Dog poo digesters

A while back, I got a bit annoyed at the quantity of land mines that Athena was leaving. That, plus the frequency, and the location (always right by the gate and next to the driver’s side doors of the cars). To this day, she is continues her campaign of maximum inconvenience.

I know, it’s one of the joys of having a large dog that lives mostly on veggies. Our biggest problem is getting rid of it all.

Pondering the problems of smell and hygiene lead me to think of an anaerobic way to compost it that would keep it out of sight and out of mind. I came up with this first system of in-ground Bokashi composting that uses old 20 litre plastic buckets and deep holes. The second system is detailed later in the page.

You will need to make multiple bins. When one is full, you start to fill the next, allowing the contents of the first to decompose peacefully. At Ligaya Garden, we’ve found that a three bin cycle works for us. By the time the third bin is full, the first is ready for emptying and the cycle repeats.

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System 1

This system is best for those who have access to soil for digging into, It is essentially, a bucket with holes in it to which the dog poo and inoculated Bokashi material is added. The bucket is located below the ground, filled, then sealed. The next bucket is filled while the first processes.

Processing means that the dog poo is colonised and part digested and fermented by the microbes in the Bokashi material, then, slowly soil fauna find their way in a and digest both the Bokashi microbes and the part-digested poo. The firm packing of the poo and Bokashi material as well as the sealing and burial of the bucket provide a temporarily anaerobic environment for the Bokashi microbes to do their thing. Over time, as the soil biota find their way in through the sides of the buckets, they begin to convert the environment to an aerobic one in which they can thrive. After a time, the bucket is opened and the converted poo is distributed into the garden as a compost material rich in soil fauna and microbial life.

Making the bins

Step 1

Drill a couple of holes around the wall of the bucket, a couple of inches up from the base. Then drill a couple of 10 mm holes in the base. These holes are for drainage, and to let worms in later on. It’s pretty rough when you haul up a bucket after a couple of months and it’s full of black, smelly liquid!

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Step 2.

Cut some sort of cover that can act as a plunger. I’ve found that the bottom cut out of one of the small buckets works well and can slide down nearly to the bottom of the big one.

Because Bokashi is an anaerobic process, it’s good to press the poo and bran down firmly when you put it in the bucket. I tend to use a shovel to press it, that puts a good distance between me and the mess!

Add a handle to the presser, I used off-cuts of wood as handles. You don’t want to be prising the plastic off of the uncompleted compost muck by hand!

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Step 3

Dig a hole deep and wide enough to fit the bucket in. Then, put the bucket in it and fill around the sides with the dirt you dug out.

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Using the bins

Every day we clean the paths, the produce goes into a small bucket. Every two or three days the contents of this bucket goes into the Bokashi dog poo digester bin that is currently in use.  By only adding it every few days, we minimise the amount of fresh air entering the bin.

To start a fresh bin, put a big handful of Bokashi bran in the bottom of the bucket. I add some Comfrey or Nettle leaves too to kick off the composting. You can add anything that you think will work. You can use EM1 or Bokashi culture spray if you want instead of bran at every stage of this project.

Add the excrement, then another big handful of bran.

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Put the lid on the big bucket and cover it with dirt. The extra dirt on top helps slow oxygen getting in as well as stabilising the temperature.

Repeat these steps over time until the bin is full, cover it with a layer of dirt, at least 5 cm, then move on to the next bin. If you have a big block, don’t forget to make some kind of marker so that you don’t forget where the bins are.
To save any possible contamination, place each bin as far away as possible from the others and don’t place them in wicking beds .

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Results

We’ve found that with Athena, being the kind of dog she is, three of these bins are the amount we need in the warmer weather. We could add a fourth bin for winter to compensate for the lower temperatures slowing the bacterial action.

You’ve really got to try a couple of bins to see how the system suits your dog’s output.

Our bins are numbered and positioned so that when one is full, the next one in sequence is at the maximum distance from the previous. This it a precautionary thing to minimise any kind of build up that may occur. They are also positioned by trees and perennials and away from our daily vegetables. Once again, this is a precaution to minimise the risk of any kind of pathogens reaching our daily veggies.

What to expect when you open the bin

It’s quite surprising, especially when you consider what went into the bin. There’s only a faint fermenting kind of smell, kind of like vinegar. The solid material is dark and crumbly and full of worms. If it’s all gone well, there should be no trace of dog poo odour – you’ll know straight away!

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Can it go on the garden?

We’ve had no problems putting it straight into the garden, though I usually bury it in the mulch or fresh compost to help the worms enjoy their lives. By this time, the anaerobic bacteria (the ones that would normally cause sludge and smell) have long departed. It is best to err on the side of caution as there may be some pathogens remaining and it only takes 1 to get you sick, so don’t add it to your leafy greens or anything that you’re going to eat in the next couple of days.

If you decide to err on the side of caution and add the fresh compost to an aerobic compost heap, it will kick off that heap remarkably well as all the nutrients that came out of the end of your dog are now readily available for the aerobic bacteria to feed on. Your compost bin or heap will heat up quickly as the microbes do their work.

As with anything concerning any kind of feces, the recommendation is that you don’t put it directly onto fruit or leafy vegetables that you are going to eat in the short term.

How much do you get?

It’s really a worthwhile process but it really depends on your dog and their diet. From three bins, we get about 12 kg of rich fertiliser for the garden and the cycle takes about three months in the warm weather.

We don’t get the 12 kg in one hit, the first bin is emptied after the last is filled with fresh poo. This takes about two months. Each bin yields about 4 kg. It may be different for you depending on many things such as –

• type and diet of your dog(s)
• type of soil and how much life there is in it to digest the poo
• weather and rainfall
• time spent in the ground
• frequency of adding new material

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System 2