NMSU professors patent unique process to convert waste into useful products

Writer: Lorena Sánchez

A New Mexico State University professor is working to revolutionize the way we dispose of our waste.


NMSU civil engineering professors Zohrab Samani and Adrian Hanson have received a patent for ta process that economically converts municipal and organic waste into methane gas and a soil amendment. (NMSU image by Darren Phillips)

In December 2009, civil engineering professors Zohrab Samani and Adrian Hanson received a patent for a process that economically converts municipal and organic waste into methane gas and a soil amendment. Samani said although converting waste into fuel is nothing new, creating a functional and cost-efficient device to achieve this is new.

“Our accomplishment has been the simplicity of the design. We can build something that is functional and economical,” Samani said.

The machinery acts as a dry digester. The patent, received in 2009, is for the design of a digester that would convert organic waste, such as food waste, municipal waste or household garbage, into an energy source and soil amendment.

Utilizing alternative means of waste disposal is important, and Samani provided insight into how our current methods negatively impact the environment and our quality of life.

“The problem with landfills is that landfills are a major source of contamination. They are major expenses and have to be monitored for 30 years after they are closed down because they release methane into the atmosphere, and methane is 21 times more potent than carbon dioxide” as a greenhouse gas, he said. Landfills also have the potential to contaminate ground water, Samani said.

Based on the design of the technology, the researchers have developed a process to convert the waste in existing landfills. A landfill can be then be recycled and used continuously.

According to the Environmental Protection Agency, in 2008, 250 million tons of municipal waste was generated by Americans. Less than half of that was recycled and composted. Samani and his fellow researchers view these figures as a potential source of energy that is not being effectively utilized.

Hanson, professor and current interim department head of civil engineering at NMSU, and former graduate student Maritza Macias-Corral worked alongside Samani to construct a pilot scale system, or prototype, of the digester and are listed with him on the patent.

For 12 years, Hanson collaborated with Samani on the project and contributed his environmental expertise to the development of the process.

“From our perspective, there is potential in the Southwest to reduce the volume of solid waste,” Hanson said of the contributions the digester would make to the state.

One agricultural industry in New Mexico could provide an ample source of energy for the state. Recently, New Mexico dairy farmers have come under scrutiny over their disposal methods for manure. The industry itself is a vital source of income for the state, which ranks seventh in the nation for milk production and first in herd size.

To put this into perspective, New Mexico has more than 300,000 cows. With the average cow producing 18 gallons of manure a day, New Mexico alone accumulates roughly 5.5 million gallons of manure a day.

Samani’s dry digester has the potential to utilize the tremendous amount of waste accumulated and dispose of it in a manner that would be clean and energy efficient. These benefits include the production of pathogen-free compost, high-nitrogen compost, no odor, and the capture and use of methane.

Receiving the patent will now provide Samani with the opportunity to build an intermediate system within a year that will be used primarily for developing design scale-up relationships. It will act as a model for a large-scale production that would have the capacity to convert such tremendous amounts of waste.

Funding for the decade-long research came from numerous sources, including the U.S. Department of Energy through WERC: A Consortium for Environmental Education and Technology, part of the College of Engineering, and the U.S Department of Agriculture.

One surprising source of funding came from the Japanese government, which is searching for an alternative way to dispose of their waste, because they are running out of land for landfills.

“They are interested in finding a technology where they can convert waste into a useful product that won’t tie up the land,” Samani explained.

Metropolitan areas and the dairy industry are what Samani considers ideal customers for his technology.

“We think it could be used on a relatively small scale,” Hanson said. “However, it is at a large scale that it becomes most profitable.”

Some additional benefits come in the form of educating NMSU engineering students who Samani said will have the opportunity to train and have access to technology that no one else has.

“It provides a unique opportunity for our graduates to benefit from and understand technology, and use it in their jobs once they graduate,” Samani said.

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