Between global population growth and the constant advance of urbanization, human waste is becoming an increasingly critical environmental challenge. For a growing number of companies, it is also a business opportunity: many are developing cost-effective methods to extract nutrients from human waste, recycle wastewater, and burn captured methane gas for use in onsite energy production.
The waste disposal problem has a long history. Before the invention of the modern sewage system, humans waste was discharged directly into city streets or open fields, where it then filtered back into nearby waterways. This practice, which is still used in many parts of the developing world, propagated disease and contaminated fresh water supplies.
Separate water and sewage systems, such as those completed in Paris in 1878, were a great leap forward in solving age-old problems of sanitation and disease. However, while these early systems moved human waste downstream and away from cities, they rarely addressed environmental impact. In fact, it wasn’t until the 1970s that municipal wastewater utilities in the US were required to meet discharge limits for phosphorous and various heavy metals introduced from industrial processes. Until then, sewage sludge - a brew of human waste and treatment chemicals - was often discharged directly in downstream waterways.
Despite drastic improvements, most modern wastewater treatment systems are still not designed to recapture or reuse the valuable resources and energy contained in human waste. However, with fresh water and virgin phosphorous supplies growing increasingly scarce, municipalities are experimenting with new technologies to recapture nutrients, recycle water, or produce energy by burning biosolids or methane gas.
And they are trying to do so despite being cash-strapped.
“Money is tight right now,” says Ken Kirk, executive director of the National Association of Clean Water Agencies. “Public utilities are doing everything they can - not only to save money - but also to make it by recapturing valuable elements contained in human waste.”
Ostara and Multiform Harvest are two companies helping utilities do both. They have developed technologies that enable wastewater utilities to extract phosphorous from sewage, and then sell it for use as agricultural fertilizer. This has multiple benefits: by removing phosphorous before it scales up inside piping (into a compound called struvite), mid-sized utilities can save between $500,000 and $1,000,000 per year that they would normally spend on chemical cleansers that must, in turn be reduced from sewage sludge farther downstream. They also can eliminate concerns about phosphorous discharge limits while creating another income stream. Ostara, for example, pays utilities for phosphorous by the ton, which creates a reliable source of revenue.
Recapturing energy and water
Municipalities in arid regions are also finding that wastewater, which they have historically treated and then released into the environment, is a marketable commodity when recycled. Oklahoma City, in partnership with Veolia, an environmental services company, has created a system to treat wastewater up to a non-potable standard. The city then sells the water to golf courses and resorts, which don't need drinking water for irrigation. Because it take less energy and fewer chemicals to recycle water, the city is able to sell it for 33% less than the cost of fresh water.
In Australia, Veolia has partnered with AquaNet Sydney to enable Sydney's municipal wastewater utility to divert recycled wastewater for uses as diverse as industrial cooling, irrigation and fire fighting.
Utilities are also working to recapture the potential energy that is bound up in waste. KORE Infrastructure created a chemical process that converts biosolids into a market-ready, drop-in, No.2 diesel fuel. After operating a pilot project for the past five years, the company is building a modular operational plant in Southern California.
The developing world
In the developing world, one of the biggest problems in dealing with human waste is the utter lack of toilets or any sewage system at all. According to the Bill & Melinda Gates Foundation, 2.5 billion people, 40% of the world’s population, practice open defecation. Another 2.1 billion people use toilets that are connected to septic tanks that are not emptied properly, or else discharge raw sewage directly into rivers or other surface waters.
That’s why the foundation launched the Reinvent the Toilet Challenge. Established in 2011, the competition has resulted in a handful of innovative, off-grid toilet designs. Though none does anything as sophisticated as extract phosphorous, many reliably remove bacteria from human waste. In some cases, they even recover clean water, or produce energy for less that the foundation’s target mandate of US$0.05 per user, per day.
North Carolina's Research Triangle Institute (RTI) is among a handful of grantees close to field testing a design. The RTI prototype separates liquid from solid waste, burns the solids to produce energy to power the toilet, and uses an electrochemical process to purify the liquid waste to a level sufficient for use as a hand and body wash. Brent Rowe, a senior economist with RTI, says the team is thinking of marketing the toilet in India.
“The reason we’re looking to India is that they have enormous population of people that don't have access to adequate sanitation and densely packed population," Rowe says.
But Rowe admits that getting Indians to accept the notion of rinsing with what is effectively cleansed pee may be a bigger hurdle than overcoming the technical challenges of designing the toilet itself.
Other Gates Foundation grantees — among them Caltech, the Climate Foundation, and Loughborough University — have produced designs that generate everything from clean water to biochar, a sanitized form of human waste that can be used as a soil supplement. In the process, the Reinvent the Toilet Challenge has highlighted how “wasteful” sewage treatment plant are in the developed world, and opened a debate as to whether they should be redesigned to consume much less energy and water.
Doulaye Koné, the senior program at the Bill & Melinda Gates Foundation who heads up the challenge, says it may be a bit too early for that conversation. “We’re not trying to replace the existing wastewater industry,” he says. “We’re trying to create business models to serve the more than 4 billion people in the world who aren't served by sewer systems and wastewater treatment plants.”
Given that 700,000 children in the developing world die each year from chronic diarrhea caused by poor sanitation, any innovation that helps save lives would a qualify as a moral victory as well as good business solution.
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