Johanna has a question here:
When watering the 10.32 Wet Food patch,
are there any concerns about health risks
or interactions with soap or grease in the water
being applied directly to these food crops?
I was under the impression that some processing
would be better or that less cleaned gray water
should be used for tree crops.
Okay, so, I'm sitting in a banana circle
which I've used on aid projects in exactly the same way.
But you're referring to the Permaculture manual page 273,
and what it has, it has a feed line from the septic tank,
you'll see in the diagram,
into a large open pit that's about eight meters by five.
And on the bottom of the pit,
it's about half a meter deep,
you have a layer of rocks.
So there's half a meter of rocks at the bottom of the pit.
And then on top of that,
there's lots and lots of either banana leaves
or thick leaves or paper or cardboard,
and on top of that is a thick layer of mulch,
and that's planted to comfrey and legume ground covers.
And they're regularly cut
and put to the mounds on the outside.
There's no food in the middle.
Everything's soaking through the mulch,
through the paper, and through the gravel,
into the bottom of this big shallow pit
and there's a raised mound around the outside impounding it.
And on the raised mound, not in the pit,
there's papaya, banana and pigeon pea.
Well, that's very much like this big mulch pit
I'm sitting on, it's over a meter deep
and these bananas are actually on a mound,
'cause I'm up, raised above the ground
on the pit that's overfilled.
So they're growing on the mound on the outside.
Now you can put gray water in here,
I've done it many times.
And if they're biological soaps,
and they might be a little bit alkaline,
the breakdown of organic matter
and the humic acid created by so much mulch I'm sitting on,
is going to compensate with it's humic acid acidity
to the alkalinity and bring it probably close to neutral.
It could even actually help having a bit of alkalinity
coming in to so much humic acid breakdown.
And grease is just going to,
it's just got lots of embodied energy, grease.
And it heats up the compost when you put it in
and improves the breakdown of the organic matter,
so that won't be a problem.
But the food crops are on the outside mound
in the demonstration,
they're not inside the pit anyway.
So there may be regulations wherever you are,
if you're in the over-regulated world,
might be difficult to do.
The reason that it's got papayas and bananas
on the outside of the pit is most of the time
these systems we put into the under-regulated world,
where we're working on aid projects.
Now if governments fall over and we go into an unregulated
type of world then you need to know these systems work,
because you're taking the mild pollutants of gray water
after a septic tank into a soakage pit
which on the mound on the outside
can grow quite good crops.
But even so, the crops we're talking about,
banana, papaya and things like pigeon pea,
they're all fast growing,
they're not long term with roots
that are going to go right into the pit.
They're just sitting on the outside of the mound,
getting that secondary soakage or the secondary moisture.
Now another crop that Bill talks about potentially being
inside the mound is bana grass,
which is a variety of pennisetum.
So it's like clumping cow cane, very very prolific.
But what he also says, quite distinctly
is that everything inside the mound is continuously cut
and the foliage is taken to the mound.
So inside the soakage pit, there's a continuous cutting.
It's not meant to go out of control and clogged up,
it's continuously cut and the top mulch
is taken over to the food trees
or the fast growing crops
that are on the mound on the outside.
So it's a biological function of extraction
through particular crops, comfrey, probably sweet potato.
You might be tempted to eat the sweet potatoes.
So ground cover legumes, comfrey, bana grass,
things like that, regularly cut,
extracted to the outside.
And then on the mound, yes,
there can be food crops
but they're not necessarily large trees
with big tree roots that are going to go under the pit.