Two courses: Urban Gardening and Terra Preta


Recently I came across two one-day permaculture workshops, and of course I couldn’t resist: The first was a permaculture starter course with a focus on urban gardening on October 5, the other was a practical course about terra preta on October 19. Both took place in our local climate garden (part of the university’s climate farming research project).

Urban gardening

Can’t write all that much about this one since it was mostly theoretical, and I’d read most of the stuff already. It was still good to be there, though, because there were new and interesting people to meet and talk to and a couple of exciting ideas cropped up somewhere too. Like, we now have a yoghurt bin full of old coffee filters and (hopefully) growing amounts of oyster mushroom mycelia – we’ll see what comes of that. And I really liked the aquaponics idea: Setting plants and fish up so they can mutually profit from each other’s existence, I like that. I’m not much of an animal person otherwise, but I like fish. Both ways. ;-) Oh, and the hanging strawberry gardens!! A must have, don’t you think?

Terra preta

Now that was great! We were really lucky with the weather, and on the southern slope of the climate garden it felt like midsummer, so at the end of the course in late afternoon all of us were rather knackered. We spent the morning learning about the history of terra preta, its rediscovery and the theories of how to make it and the different kinds of charcoal and biochar, and after a short noon break we went outside to the garden. Where we took a while figuring out what to do where and where to strategically place all those many people (there were well over twenty of us!) so everybody could get busy doing all sorts of things: chopping up wood, clipping the hedge, scything grass (I had a go, yeah! And the scythe was BLUNT and it was difficult. But I also had the honour to watch a true master doing it, that was good.), raking up loads of leaves, digging a hole, digging up some mud, carrying the charcoal around, and then making a huge mound of terra preta mixture.

Leaves and chopped bits of wood and wood shavings and kitchen scraps and charcoal…… and water…It REALLY was sunny.And that’s what becomes of the whole mess after a year has passed!

This huge mound was put to three different uses:

  1. packed into an airtight barrel for pre-fermentation,
  2. piled onto the compost heap and the remainders of last year’s terra preta (see picture),
  3. filled into a hole in the ground and covered with earth (as an experiment).

My impression is that experimenting is very much asked for with terra preta, and I definitely will, once I have a garden to care for. It’s good fun to rethink all those bits of “waste” into ingredients for a lovely change-the-world-for-the-better cake. Now every pile of leaves I shuffle through makes my fingers itch for a large bag to put all this wonderful mulch into! :-)

You can read about terra preta in this wikipedia article, as a starting point.

Solar desiccator & biochar cookstove

Two exciting examples of low-tech I first met in the climate garden are the solar desiccator and the biochar cookstove. Their solar desiccator ist just a big wooden box with shelves raised on four legs where you lay out your fruit slices, herbs or whatever. Leaned against the backside is a wooden board, painted black, with an old window on top and a gap in between that opens to the top and bottom. The top gap connects directly to the desiccation box. Now the air that comes in through the bottom gap is heated by the sun shining onto the black board, rises and goes into the box where it dries all your lovely smelling fruit and lavendar and whatnot. (And then it goes elsewhere, I presume, since the desiccator isn’t airtight.) And you’re done! I’ve been wondering if it makes any sense to use this technique for drying laundry in the winter. Hmm…

The solar cell of the desiccator

The biochar cookstove is of course very neat in conjunction with making terra preta. The basic idea is that you pyrolyse wood and only burn the released gases for cooking. To me, this is clamouring for some diy experiments with a couple of tin cans, and I’d actually planned some for the last weekend. But I was one tin can short (cat food only comes in one size, it seems), and so I decided to postpone this a little and start on the homemade playdough to help with the room planning. I’m coming back to that soon! (And I don’t have a picture either since I’d forgotten to recharge my smartphone.)