And another question I thought might play into this... If the chemicals persist in the compost, do the plants take them up or not? Or is only contamination from soil contact a worry?

Sandy

If you are unsure about the compost, then test it by germinating and growing sensitive plants - peas, beans, tomatoes. Make a soil-compost mix that is much richer in compost than you plan to use. If all goes well with this test, then you should be safe to use the compost.

In any case, know the pesticide's active ingredient and its presistence and toxicity. This will determine if the plant material can be added to the compost and when the compost can be used.

Here is a link that might be useful: Clopyralid and Other Pesticides in Composts

Virtually all pesticides breakdown over time and with the composting process into harmless compounds. And unless you adhere to totally organic practices both in the garden and at the grocery store, there's probably a variety of these products making their way in to your compost anyway. Generally, they are in such small concentrations as to pose no issues. Only a couple of herbicides are known to be extremely persistent in a normal composting process and they are no longer registered for use by homeowners or non-professionals. And their effect is to deter the growth of a specific type of plant rather than be taken up into the plant tissues.

The compost temperature will make a difference - a hotter compost will speed up the process and the reduction of any substance into its basic chemical elements will be accelerated, but it will also happen naturally over time. That is the nature of composting and its biggest virtue - it is a great neutralizer and even potentially harmful pathogens or toxic chemicals are eventually reduced to their basic, non-toxic components. That's why compost is used to remediate contaminated soils and toxic waste spills.

It's not exactly correct to call compost a neutralizer. Two banned products---DDT and chlordane---persist for a long time in soil and are virtually unchanged by composting. Clopyralid is also extremely persistent even after composting.

A concern about composting pesticides is the leaching that may occur before adequate composting temperatures and times are achieved. There is a concern about those leached pesticides contaminating ground water. Of course, that is a concern whether you're composting the material or not.

I think you are overstating things a bit. Both DDT and chlordane have been banned in this country for years.....the chances they'd show up in Sandy's compost are pretty remote and she's certainly not going to be applying them. Chlordane is also not taken up by plant tissue. And if you'll review the recent scientific literature on the subject, they ARE degraded by the composting process - perhaps not as rapidly or quite so thoroughly as one would hope but they are degraded and concentrations reduced substantially. Clopyralid is the herbicide I was referring to but since it is now no longer available to homeowners.....and unlikely to be used by Sandy even if she could get hold of it.....that's pretty much a non-issue as well. It IS possible for clopryalid contaminated produce to make its way into the compost if you are not buying organic - agricultural use is one of the few approved applications - but it's bit too late to be concerned then.....the product has assumedly already been ingested. And it has a very low toxicity rating anyway.

And you'd have to have soaked your garden pretty thoroughly for concentrations of most common, readily available, registered for home use pesticides to reach levels where they would leach readily.

It doesn't hurt to be cautious but it doesn't serve any purpose to discuss banned pesticides in view of Sandy's query......these are not products any of us are going to be applying to our gardens and therefore including in our compost.

Here is a link that might be useful: pesticide persistence in home composting

Each year more and more chemicals are banned from home use. This does not stop friends giving friends chemicals to use that are banned or supposed to be used only by trained people. In some states the training is only a one day session. She is correct to be worried about banned pesticides etc. Think of the people that have malathion still sitting in their sheds. Father in law used straight chlordane on his foundation for years. I sincerely doubt if the foundation is chlordane free after all these years.

If the chemical is known look it up. If safe use in compost. If any question don't use.

I thought that calling compost a great neutralizer was an overstatement.

Here is a link that might be useful: Questioning that

Whether any pesticide, a term that includes both insecticdes and herbicides, will be rendered harmless through the composting process depends on many things. Most of the materials available to homeowners will fairly quickly, when exposed to sunlight, degrade so materials sprayed by those products could be composted after several weeks after application.
However, the products avaiable to licensed pesticide applicators (not just trained) are much more persistant and some are known to be harmful for years after application. Clopyralid is one of these and compost made from material treated with it is known to be potent enough to kill plants 2 years after the initial application.
Can you compost material that has been treated with pesticides? Yes, but with care and caution.

And, unless I misread my article, concentration, is also a variable.

Well it IS a great a neutralizer! And is pretty widely acknowledged as such. I'm not sure why it's necessary for some to take such a hardline approach contrary to what is commonly accepted.

From the WSU extension service guide to composting:
Is it safe to use compost from yard wastes that have come in contact with pesticides, or other toxic chemicals? The major route of breakdown of pesticides is through microbial degradation, which is the process of decomposition. Any pesticide a homeowner can buy without a license will be broken down in the compost pile before the end of the process.

From the EPA Composting Fact Sheet:
The composting process has been shown to absorb odors and treat semivolatile and volatile organic compounds (VOCs), including heating fuels, polyaromatic hydrocarbons (PAHs), and explosives. It has also been shown to bind heavy metals and prevent them from migrating to water resources or being absorbed by plants. The compost process degrades and, in some cases, completely eliminates wood preservatives, pesticides, and both chlorinated and nonchlorinated hydrocarbons in contaminated soils.

Composting organic materials that have been diverted from landfills ultimately avoids the production of methane and leachate formulation in the landfills. Compost has the ability to prevent pollutants in stormwater runoff from reaching surface water resources. Compost has also been shown to prevent erosion and silting on embankments parallel to creeks, lakes, and rivers, and prevents erosion and turf loss on roadsides, hillsides, playing fields, and golf courses.

Again, referencing banned chemical pesticides that have been off the market for decades is certainly not helpful to the OP, who clearly states she is disinclined to use many pesticides anyway

Here is a link that might be useful: persistence and degradation of pesticides in compost

Strictly speaking, off-topic, but there was a big scare last year here in the UK about using manure that had been contaminated by aminopyralid in animal fodder. Veg grown using this manure showed a range of serious problems. DowAgro withdrew aminopyralid products for a while, but the UK government has since allowed them to be reinstated, accepting Dow's assurances that the herbicide may harm plants, even after manuring, but not humans.

More info in the link

Here is a link that might be useful: Association for Organics Recycling

annpat, that was an interesting article.

From my prior link, written in 2007:

"Even with pesticides that break down rapidly in compost, questions remain. Only a small amount of pesticide "disappearance" during composting is due to mineralization, whereby the compound is reduced to water and other inorganic compounds. Much of the pesticide volatilizes, vaporizing into a gas. Depending upon the compound, the vaporized pesticide may or may not pose environmental risks. Another large portion of the pesticide is adsorbed (or bound) to organic matter in the compost. While bound, the pesticide is unavailable for uptake by plants; however, as the organic matter breaks down further over time, the pesticide may again become bioavailable."

And many links refer to the concerns regarding pesticides leaching out of the piles (prior to reaching composting temperatures) and contaminating ground water.

Let me see if I can restate the basics of these answers. If I'm wrong, please correct me. If I leave something significant out, please add it.

In general, MOST pesticides available to homeowners will degrade in compost to the point they are not harmful to humans if used in home vegetable gardens or other applications. That said, in the past there have been pesticides that homeowners could use that were later found to be persistant in compost and damaging to plants the compost was applied to. Chemicals available today are deemed "safe" TODAY, but that doesn't mean they won't be banned tomorrow.

So what I take from this discussion is, if I want to err on the side of safety, I should not use pesticide contaminated OM in compost that will go on my veggies. If I'm willing to gamble a bit, I can feel RELATIVELY safe that there won't be any harm if I do use it.

If I've understood this correctly, this is what I've felt all along to be the case. I just wanted to throw it out for you to discuss and see if I was missing something.

Thanks for all your input on this. It's been fascinating reading. Oh, and be aware that some of the materials you've referenced are quite a few years old and they MAY not still be considered accurate. Information on these chemicals changes so rapidly that we all need to be sure we're looking at the most up-to-date data.

Flora, aminopyralid is closely related to clopyralid - they share some of the same chemical compounds - so it is not unreasonable that it would share some of the other herbicide's characteristics for extreme persistence as well. However, like clopyralid, it is considered of very low toxicity and the residue in compost (or composted manures) is only of concern with its affect on the growth of certain plant types, primarily members of the Solanaceae and Asteraceae (although together that's a pretty darn big group and does include a good many veggies), not with the human (or animal) consumption of what may be grown in it.

annpat...so I guess the EPA and hazardous waste study groups and composting associations are just full of a lot of noise and hot air? BTW, your newspaper article refers to the link I posted above.....perhaps reading the full article rather than just a journalist's excerpt might be beneficial to the issue.

Well, to be fair, I don't think the EPA has been doing so great in the 21st century ... lack of funding being one reason. So it's understandable, imo, to be somewhat skeptical.

gardengal, I read the full article. My article written five years after both of yours refers to your link. You have implied that my article is derived from it. It isn't. In fact, it questions it.

And the following quote that you extracted from your article is misleading. It refers to compost in general and was not referring to compost with pesticide treated "feedstock".

"Composting organic materials that have been diverted from landfills ultimately avoids the production of methane and leachate formulation in the landfills. Compost has the ability to prevent pollutants in stormwater runoff from reaching surface water resources. Compost has also been shown to prevent erosion and silting on embankments parallel to creeks, lakes, and rivers, and prevents erosion and turf loss on roadsides, hillsides, playing fields, and golf courses."

It makes a difference whether you are concerned about the pesticides being taken up by your vegetables and consumed by you, vs. persisting in the compost enough to harm your plants (herbicides, for example). The latter can be concern - but in fact in my garden I just put other people's grass clippings into the compost first and don't use them as a mulch, just in case.

Regarding plant uptake of toxins, my gut feeling as an environmental chemist who has watched this issue for years, is: IF you are dealing with normal average yard waste with normal average modern pesticides in a normal average compost pile and a normal average garden, by the time the stuff that survives the compost pile is mixed into your soil, there will not be a significant uptake by normal average plants to put you at risk. IF you are a stickler about toxins, and your garden is organic, and you eat only organic produce, maybe you should not use those yard wastes. IMHO it's overkill to exclude them, for the normal average situation. YMMV.

And groundwater, you'd have to be using an awful lot for it to leach out of the pile into a perceptible plume.

Tox

I don't exclusively buy organic fruits and vegetables from the store. So I know that my kitchen scraps, though washed, still would have the potential for some pesticides on them. This does not prevent me from composting them.

I only use herbicides on poison ivy and I don't compost that.

I don't use any other herbicide or pesticide, so the only potential contact for pesticides to be in my pile would be kitchen scraps from non-organic veggies bought at the store OR organic matter stolen from someplace else(and I don't do much of that either)...

Tox, thanks for putting this in a "normal average" perspective. LOL I needed that enlightenment!

Basically, I try to stay reasonably well informed and err on the side of caution when it comes to these chemicals. I used a systemic insecticide (Orthene) a few years ago and wasn't happy doing it but at that time I felt it was the logical solution. I don't think I would do the same thing today unless I was trying to protect a particularly prized specimen of some shrub or tree. I didn't compost the OM subsequently pruned from those shrubs. I wondered if I was being overly cautious but I did sleep better for being sure my veggies didn't carry much trace of acephate.

No, I'm not totally organic and I don't worry too much about well washed veggies and fruit from the market. But I try to be sensible with these things since, like I said earlier, today's safe pesticide may turn out tomorrow to be not so safe after all.

From the EPA 2008:
Please note the very last item on their Do Not Compost List.
They listed pesticide for a different reason than the one we're discussing, though.

I don't really have a horse in this race. I compost possibly pesticide treated grass clippings from the municipal dump, (but not comfortably). I was merely pointing out that there are differing views on how well compost neutralizes chemicals.

Here is a link that might be useful: EPA -- Do Not Compost List

I agree with annpat, that composting is not going to neutralize all pesticides...

I'd not compost anything that I thought was laden with chemicals.

However, I would compost stuff that I thought might have trace amounts of chemical residue on them. Figuring that some of it may be broken down and much of it would be diluted by chemical free stuff in the pile, such that it won't be harmful.

I just don't think that some of these subjects are as unequivocal as other people think they are.

The only thing that I don't compost because of pesticide residue are commercial flowers. I once read that they are highly pesticided and I don't really need them for the compost. I put them in the pile in the woods that I don't really harvest from very much.

Clopyralid is an herbicide and the reason it was found that compost made from material that had been treated with this is because people applied that compost to their soil the plants growing there died. It took about 2 years of study before the root cause of the problem was determined.

kimmsr, is clopyralid a consumer/household use chemical or is it used only in agriculture? I am also curious whether the compost in question was made by a large operation or in people's home compost bins. I think you see my line of inquiry.

Tox, thanks for your very realistic attitude. Apparently I was not doing a very good job of attempting to convey that same message, even though I offered several respected cites to support it :-) For the average homeowner who tries to avoid using synthetic pesticides whenever possible, there shouldn't be much concern about persistent chemical residue. And the risk is even further reduced if one creates and maintains a high quality composting process.

The EPA cautions about what NOT to compost err on the conservative side, most likely assuming the average home composter simply doesn't have the patience or skill to make a quality finished compost. Previous statements issued by them regarding the degradation of pesticides and other potentially toxic materials by composting are in direct contradiction, so it seems reasonable to assume they are making some sort of quality distinction between a professional or commercial composting operation and one generated by the average homeowner.

And while I expect you already know the answer, clopyralid is NOT a product available to Joe Consumer (although at the time the problem became known it was) and the compost in question did originate from a commercial facility(s) and not someone's backyard. This herbicide now is restricted for use for agricultural purposes or certain limited commercial uses and organic matter that has been treated with clopyralid must be composted or disposed of separately and not sent to any municipal or commercial compost facilities.

The site linked below also talks about "Organic Chemical Contaminants" lower down in the report.

I am sure there are more than a few products being used, that should not be used, by the "normal average" person. I am also sure that even some approved products are improperly used by some. Nature of the beast I guess.

I don't sweat it too much as I blend many different sources of feedstock together, get high temperatures and cure for a long time so it should all revert to the mean. Maybe someday I will get a test done but haven't so far.

Lloyd

Here is a link that might be useful: OSU Testing Compost

clopyralid was only available to licensed pesticide applicators, but it was used by commercial "lawn care" companies on residential lawns as well as many other places.

Clopyralid was originally registered as General Use pesticide and was available 'over the counter' to homeowners in various applications, including being in some weed 'n feed products and as a direct application herbicide (Confront, Curtail, etc.). After it's persistence became known and problems with contaminated compost arose, Dow pulled all residential use registration. Not only can it no longer be purchased and used by homeowners, it is not registered for use for ANY residential turf applications, even by licensed commercial applicators. Clopyralid's use is now restricted to certain specific agricultural applications, DOT and right of way use, forestry applications and on golf courses and cemetaries. And any clopyralid treated refuse generated by golf courses or cemetaries MUST be composted and recycled onsite.

After looking further at this clopyralid stuff I find out it is also the active ingredient in Lontrel (Dow product). This product was certainly available last spring in Canada. It is registered for use on wheat and barley and I remember my neighbor a few years ago talking about it's thistle control. I have never used it on my wheat or barley but I would suspect others have if it is as good as they claim it is for the broad leaf control.

So now I am left to wonder about the straw that people "pick up" for their gardens as well as any manure that might contain this straw as well.

I guess I will now keep a record of which spray I use on my fields and include that as information with any compost I have used my straw as a feedstock.

Lloyd

Maybe this stuff needs it's own dedicated thread?

Lloyd, Canadian pesticide regs will be different from those in the US so the above info may not apply. Assuming you are using Lontrel 360, it is registered in Canada for ag use only. You are correct in assuming that any treated material - straw, etc. - could pose a hazard if obtained for home composting purposes. And for your own compost, as well. Keeping good records is definitely one way around that, as well as avoiding any contact with susceptible plant types.

P

Looks like gardengal is way more up to date on allowed uses of products than I am, in spite of my moniker. :-] I was indeed really asking about the clopyralid (it was not a loaded question), and the answer does bolster my thinking that under most conditions we're fine with our household composting. The trend in pesticides over the decades has been towards faster breakdown to more innocuous degradation products. But there are notable exceptions and it may not hold true in every case.

Hi Pam

I use Buctril M and Horizon for my wheat so I've never used the Lontrel. I'm thinking my straw should be okay then. I know my neighbor has used Lontrel in the past so I will stay away from using any of his straw.

I thought I saw somewhere in amongst all the links I was searching this morning that there had been Clopyralid found in the actual barley grain as well as the manure from the animals it was fed to, can't find the article now. Ugh!

This leads me to wonder if one has to be concerned with manures that come from these animals and the straw from the crops. People who obtain free straw from displays in the fall might want to ask if anyone knows what the crop was treated with. Opens up a whole new can of worms (no pun intended) in my mind. Methinks more searching/reading is in order.

Lloyd

Found it, but it was from 2002.

Lloyd

Here is a link that might be useful: CLOPYRALID IN COMPOST

I don't think I would use anything that kills critters in my compost piles; I'm a critter, too, and those toxins are too close to home.

I had read an Ag University study on the use of Roundup (glyphosate) in corn crops and its persistence in soil. It does break down and they report that the rate of breakdown is increased by the amount of organic matter in the soil. In other words, Roundup breaks down via natural processes. I think that is a design requirement of many agricultural chemicals.

Unfortunately, Roundup is linked to non-Hodgkin's lymphoma, a form of cancer, so I won't use anything like it in my yard.

Here is a link that might be useful: Study of Roundup and cancer

"The EPA cautions about what NOT to compost err on the conservative side, most likely assuming the average home composter simply doesn't have the patience or skill to make a quality finished compost. Previous statements issued by them regarding the degradation of pesticides and other potentially toxic materials by composting are in direct contradiction, so it seems reasonable to assume they are making some sort of quality distinction between a professional or commercial composting operation and one generated by the average homeowner."

What? Now you got no respect for the EPA? I was mocked for quetioning their statistics. Now it "seems reasonable to assume" "they are making a some sort of quality distinction" etc. etc.

I don't like to assume.