Thursday, 14 April 2016

The Humanure Project : Potty Milkshake

Human Excreta was alternately layered with sawdust, grass and leaves in different containers on Tuesday, 5 April 2016 as documented in a previous post.

Since the piles had been left for a week, the temperature was expected to rise to 50 degree Celsius due to the intense microbial activity happening inside. When organic material is layered, nature seeds it with microscopic creatures that proliferate and digest the pile created. In the process, the heat generated is so much that disease causing pathogens resident in the humanure are destroyed.  

Equipment for Temperature Measurement: 

Above is the equipment used to measure the temperature of the compost piles.  3 tiny holes have been drilled into the buckets at different levels to measure the temperature in different areas of the pile and perhaps identify a heat patch. The temperature is measured using a food temperature probe

On day 1 - i.e. 12 April 2016, the maximum temperature was 37 degrees Celsius. To increase the temperature to about 50 degrees and make the process of 'thermophilic composting' faster, the piles were churned on day 2 - 13 April 2016. 

Turning a pile :

a)  Adds oxygen to the compost pile which is good for aerobic microorganisms
b) Ensures that all parts are subjected to high internal heat which results in successful pathogen elimination. Usually, continuous compost piles have a thermophilic layer, which is located in the top 2 feet of the pile
c) Makes the pile more chopped and mixed. This eliminates odors and prevents the material from matting  
d) Speeds up the process of composting. 

Equipment for Churning: 

4 pieces of a 10 mm mild steel rod were welded to make a structure like a tuning fork. It was inserted into a drill machine. (An affordance on the part of the drill machine). 


Fortunately / unfortunately, the speed of this drill machine cannot be controlled and owing to the high speed, when the rotating tuning fork was inserted into the bucket, a few bits of the top layer spewed out like a mini tornado. The other underlying layers were not disturbed. Was fun, I must say. I recommend you to not try churning a compost pile with a drill machine.

A better approach :

The piles were churned without any machine this time. I poked around and broke down the lumps that had formed inside manually to increase the surface are of the material being exposed to air. Hopefully, the churning will turn up the heat by a few notches. Turning a compost pile does not come without its disadvantages. Although turning is known to speed up the process, it leads to organic matter and nitrogen loss. Therefore, the pile should ideally be turned once every two weeks
(Source: Brinton, William F. Jr. Sustainability of Modern Composting, Maine, USA)

My classmates think I am making a Potty Milkshake. So it's true that ' My Milkshake brings all the boys to the yard'. (For those who don't know what I am talking about, you can listen to the song here)

Documentation credits: Aboli Joshi 
Bibliography: The Humanure Handbook by Joseph Jenkins

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