Nutrient cycling

markh at sonic.net markh at sonic.net
Wed Nov 6 01:56:36 EST 1996


I hope some of you sharp microbiologists can help me out.  I'm involved in Permaculture (Sustainable 
Agriculture)  I'm looking at ideas for maximizing the ability to cycle and reuse nutrients in a low tech 
manner which would be suitable for developing countries, or life in the future.

Human wastes are of course one of the most underutilized nutrient sources primarily due to sociological 
conditioning and the real problem of pathogen cycling.  I'm looking at ideas for systems which are able 
to safely utilize these nutrients in the most effective and entropically efficient manner.

The anerobic digester seems to be tool which may be effective for this means.  From what I've read 
"Future Fertility" John Beebe, ascaris is one of the most difficult parasites to eliminate from human 
waste.  John states that 18 months in a digester should kill the parasite and it's ova.   Are there other 
pathogens that are likely to remain after this time?

I'm looking at either composting (aerobically) the digester sludge and then using it for agricultural crops, 
applying the sludge directly to the fields, or using it as a food stock/nutrient source for fish, algae or 
pigs.  Is their likely to remain a pathogen risk for any of these activities.  Of course i consider the former 
to be the safest and the later as more risky, but I'd like some professional feedback.

Another big issue with the biogas which is evolved is the loss of carbon in the form of CO2 and 
Methane.  Of course the gas can be used as a fuel and I'm aware that most sewage treatment plants 
use it to operated their process turbines.  But if it was possible to biologically scrub the CO2 from the 
gas by carbon fixing bacteria, perhaps by circulating the gas through a honeycombed chamber or cell 
containing Carbon fixing bacteria, then this carbon could be recaptured to maintain soil fertility and this 
would also boost the caloric value of the gas.  Using such a scenario would the carbon fixing bacteria 
also assimilate or break down the methane gas?

Could you add an additional cell which would biologically scrub the H2S from the gas??

If we used the sludge to fertilize a pond with algae, hyacinths(N2 fixing) and say cat-tails(Carbon fixing)
how efficient of a system would this be if the harvested biomass was then composted for soil 
ammendment to the resident farm?

How about Nitrosonomas??  I've been told that it can fix both N2 and Carbon.  Is it practical to raise 
and harvest?  What are the propagation variables such as temperature, nutrients, etc..?

Thanks in advance for any ideas, feedback or leads you may provide.

Mark Harrington

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