Study: Human waste could be resource-rich fertilizer for global agriculture
Monday, August 27, 2018
Well, if this isn’t a load of … then nothing is. But, that’s what we’re talking about: human waste.
While the subject is often taboo, human waste actually is full of nutrients that can be recycled into products to promote agricultural sustainability and better economic independence for some developing countries.
Used properly, our own waste may be nothing more than the animal manure that makes the foods we grow so abundant, and our gardens so strong and attractive.
Researchers at the University of Illinois at Urbana-Champaign recently developed a model to clarify what parts of the world may benefit most from “re-circulation” of nitrogen from human waste, potassium and phosphorus from cities and back into farm fields. They report their findings in the journal Nature Sustainability.
The school’s research team set up an exploratory exercise that examined 56 of the largest cities across six continents to assess the feasibility of this form of nutrient recirculation. The team looked at factors like transport distance, population and cropland density, crop nutrient requirements and what types of products would do best where.
Through the school’s study, the researchers found that a number of cities throughout the world could benefit from this proposed approach, not only for helping grow crops, but also "for their economic independence."
"We found, for example, that in Cairo, Egypt, if all of the nitrogen resources from wastewater were utilized, the city could cut Egypt's nitrogen fertilizer imports by roughly half," said John Trimmer, an Illinois graduate student and lead author on the study. "This type of approach could also help smallholder farmers in places like sub-Saharan Africa gain better access to fertilizer than what is currently available."
The researchers also suggest that treated wastewater could be an option for places where crops grow close to cities, but water transport is a major challenge to such a program becoming a reality, because of its weight and relatively low nutrient content. In areas were such brown water would have to travel long distances would not be a good option for such a program, the researchers said.
"We grow our crops in the field, apply nutrient-rich fertilizers, eat the crops, excrete all of the nitrogen, phosphorus and potassium and then those nutrients end up at the wastewater treatment plant," said Jeremy Guest, a civil and environmental engineering professor and study co-author. "It is a very linear, one-directional flow of resources. Engineering a more circular nutrient cycle would create opportunities that could benefit the environment, economy and agriculture."
Another setback to such a program may include lack of advanced technology that is able to recover a more concentrated product suitable for longer transport distances.
In the U.S., most cities examined appear to be poor choices for such a recirculation plan because much of the more densely populated places, like New York and Boston, are too far from intense agriculture areas. Chicago, though, received a better score in the research team’s analysis, because it’s close to the heartland of U.S. farming and crop production.
Researchers on the project say that the results of their "exercise" should be taken as estimates of nutrient transport distances and are useful for identifying broad trends and locations that may warrant further investigation into reuse strategies.
No word on whether or not there’s any real chance that such an exercise as human waste recirculation on a mass scale will ever catch on as a fertilizer source for mass produced farm goods. Nevertheless, the researchers have gotten us to discuss this taboo subject and how it might make all of our lives better.
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