It was a busy week at the state Capitol. We’ll recap all the week’s top stories.
Methane Gas From Landfill Generates Electricity For Southern Arizona
One of Arizona’s largest utilities is using natural gas from a landfill to generate electricity. Methane is keeping the lights on for thousands of people in the Tucson area.
There’s a lot of science behind methane gas. So to find out how it works, we contacted a local expert.
“Hi, I’m Emily Viau, CEO of Biofronts. Some people know me as Doctor Sludge,” Viau said.
She got that name because she has a Ph.D. and researches how food and organic things decompose in landfills. She said they’re a lot like the digestive system of the human body.
"You put food into a landfill, you close it off and they make gas, so we can collect that gas — known as human farts in our case— but in landfills we call it methane gas and we can collect that and make energy out of it,” Viau said.
Every landfill creates methane but not all of them produce enough gas for commercial use. Viau said it depends on how long it takes food to decay when its buried underground. For instance, when you throw away a banana peel, don’t expect it to create methane right away, especially in Arizona’s dry climate.
"It would probably take ten to 20 years. It could take up to a hundred or so years if everything was packed in there really tight,” Viau said.
In parts of the world where there’s a lot of rain and humidity, that banana peel might break down within a few months. So, why not just add water to Arizona landfills to make more methane?
Well, it’s illegal to do that in our state. But there’s still enough methane at one place to power local homes and businesses.
Tractors flatten out mounds of garbage at Los Reales landfill in Tucson. It opened in 1967 and the garbage here is buried more than 400 feet deep across hundreds of acres. Andrew Quigley is director of Tucson’s Environmental Services.
"You can see what they are dumping. I mean America, right? I mean it’s what we throw away everyday,” Quigley said.
He pointed to piles of plastic bags, cardboard, landscaping waste, and even old exercise equipment in one part of the landfill. The garbage is really stinky, but Quigley smells green energy. He said burning methane to make electricity prevents it from going into the atmosphere, and that’s helping to slow down climate change ever so slightly.
"Methane is a nasty contributor to greenhouse gasses. It’s 28 times worse than carbon dioxide. It stays in the atmosphere for 13 years,” Quigley said.
Captured methane from Los Reales is piped four miles away to the H. Wilson Sundt plant. It’s a Tucson Electric Power generating station that uses coal and methane. Engineer Byron Brandon says the purified methane is burned to boil water.
"We’ll be going up to see where the igniters for the methane are and everything that goes inside the boiler. Inside the boiler there’s just miles of tubes that heat the water to steam, so it’s a pretty complex unit," Brandon said.
Since 1999, steam created by the methane has turned massive, noisy turbines. It’s sending electricity to some of TEP’s customers. Carmine Tilghman is the utility’s director of renewable energy.
"For the better part of 15 years we can legitimately say a thousand homes get their energy from repurposed waste. Now, is that significant compared to the 400,000 customers? Percentage wise no, but stand alone on its own, yeah, that is significant” Tilghman said.
Tucson Electric Power’s methane plant is the best example of how landfills can produce energy in Arizona. Its proximity to Los Reales dump makes it convenient to transport the gas. You may have seen pipes with flames shooting out of them at other landfills. That’s required to convert the unused methane to carbon dioxide which doesn’t do as much damage to the environment.