Sewage Sludge or Store-Bought? The Tests Are In.


On the face of it, there's no good reason for a gardener to object to sewage sludge (which we will henceforth call biosolids) in the garden.  It's just manure, right? And if they can cook the salmonella and other microbes out of it–well, why not put the stuff to good use?  Otherwise it just takes up space in a landfill.

Well–it's not that simple.  Critics worry that everything we put down the drain and into our bodies–from antibiotics to vitamins to household cleaners to industrial solvents–could end up in the biosolids. The processing plants, after all, are designed to remove the living microbes but not necessarily the heavy metals and other nasty bits.

(I'm not trying to push books here, but if you want an overview of how a modern wastewater treatment plant works, check out The Ascent of the Worm, the last chapter of The Earth Moved.)

So the San Francisco Public Utilities Commission has, for years, distributed a composted biosolid product called SynaGro CV Compost–a name only a public official could come up with–and has tried to defend its product against criticism about heavy metals and other toxins.

And now the PUC has released a report comparing its product against a number of store-bought composts.  They tested for 127 different contaminants–still not enough, according to critics, who also have questions about whether the right sorts of samples were taken. 

But the study is interesting reading regardless, mostly because it shows the levels of lead, mercury, and other such things in compost products you might regularly buy–EB Stone, Kellogg, etc.

Read the study here. And answer me this–is there enough data in the world to reassure the public about the use of biosolids in gardens?  What about in some kind of agricultural setting for non-food crops (like biofuel, fiber, etc).  Or would you rather see it all go to the landfill? Discuss.


  1. Ok, “biosolids” is my new favorite euphemism.

    That aside, my husband’s grandmother grew up in pre-war Poland, and she says everyone fertilized their crops with “biosolids.” To this day, she refers to it as “human manure,” a terms which always makes me giggle.

    I don’t know. The antibiotic thing bothers me a lot. One of the reasons we don’t give any preventative meds to our hens is b/c we use the stuff in the coop as compost.

    I heard somewhere that remnants of viagra and antidepressants are making it into our water supply, so they’re probably in our food chain also.

    Oh well. You can only do the best you can do, right?

  2. The tests are in – hooray! But yikes. I’m at work and don’t have time to decipher that entire document. Can someone summerize it, please? Thank you.

  3. Not thrilled with the idea of using sewage or biosolids on my veggies, despite the evidence that this version of it is not as filled with heavy metals as I would have thought. Still would like to see info on whether prescription meds are present in any concentration – synthetic hormones, antibiotics, etc. I’m sure there are other compounds to test for which I don’t know about but might care to see as well.

    Even with all this evidence, I’d hesitate to put it on my food-producing plants. And since my edibles are interspersed with my ornamentals, I’d likely not have a place for it at all. Makes me think a bit more about the other products I’m using too …

  4. I find the metals a possible concern, but am a bit confused by the comments about antibiotics and hormones. That is certainly not stuff I would want in, say, my drinking water, but I seriously doubt they would persist in the soil or be taken up by plants.

  5. In relative terms the phthalate count (plastifier) is higher than average, as are a lot of the heavy metal counts. In absolute terms are very, very low.
    In terms of toxicity, i doubt that using a large quantity of bags grow vegetables, let alone say a one inch layer each year, would constitute a significant source of intake.
    Only a fraction of these things get into the consumable part, let alone what gets washed off or taken by bugs or weeds (ymmv for different plants or those which are consumed in whole, eg between parsley and okra).
    Taking a multi-vitamin daily probably accounts for several orders of magnitude more intake of metals. As for plastics, the leaking that occurs from plastic containers used everywhere is probably magnitudes more there as well.

  6. I did a post along these lines in March on my blog. I use it on my lawn areas for fertilizer and I do compost those grass cuttings and use them on occasion in my veg garden. Is the degree of separation enough? Shrug. It’s hard to say, but I’m not worried about it.

  7. Here’s the thing…
    Upstream-ville treats their sewage and dumps the water into the river.
    Downstream-ville takes the water from the river, treats it, and the residents drink it and use it on their yards.
    Since most medicines are water soluble and typically not at all effected by water treatment, seems like the water the downstream-ville people use is likely more of a contamination issue than the biosolids they might purchase from upstream-ville.
    That said, I’d drink the water. The risk is low. But you know what? We still need to do something about it.
    And buying bottled water if you’re concerned at all about water quality is only compounding the problem and showing the world what a hypocritical idiot you are.

  8. Sewage sludge, treated or not, called “biosolids” or not, is always an unpredictable mix of chemicals that is harmful to human health and the environment. The SFPUC tested for “priority pollutants,” a 1970s list of chemicals that is virtually meaningless as a scientific benchmark for toxins in today’s sewage sludge. A better look would be the EPA’s own sewage sludge survey (January 2010), available at Or better yet, ask the PUC to start talking about the nasties in its sludge: flame retardants; endocrine disruptors like triclosan and DEHP; and pharmaceuticals. Don’t swallow the PUC’s lies (or its sludge). Why take the risk when safe alternatives are available (look for OMRI certification or call the manufacturer and ask if they use sludge or biosolids to be sure fertilizers and soil amendments are organic).


  9. Amy, Thanks for your thoughtful and considered blog post. While Food Rights Network opposes growing food in sludge based on what little is known now, period, what the SFPUC’s “new” test results indicate is what we and many others have complained of all along: the testing regimes are completely inadequate, and that determination can be made based on EPA documents. As Kat points out, the EPA’s 2009 TNSSS identified dozens of dangerous, unregulated pollutants in ALL of its samples nationally. This stuff is not tested for. SFPUC relied instead on the 1989 NSSS – only 20 yrs old. Also as Kat points out, the Priority Pollutant list is based on science and standards that are 34 yrs old, from 1976. SFPUC did not test for dioxins, PCBs, pharmaceuticals or flame retardants (which EPA says are prevalent nationally). We believe that what is known now is ample enough to determine that sludge is unsafe for growing food, for feed crops, and likely is unsafe even for supposedly benign applications to median strips, parks, golf courses, etc. This is a toxic stew, a chemical cocktail, and it is accumulating. It is good to know that its dangers are gaining visibility every day.

    John Mayer
    Food Rights Network

  10. I’m including a link which is a good summation of what’s going on with the SFPUC, and with the Chez Panisse Foundation. Why the Chez Panisse Foundation? Well, the veep of the SFPUC is also the executive director of the Foundation. Which drags Alice Waters, the originator of the Edible Schoolyard Project in Berkeley, into the fray.
    Link here:

    In the SF Bay Area, we have so much to overcome in terms of reworking abandoned lots and public land into community gardens, squat gardens, and the like, without being offered this very contaminated material gratis. This is not the compost from the SF foodwaste program. This is sewage sludge which has nothing to do with compost.

    And it speaks volumes that they’re no longer giving this crap away (no pun intended).

    The greater issue here is that sewage sludge is dumped on farmland across the country. It is greenwashed as this great fertilizer, not unlike coal ash being greenwashed as something to amend your garden with just so the coal burning power generators don’t have to pay to dispose of it properly.

  11. First, in the interest of full disclosure, I work for EB Stone, several of whose products were sampled.

    A couple of housekeeping points:

    Contrary to the language of the report, fertilizers and inputs are not ‘certified’ for use under the NOP (National Organics Program). They are ‘approved’ by third party organizations like OMRI, CCOF or other Acredited Certifying Agencies approved by the USDA under the NOP. All materials must be compliant with the requirements of the NOP for use in organic fertility managment. Only farms and products of farms are ‘certified’ as organic.

    Very important to note that under the NOP, Sewage Sludge (aka biosolids) are specifically prohibited. See rule 205.105(g). Not allowed for use on an organic farm in the US.

    At least one product on the list, Nitrohumus, is still to my knowledge made of sewage sludge ( thouugh I am not sure it is labeled as such.

    To put these discussions into context it is critical that Parts Per Million or Billion be given some sort of meaning, and the metal content of the products needs to be balanced against the metals content naturally found in local soils as a result of the weathering of the underlying parent rock. That data is easily Googled for many areas. What can appear to be horrifying levels of metals for the less educated may actual be a small fraction of what already exists naturally in local soils and the use of the products tested would not significantly alter the total content at normal application rates.

    I would also add that the presence of compounds like dioxin in all the samples is indicative of how present these pollutants are in our environment. Very sad commentary on the condition of our world.

    As the source of several of the products tested, I also wanted to comment on the origin of the materials found in the test. All of those metals exist in nature. Copper and Zinc, for example, are necessary plant nutrients, and arsenic is common to many soil types throughout the US (I believe the national geometric mean is around 5 ppm for As). At EB Stone, we use natural products like Fir Bark, Redwood Sawdust, Volcanic Pumice, Earthworm Castings, and Chicken Manure. The metals in the product are naturally occuring in the materials we use to make the product. Very probably a result of the soils in which the fir and redwoods grew. The chicken manure will certainly bring other metals to the mix. But, I guess in the end, the metals in our soils will manifest in our gardens, and even if you did not import any materials into your yard and relied exclusively on your own compost (which despite what I do for a living I believe we should all do a lot more of!), there would be metals present in that compost and in your soils.

    We work very hard to comply with the NOP rules. We have not gone through OMRI due to the cost for a company of our size, but I have personally been working in the world of organic fertilizers since the early 80s. Even organic fertilizers will have ‘contaminants’. That is the most honest answer I can offer. All organic products are manifestations of the natural world, and since the natural world is a very confusing and complex place our products will be reflections of that world. They do not exist without it.

    Sadly, the whole notion of sustainable agriculture, to me hinges on our ability to return what we take from our fields to our fields. Even our organic farms today laregly export the nutrients of their soils to our cities, and there is no return loop. Many of the largest organic farms are probably net importers at some significant carbon cost of their inputs and not relatively contained systems generating their own nutrient inputs.

    Enough from me, but to close, grow your own, and support your own local farmers whenever you can. Is it better to dump biosolids in landfills than to use it in gardens? I don’t know. But I do know it is tough to live completely independently of the waste stream and not to contribute to it. Perhaps these materials would best be used as amendments in commercial landscapes and returned to the cycles of the earth, but not applied to our farms and gardens.

  12. Milorganite is another bio-solids product put out by Milwaukee. I’ve used it on my ornamental garden a few times, and I wrote about the worries of sewage sludge earlier in the spring. There is cause for concern I think because the stuff smells like chemicals.

    Also, there is a “natural” rose fertilizer out there which uses sludge, Rose Magic I think. It does work really well, but again, the poop smells like something other than. It’s something to think about.~~Dee

  13. Where is the control study to determine the levels of all of these things and more in compost (and soils) from before these compost products were available 🙂 Of course, I’m saying this tongue in cheek! But only to make the point that we don’t know to what we have been exposed for many years before these kinds of tests were possible. It’s good to be informed, in order to make conscious decisions and changes to make things better. But living in fear takes it’s toll too.

    Putting the biosolids in the landfills puts them in concentrated amounts that would be hard to dissipate, I would think; and eventually what is in the landfills will come back to haunt us in the water cycle. I would like to see a study that shows exactly what happens to these chemicals once the compost goes back into the soil. Perhaps they can be broken down faster in small amounts in gardens than in huge amounts in landfills.
    The one I’m really worried about is triclosan, the main antibiotic ingredient in soaps and cleaners….google it and read the horror stories about it (it doesn’t break down easily in water, for starters). The FDA regulates this one, and it isn’t up for review again until 2013.

  14. Exposure to Class A sludge “biosolids” has caused serious adverse health effects:

    Sewage sludge “biosolids” contain hazardous industrial chemicals, drugs, radioactivity, landfill and superfund leachates and virulent antibiotic resistant microbes.

    Class A sludge “compost” is promoted as being virtually pathogen-free”. It is not. All sludge – both Class B AND CLASS A – may contain infectious human and animal prions which cause always fatal transmissible spongiform encephalopathies (TSEs)

    In a September 2008 report, the US EPA lists prions eight times as one of the emerging contaminants of concern in sludge biosolids. Scientists have found
    prions can become 680 times more infectious in certain soils and survive for years. Human prions are 100,000 times more infectious than animal prions.

    Prion researcher Dr. Joel Pedersen, Univ. of Wisconsin:

    ” Our results suggest that if prions were to enter municipal wastewater treatment systems, most of the agent would partition to activated sludge solids, survive mesophilic anaerobic digestion, and be present in
    treated biosolids. Land application of biosolids containing prions could represent a route for their unintentional introduction into the environment. Our results argue for excluding inputs of prions to municipal wastewater treatment.”

    “Prions could end up in wastewater treatment plants via slaughterhouse drains, hunted game cleaned in a sink, or humans with vCJD shedding prions in their urine or faeces, Pedersen says”

    In the July 3, 2010 issue of VETERINARY RECORD, Dr. Pedersen stated: “Finally, the disposal of sludge was considered to represent the greatest risk of spreading (prion) infectivity to other premises.” Interestingly, PrPSc present in urine maintains its infectious properties. Our data indicate that low quantities of infectious prions are excreted in the urine. These findings suggest that urine is a possible source of prion transmission.

    Prion researcher, Dr. Claudio Soto, states: ” Interestingly, (prions) present in urine maintains its infectious properties. Our data indicate that low quantities of infectious prions are excreted in the urine. These findings suggest that urine is a possible source of prion transmission.”

    Recently, researchers at UC Santa Cruz announced that Alzheimer’s Disease (AD) is a prion disease. Nobel Prize winner (for his prion research) Dr. Stanley Prusiner, UCSF, recently wrote that Parkinson’s Disease may also be a prion disease (over 1 million US victims).

    Thus, 6.3 million US Alzheimer’s and Parkinson’s victims may be shedding infectious prions in their urine and feces to public sewers. The wastewater treatment process does NOT inactivate prions, They are concentrated in the sludge.

    Sludge topdressed on grazing lands, hay fields and dairy pastures poses risk of prion infections of wildlife and livestock. Class A sludge “biosolids” spread in home gardens poses prion risks to humans, including “eat dirt’ children, and family pets. An infective dose is so small, it is measured in molecules.

  15. How ’bout the cities first spray some of this in their own city limits (landfilling is only part of what’s done… it’s cheaper to spray it on farm fields). So, spray it in the city limit, and the solutions will come soon, as many more people are affected than just those in the rural places receiving the spray, into their communities, at present.

  16. I wouldn’t hesitate to use biosolids in ornamental gardening. Better used than in the landfill. I spent three years in Korea eating spinach grown in “night soil” and lived to tell the tale. Still I’d rather my vegetables were grown without it.

  17. Those growth hormones, steroids and antibiotics are also in dried blood, bone meal and animal tankage
    So much for “organic gardening” as there are not enough free range, Bgh free cows to fill one bag or manure let a lone a truckload

    The TROLL

  18. To the dioxin point- dioxins are fat soluble, so they will not be absorbed by plants.

    Also, if it’s that serious a concern, don’t put bleached paper into your compost heap, smoke cigarettes, use herbicides, eat meat/fish or dairy, or use “antibiotic” soap that contains triclosan. In other words, it’s freakin everywhere. You’re better off worrying about antibiotics and other water soluble drugs entering plants.

  19. This is in reference to the person talking about prions: do not scare people with faulty and misleading information please.
    The Alzheimer’s and prions link is referring to the normal prions that are found in everyone, not the infectious “mad cow disease” causing prions.
    Alzheimer’s disease: A prion protein connection
    Moustapha Cisse, Lennart Mucke
    Nature 457, 1090-1091 (25 February 2009) doi:10.1038/4571090a News and Views

    The study of biosolid safety needs to use objective science not scare tactics!

  20. I thank you very much for this eye opening post. I am a Master Gardener and a fellow Master Gardener has been recommending this product as a miracle fertilizer. He has said that the treatment plant warns against using it on food crops, yet he does so. I suspected what you printed was true all along and have refrained from use, but so many people are getting misinformation and using it blindly.

  21. What about planting near my own septic drain field? I know what goes down my drain… it’s not pretty but most of it has been through me once already. Is this safe?

  22. This is really something to consider. I would not want to use the biosolids simply because we do not eat only natural things. Therefore, how can we really be sure it would be alright to use. I will not use treated sewer water that they say is ok to drink from my own sewer tank. I would not let my dog drink from it.

  23. I could not careless what the test came up with. I will not put biosolids in my garden. I do not care if, they would give it away. The answer is no.

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