You Can Compost Human Waste!

By Carol Steinfeld
Published on March 2, 2011
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Nance Klehm demonstrates that human waste can be composted and used to safely fertilize soil. 
Nance Klehm demonstrates that human waste can be composted and used to safely fertilize soil. 
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Properly recycled human waste contains no dangerous bacteria. 
Properly recycled human waste contains no dangerous bacteria. 

Oceans of sewage. Tapped-out water sources. Ever-costlier fertilizers. A flurry of recent studies warn of resource scarcity for the world’s cities. Fortunately, a growing legion of urban dwellers think the nutrients and water in their toilets are too valuable to flush away. From Boston to San Francisco, city dwellers are taking the “waste” out of wastewater, and showing that recycling at the toilet isn’t just for homesteaders anymore.

Don’t Waste Your ‘Waste’

Although his Boston apartment has a comfortable modern bathroom, Patrick Keaney usually trudges down two flights of stairs to use a waterless, urine-diverting composting toilet.

Keaney and his housemate, David Staunton, constructed the simple toilet system after learning that most of the nutrients in human excrement?–?as much as 90 percent of the nitrogen and half of the phosphorus?–?are in urine alone. The two saw an opportunity to capture free fertilizer and cut their water bill.

Knowing their landlord wouldn’t allow plumbing changes, Keaney and Staunton installed their toilet in the basement next to the warmth of the water heater. The toilet consists of a wooden bench with an opening to which a plastic diverter is affixed (you can also use a trimmed funnel) to drain urine into a 3-gallon pail. Solids (feces, toilet paper and any wood shavings or mulch added) drop to an 18-gallon plastic bin. When the bin fills up, they cap it with a perforated lid, let it season for a year, then shovel its contents into a composter. “We use it to build up the soil around fruit trees and flower beds,” Keaney says. As for the urine, it’s composted with woody material or poured onto well-mulched and well-watered garden beds.

Is using urine this way safe? Most pathogens we excrete are in feces. Urine is almost always pathogen free. Any trace pathogens get deactivated as the urine ages. Some experts say one month of aging is sufficient for a household’s urine used on its own garden, while six months is advised for urine from combined sources. If applying directly to plants, you must dilute it with eight parts water to one part urine to avoid burning plant roots (some sources recommend 20 parts to one).

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