Skip to Content.
Sympa Menu

permaculture - Re: [permaculture] Aquaponics: artificial?

permaculture@lists.ibiblio.org

Subject: permaculture

List archive

Chronological Thread  
  • From: Toby Hemenway <toby@patternliteracy.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Aquaponics: artificial?
  • Date: Mon, 30 Dec 2013 10:17:52 -0800


On Dec 30, 2013, at 9:43 AM, Pete Gasper, Gasper Family Farm wrote:

> To me, fish food is a huge input, and one that is often unsustainable. What
> examples do you know of that do it without fish food inputs (or very
> little)?
>
> Pete

Yes, fish food inputs are one weak point, for sure, just as are fertilizer
inputs or farm-animal feed in manure-based farming. I've seen some systems
that use compost to grow black soldier fly larva to feed insectivorous fish.
Vegetable wastes are recycled from the growing beds to feed the larvae, but
since the 2nd law of thermodynamics is in effect, they still need a few
additional sources of food, though minor ones. And I've also seen algae and
duckweed being grown to feed tilapia.

Feeding the animals that provide manure, or generating permanent compost for
crops, is the hidden defect of all organic farming. John Jeavons and others
have calculated that for every acre of food production, 4 to 6 acres of
compost or animal-feed crops are needed to have a sustainable system.

One obvious open loop that remains to be closed is for the people being fed
by these systems to recycle their urine and feces back into the aquaponics
(or farms) in some way. That open loop exists for almost all western
agriculture.

To me the biggest weakness of aquaponics is the high-density fish population
needed to supply manure. This stresses the fish and makes them subject to
disease, and I can't imagine they are happy at those densities. One solution
might be to grow at lower fish densities and filter the manure-water to
concentrate the nutrients before it goes to the plants, but then you are
adding another layer of technology on the system.

Toby
http://patternliteracy.com






Archive powered by MHonArc 2.6.24.

Top of Page