Turning the compost heap for the first time

Back in late August I described the process of putting together an 18-day compost heap.  That heap was made on August 26.  When I measured the temperature on August 30 it was just over 50 degC.  I suspected at the time that the temperature had been higher during the four days in between, because of the amount of green vegetable matter used, but I couldn’t be sure of this.

On September 5 I turned the heap for the first time, but before turning it I checked the internal temperature – 52 degC – still within the thermophilic phase of composting(1) where composting is at its most rapid and is bacterially dominated.  The thermophilic phase occurs around 40-65 degC and at these temperatures pathogens and weed seeds will be killed, but “heat loving” organisms will thrive.  Above 70 degC it is necessary to start thinking about reducing the temperature so as to avoid death of the beneficial composting organisms.  This heat is being produced by the metabolic processes of the organisms doing the composting, so it is good to see that they have been hard at work for a week or more.  The fact that it is progressing so well indicates that, during the time I wasn’t taking measurements, the temperature didn’t get into the 70+ degC, or at least not for any appreciable time.

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Part way into turning the heap. It looks a long way away from the original heap, but that’s caused by the camera lens. In fact it is a comfortable reach from one to the other with the long-handled manure fork.

The first surprise was the extent to which the original heap had subsided – it was right up to the top of the frames in the background. I should have expected this, for two reasons: first, the green material was pretty coarse, so there would have been a lot of air spaces in the heap to compact down under the weight of the overlying material; and second, that green material made up a large proportion of the heap, and once it started to break down there would have been a lot of water released, thus reducing its volume.  It is still well above once cubic metre, which is roughly the size required to reach and maintain hot composting.

You can see that a lot of the drier/harder materials have only started to break down, but what isn’t so obvious is that the vast majority of the original green material is difficult to identify – this is after 10 days of composting (in true 18-day compost procedure the first turn would have been after four days, but I did warn in the earlier post that this would be “more or less” 18-day compost).

What is important, but not obvious from the photo is that the heap generally had a good water content, though of course the outer layers (and in this case the bottom layer too) were on the dry side.  I had a hose handy to water both the working face of the old heap and the new heap whenever I came across material that was too dry.  A heap at this stage is too wet if you can squeeze water out of a handful of material, and too dry if a hard squeeze cannot produce any “cohesion” of the material (it doesn’t have to produce wet clumps, just some cohesion resulting from its wetness).  If in doubt, a bit too dry is way better than too wet, because too wet leads to anaerobic processes.

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The edge of the new heap as it grows. Key things to note are: (a) the mix of fine and coarse material, (b) that some of the material is loose and dry (I need to water the heap before adding more), and particularly (c) the fungus-matted material on top of the heap.

The first thing I noticed was that there is quite a bit of woody and dry leaf material.  The woody stuff is expected because of the use of coarse mulched tree material from under the power lines in the area.  The bigger bits of this won’t break down fully in an 18-day cycle, but they will during the later “maturing” phase of fungal-dominated composting.  Among these larger components was a matrix of fine material well on the way to becoming compost; this would have derived from the green vegetable waste and the matured broiler manure.

The second thing, and this was a bit of a surprise, was that the 20cm of chip mulch base which had been in the bin for a couple of weeks before I made the heap had become fungus-matted, rather like tempeh (the Indonesian fungus-impregnated soya bean delicacy).  You can see where I’ve thrown this material onto the top of the new heap in the photo above.  Clearly the temperature at the bottom of the heap had not gone high enough to kill off the fungi but was within the mesophilic range (25-45 degC) where fungi are encouraged.  Here’s a close-up of that material.

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Fungal-matting of some of the chip mulch which had been on the bottom of the original heap.

This material provides a lovely base of fungal inoculation of the heap, so I made an effort to include it in as many layers of the new heap as possible.  I did worry a bit about the possibility of “matting” of these clumps into impervious layers, rather like paper tends to do in a compost heap if you add too much in one layer and make it too wet.  All the more reason to spread it through the new heap as much as possible.

That reminds me – it is very important when you are making or turning a hot compost heap to keep it “fluffy”, i.e. to incorporate as much air as possible, because without air the (aerobic) organisms you want to do your composting can’t survive.  They will be replaced by anaerobic(2) organisms, and where these dominate they produce intermediate compounds including methane, organic acids, hydrogen sulphide and other substances. In the absence of oxygen, these compounds accumulate and are not metabolized further – many of them have strong odours and some are phytotoxic (poisonous to plants(3)).  One of the things I like about my long-handled manure fork is that it is very easy with a flick of the wrist to turn a forkful upside down as I throw it onto the heap, thus loosening it up as it falls.

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Putting the loose straw cover onto the heap to keep it from drying out while still allowing air to circulate.

So that’s it.  With the heap covered with a thick layer of loose straw it can sit and do it’s thing until the next turning.

The open area in the back of the above photo is where I can turn the car when I’ve got a trailer behind.  In the background are the sections cut out of an old water tank that had been through a bushfire.  These now hold maturing broiler manure and horse manure.

(1) There are many good sources of information on the stages of composting and the factors affecting the process.  For a quick overview of the main points you can go to the Cornell Composting web page.

(2)  Misra, R.V., R.N. Roy and H. Hiraoka (2003). On-farm composting methods.  Land and Water Discussion Paper 2. FAO, Rome.  [This publication has details on many composting techniques, including a number of anaerobic methods.  You can download the whole document here].

(3) Brinton, W., & Trankner, A. (1999). Compost maturity as expressed by phytotoxicity and volatile organic acids. In Orbit-99 Conf Proceedings, University Bauhaus Weimar. Retrieved from http://www.solvita.com/pdf-files/voa_eu2.pdf [Gives some idea of the potential for composts to become phytotoxic and the compounds involved].

A refreshingly different approach to food forests

I’ve just been reading a post by Tom at Sustainable Veg with the intriguing title: A Forest Garden Without the Forest.

It first caught my eye because of my scepticism about permaculture “food forests” as an efficient use of land for producing our daily meals.  I’m not talking about the food forests that surround hamlets and households in Southeast Asia and other parts of the world.  I’ve had a lot of contact with these, and in general these food forests are fruit, leaf and herb production areas, often with some poultry, and which also provide shade to cool the area around the house.  Their production supplements the range of day-to-day basic foods from more distant wet or dry rice areas or upland gardens.

My scepticism relates to the tendency of many permaculture followers to focus the majority of their production efforts on food forests dominated by fruit trees of one type or another.  And there seems to be a common belief that if it doesn’t have a food forest, then it isn’t permaculture.  Permies coming into a new garden will frequently ask “where’s your food forest?”.  Of course, many people with food forests also have “kitchen gardens”, but even so, there is often a serious over-allocation of area and effort to the food forest, out of all proportion to the negligible volume of “staples” produced there and the generally low productivity per unit area.

As Tom says in another post: “Billions of people need feeding … (w)e can be an alternative, organic movement but we need to produce carbohydrate, protein and vitamin dense food, in large amounts…” (I’m not suggesting here that Tom shares my views on food forests – to be honest, I don’t know).

A view of part of Tom’s garden – click on the image to go to a gallery of photos of the garden

Tom’s describes his back garden (he also has an allotment) as “a productive, organic, kitchen garden with substantial amounts of perennial vegetables, some annual vegetables and five dwarfing fruit trees”.  But he also calls it a forest garden, and refers to his techniques as forest gardening, and for good reason.

His reason for classifying his approach as forest gardening is that he is concerned with the ecology of the garden and of the soil, and therefore uses many of the techniques of forest gardening, while stopping short of trying to create either a closed tree canopy or a climax forest situation – not least because he doesn’t have the space to grow more trees without shading out his vegetables.  Nevertheless he has adopted an impressive array of permaculture / food forest techniques –

I’ll don’t want to spoil the pleasure of reading his post for yourself, but in summary these are the forest gardening techniques he uses:

  • Vertical stacking, with three diverse layers of plants, in association with individual fruit trees.
  • The use of support plants, with half the area of his garden devoted to these, but with the difference that he composts the prunings from the support plants before putting it around the food plants.  In this way he can focus on the needs of the support plants in one area and those of the food plants in another.  I also suspect, from what he writes and from the photos in his gallery (including the one above), that many of the things growing in his food production area are supporting each other.
  • Growing a wide range of perennial vegetables.
  • Adopting a “closed loop fertility” approach whereby he grows all of the ingredients for the compost on his own land.  You can see a separate post on it here.  I find this an admirable but daunting prospect.  I certainly wish I could imagine getting to that stage on our stony dry ridge.  At the moment the bulk of our compost ingredients come from off-site (but within 10km).

Please do yourself a favour and read Tom’s article for yourself.  What Tom has done is to apply the key food forest approaches without having his productive area dominated by forest.  I’m in awe of what he’s doing and the strong ethical approach he takes, and I’ll be adopting some of his approaches as I develop and expand our food production area.

As I finished writing this I noticed that Tom has added a post about compost which gives more insights into his approaches.  Enjoy.

DIY Composting toilet with worms

We decided from the outset that we were going to have a composting toilet.  There were a number of reasons for this, principal among which were that we didn’t want to waste an extremely valuable resource (humanure), and that we don’t have sufficient water to operate a flushing toilet.

The first model that we built, and which we used for more than ten years, was based on one of the 200L barrels used for shipping olives.  These barrels are usually available from places that recycle poly barrels.  The only reason that we stopped using this model was that it gets to be a bit of a chore to move a 200L barrel full of poop when the time comes to change it over.  It was taking me about half a day to undo the connections, replace the full barrel with an empty one, and re-connect it – and I always seemed to put off the change-over until it became urgent (i.e. a very full barrel) and that always seemed to coincide with another urgent priority.  Of course you could always install two 200L barrels side by side (both plumbed to drains and the air vent) and simply move the seat from one to the other, instead of changing over the barrels.  I’ll describe the new system which uses a 60L barrel in another post.

The basic principles of the design we adopted are: a) air is drawn down through “the mass” in order to keep up a supply of oxygen to the composting process and to remove smells through the bottom of the barrel and up to a high vent; b) a sufficient mass builds up to start and maintain an efficient composting process; and c) worms can be introduced to the mass while the toilet is in operation to promote the production of a rich compost loam.

A rich loamy compost with lots of happy worms

The final product – a rich loamy compost with lots of happy worms (the bits of straw don’t indicate that it is not fully composted – the straw was a top layer to help keep the mass from drying out)

In order to reduce the amount of text required, I’ll use photos to illustrate the construction of the unit.  Here’s a view of most of the components associated with the barrel.

Internal fittings and outside connections

Internal fittings and outside connections

In the background is the barrel with, on the left, a connection for extracting air from under the mass, and on the right, a drain for liquids.  The connections are made up from standard plumbing fittings.  In the left foreground is the base which supports the mass, made up of a circular section of 25mm galvanised mesh resting on some sections of plastic pipe – in the centre is some 225mm stormwater pipe (got it cheap as an offcut at the local irrigation supplies place), and some offcuts of 90mm stormwater downpipe (these dimensions aren’t critical, your pipes can be larger or smaller).  These are bolted together with galvanised 6mm bolts that have lasted for ten years, though they are now unrecognizable under a layer of rust.  You can also use reinforcing mesh supports  instead of the pipe sections as in this post on the Milkwood Permaculture site (though this gives a smaller space under the mass). This unit goes into the bottom of the barrel (after the drainage fittings are connected).

In the right foreground is the unit for drawing air down through the mass.  The vertical components are 50mm pipes with many holes drilled in them to facilitate air exchange with the mass (you could use polypipe for this – it’s more flexible and cheaper).  These are bolted onto a short length of 225mm stormwater pipe.  Note that the vertical pipes extend down past the 225mm pipe – the distance they extend downward is the same as the height of the stormwater downpipe lengths under the galvanised mesh on the left. These “legs” go through holes cut in the mesh (visible in the photo), so that the 225mm pipe section sits on top of the mesh.

The photo below shows the two units sitting in the barrel.  Short lengths of polypipe have been inserted into the tops of the vertical pipes to extend the aeration height.  The top ends of these extensions will be pulled to the sides of the barrel just under the top lip and fastened with wire loops through holes in the barrel.  If they aren’t pulled to the sides they tend to snag toilet paper as it is dropped into the barrel.

All components in barrel

All components in barrel

When the barrel is in place and ready to be used a layer of newspaper is placed over the mesh and then a thick layer of straw (we use barley straw) is put on top of that.

The photo below shows the detail of the air outlet.

Air outlet detail

Air outlet detail

There are four parts to this connection.  A male/male connection is screwed into a hole cut in the side of the barrel with an appropriately sized hole saw (keep it close to the bottom, but not so low that it will be lower than the liquid drain) so that the thread protrudes inside the barrel.  A connector (i.e. with internal thread) is screwed onto this inside the barrel so as to clamp the fitting onto the wall of the barrel.  Before tightening this I’ve put some bathroom silicone into the space around the connector on the inside and outside of the barrel to make a good seal.  Reaching to the bottom of the barrel will almost certainly require getting your head and at least one shoulder into the barrel – not easy to do.  I once rolled some distance down the hill with my head and part of my upper body inside the barrel!  The fitting on the outside end of this connection has various names.  My local plumbing supply calls them “dress flanges”.  Anything will do that will fit into the flexible pipe shown in the photo below.

I won’t show the details of the liquid drain.  It’s the same principle as the air outlet, but with appropriately sized fittings, and as close to the bottom of the barrel as you can place it.  Just make sure that the connection between the pipe coming out of the barrel and the drain to take the liquid away is easy to connect and disconnect. After a lot of frustration I settled on camlock fittings (you’ll have to ask your local hardware or plumbing supply place what these are as I don’t currently have a photo of one – there are some details on these fittings here).

Air outlet with flex pipe

Air outlet with flex pipe

The flex pipe can be difficult to source in our area.  Most places sell this pipe with many slots in it for use as a greywater distribution pipe but we need it without any holes.  In the end I got mine from an agricultural machinery parts supply place that sells it as a spare part for seeding machinery.

This pipe is connected to a vertical vent pipe (another length of 90mm stormwater downpipe).

Bottom of vent pipe

Bottom of vent pipe

The fittings here should be pretty obvious.  The reason for the Y-junction at the bottom of the vent pipe is to allow condensation or rainwater to be drained out (in practice it seems to collect here and then evaporate without needing any intervention).

At the top of the vent pipe you’ll need a sewer vent whirlybird. They’re available from plumbing supply places.  You can get one to fit onto 90mm or 100mm stormwater pipe, but I added a short length of wider pipe at the top and got a whirlybird that would fit onto that.  The top of the vent pipe (or all of it) can be painted black so that the sun heats the air in the pipe and starts it moving upward, assisting the whirlybird to draw air down through the mass in the toilet.  The wider pipe at the top just provides a larger volume of air to be heated – I’m not sure whether it makes any difference or not.

Whirlybird on top of a section of wider pipe

Whirlybird on top of a section of wider pipe

That’s about it, apart from putting a seat on top of the barrel.  I used the screw-down flange that holds the top of the barrel in place (photo below) and just trimmed a bit of the edge of it at the front to allow well endowed males to use the toilet without incurring any risk.  Ignore the white insert in the barrel, this is part of a trial of  new approach that doesn’t allow for composting in the barrel but removes the need to wrestle with a full 200L barrel when full.  I’ll describe it in another post.

Top on barrel

Top on barrel

The seat base in the photo below is made from two layers of marine ply.  The top layer is large enough to sit over the top of the barrel and to carry a standard toilet seat.  The lower layer (not visible here) has the same size hole as the upper layer and is glued and screwed to this.  It is just large enough to fit into the screw-on top of the barrel without too much free play.  In this way the seat stays in place without moving around when you sit on it, but can be easily lifted off the top of the barrel.  This doesn’t have to be marine ply, but since it was going to be out in the weather for years I thought it was worth the extra cost.  You can see the toilet seat to the left of the photo and in the lower photo – it came from a recycled timber yard.

Seat base

Seat base

Seat_webHere’s a shot of the two barrels in place.  The “resting” barrel on the left finishes composting while the barrel on the right fills (you can’t really see it because it’s covered with shade cloth – the photo was taken in summer and the shade cloth is needed then to keep the barrel from getting too hot for the worms).

Two barrels in place

Two barrels in place

Once the barrel is about one-third full we add some compost worms from one of our worm farms to it and cover them with a layer of damp soil.  At first we doubted that they would tolerate this environment, but they take to it readily and by the time the barrel is full it has a good population of worms and a lot of the mass has already been broken down by them.

With just the two of us using it the barrel takes six to nine months to fill.  In fact in the later stages the mass is reducing in volume, as a result of the composting process and the actions of the worms, just about as fast as we are adding volume to it.

There aren’t any special precautions to take with this type of toilet, apart from making sure the mass is damp enough to keep the composting going – we keep a spray bottle near the toilet, but seldom need to use it.  People who are taking antibiotics should refrain from using the toilet in case the antibiotic residues affect the composting process, and no non-compostable material (e.g. cigarette butts, tampons) should be put into the barrel.

When the full barrel is first moved to the resting position we put a layer of kitchen scraps on top and cover it with damp newspapers.  This encourages the compost worms that are already in the barrel to come to the top and start work on the top layer. If the worm population isn’t obvious in the top layer within a couple of weeks we add more compost worms.

The resting barrel has a liquid drain and a flexible hose connected to it, but the latter is mostly to keep critters from getting into the bottom section of the barrel.  I always intended to connect this to the vent pipe but never got around to it, and in the end it didn’t seem to matter.  In fact increasing the air flow might have dried out the mass too much.  Keeping the top of the mass damp is one of the few management measures that the resting bin requires.  We generally cover it with a thick layer of wet newspapers or hessian, and try to remember to add water to this occasionally.

You can wait for all of the mass to be composted and then empty the barrel just before changing it over with a new full barrel, but we have found that the worms population will be larger and work more effectively if we regularly take off the top layer of composted worm castings.

I’m happy to answer any questions about this system or to give advice on construction.