working on my first design, and planning to install a biofilter system for greywater leading into mulchpits next to an edible fence.
Now since we are in the Berlin area, where the winters can get down to -5°C, I was wondering if there's a way to insulate the pipes with mulch? Thinking here about the same process which heats up the hugelcultures.
So the concrete idea is to lay the pipes underground (sandy soil) and fill mulch around the pipe (bottom, sides, top) and top it up with the sand, for the distance they need until they reach the mulch pits, where the water is to be processed by microorganisms and feeding an edible fence.
I got the idea from the milkwood farm in australia and saw other people using the same system. Oasis design gave me the idea of the "mulch-insulation" for the pipe. Does that really generate enough heat to keep the are around the pipe above 0°C?
Insulation does not generate heat. It only slows existing heat from escaping by conduction. In any place with a freezing climate in winter, there is a known "frost line," ie the depth below ground below which the ground won't go below 0C.
If your climate doesn't go colder than -5C, the frost line is probably not very deep. Google around or ask some people who are involved with building or landscaping, and find out what depth it is. Then just make sure to bury your pipes at the frost line or below. If you insulate at all, only insulate above the pipes, not below, because you want the pipes to enjoy the heat of the deeper ground. Filling above the pipe with soil rather than mulch should be adequate, and since mulch will eventually decompose and shrink, then soil might be better for the long term. And maybe save all the mulch for the pits where the greywater comes out.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.