Aquaponics, worms and E. coli

[Kobus Jooste]

I have been made aware of a section in the latest newsletter of an aquaponics trainer making some rather interesting statements around the risk of introducing "deadly" E. coli HO157:H7 into aquaponics systems through the introduction of worms.

 

Like most promotional material, it contains enough reference to some form of correct base statement to make their argument appear compelling, but I have found the way that the section was written distressing in many ways.  On one front, we are trying our level best to ensure food safety and hygene in our units and to educate people on the safety of aquaponic production methods.  To have someone from within the community write something down the line of "if you dare put worms in your system you run a very real risk of introducing a deadly pathogen into aquaponics" is not conducive to building a fair and realistic impression of aquaponic production methods.  Worms in media beds have been in use for many years outside of the design of the group in question, with no reports of any health issues.

 

The inference made was that (without stating how many worm growers use cattle poo) red wrigglers are likely or potentially all grown in manure from corn fed cattle and this all contains the "man made" (?????!) strain of E. coli that will then most likely survive the transfer from worm to your system where you will contaminate your crops, your family or your customers.  If you are extra unlucky, a fly from a pasture containing corn fed cattle poo will also do the trick (then why bash the worms?) if they can make the trip in under 10 seconds. 

 

The article would have had more use if it simply said something down the line of "pick your worm supplier carefully - if you are cautious about E. coli, steer clear of using worm growers that cannot guarantee that their worms were not fed corn-fed cow poo from feedlots." I do not know what the ratio is of worm producers that potentially use this feed method compared to those that do not, but if it is the case that very few follow this practice, this article borders on reckless.  Then one can write follow-ups warning people on the next one in a gazilion risk such as a bird-flu contaminated duck landing in your fish tank.  As stated before, in theory, the conditions described in the text can potentially occur. Just as, in theory, a monkey can sit down in front of a typewriter, hammer away at it and write something recognisable. Not impossible, but likely? 

 

I wrote a blog a while ago about the responsibility of perceived role models in the industry related to statements made and perceptions created from a "credible" source.  This type of statement was exactly what I was talking about.  Not worth the negativety and not worth the potential bad press and poor PR for what many aquaponic producers see as a staple - media filled beds with worms in them (is there a reason for this?).  As a scientist, I would like to see some concrete evidence related to instances of the scenario described having been observed at worm farms and in aquaponic systems.  If no such data exists, is this statement fair and accurate? Why was it made? I do not want to appear to downright rubbish their concerns, but I will appreciate a percentage risk description to back up this claim.

[TCLynx]

Solids go to the compost provided they are bio-degradable mistakes and not plastic.  Since I humanure compost, my compost gets hot enough to safely handle most of the normal "compost no nos."  The body of a fish or chicken are no problem to compost for us.

 

Liquid mistakes well I'm not sure what constitutes a liquid mistake (overflows?) but they usually water the plants near by or the bamboo or some deserving banana.  Some liquid from inside goes to the compost.  The liquidish sludge from cleaning the duck system goes to the fruit trees or moringa trees.

 

I try very hard not to let anything on my property go "away."

 

 

[Sahib Punjabi]

Well said TCLynx,

 

"Think" before you act...

 

It will take just ONE such serious case and this whole way of life will be tarnished....

 

"See, I don't really think they are actually so negative about worms.  I'm thinking they are more worried about people getting too carried away with vermiponics and creating an atmosphere where if there is an outbreak it may be too easy for fingers to get pointed at aquaponics even if aquaponics is not the actual culprit.  Remember that a passing suspicion during one of these food born illness outbreaks can ruin farms even if the contaminated food had nothing to do with them and there isn't really any compensation when later the true source is found since the suspected food has usually already been destroyed."

 

God bless, 

TCLynx said:

I too am very keen to close the loop.  Instead of being scared of things, I would rather make sure the compost is managed properly to make it safe.  I have worms in my system and I even use worm castings as my start up bacteria source.

 

But I do understand that most worm bins don't really have a way to guarantee that the worms and worm castings harvested have not touched new uncomposted materials before getting harvested so some caution about the feed stock for the worms being transferred to an aquaponics system.  Or caution about how a vermiponics system is set up so you are not attracting flys that might have come from a pile of doo doo before visiting the vermiponics.  Basically make the worm feeding area fly proof or covered and non stinky in such a way as to avoid the pests in the first place.

 

Here is a blog post about it.

Aquaponics and food safety

 

See, I don't really think they are actually so negative about worms.  I'm thinking they are more worried about people getting too carried away with vermiponics and creating an atmosphere where if there is an outbreak it may be too easy for fingers to get pointed at aquaponics even if aquaponics is not the actual culprit.  Remember that a passing suspicion during one of these food born illness outbreaks can ruin farms even if the contaminated food had nothing to do with them and there isn't really any compensation when later the true source is found since the suspected food has usually already been destroyed.

[Sylvia Bernstein]

@Carey Ma - not sure what prompted your kind remarks, but thank you for that.

@David W - totally agree with you - as usual - and I would carry it even further. You said "Even if you did get a worm with ecoli in its system"... Based on the article summarizing the use of worms in pathogen elimination you won't ever see a worm with e coli in it's system...and certainly not coming out the other end.

@TCL and Sahib - I of course agree that if you use uncomposted manure and dead animals in your compost that you should be extremely careful about using worms from that pile in your AP system...perhaps following Converse's excellent tips for cleaning them first.  Coming from a very dry climate, however, we would never, ever do that here...just to give another perspective.  It would attract rodents to your pile long before it would decompose and that is a major composting no-no around here.  I used to live in Illinois and got used to compost happening in 2 - 3 months...here it can take up to a year!

As to what I do with liquid and solid mistakes...well... if I ever have to flush out my system (I'm assuming that is the liquid mistake you are referring to) I spray it onto my dirt gardens and grass...it is great stuff!  I'm faced with needing to completely drain my new outside system in the next few days because we just has our first snow yesterday (!).  All that water will go onto my dirt veg gardens.  I bury dead fish about 18" down into my veg gardens and put a large rock or pot on top for a few weeks so the dog, raccoon, foxes, or whatever else roams around here don't dig it up before the worms take care of it.

 

[TCLynx]

It's not the wet climate that makes hot composting able to take care of a carcass but the fact that it is really hot compost.  A rodent isn't likely to dig into the hot top center of a humanure compost pile where it is 155 F.  That kind of compost with a good layer of cover material doesn't even seem to allow the stink of rotting to escape and attract the rodents.  But you do gotta watch the cool edges of a pile/bin in winter to make sure the rodents don't find it to be a good place to nest.  1/4" hardware cloth helps.

[Sylvia Bernstein]

TC, I believe you will have a very hard time consistently reaching that golden "hot center" temperature over a long period of time within the center of a compost pile without Either a wet climate OR the addition of moisture...which is what I would need to do to insure reliable decomposition of manure and animal carcasses without odor so it wouldn't attract rodents.  Therefore, we are told just not to do it here.  This is from the Colorado State University extension office:

Animal wastes (meat, bones, grease, whole eggs and dairy products) may cause odors and attract rodents; they are not recommended. Human, cat or dog feces may transmit diseases and should not be used. Some animal products that can be used as organic sources of nitrogen include blood and steamed bone meal and livestock manures from plant-eating animals (cows, sheep, rabbits and chickens).

Manures may contain new strains of E. coli and other bacteria that cause human illness. The use of manures added directly to the food Garden is questionable, although use on ornamental plantings is still recommended. Research shows that 2 to 10 percent of bacterial pathogens survive the composting process. If manure is composted for food Gardens, a two- to four-month curing process following composting is necessary to reduce pathogens. Favorable moisture and temperature conditions during curing allow microorganisms to develop and outcompete the pathogens.

followed by...

In a region of limited rainfall such as Colorado, add moisture regularly to maintain composting. If parts of the composting material dry out, many microorganisms in the dry areas die. Even when moisture is added, the microbes that remain require time to multiply and resume plant digestion. The net result is slower composting.

Being a busy (AKA lazy) gardener, I don't add water to my compost...I just wait a year for each pile to "happen" by turning it once, and maybe running it through a chipper / shredder (AKA "the beast").  About to go do that right now, in fact ;-)

 

[TCLynx]

I guess that is why humanure composting works.  "liquid gold" provides enough moisture and high nitrogen content to create hot compost with solid manure mixed with sawdust and straw or leaves.  People who try humanure composting without at least about half of the liquid gold from the people also providing #2 find that it doesn't work.  The liquid part of manure is very important to proper composting.

 

If you do not do really hot composting, then correct you should not add any of the "no-nos" and are better off following the extension service guidelines.

 

We are also lazy gardeners and so follow Joseph Jenkins recommendations of just build the pile for a year and let it sit for a year.  No turning of the compost.  When you add new stuff you are adding it to the hot top center of the pile and the leaves around the outside edge might never compost but all the important stuff breaks down in the hot center core.  When it's time to add more, you dig a hole in the hot top center (spreading the already heated material out a bit to add the new material into the hot zone) and then cover it all over again with a good layer of the cover material.

 

No turning and not chipper shredders here, just stolen bagged leaves and some bins of sawdust.

[Carey Ma]

Good to hear some clear thinking. Personally I use "Mistake" water two ways. One is in my compost teas and the other is in my bio-digester where I dump carcasses and get methane (anaerobic), then it goes through a dry compost (aerobic), before I add it to my garden compost pile.

[Gina Cavaliero]

@Carey Ma - Thank you so much!  I too am not sure what I have done to deserve those kudos, but it is much appreciated.  You are too kind.  Have a great and safe trip. 

Carey Ma said:

TLC, Sylvia and Gina are my new fem idols. Always so positive and encouraging. 

 

This is porb my last post on this site for another two weeks. I'm heading to Seattle for a week to take care of some things. Hope I have time to pop in. 

 

Anyway, I'd like to point out that a well stocked, mature pool/ tank is a bowl of nutrient soup for many forms of life and it is up to us to keep it in balance and bring us rewards instead of sorrow.

 

Now I have a question. What do you all do with your (liquid and solid) mistakes (for a lack of better word)? Do you drain it to sewer or flush it out to field? Ditch and bury? Incinerate? Just curious.

[Jane]

Growing Power uses compost to grow their tomatoes in pots with compost in them.And I was thinking of trying that , using organic compost... the tomatoesshould taste better than just grown in the fish water right?

Sylvia Bernstein said:

I too was puzzled by this newsletter.  First, there is the lumping together of compost and worms.  While they may arrive together, generally most AP gardeners I know don't ever add compost to their systems...they just add worms and let them do their job of converting solid fish waste into excellent fertilizer.  Second, there is the unreasonably strong assertion that adding worms to your system could kill someone "incorporating worms that may have been in manure and may carry E. coli with them is not the inability to achieve organic certification, but the very real possibility that your produce (contaminated with E. coli  H0157 from the compost and/or worms you added to your aquaponics system) kills someone who eats it uncooked."  I'm with Kobus here...what is the chance of that, seriously? Add anything that has been in contact with raw manure to your system and you risk e. coli.  The fact is that worms are one of nature's great clean up crews, and in the truth is that there is something inside the worms that actually destroys pathogens and vermi-compost is actually pathogen free. Scientists have actually spiked manure piles with E. coli, added worms, and watched the pathogens die-off rather than multiply (see the highlighted section of the attached article). Their entire issue seems to be with improperly decomposed compost...which no one (anyone?) uses in AP...and yet they are extending this to the worms that are actually working to digest and render those pathogens harmless.  Bizzare, and somewhat reckless, frankly, given how many people this newsletter reaches.

 

[Jane]

I want to clarify a bit Growing power has tomatoes grown in pots filled with compost sitting part way down in the recirculating fish water.

[Ryan Chatterson]

Filling them with compost wont make them taste any better.

[Harold Sukhbir]

Hi Kobus,

You're right its too early as there is little in the way of AP/e coli studies done this far. I've been gathering bits and pieces the past months but no direct AP studies so far. I think we ought to pay attention to the any and all possibilities where E coli is concerned but I think AP in conjunction with the worms natural defenses is probably one of the most intimidating environments on offer for their prolonged survivability.