Sparking new ideas on sustainable phosphorous

Nestled between silicon and sulfur on the periodic table of elements is a mineral that spontaneously combusts when it comes in contact with air and can be found on the tip of a match. Without it, we would die.

“Phosphorus is essential to life,” said Matt Scholz, program manager for the Sustainable Phosphorus Alliance, an organization that promotes phosphorus recycling in the food system. “It’s in your bones and it’s in your DNA, and it’s the energy currency for the cell.”

What is unknown to most people, is that the way we use this element — abbreviated as "P" on the periodic table of elements — is the cause of growing environmental and economic concern. Environmental because a large percentage of annual mined phosphorus ends up in fertilizers for farms; then the runoff leaches from fields and ends up polluting water. Economic because global agriculture is dependant on phosphorus to feed the more than 7 billion people on Earth; however, most of the world’s mineable phosphorus is located in Morocco.

“One of the issues is that it is really essential for agriculture,” Scholz said, who is also a senior sustainability scientist with ASU’s Julie Ann Wrigley Global Institute of Sustainability. “But phosphorus wastes can contaminate waterways and create water pollution and algal blooms.”

Algae blooms can occur when there is an increase in nutrients in water that cause algae to grow to a large quantity, taking over large areas of lakes, rivers and the ocean. These blooms can cause fish to die due to toxins that some algae species produce, due to the depletion of dissolved oxygen that can suffocate fish.

The Sustainable Phosphorus Alliance is trying to tackle this problem by working with stakeholders to develop or implement better ways to collect and recycle phosphorus from the food system before it has a chance to reach waterways.

Origins of the alliance

The idea for the Sustainable Phosphorus Alliance grew out of a five-year ASU National Science Foundation grant to create a phosphorus sustainability research coordination network (RCN). The goal was first to build a network of scientists, fertilizer and agricultural representatives, policy makers and farmers. Then the stakeholder network could work together to advance research that would highlight the most promising ways to improve how phosphorus is used in agriculture and discover new methods to recycle it.

Jim Elser, a lake ecologist, is the principal investigator for the phosphorus network, which includes over 40 scientists, engineers and many other stakeholders. They have made substantial progress over the past four years highlighting emerging solutions, like plants that require less phosphorus to grow, and methods to recover phosphorus at wastewater treatment plants.

“There’s hope on the horizon,” said Elser, an ASU Regents' Professor who recently became director of the University of Montana’s century-old Flathead Lake Biological Station. “People are getting mobilized and focused and interested in these issues. There are a set of technologies and innovations and policy approaches that are starting to emerge that will help address the problem.”

The eventual ideal future that Elser envisions is one where phosphorus is intensively recycled. Where smarter fertilizers and smarter plants don’t allow phosphorus to flow into waterways, but stay in the land until needed by the crop. Where the phosphorus from wastes like unused food, animal manure and human waste are not thrown in landfills, but collected and turned into recycled fertilizer.

“The good news is, when all those things are taken care of, then part of the food system will be secure,” Elser said. “We’ll have a long-term fertilizer supply for the future, and then also we’ll have clean lakes and rivers and oceans.”

Now in the last year of the funded research coordination network, Elser and the other stakeholders are looking toward that future and how to implement what they have learned these past four years to make it a reality.

“In a lot of ways, what this Sustainable Phosphorus Alliance activity is, is a way for the RCN to continue having impact,” Elser said.

And it won't happen overnight.

“Recycled fertilizers are still a long way off,” he said. “There are technologies that are coming and getting started, but it’s going to be some time before we have any impact in the market.”

From waste to resource

Once we flush waste down the toilet or down the garbage disposal, it heads to a wastewater treatment plant. There, it is whisked with air and bacteria that break down organic wastes and remove inorganic compounds, like phosphorus, from the water.

“Current wastewater treatment has been around 100 years or so,” said Bruce Rittmann, who directs ASU’s Swette Center for Biotechnology at the Biodesign Institute. “It works really well, but it costs a lot of money and it costs a lot of energy.”

In a recent review article in Nature, Rittmann and his co-authors calculated that a conventional wastewater treatment plant in China serving a city of nearly half a million people would cost $4.6 million per year to operate and would consume 50,000kWh of electricity. That is enough energy to run five average American households for nearly a year, according to information from the U.S. Energy Information Administration.

“My philosophy is to transform wastewater treatment,” Bruce Rittmann said. “We have to stop doing what we’re doing and completely change.”

To do so, Rittmann likes to partner with microbes to engineer solutions. What we consider as societal problems, microbes consider as food. Rather than break down waste aerobically, with bacteria and oxygen, he suggests breaking down the waste anaerobically, with bacteria, but no oxygen — similar to the way beer and bread ferment. This new system would produce energy and collect nutrients that could be recycled.

“We’re now technologically at a point where where we can break away from 100 years of our profession and start over,” Rittmann said. “But if we went to anaerobic treatment, we can then make it an energy-output system instead of an energy-input system. Now, with some new technology developments that are just coming along, the treatment can be equally as good as it was with aerobic treatment.” With anaerobic treatment, wastewater treatment plants that produce methane gas that can be electricity producers rather than consumers.

Phosphorus can be collected and sold to fertilizer companies instead of being buried in landfills. This way, farmers don’t have to rely on the phosphate supply of other countries. By making the phosphorus system cyclical, phosphorus can be used in food without polluting waterways.

And phosphorous recycling can begin to have a lasting impact.

“Resources in the wrong place are pollution, but resources in the right place truly are resources,” Rittmann said. “We want to take these huge environmental risks, and turn them into environmental benefits.”