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From Flying Toilets to Free Methane
Ethan Zuckerman, 4 Mar 07

Afrigadget has some excellent photos of a novel design for a latrine in the Nairobi Kibera neighborhood. Kibera is a huge neighborhood, home to approximately 500,000 residents, very few of whom have access to running water or sanitary facilities in their homes. Some Kibera residents live close enough to pit latrines to use these facilities - others are forced to rely on the less sanguine system of “flying toilets” (i.e., putting human waste into a plastic bag and throwing it as far from your house as you can) because of the cost of latrines or the danger of walking the neighborhood at night.


Photo from Afrigadget.com

The biolatrine probably won’t help with the safety issue, but may well help with the issue of cost. According to an article on IslamOnline.net by Wanzala Bahati Justus, the latrine uses a biogas system used widely in Southeast Asia to convert animal waste into methane and adapts it for human waste. The latrine looks much like a standard pit latrine, but waste goes into a huge “bio-digester”, a large underground dome, which stores sludge for 120 days, releasing methane.

The methane is being used to light and cook meals at a nearby school. The volume of methane produced is large enough that the latrine may be able to sell some of the gas and use the profits to subsidize the costs of operating the latrine. There’s a second environmental benefit from the use of methane as cooking gas - the more common alternative of charcoal has major negative implications for Kenya’s forests, especially those near urban areas. If the latrine operators are able to find a market for the fertilizer (the solid remains of the sludge after it’s processed for 120 days), the chances for fiscal sustainability increase.

One of the major challenges with launching projects like these in informal settlements is questions about ownership of the land, as Robert Neuwirth outlines in book “Squatter Cities” - it’s hard to invest in building structures like this one if there’s uncertainty about whether the “legitimate” property owner will order the structure bulldozed. Here’s hoping this experiment with biogas latrines will survive and inspire more of the same in the Kibera area.


My friend Cyrus Farivar points out that there have been other experiments with human waste to methane, including an award-winning project at a prison in Rwanda - Cyrus wrote an excellent story for Wired News on the topic.

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Comments

Excellent - I've been looking for info on biodigesters using human waste, to add to Appropedia.org. Thanks!


Posted by: Chriswaterguy on 4 Mar 07

Then you may want to look into George Chan´s "dream farm", a full "integrated farming and waste management system" which starts (if cycles start) with pig´s waste and ends with tilapia etc.


Posted by: Lucas Gonzalez on 5 Mar 07

This is a wonderful idea. I'm wondering though, has anyone suggested it to some of the Asia-Pacific countries? From what I've heard, this would be very useful in Bangkok, as the canals in the poorer parts of the city are polluted with human waste.


Posted by: Wesley Parish on 5 Mar 07

This comment is not meant to be negative but rather informative.

The process will not remove all of the pathogens from the human waste. It is likely to remove over 50%, exact figure depend on what types of pathogens. Using it as fertilizer without processing it further to remove the remaining pathogens can lead to contamination and spread of a number of diseases that are responsible for high mortality (particularly among the young) in developing countries.

There are a number of ways to due this through technical or biological systems. Chan's work mentions many of these but a biodigester is insufficient alone. There is no best practice, but I prefer biological systems eg(algae, duckweed, waterhyacinth, wetlands) in these cases the resulting plants can be used as animal husbandry/aquaculture feed.


Posted by: Jakub Olesiak on 9 Mar 07

Methane digesters are all over the world.
However, anaerobic digestion is a tricky process to manage.

Look up Hamarby Sjostad for a very interesting methane digestion scheme in Stockholm. Adding carbon-based solid waste, food scraps, waste vegetable oil, etc. helps boost the carbon. Look to India, China, Sweden and Germany for methane digesters. Of course most landfills and some wastewater treatment plants in the U.S. feature some methane conversion to power.


Posted by: Carol Steinfeld on 9 Mar 07



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