How to turn beer, manure, rotten milk, and chocolate-covered cherries into electricity
When you find an anaerobic digester in Michigan, they’re usually set up on large scale dairy farms.
Michigan State University has a good YouTube video showing how the process works at the digester on their campus.
Bacteria turn all that cow manure into methane, which is burned in engines to create renewable electricity. But now there’s a new kind of digester in Fremont, Michigan that’s consuming much more than cow poop.
A steel tanker truck pulls into the loading bay at the Fremont Community Digester.
A worker connects a wide hose from the back of the truck to an underground pipe. It only takes about four minutes to unload about nine thousand gallons of manure.
“It’s a high-speed connection; transferring at a rate of about 3,000 gallons a minute,” my tour guide, Anand Gangadharan explains. He’s CEO of Novi Energy, a small energy developer based out of Metro Detroit.
It smells a little like cow manure in here, but the air outside is fresh. Shoppers at a nearby car dealership don’t even notice, thanks to a bio-filter that’s nearly two stories high.
In a much quieter storage warehouse nearby, Gangadharan shows me what else he’s going to feed the bacteria today. “This pail consists of pureed peach,” Gangadharan says as he peels the lid from a plastic bucket the size of a slow cooker.
There’s a whole pallet of these pails packed with frozen peaches. For whatever reason, food inspectors or the company that bought this puree rejected it. There are pallets of blueberries; whole and pureed cherries, those little snack-pack puddings, gallons of old ice cream. But Gangadharan’s bacteria, they’re not picky eaters.
“We, in fact, last week had boxes of chocolate-covered cherries. For whatever reason, it got rejected and our bugs are having a happy time eating some good stuff,” Gangadharan said with a smile.
His bacteria colonies also love beer, restaurant grease, and cheese whey. They’ll even eat pharmaceutical by-products, like the flavored syrup in cough medicine.
If this stuff didn’t come here, it would get buried; cardboard, plastic and shrink wrapped as whole pallets in a landfill. At the Fremont Community Digester uses food waste and turns into energy and the packaging gets recycled.
“Essentially what we’re helping the industrial plants do is achieve a zero landfill goal,” Gangadharan said.
One of the digester’s biggest clients is Gerber Products. All those carrot and strawberry tops left over from making baby food end up feeding the digester.
All that material, about 20 truckloads a day, ends up in one of three tanks. Each has more than a million gallons of food waste, manure, and hungry bacteria swirling around inside.
“The bacteria are swimming in nice warm liquid,” Gangadharan said as he stood outside the large evergreen-colored tanks. “Through that process it digests it, produces a lot of gas. That gas is the top 15 percent of these large tanks."
The methane gas travels from here to an accumulator, basically a big bubble, which sends a steady stream of methane to power two giant engines that create power for the electric grid.
“This is very different from other renewable like solar or wind," Gangadaharan said. Solar only works in the daylight. Wind when it’s windy. “Whereas here, we produce baseload 24/7 power. That is the beauty of this technology.”
Another advantage is the waste from the digester is turned into fertilizer that the digester sells to farmers. Plus, the extra heat created by the engines burning the methane is used to heat the entire plant and the three digester tanks.
The plant produces three mega watts of power a year. It cost more than $20 million to build.
Gangadharan admits Consumers Energy probably would not have agreed to buy this electricity if the state didn’t require utilities to get ten percent of their power from renewable sources by 2015.
But he sees a long term market for bio-digesters, especially in agricultural communities with a lot of non-hazardous, organic waste. “We just think anaerobic digestion now deserves mainstream attention as a decent, nice, small, proven technology in the United States. Anybody with doubts please come and see me,” Gangadharan said.
In fact, Gangadaharan says Novi Energy is working on several new projects already.