Drywall Gypsum Sheet Rock Composting

The International Compost Sanitation Forum and Message Board: Humanure Composting Around the World: Drywall Gypsum Sheet Rock Composting
Author: TCLynx (Tclynx)
Saturday, July 28, 2007 - 7:00 pm
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Before doing anything to change your soil PH it is best to know your existing soil PH so you know if you need to change it and in what direction.
Some one might want to check the details about which direction gypsum would actually cause the pH to go. Calcium usually drives pH up but Sulfur tends to bring pH down. I've heard of people who grow in areas with clayey soil of a high pH tend to use gypsum to improve soil which makes me think the sulfur may win the battle on the pH front.

Anyway, I don't know that the drywall would do your compost bin much good but it might be interesting to run some experiments and see what you get from composting drywall scraps.

Author: FHJOHNSON (Fhj52)
Friday, July 27, 2007 - 1:03 am
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Gypsum yes but sheetrock is drywall and sheetrock/drywall is not all gypsum.
Among other things, it also often contains Sodium Pyrithione which is used as a MicroBiocide (bacteria, yeast, mold inhibitor). Sodium Pyrithione content is typically less than 1% by weight however that could have an adverse effect on the beneficial microbes that the garden soil (all soil really ...) needs. In time or with enuf sheetrock, I suppose it could kill the dirt, so to speak. It certainly is not an "organic" amendment.

Using "drywall" in a compost pile sounds like a particularly insidious problem to me because of the pyrithione. Without those beneficial microbes, the trash will never become compost. One might never know why the compost pile never did finish.

FWIW, I had considered using some (very) old sheetrock as a mulch for a path and then working it into the soil later as a calcium supplement. Although I suspect the fungicide is applied to the paper( Sodium Pyrithione (NaPT) is available as a very alkaline(pH 9-12) aqueous solution ) and one could remove most of the paper manually or burn it perhaps(?), that sort-of defeats the purpose of using scrap. The amount of time required will cost more than purchasing lime.

On the bright side, if one has problems with the soil and _needs_ to kill certain bacteria(e.g., those responsible for bacteria wilt) it might be a good amendment to use if one is not doing "organic" gardening.
I have _no_ information if (sodium or zinc) pyrithione will selectively kill "bad" bacteria or if it just kills them all. As a *cide used in living spaces I would suspect all so using it to kill 'bad' bacteria does bring the downside of killing the good microbes we need for healthy soil or compost.

With all of that being said, I must also say that small amounts of drywall in the soil or compost might not matter, particularly if one takes the time to rip-off or otherwise remove the paper first.

Hope that helps. There is more info on the net ...Google for it.

Author: Joe Jenkins (Joe)
Friday, June 29, 2007 - 9:13 pm
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Hi pH is used to kill bacteria in sludge, so you would want to be careful about raising the pH too much.

Author: John D. Younkin (Deconstructer)
Monday, June 25, 2007 - 10:34 am
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Gypsum is calcium sulfate dihydrate (CaSO42H2O). Large amounts of scrap drywall are generated in new home construction. Does anyone have any experience with composting drywall scraps? I imagine you could add them to your compost pile after cutting them into little 3"x5" pieces or crumbles. The paper would decay and the gypsum would supply good minerals if not added in excessive quantities. Do mushrooms grow well in gypsum? Gypsum is good for gardens as a soil amendment, right? Does anyone see any problems or solutions with this suggestion?

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