I believe universities have an obligation to help our students become aware of the need for sustainable systems.

Tom DiStefano

Who wouldn't want to convert 127 million tons of trash into $1.5 billion of energy and reduce greenhouse gas emissions by 146 million tons (CO2e) per year? That is the annual potential for U.S. landfills if they all install anaerobic digesters, according to a recent paper by Professor of Civil and Environmental Engineering Thomas DiStefano.

In anaerobic digesters, microbes that don't require oxygen - anaerobes - break down organic matter into methane and hydrogen, which can be captured and used to generate electricity. The technology isn't new - several countries in Western Europe already process their trash this way. Those countries, however, require homeowners to separate easily biodegraded materials, such as kitchen scraps and yard waste, from other garbage.

DiStefano has worked with a landfill in Lycoming, Pa., to evaluate the feasibility of the technology for American rubbish, where everything is usually tossed together. Large-scale tests were promising enough that the landfill has contracted with a Belgian company for a full-scale assessment of the economics.

Anaerobic digestion happens naturally in landfills, but not as efficiently as in the digesters. "Diverting biodegradable trash to an engineered vessel has the advantage that the biodegradation happens much more quickly than it does in the landfill," DiStefano says. "Landfills biodegrade trash and produce methane also, but sometimes the degradation takes years, whereas in vessels it takes weeks."

Confining the degradation to enclosed vessels also allows all of the methane to be captured. Even in well-designed and operated landfills, approximately 15 percent to 25 percent of the methane escapes to the atmosphere. Methane is a potent greenhouse gas, so capturing it reduces greenhouse gas emissions in two ways - it isn't released directly from the landfill and it displaces fossil fuels that are typically employed to generate electricity.

DiStefano brings his passion for economic, environmental and social sustainability to the classroom. "I believe universities have an obligation to help our students become aware of the need for sustainable systems," he says. Whether he is teaching future engineers, lawyers, CEOs, lawmakers or others, "they are our leaders of the future. That sounds cliché, but it's true, and they are going to be faced with these problems much more than I will be."

As the Robert L. Rooke Professor of Engineering, DiStefano is also developing a new degree program in environmental engineering that will enable students to study and practice sustainable engineering principles.

Posted Sept. 13, 2010

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