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Is the effluent produced by a biogas generator enough to feed plants in a hydroponic system? Answered

I'm looking at various ways to grow food free/almost free in a small space.  I would like to grow enough veg to feed myself comfortably.

Hydroponics in a vertical farm set up would allow me to grow lots of veg in a small space, trouble is I now need nutrients to feed my plants.

After much reading, it looks like I could anaerobically digest all my food waste (including meat, diary, plant stems and anything else that decomposes) in a biogenerator.

If I use the resulting liquid effluent, would this alone be sufficient to grow healthy plants.  Are all the nutrients they need going to be in sufficient proportion and are they all in an accessible form for plants.

Will I need to add bottled nutrients from a store to top it up?

Another question is if the effluent is safe or a biohazard?  My reading so far suggests that most pathogens are killed off in the anaerobic process.

Is there anyone who has tried anything like this already? So far I can only find people who are fertilising crops in soil with the effluent.

Any comments are greatly appreciated.

P.S: for those who do not know what a biogenrator does/is.. a quick description.  Its a sealed tank filled with water, waste (shredded) is added, naturally occuring bacteria in the water (not dependent on oxygen to survive) breakdown the waste into their nutrient parts, methane is also produced by the bacteria (methane is CH4, carbon is in the waste and hydrogen is in the water), the methane can be tapped off for burning and the old liquid can also be tapped off, supposedly this liquid is an extremely good nutrient source, though I don't know if it could sustain plants grown hydroponically on its own.



1 year ago

Did you ever have any success with this form of fertilizing hydroponics?


6 years ago

My company does this on large (20-150 tons per day), medium (5-20 tons per day) and small scales (waste from a typical family of 4 and above).
The short answer to your question is: "it depends" (sorry I cannot be more definitive)
... the liquid effluent IS high in nutrients, but the actual amount of total solids (TS) and the chemical makeup (NPK) will depend on several factors: 1) what goes in in the first place, 2) how long it stays in the digester and 3) how long it sits around before it's used after it is expelled.
I am installing a "BackYard Digester" that will be plumbed to my sink disposal and will be a dump tank for my garden waste. The biogas (a mix of CH4 and CO2) will be used to run my gas fireplaces in the winter and to preheat water prior to going to my regular heater... and/or if there is enough, I will use in a radiant floor heating system.
The solid effluent is great organic fertllizer and the liquids I plan to use to irrigate my garden (not hydroponic, but I think hydroponics would work fine...even if you had to augment the effluent). The liquid effluent MAY be high in ammonia, so be a little careful.
We hope to be selling our BackYard digesters here in the US and Canada by this fall ... you can see more about AD in general on our website www.TerraStarEnergy.com
In general, you are correct, a well designed system is a circular deal where the waste on one hand is used to create energy and nutrients to grow more stuff the becomes waste again!! The Chinese have been doing this for centuries!


8 years ago

It sounds like you'd be making anaerobic compost tea in essence, and you would still have to test for nutrients which isn't exactly cheap.  If you're lacking a nutrient, what's your plan for that?  I mean it's something I've also considered but ruled out because of testing.  Plus I don't really know if hydroponics is for me, but it's certainly on my bucket list.  However, from experience with new techniques and concepts, I would recommend doing it the standard way and then altering from there.

If you have a recipe for chocolate cake, you should make the cake according to the recipe, and then you can alter the recipe according to your needs and desires.

Hydroponics is hailed for its efficiency, and there are loads of hydroponic enthusiast boards dedicated entirely to hydroponic gardening.  Try it the recommended way and then start tweaking.  Or go commando and jump right in!  Just be sure to keep a gardening journal of your exploits.


8 years ago

What sort of scale of system are you planning here ? What area do you need to grow enough to feed yourself ?