Compost In Aquaponics


Some aquaponicists are doing really good things with their projects. However, some don’t have a clue how dangerous what they’re doing may be.

 If you introduce compost and/or worms into your aquaponics system, you run the risk of bringing in dangerous or deadly varieties of E. coli such as H0157, 11 of which can kill an otherwise healthy adult human. There are 13 other species of E. coli that will make us very sick but not kill us, and they all come from warm-blooded animals and their excrement. Worms that have been bred in compost with even a microscopic amount of E. coli contamination, or compost containing even a microscopic amount of warm-blooded animal manure are safely usable on field crops according to organic certification standards. However, there is a requirement that the most recent application of such compost or worms (or worm castings) be at least 120 days prior to harvest of the produce. If your compost doesn’t contain manure, the problem is something else entirely, especially if you want organic certification.

If this is the case, you can’t use the compost because there is no way (currently) to prove to the satisfaction of the organic certification agencies that the compost truly does NOT contain any E. coli, and is safe for use. If you go ahead and use the worms or compost anyway, doing so will jeopardize or eliminate the possibility of your ever getting organic certification. This not only means your produce is worth less to the market, but also that you cannot ever legally use the word organic in your packaging or on your product or you will face a $10,000 fine per occurrence (which can mean per bag of product!).

The REAL problem with this technique is not the inability to achieve organic certification, but the very real possibility that your produce (contaminated with E. coli H0157 from the compost you added to your aquaponics system) kills someone who eats it uncooked. If we can develop composting systems that only use vegetable inputs and never any from warm-blooded animals, and keep them uncontaminated, then there’s a chance that we can obtain organic certification for these systems. Unfortunately, a visit from a single housefly that visited a pile of excrement ten seconds before is all that’s necessary to contaminate the compost, and compost is attractive to houseflies in a way that a row of aquaponic plants is not. This kind of technology needs to be carefully and methodically developed and tested before we depend on it to give us healthy food.

Now, having said all that, IF you are going to cook EVERYTHING that comes out of your aquaponics system to at least 165 degrees for at least 5 minutes (as the Chinese do), then you are safe from E. coli H0157, and you can go ahead and use whatever you wish in the system (even “night soil” as the Chinese have been doing for thousands of years!).

But these systems don’t NEED compost: we’ve had 200 lbs of tomatoes in a 3-month period from a single plant, and there is NO compost in our systems, just fish poop. ALL the dangerous E. colicome from warm-blooded animal excrement or waste products. There are no dangerous E. coli that come from cold-blooded animals, SUCH AS FISH. This is why pure aquaponics systems are safe for producing vegetables that will be consumed without cooking, such as tomatoes, lettuce, greens, and strawberries.