Festiliser in Malawi
The price of artificial fertiliser has been on the rise for several years now. The effect of this is that beyond the allocation of subsidised bags that each family is allowed, it has become beyond the financial reach of most Malawians. On top of this, the land in Malawi (particularly the more arid regions such as Balaka) is poor in nutrients, meaning that more fertiliser than is subsidised is invariably needed to keep a whole family fed. The result of this is of course wide-spread malnourishment.
Benefits of Composting Toilets
Composting toilets use resources that are in abundance to combat these difficulties and have the potential to ensure free fertiliser for everyone. Besides this obvious benefit they eliminate all of the environmental issues caused by artificial fertiliser. Artificial fertiliser will often overload the earth with nitrogen, much of this cannot be absorbed by the earth and so runs into rivers and lakes. The effect of this causes too much algae to drain the oxygen from the water, destroying waterborne life. Compost from toilets does no such thing.
Artificial fertiliser will also degrade the quality of soil, necessitating that more and more fertiliser will be needed over time whereas there is evidence that suggests that not only does Humanure compost not have this effect, it actually improves the quality of soil over time.
How it works
Fertiliser mainly consists of Nitrogen. Our excrement is also full of it so can be used in exactly the same way. That said using raw manure will not use the full potential of the nutrients in human waste. To unlock this potential the composting process needs to take place.
This is the process of good, harmless bacteria breaking down the raw waste matter and converting it into compost which is easily absorbable by the soil. The best of this bacteria, that not only converts waste faster but also destroys potentially harmful pathogens quicker, is called thermophilic bacteria. These bacteria need several environmental factors to thrive which composting toilets aim to provide. They consist of:
Temperature – As is hinted in their name, thermophilic bacteria thrive at certain temperatures, from around 45 degrees up to above 100
Ventilation – Thermophylic bacteria need air to survive, just like any organism.
Moisture – The moisture level cannot be too high or too low. As such the compost piles must be primed with absorbent material. It’s also an option to separate the urine from the pile to keep it from getting too wet,
Time – Like any biological process composting takes time, how much depends on the conditions provided. When thermophilic bacteria are present the process will speed up – particularly the essential destruction of pathogens.
Carbon/nitrogen balance – Composting will not take place if the nitrogen level is too high as the bacteria needs a balanced diet to survive. Carbon matter must be added to a compost pile to give the right diet for the bacteria to thrive.
The toilets in Mlambe
Our toilets in Mlambe were completed just two weeks ago let by our volunteer Theo Kotz. They are designed around the Skyloo concept. This is a series of toilets a metre above the composting chambers, meaning that the deposits needn’t be handled before the process is complete. The design is set up to encourage all five of the aforementioned conditions in the following ways:
Temperature: The climate in Malawi is very hot and we have painted the chamber walls to encourage maximum solar absorption.
Ventilation: The chambers have ventilation holes in the sides to allow air-flow through them.
Moisture: As well as a good priming layer, we have elected to separate the urine from our compost deposits for the initial trial period, his will keep the moisture levels down and keep the variables to a minimum.
Time: Each cubicle has two chambers, only one of which will ever be in use at one time. Once one is full, it is locked closed and the other is used. During this period when the second is filling, enough time will pass (a minimum of 6 months) for the process to take place and the compost to become safe and valuable to use.
Carbon/Nitrogen Balance: This is the main difference with traditional toilets in terms of their use. With each deposit the user must add a measure of sawdust and ash to redress this balance. Other dry plant matter can be used in their place. Together with the initial priming with brown plant matter, this ensures that the right diet is in place for thermophilic composting to take place.