Wastewater treatment plant sludge has been considered a potential source of energy since these plants were first built in England about 150 years ago. The idea seems so obvious that every elementary environment schoolteacher is convinced that only stupid or evil people is stopping it from happening. During the years I was a Plant Manager and later in the Water Authority, I was bombarded with ideas and proposals from all kind of idealistic but naive "green" people, normally a young female school teacher, who wanted my co-operation for her pilot project. Instead of the futility of explaining the energy balance of the process, which is negative, I always said yes and watched her to fade away when the practical issues started to appear.
Now I read in a trade paper that a Nevada university has designed yet another of these sludge-electricty schemes.
Our plan is to test the unit by about May 15," Chuck Coronella, principle investigator for the research project and an associate professor of chemical engineering, said. "We're designing, building and assembling a continuous-feed system that will ultimately be used to generate electricity. We'll run experiments throughout the summer, creating a usable dried product from the sludge." The experimental carbon-neutral system will process 20 pounds of sludge per hour, drying it at modest temperatures into solid fuel that will be analyzed for its suitability to be used for fuel through gasification and, in a commercial operation, ultimately converted to electricity. The refrigerator-size demonstration unit will help researchers determine the optimum conditions for a commercial-sized operation.The obsessive designing of small-scale pilot sludge to electricity models reminds me of India's scientists eternal building of cow-shit to cooking-gas projects. America is a very large and diverse country, so fortunately this project is not representative of its intellectual level.
"The beauty of this process is that it's designed to be all on site, saving trucking costs and disposal fees for the sludge," Victor Vasquez, a University faculty member in chemical engineering said. "It uses waste heat from the process to drive the electrical generation. It also keeps the sludge out of the landfill."
Estimates, which will be further refined through the research, show that a full-scale system could potentially generate 14,000 kilowatt-hours per day to help power the local reclamation facility. The demonstration-scale project is a collaboration with the cities of Reno and Sparks, operators of the wastewater plant. The city councils signed an interlocal agreement recently to allow the research to integrate into their operation, providing space for the experiments, the dewatered sludge and other resources to help make the project a success.
"Economically, this makes sense," Coronella said. "Treatment plants have to get rid of the sludge, and what better way than to process it onsite and use the renewable energy to lower operating costs." Coronella added, "This demonstration gives the University an opportunity to involve students in development of waste-to-energy technology, which ultimately will benefit the community. It's a win-win for everyone involved."
The University's Technology Transfer Office, with assistance from the College of Business, is supporting the project with plans to make the system available to hundreds of communities around the country that operate water treatment plants.