Pitlatrine-Biodigester Converter and Gas Purifier

About Solution

The PBC+GP is an extremely affordable and efficient biogas energy technology.

As a relatively expensive and complex technology that is socially misconceived and ridiculed, locally-sourced-and-creatively refined waste plastics are used to develop a most socially accepted, affordable and efficient technology. Specifically, this is where existing pitlatrine toilets would be converted to biogas generators using human and kitchen waste.

In brief, a small toilet tank is constructed on top of existing toilet floor using locally available materials (bricks and wood planks). This functions as a biodigester where the feaces, food wastes and grey water (sludge) are disposed of and digested by anaerobic bacteria. Methane and other gases in smaller quantities are produced and collected through a pipe that is connected to the tank. The other gases which include Carbon dioxide, Hydrogen sulphide and Nitrogen are scrubbed off in the gas purifier that is attached to the pipe before proceeding to appliances for cooking and lighting. The liquid and solid by-products (slurry), which function as agricultural fertilizer, are tapped out through different outlets.
Once constructed, the unit will provide energy for cooking and lighting without any further costs except maintenance. Since production of feaces as well as food wastes is continuous, it means steady access to affordable and clean energy for the larger population of poor people.

Biogas is rarely used in many homes and institutions. But it's not because there are no technologies or innovators out there! There are many!
The reason has been social unacceptability and lack of knowledge over biogas. The existing technologies tend to be relatively expensive (HomeBiogas 2.0 unit costs US$650).
The PBC+GP is a biogas generator unit that will cost as low as US$35 to install, while highly satisfying users in efficiency.

In reference to the sketch provided, the following is how the PBC+GP works.
The biodigester is constructed on top of toilet floor using bricks and wood planks to act as a small tank (5). A polyethylene tube or similar material (6) is inserted inside the tank to prevent air from escaping or create a biodigester. The toilet hole is made from used plastic bottles (4). This is connected to a water trap (8) that keeps the toilet airtight. Used plastic bottles are used as slurry outlet (10) and (12), liquid and solid respectively. Solid slurry (12) may be taken away or directed into the pit (13). Gas accumulates on top of sludge/feed inside the tank and is collected through pipe (14). (15) is the gas purifier that  contains steel wool and Sodium hydroxide solution which are meant to trap Hydrogen sulphide and Carbon dioxide respectively. The gas comes out of valve (16) much purer and ready to be used for cooking and lighting



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