Conrad Wilson recently posted an intriguing story at National Public Radio. It’s about a a practical approach to sustainability: converting sewage to energy.
“It turns out,” writes Wilson, “a sewer — the place where a city’s hot showers, dishwashing water and organic matter end up — is a pretty warm place. That heat can generate energy — meaning a city’s sewer system can hold tremendous potential for heating and cooling.
“It’s just that unexpected energy source that Brainerd [Minn.] hopes to exploit.
“Scott Sjolund, technology supervisor for Brainerd Public Utilities, is standing on the corner of 6th Avenue and College Drive in Brainerd, as sewage rushes unseen through underground pipes.
” ‘Everybody heats water up … and all that gets drained down the sewer, and that’s potential energy that could be extracted. That’s part of the equation,’ Sjolund says.
” ‘Actually extracting it in an economical fashion,’ Sjolund says, is the equation’s critical second part.
“The idea for this project comes from Brainerd-based company Hidden Fuels. In 2009, the business partnered with the city and the school district and received a $45,000 grant from the federal stimulus package.
“Hidden Fuels’ Peter Nelson says the first phase of the project involved installing sensors in the city’s sewers. For more than a year, the company and the city measured the temperature and amount of sewage running through the system to create a thermal energy map.
” ‘It shows that there’s a significant amount of energy — literally enough to heat hundreds of homes — within the streets of the city of Brainerd,’ Nelson says.
“Earl Wolleat, director for buildings and grounds with the Brainerd School District, says there’s enough energy running in just one of the sewer pipes to heat the entire high school. That could save tens of thousands of dollars every winter.”
Public Utilities’ Scott Sjolund at a sewer site. Photograph: Conrad Wilson