I used stacked concrete blocks for a compost bin a while back, just on soil, and had no problem with moisture or air exchange in the compost. The bins, 2, were 6 x 6 x 4.

I live in an arid climate as well - Everything you're doing sounds great, but if it is feasible - speaking of health, strength, dedication - your problem of aeration might best be solved by building into the walls a slot for a pry bar in each bin. So, once every few weeks, you go out and stir it up a bit, using a lever. A really long steel pipe will do wonders.

My 'bins' (made with old plastic swimming pools) are also solid around the sides, and I'll cover it with a tarp to keep in the moisture. I will now and again ram in a metal bar to get some air in it, or use an electric drill and a long auger. But these things are 1.5 meters high, shy of 3 meters in diameter.

In practice though, being lazy, I often go with the theory of let it rot for two years, it will be ready.

Hi, I live in a very dry climate also (although it's raining today for the first time in months!) My piles just sat and did nothing until I started watering and turning them frequently. Keeping that "wrung out sponge" moisture level is just about impossible in an open pile. In a dry climate, if your pile has large pieces and no moisture, it can sit for a lot longer than 2 years and never break down at all.

But aeration and frequent turning are just as important, so don't make your bins too big. Unless you have heavy equipment (tractor/backhoe) you need to keep your piles small enough that you can stick a fork in them and turn them without hurting yourself, at least once or twice per week. They say a pile should be at least 3'x3' in order to compost properly, but I wouldn't go much bigger than that, maybe 4'x4'. And build near a water source, like a hose or a rain barrel.

When I dump the chicken poop bucket (I clean their coop daily) or the kitchen compost bucket on the pile, I rinse them out and dump the water on the pile, too. Oh, and if you have access to used coffee grounds, they are a GREAT source of moisture in the pile. My big "Earth Machine" plastic bin has heated up and stayed moist much more easily since I started putting in large amounts of UCG. Do you have Starbucks in Karoo?? I don't even know what continent that's on! LOL Any cafe or restaurant would do, of course, as long as they're willing to save their coffee grounds for you.

--Maureen

I recall this compost starter called Biozome where you don't need much water to help break down organic matter.

No idea if it works on my plants but they all seem to grow faster. N=1 though.

Here is a link that might be useful: Biozome

..
Semi arid here. I think you're a little closer to the equator than I am but I'm about 15 miles from the ocean. I'm about 34 degrees from the equator. I get desert influences and marine influences. We can get 80 point swings in the relative humidity in 24 hours. Mostly the low humidity in the day from desert winds and high humidity at night. Rainy season is in the winter.

A lot of citrus and avocado is grown around here.

My bins are slightly smaller made from pallets. They get plenty of air and they are built on pavers or or thin bricks - a permeable hard base. The base allows for worms to get in - big time during the rainy season - but keeps the burrowing animals and the tree roots out.

I run my bins on 18 month to 24 month cycles. I generally just feed the bin stuff once a month and cover with grass clippings and whatever. After about 3 months I start to see the volume reduce. I can keep feeding forever I think but at some point around a year, I stop feeding and just water. I've usually topped it off several times by then. During the dry summer I'll water a full bin with about 4 liters a day with a watering can. After feeding a bin for about a year, I'll just water for 6 months to a year. Right now with the cooler and wetter weather I'm getting lazy and I am only watering about once a week. The outside parts might look dry but the inside is moist enough.

You've got a chipper so I'm guessing you don't have to worry about large pieces. Your arid climate means your materials aren't going to be too wet so you will have moisture issues and if you're not turning like I'm not turning, the process will be slow.

I like the pavers versus a concrete base because of the worms. If you turn like I used to, you can still sweep up afterwards so less mess and loss.

Yeah let air in through the walls. Keep the bins out of the wind and the sun and you'll go a long way to retaining moisture. I don't like the tarp because of the lack of air. Better a cover that will block the sun and the rain if the season starts dropping too much rain at one time.

Once the bins get some bulk and age they will retain moisture better. You can always piss in them at that point and it will never touch the bottom.

I don't think you'll go too far wrong with what your thinking right now. What is going to work best is what works for the way you do things. Make the process fit with the way you live and not the other way around. If that means it takes a little longer - no big deal. Once you get into regular cycles, you won't notice so much how long it takes. The compost works for you. You don't have to work for the compost.

Don't fuss too much and good luck.

two cents
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I have brick walls on my compost compounds but no base. In my arid summers, I do have problems trying to keep the heap moist, even with a black plastic sheet on top to stop evaporation. So I think a concrete base would be a good idea. I'm in a mediterranean climate though and get really heavy rains in the winter, so I don't want a concrete base on mine as I want excess water to be able to drain. I've never had problems with aeration, and I didn't leave gaps, and I never turn. I often have fairly course material in the heaps though, so your milage may vary.

I lived in the high veldt for a few years and am familiar with the frequent droughts there, it would seem Karoo would have worse conditions.

The solid base is a good idea on both counts. Where I live now, a solid base would prevent soil activity from inoculating the pile and earthworms from cold finishing; do you have worms? Not an issue if you always "hot" compost. A permeable base could be superimposed on the solid if needed.

Given the aridity, rain/grey water catchments might be advisable to maintain proper moisture. You will have to look into hazards involved with greywater storage if it can't be used directly.

Wow everyone, thanks a bunch for all the replies! You're really helping me with ideas, I just love tinkering and refining techniques! I've just spent the whole morning weeding in my garden, got about 3 wheelbarrow loads so far and its really hot and humid today. Must be about 32 degrees C today!!! Sweaty stuff lol.

I'm in South Africa. Sorry for the confusion! We border on a Mediterranean climate, but not so much rainfall in the winter, it's sparser and spread throughout the year, not really concentrated in any one season. Unfortunately their aren't any Starbucks around here, I think they have them in Cape Town. There is a local franchise of coffee shop called 'Mugg and Bean', but the nearest one is at least 150km away :( On the bright side there are a number of restaurants in my hometown, which get through quite a bit of coffee so I can always ask them to save me their grounds. I'm sure they'd be more than happy to.

As far as not having a semi permeable base is concerned. I've thought about that, but I already have a big worm farm, which is housed in a converted bath. Eisenia foetida I believe so I was going to inoculate the piles from that now and again. I tried to do that to my exposed piles, but I think it was way too dry for them, because I dug in there a few weeks later and only found a couple (1 or 2) out of hundreds I'd introduced previously!

My chipper is a great help, like you say rott, I'd probably have to wait for ever for it to breakdown if the pieces weren't reduced in size and I'm a tad too impatient for that! I really don't have a problem with turning my compost once or twice a week if its going to make things speed up that much more. Still relatively young and virile and I could use the exercise haha.

I'm busy saving up for all the materials to build the composting units. I'm relying on my father to help me build it as he is a builder by trade. Need 7 square meters worth of bricks and two bags of cement for the walls. Plus about a square meter of stone chippings and two square meters of sand for the base. Not cheap, but I'm confident it'll be money well spent in time!

It rained for the whole night two days ago so the soil is wonderfully moist and perfect for planting and weeding. Must crack on and make the most of it before it dries out again.

Will post updates as the project progresses! Oh and just so I know is it possible to upload photos to this thread? Or would I need to do that in the gallery?

Alex

Cheers alphonse, ja I reckon you may be right that it's a bit more extreme out here. At least they have rainfall in the summer up there in the highveld, down here it's mostly dry as a bone. We get very cold frosty conditions in the winter though. Yes I think the worm idea is good, not so sure about the grey water though as that would possibly contain chemicals, toxins, detergents, etc. that could potentially harm the beneficial microorganism fauna in the piles. If I knew we were only using biodegradable shampoos, soaps, washing liquid, etc. I might consider that. The other problem I have, which I haven't mentioned yet are baboons. They are real scavengers and will cause tremendous damage to garden and house alike in their search for sustenance. It's nigh on impossible for me to grow to maturity, fruit and vegetables, because of them :( This particular troop is quite small consisting of about 20 members, but a single baboon can cause a lot of grief, multiply that by twenty and you'll be shocked at the amount of problems they can give you! The only feasible deterrent that worked was a baboon monitoring program with chasers that were paid to keep them out of town, but the local council decided they didn't want to fund the program so it abruptly came to a halt and the problem is getting worse!

Hi,
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It's so very interesting reading these forums, not only for the educational value and the banter, but to read the problems people have from all parts of the world. I got a kick out of reading protea king's post about having problems with baboons. Baboons? Here in the states we have rabbits - racoons - voles - moles - gophers and an assorted list of other critters that attack our gardens, but a Baboon? I can just see me now walking out in the garden and seeing a Baboon.

So protea, is there anyway you can fence-off your garden area to keep these Baboons out?

Greg
Southern Nevada

I think your problem will be keeping moisture in, rather than shedding excess moisture, so I would go for the bigger size- 4x4x4 (2.4 cubic feet) rather than 3x3x4 (1.3 cubic feet).

If the pile is too dry, composting stops. If too wet, composting is slowed until the excess water can drain away.

Cinder blocks are permeable enough without adding gaps.

I kind of think the worms will find a way in regardless of what kind of base you use.

Love the photos!
Your raised are so well made( most of mine are just soil or 1 X 6 inch boards) that you could compost in a new bed, until everything was compost & cool( in more then one way). Then just plant in it, start another bed.
All the post here are really good compost bins.