Author Topic: How much contamination in potential mulch is OK?  (Read 598 times)

Offline lagori

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How much contamination in potential mulch is OK?
« on: January 07, 2020, 04:22:06 AM »
I've got access to a large amount of wood waste from a workshop. Volumes of the stuff. The work is almost all with hardwoods (tropical some but mainly ash, oak, maple, beech etc) and the odd softwood. However, every once in a while a kerf is made on a piece of MDF or Plywood and as such, there is some contamination there. I would estimate 5% or less.

I can access the material for free and obtain a large volume as mentioned, but I'm unsure as to the dangers or concerns I should have in doing so. The glues and resins in these are not nice at all - but the volume is going to be tiny so is it any worse than say, using cardboard with glues in it? The soils here are clay and waterlogged so my intention with the material is to use it to create either masses of mulch before replanting sections of the garden, or to add to composting before use. In either instance though, the intent would be that eventually that piece of soil is going to be used to create food plants, not ornamentals.

I will be able to visually inspect the waste and the MDF / Ply dust is imperceptible - but I know it will be there. Any instance where I could see a clear volume of that material, I can ignore those bags of waste so can limit some of the exposure (at least with MDF dust that is green in colour). I've done some research and have found some advice suggesting that MDF shavings added to a compost at a volume of 10% of the overall or less, might even be of benefit for agriculture or horticultural use.

I am struggling to assess the risk of adding a material to the garden that will, in however small a dose, have glues and chemicals in that I would not knowingly add in isolation. Does anyone access a similar sort of waste to this and use it without concern? Should it be avoided at all costs?

Appreciate any views.

Offline DDJ

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Re: How much contamination in potential mulch is OK?
« Reply #1 on: January 07, 2020, 10:12:58 AM »
Great question.

You also may need to understand the amount of Black Walnut.  I know that my parents used to compost walnut leaf litter and that poisoned the ground for Tomatoes.  I have been trying to word a similar question but focused on the Walnut material.

Offline lagori

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Re: How much contamination in potential mulch is OK?
« Reply #2 on: January 07, 2020, 01:35:51 PM »
Thanks, and great addition - I hadn't considered the knock on of that sort of material too.

American black walnut will make up a little, but not regular amount of the material. I would estimate 3% over a year, but will comes in pulses so its one I should absolutely look out for if I do use the material. I'm not sure there is much data on this, but all of this material will be coming from seasoned hard woods and so, they have been out of the round for a while, moisture content circa 12-15% I would guess. Not sure if that has any affect on the stunting properties of the likes of a black walnut...

Offline Stwood

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Re: How much contamination in potential mulch is OK?
« Reply #3 on: January 07, 2020, 03:31:01 PM »
All of my wood chip and dust waste is blown outside into a pile, then transferred into the garden as mulch, or as compost.
I've never worried about the minuet amount of glues in ply that might be there.

Offline bigbear

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Re: How much contamination in potential mulch is OK?
« Reply #4 on: January 09, 2020, 12:26:58 PM »
I haven't used plywood saw dust.  I would consider it though if it was free and I didn't have other free sources.  If you can figure out what types of glues they use, you can do a little deeper research. 

From what I've read, I'd be more concerned about the fungi inhibitors (not in all plywood) than chemical breakdown and contamination though.