enough that it is a far cry from the treated woods of even the 1980's.
For a treated wood to have lead in it the building it comes from would have to have been built before 1979, when the lead laws on paint were put into effect, they also had bearing on wood treatments.
copper was (and is) used for ground contact wood treatments but these chemical compounds today are less harmful than those used prior to 2000 since the actual compounds were changed.

Still, never burning any treated wood is highly recommended, just cause it won't kill you if you sweat while holding it and then wipe your face doesn't mean you will survive well if you inhale it.
I liken it to poison ivy, oak or sumac, you really want to breathe in that stuff that makes big blisters on your skin and itches enough you will make yourself bleed from scratching?
Sawdust should be thought of in the same light, think black lung squared.

I have always like the saying "when in doubt, toss it out!" taking risky chances is not a good idea, ever.
Fungi are our friends when you want to incorporate any construction materials. Add bacteria to the fungi and you can over a two year period, greatly reduce (not eliminate) the yuck from these materials.

Redhawk
 
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