Pasteurization

Pasteurization

Composting Bins at the Soil for Life Garden

Composting Bins at the Soil for Life Garden

Pasteurization, named after its inventor Louis Pasteur, is a process that uses heat treatment to kill spoilage organisms. (Pasteurization) Traditionally used to kill bacteria in milk, the same concept can be used to kill the harmful pathogens found in human waste. A solar pasteurizer could take sludge from the Water Centre’s composting toilets and turn it into class A compost, which can be safely used in any type of garden, including food gardens.

In order for a pasteurizer to be effective, it needs to hold the material inside at a certain temperature for a specified amount of time. The time required depends on the type and amount per unit volume of bacteria in the substance and the U.S. Environmental Protection Agency has specified an equation for computing it for the pathogens in human waste. Yosemite National Park tested this equation in a solar pasteurizer and found that by following these parameters, it is possible to quickly and efficiently transform human waste to compost that can be used safely in food gardens.

One drawback of this system is that the temperature needs to climb up to 62 °C, which could be a slow process. A way to speed the process is to create the optimum carbon to nitrogen ratio within the sludge of 30:1.(Sutcliffe) This can be achieved by adding the appropriate amount of wood chips or dry reed plants from the wetland system to the waste after every use. A bin of the carbon rich material can be kept inside the toilet stalls for this purpose.

Benefits

A solar pasteurizer is a relatively simple system. Maintenance is not required often and the only labor needed during the process is for a caretaker to check the internal temperature to make sure that the compost is kept at approximately 62 °C. Construction is also simple, though systems designed for quicker composting may have more pricey materials. This cost would, however, be paid back once the pasteurizer created safe compost that could either be sold for profit or used for food gardens, saving the community money on food.

Read More about Composting Options for the Sanitation Facility

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