Urine fertilizer could save energy and water

A Brattleboro company has located itself at what one of its founders calls “the intersection of sanitation and agriculture” — where researchers are learning to manure with urine.

Using methods still under development, members of the Rich Earth Institute are growing crops with “a local and abundant source of fertilizer,” said co-founder Kim Nace, speaking at a conference on water quality held Wednesday at Vermont Technical College.

Humans produce enough of the aurulent liquid each day to fertilize a loaf of bread’s worth of wheat, Nace said. That amounts to between 100 and 150 gallons per year, she said.

Diverting the fluid to crops saves water and energy, and forestalls carbon dioxide pollution, according to Nace.

Ordinary toilets require one to three gallons of potable water to carry away less than a liter of urine, Nace said. The resources needed to produce and distribute potable water mean that “every time we save energy, we save water, and every time we save water, we save energy,” she said.

The water and energy savings are one reason to recycle number one, Nace said. But spreading it on crops also reduces the volume of carbon dioxide released into the atmosphere, she said.

One percent of worldwide atmospheric carbon pollution can be attributed to chemical fertilizers, Nace said. Replacing those fertilizers with one humans produce every day would eliminate a significant source of pollution, she added.

Although urine typically emerges pathogen-free into the world, the Rich Earth Institute pasteurizes the roughly 5,000 gallons used each year for their research efforts, she said. The organization uses solar energy to heat the effluent to 158 degrees for half an hour, voiding it of harmful microorganisms, she said.

Urine contains significant concentrations of both nitrogen and phosphorus, which are the two most common nutrients plants require, Nace said.

Wastewater treatment plants would ideally remove those nutrients, as in large enough concentrations they pollute surface water, she said. But the technology to do so, once they enter the septage stream, is costly enough to prevent such efforts outside very large cities.

For example, current wastewater treatment methods require costs of between $200 to $275 to remove a pound of nitrogen from sewage. By diverting urine before it enters wastewater systems, the cost of producing nitrogen from liquid human excreta falls to around $20 per pound, Nace said.

Each person eliminates around eight pounds of nitrogen per year, meaning that costs associated with pulling these nutrients from wastewater aren’t insignificant, she said. Diversion of urine to cropland would also save almost a trillion gallons of water each year, she said.

The Rich Earth Institute is currently soliciting urine donations with which to conduct further research. Additional information may be found at richearthinstitute.org.

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