Yeh Awarded Gates Grand Challenge Grant

From commode to clean water, USF’s Yeh wins Gates Grant to make usable byproducts from waste.



By Vickie Chachere

USF News


TAMPA, Fla. (Nov. 7, 2011) – For University of South Florida Associate Professor of Engineering Daniel Yeh, there are some unvarnished facts about life on our planet that need addressing.

First, there are 7 billion people who live here. They need clean water to grow food and energy to power their communities.

And another fact about those 7 billion people: they all poop.

So what if you could take some of the things humans really need - such as clean water and energy - and harvest those necessities from the one thing everybody has to do? Even better, what if you could get Bill and Melinda Gates to agree this is a really intriguing idea?

That’s exactly what Yeh has done.

The Bill & Melinda Gates Foundation announced Monday that Yeh is one of this year’s winners of a Grand Challenges Explorations grant to support his innovative anaerobic membrane bioreactor, a device trademarked as the NEWgenerator. The machine recovers nutrients, energy and water from human wastes, leaving very little to be disposed of and producing new products which are in short supply.

The project is one of 110 in six categories selected for support from the Gates Challenges fund, which is designed specifically for researchers to explore unconventional ideas that could solve persistent global health and development challenges.

Ana Prieto

USF Assoc. Prof. Daniel Yeh has worked on developing the NEWgenerator, which harvests clean water, methane and nutrients from sewage, for nearly a decade. Photo credit: Vickie Chachere | USF News

Yeh will use the $100,000 grant to develop a prototype device that, once linked into a septic system, will convert human waste into water that has been thoroughly cleaned of pathogens and is suitable for crop irrigation or household uses such as in cooling systems or flushing.  The process, which uses microbes to break down the waste, also produces methane gas which can be captured and used for heating and as a clean energy source.

Yeh – who started working on the project as a post-doctoral researcher at Stanford University in 2002 – is not the first to look at waste as a renewable energy source. Cruise ships and “green” buildings are already filtering wastewater to near drinking-water quality and recycling it for cooling systems and to flush toilets.

With the world’s clean water supply reaching a crisis-level in depletion, many experts acknowledge that using potable water for uses other than drinking is simply a waste of a dwindling resource and new solutions are needed. Yeh has developed a contained refinery system that is relatively inexpensive, doesn’t consume too much energy itself and doesn’t leave much byproduct from the waste processing.

The Gates grant will help fund the construction of larger prototype that will be put into use at Learning Gate Community School, a Hillsborough County charter school that has built its curriculum around sustainability.

“I keep going back to the fact there are 7 billion people on the planet,” said Yeh, citing the milestone the world’s population passed just a week ago. “It’s kind of a wake-up call.

“How are we going to make enough food? Where’s the energy going to come from? We have to stop having everything being a one-way street. We need to close the loop.”

In most developed countries the magic of indoor plumbing, urban sewer systems and wastewater treatment plants quite literally make human waste an “out of sight, out of mind” issue. But developing nations struggle with sanitation issues at the same time they are managing growing needs for water for crops and industry. Experts say that given strains on the planet’s resources, it’s only a matter of time before water and energy shortages become issues in the modernized world as well.

The NEWgenerator could change all that, said Ana Prieto, who completed her Ph.D. this year as one of Yeh’s students and has worked on fine-tuning the project since 2007. The development of the project has been supported by grants from the Florida Energy Systems Consortium and the USF Graduate School’s Sustainable Healthy Communities grant.

Ana Prieto

Ana Prieto, a Ph.D. researcher, has been fine-turning the NEWgenerator and perfecting the system before it is put into use in a demonstration project.

The bioreactor is built from components that are not complex and easily purchased on the market to keep the cost and complexity of the system in check, Prieto said.

Yeh’s machine uses anaerobic microbes to break down the wastes – which is mostly water to start – in a process which produces methane gas and separates the water out. A very small amount of sludge is produced, and it is easily returned to the septic system for usual disposal.

The methane gas can be captured and piped out of NEWgenerator while the water is processed through a specialized membrane that removes other elements, along with bacteria and other pathogens that would make using the reclaimed water problematic.

What’s left behind, Yeh explains, is water that contains two nutrients: ammonia and phosphate.  Those are exactly the two nutrients plants need to grow, making the water especially useful for crop irrigation, he noted.

In his lab at the College of Engineering, a small version of the NEWgenerator has been built and perfected over more than four years, producing a lively tune of hums and rattles as it does its thing.  The “waste” matter used to test the machine’s isn’t what you might think; for the experimental stage Yeh uses dry cat food soaked in water which mimics the properties of human waste. (Sorry, cat lovers – this project is fraught with uncomfortable truths).

“The dirtier the better,” Yeh explains of the raw matter going into the machine. “The more polluted it is, the more methane we can recover.”

The sodden cat food is broken down by the machine – which stands more than 6-feet tall and resembles a wild collection of tubes, dials and containers – that moves the sludge through the specialized membrane that separates out the water.

The system differs from current wastewater treatment plants which use aerobic microbes to breakdown wastes. Those systems require more energy to run and leave considerable sludge byproduct that must be disposed. Yeh’s project also is intended for a much smaller scale than large centralized systems which are expensive for communities to construct.

The demonstration project at Learning Gate will be constructed in an area of the large school grounds where access is controlled, although the school will incorporate its design and planned functionality into its lessons on sustainability. The challenges in building a larger-scale device is keeping the cylinder where the anaerobic microbes do their work airtight and continually refining the design to make it rugged and affordable to operate as it would need to be in a developing nation.

The prototype model will return the water and sludge that comes out of the reactor to the septic system, but the eventual goal is to be able to plug the NEWgenerator into a variety of sanitation systems for waste treatment and recovery of water and nutrients.

 “We’re here to look for the possibility,” Prieto said.

Vickie Chachere can be reached at 813-974-6251.