Turning Effluent into Electricity
May 2, 2005 | By Andy Guy
Great Lakes Bulletin News Service
Sewer overflows regularly pollute the Great Lakes.
A key tenet of sustainable development holds that waste equals food. If that were the prevailing mindset in the Great Lakes, raw human sewage would generate electricity and organic fertilizer, wastewater treatment plants would double as power stations, and Michigan residents would keep millions more of their energy dollars in the state each year.
Instead, municipalities handle sewage as a nuisance, and overflowing wastewater treatment plants regularly pollute the Great Lakes. In 2001, for example, sanitary sewer overflows pushed more than 281 million gallons of raw sewage into Michigan waterways. In 2002, officials reported sewage spills and broken sewer lines as the source of contamination for a total of 74 beach closings and swimming advisories at Michigan’s Great Lakes beaches. With a May-through-September beach season, that works out to one closing or advisory every other day.
“We have sewage all over,” said Greg Mulder, a power specialist with Coffman Electrical Equipment Company. “But the debate is about water pollution, not energy production.”
Mr. Mulder pointed out that, using a technological tool called a digester, a municipal treatment plant serving approximately 10,000 people could generate enough electricity to power as many as 75 homes. A digester converts raw sewage into electricity and benign byproducts like compost or livestock bedding.
If Michigan municipalities installed digesters in their wastewater treatment plants, they would generate both electricity and a substantial financial payback. The statewide economic implications are impressive, because Michigan spends approximately $27 billion annually on energy. Most of that money — $18 billion — leaves the state, because nearly all of the fuel that utilities burn for energy in Michigan comes from out-state sources.
“For every megawatt of [waste to energy] you make in the state you keep a half-million dollars in the state,” said Mr. Mulder, who estimates that converting all of Michigan’s sewage into electricity could produce more than 300 megawatts each year — enough to power more than 150,000 households annually.
But the digester — a tool that is more than 20 years old — has yet to catch on in Michigan; according to experts, engineers and power companies do not believe the technology works effectively.
But David Pueschel, a retired dairy farmer from St. Joseph County, Mich., said his digester “was a good-paying operation.” He claims that the technology saved his farm $130 dollars a day for 20 years — almost one million dollars.
“We need to look at manure in a different way,” Mr. Pueschel said. “It’s a product, no different than milk. And it can be a valuable product.”
So can human waste. That is why the City of Grand Rapids, which has invested tens of millions of dollars to prevent sewer overflows into the Grand River, is now planning to install a digester.