Pauls opinion of cardboard in compost...

Hi all, I just saw this interesting video by Geoff Lawton about composting toxic elements.

Three thoughts sprung into my head at the same time.
1: Really? How cool!
2: would it work like this for heavy metals?
3: I wonder what Paul thinks of this. LOL

If this topic has already been discussed, please feel free to delete this thread.

He is talking about compost breaking down toxic organic compounds (petroleum, pesticides, herbicides, etc.) - which does work. Composting generally doesn't do anything for heavy metals. In fact, composting materials with heavy metals can actually increase the concentration of the metals in the finished compost relative to the feed stocks. Nothing much happens to the metals but the breakdown of the feedstocks results in a relative increase in the metals.

I have been involved with designing and starting some industrial compost operations (wastewater sludge mostly). Generally, the metals and some other toxics have to be analyzed before and after composting because of these effects.

Thanks for that info Ardilla. What you say about heavy metals makes sense to me. I am so new to this stuff and I have all kinds of questions. I found that video interesting because I know Paul isn't a fan of sheet mulching with cardboard because of what could potentially be in the glues, inks and other things used during the process of making it. If the toxic gick is being changed into inert molecules during the composting process, then is there really anything wrong with using cardboard? This also makes me wonder about all the grass clipping that different communities collect and compost. A lot of the grass is sprayed with pesticides and such then clipped and left on the curb. The half life of these chemicals doesn't seem to be affected by the composting process. Do you suppose that different chemical compounds take longer to be affected by the composting process? If so, how much is left behind after the compost pile has reached it's peak in the process? See I told you I have a ton of questions! LOL

Personally, I use shreaded cardboard in vermicomposting, since it holds water well and is a good bulking material for the worms. I don't use cardboard with a bunch of colored printing on it and I remove labels and such, but a little black ink on the cardboard doesn't bother me.

For my normal compost piles I don's use cardboard because it doesn't break down fast enough.

Somewhere I read that the high protein content in the corrugated cardboard glue makes it quick food for bacteria. I wish I could remember the source of that tidbit...

Angela Brown wrote:Thanks for that info Ardilla. What you say about heavy metals makes sense to me. I am so new to this stuff and I have all kinds of questions. I found that video interesting because I know Paul isn't a fan of sheet mulching with cardboard because of what could potentially be in the glues, inks and other things used during the process of making it. If the toxic gick is being changed into inert molecules during the composting process, then is there really anything wrong with using cardboard? This also makes me wonder about all the grass clipping that different communities collect and compost. A lot of the grass is sprayed with pesticides and such then clipped and left on the curb. The half life of these chemicals doesn't seem to be affected by the composting process. Do you suppose that different chemical compounds take longer to be affected by the composting process? If so, how much is left behind after the compost pile has reached it's peak in the process? See I told you I have a ton of questions! LOL

If there was any organic compound that was so stable that it couldn't be broken down biologically (or through other natural processes) we would be totally inundated by it. Think about all the millions of years that plants have been churning out "toxic" compounds - they clearly don't persist in the soil for ever.

That said there are probably some human origin compunds that are slower to break down as bacteria and fungi are not genetically adapted to eat them efficiently. Personally I have no problems using newspaper and cardboard in mulching or compost - I'm happy buying it to read after all, and I'm exposed to a much bigger dose of hypothetical "toxins" while handling it to do the crossword than I ever will be from newspaper broken down under a layer of woodchips in contact with the soil and all the fungi and bacterial.

There are some specific pesticides/weed killers which are known to persist through the composting process. Fortunately these are rare as few farmers will now use them, at least here in the UK, as there has been a huge backlash against contaminated hay, manure and compost. You won't end up eating anything grown in this though as it will kill all plants that are exposed to it!

I've had no problem composting my cardboard. I am selective about which ones I put in. Most brown cardboard gets a good fungal growth in my compost pile in a short while. I'll see the white mycelium traveling along the cardboard. I do remove tape, staples, stickers, and other potential plastics. Any cardboard with a metallic silver shine I avoid. Any cardboard with a plastic like film over the surface I avoid.

I believe like the old saying: the poison is in the dosage.

I did some research into this several years ago, and found nothing frightening.

In the US, most inks are now soy-based. (They didn't make the switch because it is 'greener', they did it because it saves them tons of money. They use much less ink than the previous inks.)

The glues used in the manufacture of corrugated paper (cardboard) are starch based - mostly from food plants.

Of concern to me now, is that my research was on U.S. based manufacturing. As we know, most of what we buy today, comes from Asia. I do not know what their manufacturing practices are over there. Is a Chinese made box using the same materials as a U.S. made box? I have no idea.

As was said above, 'the poison is in the dosage'.
With that said, I think we need to be cautious of heavy metals: All soils contain heavy metals. So, if you take the grass clippings from an acre, and compost it down to a couple 5 gallon buckets of finished compost, and then spread it on 1,000 square feet of garden, you have potentially added heavy metals at 43 times the soil's normal rate.

Another thing to consider is what did the cardboard contain. If it was used to carry chemically grown produce it could have herbicides or pesticides on it. Other things may have been sprayed with fungicides or flame retardants.

I do use some cardboard. Our food co-op has so much cardboard that comes through that I have an unending supply of pretty safe stuff. Since reading Paul's arguments against it I've decided to leave it out in the weather in an out of the way spot of pavement for a while before using in the garden.

Earthworms really love cardboard in my garden.

This is absolutely fascinating! I agree that the poison is in the dosage. Honestly, I am living in an apartment right now and I am waiting to hear from a nearby community garden if I get a spot this summer. I work in a hospital and the size of the boxes used to deliver equipment and supplies makes me want to sheet mulch EVERYWHERE!!! LOL This is great conversation! Thanks everyone for your answers.

Angela Brown wrote:... I am waiting to hear from a nearby community garden if I get a spot this summer.

Let us know and pictures are always a bonus!

Seriously I think I will be driving people crazy with questions if I do! LOL Community gardens are all the rage in my city and there is so much politics behind getting in. A lot of them have years long waiting lists. The only reason I am being considered for the one I'm trying for is because of who I know. It's really a shame and I wish I had the resources and ability to start my own. I wonder how many people walk by that garden like I used to and wonder how to become a part of that and just not knowing who to ask.

An easy way to get all of the tape and residue off is soak the boxes for a few days,matter that the tape will just peel off.

Ardilla posted a good answer.

Lots of details here: https://permies.com/t/2157/organic/concerns-cardboard-newspaper-mulch

Geoff makes an excellent point about several toxins. Some responses:

1) It doesn't eliminate all of the toxins

2) the tests were on a few known toxins, and there are a lot of other toxins that were not tested (known and unknown)

3) there are known toxins that will not break down (heavy metals for one example)

4) sometimes toxins break down to other toxins

5) sometimes edible things break down to toxic things

6) what is in or on the cardboard changes week-to-week and manufacturer-to-manufacturer, so testing just one really does nothing

7) some permies want to turn a toxic waste site into a place where plants grow again; some want to take a clean patch of land and grow super-foods

8) cardboard can be made with zero toxins - I just think that is more the exception than the rule

9) there are getting to be more and more people reporting that the cardboard and/or newspaper did NOT break down. recent example

10) Sepp, Geoff, Bill and many others all like using cardboard this way - so I must be wrong. (but I'm not :)

Way too many details on the toxins in cardboard: https://permies.com/forums/posts/list/40/2157#88497


I wish to grow super foods .... I wish to grow food that if somebody ate it, their cancer would go away. And I think a huge part of this is being freakishly anal about bringing toxins into the system. Both known toxins and unknown toxins. Not all permies are pursuing this path.