[Digestion] R.R.R. ->was-> Re Digestate as fertilizer

[bennett at frognet.net]

> As a result some people see AD as "biogas", some as "Carbon", some as
> "waste disposal", some as "pathogen reduction" and some as "fertiliser".
> What we really need to do is see anaerobic digestion as all of the above
> and as part of a larger system. This involves a move away from the typical
> Western "linear" approach (of extract, use, discard) to a more cyclic
> approach (we have a Reuse, Recycle, Reduce slogan going around, sometimes
> with a 4th R that I can't remember). I know some areas have been doing
> this for centuries, and even Westerners used to be better at it (before
> coal and oil!).
>
Okay... since we're on a roll here, tell me if you think a scenario
similar to the following sounds TOO FAR OUT:

animal manure goes into an in-ground plug/flow digester;
spent digestate goes to both sediment pond and aerobic compost pile;
sediment pond produces duckweed and nutrient for hydroponic grow beds;
duckweed is harvested and dried for animal feed;
methane produced runs an engine;
engine coolant keeps digester warm (radiator coils wrap around digester);
engine runs generator to produce electricity;
electricity lights and runs pumps for hydro
.... what have I forgotten?