Dog poo experiments

My inspiration - Dr Andrew Agnew

My inspiration – Dr Andrew Agnew

One of my lecturers at university, the person who inspired me to become an ecologist, was Dr ADQ Agnew. He was (and still is) the epitome of a dotty professor… one day he came in to the department wearing two ties because he’d forgotten that he’d put one on and so he donned a second before leaving the house. He would sing to us in lectures (I particularly remember a rendition of ‘I’m a Gnu‘) and deliver anecdotes… he even took us on a field trip to the Low Countries (Holland, Belgium, Luxembourg, France and a bit of Germany) that involved him and seven female students all in their early 20s… which probably wouldn’t be allowed these days! Anyway, Andrew often claimed to have studied the effects of population density by examining dog turd predation by lawnmowers in a park… I can find no published paper on this subject (and, believe me, I’ve looked), but it may exist somewhere. I might ask him about it next time I see him.

Max - a source of pollution

Max – a source of pollution

My experimentation, in contrast, has a rather more practical bias. One of the waste products that we have to deal with on a daily basis is, indeed, from our dogs, Sam and Max. They are terriers, so there isn’t a huge volume, but even so it is something that we do not feel happy about sending to landfill.

It is easy enough these days to buy plastic ‘poop’ bags that are biodegradable and simply to throw these away with all the rest of the trash. I wondered whether it might be possible, however, to collect the dog poo this way and then just place the entire bundle on a compost heap to break down. However, some trials revealed that even after a year, the bags were still identifiable, although the content had often disappeared. Anyway, whilst trying to reduce our impact on the environment, it seems inappropriate to ‘consume’ plastic bags in this way.

What we wanted was a composting system that was contained (to avoid flies and smells) and that was separate from our standard composing bins, so that the end product could be used separately. It’s generally recommended that you don’t use humanure on food crops and I assume that the same goes for doganure (ooh look, another new word!). However, whilst I don’t want to apply it to salad crops, for instance, I see no problems with using this type of compost when planting fruit trees and bushes, or in a bean trench.

I have written in the past about my wormery, but I have become increasingly aware that I don’t really need one except for the liquid feed: pretty much all the compostable material we produce can go on a ‘normal’ compost heap and with the aid of grass clippings, we manage to get these hot enough to break down quite quickly. In addition, I’m an increasing fan of in situ composting… so that the heat generated can be utilised by growing plants. So, the wormery has become superfluous and, thus, available for use in the composting of dog waste.

Some limited research suggested that dog waste is acidic (I haven’t tested this, but perhaps I will once I can work out the best way to sterilise my pH meter afterwards) and that some means of raising the pH would be appropriate. One of the suggestions was that adding wood ash would work – something that we produce from our Kelly Kettle and that we normally add to the compost or put straight on the garden. I was inspired by Deano’s approach to this problem at the Sustainable Small Holding, but decided to use shredded paper for some bulk rather than the Miscanthus that he has access to. We collect the faeces in a bucket round the garden, but when we are out on a walk, they are picked up in paper and transported in a plastic bag before being added to the bin, complete with the paper wrapping as an additional source of carbon.

Initially, I only added the three dry ‘ingredients’: faeces, ash and paper. But Deano’s suggestion to add urine as well seems to have been well-founded: a recent agitation of the content of the bin revealed that it was very dry and did not seem to be very active, although there was no unpleasant smell. In addition, there was no sign of the worms that I had added. So, with this in mind, I have been adding urine for the past couple of weeks, now that I have a ready source. I will give it another stir in a week or two and see how decomposition is progressing.

Despite the slow composting process and the dryness, I had extracted about a litre and a half of liquid feed from the reservoir at the bottom of the bin prior to starting to add additional liquid in the form or urine. This extract has been used to feed peppers and tomatoes… applied to the soil not the foliage… and is the only feed that I have provided them with so far this year, with good results.

Although I had hoped that decomposition would be quicker than it has been so far, I am hopeful that this will turn out to be a valuable way to add fertility to the soil and will be a real case of turning something initially perceived to be a pollutant into a valuable resource. In the past urine and dog faeces were used in the tanning industry, but since this is not an option for me, I think I’ll stick with increasing soil fertility!

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3 Comments

  1. John

     /  August 17, 2013

    I hope the nice big German Shepherd one we contributed last Sunday is useful!

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  2. Deano

     /  August 19, 2013

    I have found that if there isn’t enough air in my compost heaps, any large clumps of turd, stays relatively intact. When evenly distributed it all vanishes very quickly.
    I’m pleased that somebody is looking at this properly.
    Deano

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