Managing Editor, Biodesign Institute Communications
In an article in Slate’s Future Tense called “The Dirty Way to Feed 9 Billion People” and an appearance on local PBS affiliate KAET’s Horizon, Elser and Rittmann, underscore the importance of phosphorous as the “bedrock of modern agriculture”, which has accumulated in ancient seabeds and high-quality phosphate rock.
“P is essential to all life (it's literally in our DNA), including plants—such as agricultural crops. So, without phosphate, the breadbasket of America would be empty. This brings us to where we are now. The Green Revolution, the major mid-20th-century expansion of global food production, relies in large part on fertilizer, to the tune of approximately 20 million metric tons of P in fertilizers applied in 2012 worldwide. Without it, agricultural productivity would have to get by with phosphorus that gets into soil by natural weathering of P from Earth’s rocks, which would only yield about 10 percent of what’s currently used—and would be wholly incapable of supporting our current population, much less the 2 billion to 4 billion additional humans expected for 2050.”
And just like oil, phosphorous is concentrated in just a handful of countries, with Morocco possessing the majority (75 percent), followed by China (5.5 percent). Before an OPEC-type entity emerges and colludes to control the world’s phosphorous supply, Elser and Rittmann recommend recycling phosphorous from the leading source: human and animal waste, colloquially known as poop.
Elser and Bruce Rittmann have recommended a three-part solution to this looming crisis, which involves recovering phosphorus from agricultural and human waste.
“Animal manures, food-processing wastes, and human sewage constitute about half of the P on the conveyor belt to the environment. These waste streams offer the most immediate route to recovery and reuse because most of the P is in slurries of organic solids that also contain high amounts of energy. Anaerobic digestion, in which specialized microbes chew up organic matter in the absence of oxygen while producing methane gas, or microbial electrolysis cells, in which bacteria generate an electrical current that leads to hydrogen gas, are excellent means to convert the organic materials into highly valuable energy outputs.
These microbial processes release the P as phosphate, which can be captured in clean, concentrated, and convenient forms for reuse in agriculture. Using microorganisms this way would give us three valuable things: renewable energy, concentrated P, and water with most of its pollution removed. All three contribute to economic, food, and environmental sustainability. These technologies aren’t yet reliable and cost-effective, but their eventual deployment could create whole new industrial and job sectors.”
Elser and Rittmann are currently hard at work to obtain research funding and develop a pilot-scale project to develop these new technologies. Could poop power and phosphorous recycling be just the breakthrough needed for a whole new green job sector for Arizona and the U.S., weaning our dependence of foreign phosphorous sources? It’s a dirty job, but someone’s got to innovate.
James J. Elser is Regents' Professor in the School of Life Sciences at Arizona State University.
Bruce E. Rittmann is Regents’ Professor of Environmental Engineering and director of the Swette Center for Environmental Biotechnology at Arizona State University.