Technology

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Farmers and gardeners have harnessed the fertilizing power of urine for millennia, using urine directly as fertilizer with only the most basic of technology. This approach is still safe and effective, but technological advances now allow urine to be collected odorlessly and aesthetically using modern fixtures, then concentrated and efficiently transported large distances from urban areas to outlying farms.

Low tech

If urine is collected and sealed in a glass or plastic container with a tight-fitting lid, all the fertilizer value will be preserved.

Plastic jugs with handles and tight-sealing, threaded caps are the most popular among home-scale urine recyclers. The Rich Earth Institute has developed a low-cost portable urinal with a detachable 5-gallon screw-top container for home collection. Women either urinate directly into containers or use a variety of toilet inserts or standing urination devices.

The ammonia that develops in stored urine is a natural sanitizing agent, and it will rapidly destroy any bacteria that may be present. Home urine recyclers typically dilute urine with water and then apply it directly to the soil with a watering can.

High tech

Many modern urine-diverting bathroom fixtures are made of porcelain to look similar to conventional fixtures.

Waterless urinals in particular are becoming common, and can be plumbed directly to urine collection tanks. Urine diverting flush toilets are available that collect urine while flushing paper and feces–as well as urine diverting composting toilets that collect urine in a tank and compost feces in a separate chamber. These permanent fixtures can be plumbed to large-capacity tanks which are pumped out by a commercial service once or twice a year.

When urine is collected in large volumes, pasteurization at a central location can be a practical sanitization method. The Rich Earth Institute has developed a mobile, computer-controlled pasteurizer with a high-efficiency heat exchanger to sanitize urine quickly and energy-efficiently. High temperature composting and ultraviolet exposure are methods that may also be suitable for sanitizing large volumes of urine.

Storage capacity is a major expense and logistical challenge in large-scale urine recycling. Technologies to concentrate the fertilizer in urine into a smaller volume will play an important role in making widespread urine recycling economically viable. The Rich Earth Institute is developing reverse osmosis as a method to concentrate urine while preserving its fertilizer value. Freezing, evaporation, and vapor compression distillation have all been demonstrated to effectively concentrate urine.

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