Scrub Hub: Do landfills contribute to climate change? What's being done to stop it?

The average American throws out roughly four pounds of trash every day: Food they don’t eat, packaging for items they buy, things they no longer use. With more than 330 million people in the United States, that’s enough waste to fill more than 60,000 garbage trucks on a daily basis. 

Some of it is recycled, and some of it is donated. Most of it, however, piles up in landfills that are scattered across the country. 

There are at least 2,000 active landfills across the United States with thousands more that are no longer in use. 

In Indiana, there are more than 30 tons of trash per person in our landfills. That’s more than most states, according to recent data from the U.S. Environmental Protection Agency. 

But what happens to all that trash that sits there? 

That’s what we’ll be looking at for this installment of the Scrub Hub: What happens when all the waste decomposes? And how big of a contributor are landfills to climate change? 

Short Answer: Landfills contribute to climate change

Landfills produce gas. For those of you thinking about the smell that wafts out of your garbage can every time you open the lid, that probably comes as no surprise. 

But what you might not know is that gas — predominantly methane — is a major contributor to climate change. In fact, landfills are one of the top emitters of methane gas, along with natural gas systems and leakage, as well as livestock digestion and manure management. 

According to a 2018 report from the National Academies of Sciences, Engineering and Medicine, 18% of U.S. methane emissions come from landfills. 

Greenhouse, or climate change-inducing, gases are most commonly associated with carbon dioxide. While methane is shorter-lived in the atmosphere than carbon dioxide, it’s more powerful, according to Indiana University professor John Rupp. It’s actually more than 25 times as effective at trapping in heat, making it a major greenhouse gas. 

Methane is produced from a type of bacteria called methanogens, which feed on organic materials that are made up of carbon. Think food waste, cardboard and paper products, even things like plastic bottles, Rupp said — all things that there are plenty of in landfills. 

These microbes don’t produce methane at first, according to Gabe Filippelli, a professor of earth sciences at IUPUI. 

“But as the landfill ages, the bacteria that produces methane starts to chew away at the trash and give off lots of methane,” Filippelli said. “They can eat almost anything, and they thrive in an environment like a landfill where it’s sealed up and there’s very little oxygen to it.”

Long Answer: Capturing landfill gas

How the country has managed methane from its landfills, and why, has changed over time, Rupp said. 

Several decades ago, society looked to manage it from a safety standpoint, he said. That’s because methane is a flammable gas with the potential to catch and explode. In an effort to prevent that, landfill operators would try to capture methane gas and flare it off, or burn it in a controlled way. 

This would also help with the smell, according to Curt Publow with South Side Landfill in Indianapolis. 

But overtime, there has been more of an understanding of how landfills and methane contribute to climate change, Rupp said. With that, there is also a question of what to do about it and how to reduce those emissions. 

“It’s a tough challenge,” Rupp said, “but it’s an addressable problem.” 

There are two main ways, according to Rupp, one that's more proactive and one that’s more reactive. On the front end, states can look at better managing what comes into the landfills and diverting food waste and other materials that are prime grub for methanogens. Instead, those should be sent to compost or for recycling.

Several states such as Maryland, Vermont and California have started to pass laws about diverting certain waste streams from landfills.

Scrub Hub: Do wind turbines and solar panels go to the landfill, or can they be recycled?

There’s also something that landfills can do on the back end: They can capture the gas and reuse it just like natural gas, which is becoming an increasingly used technique, Publow said. That’s what South Side Landfill does. 

Beginning in the 1980s, South Side installed a gas collection system to capture and help burn off the gas. It’s a system of wells that are drilled into the waste and a pipe is inserted into that with a filter around the pipe, Publow said. It’s a perforated pipe that allows the gas to flow in — similar to a drainage tile system under a field, Filippelli added, but vertical. 

A few years after that, the landfill began using the captured methane to provide heat and energy to the greenhouse operation across the street, Publow said. 

The system continued to develop, then providing the landfill gas to Rolls Royce in the late 1990s, which they used to replace coal in their onsite boilers. South Side provided that fuel for nearly 20 years, Publow said. 

Then, in 2019, the methane collection took another step by building a processing facility onsite to turn the landfill gas into something called renewable natural gas, Publow said. All the wells throughout the landfill are networked back to a compressor station where there’s a pump that pulls the gas out of the landfill and pushes it downstream for processing.

At the plant, there are different kinds of membranes and filters to separate the methane from the other compounds in the gas. That concentrates the gas so it is around 95% pure methane, Publow said: “As far as being able to use it, it’s a direct replacement for natural gas.” 

The gas from the plant ultimately is used as motor fuel for the transportation sector, which can also help reduce emissions from trucks that would normally be powered by diesel fuel. 

The plant produces the equivalent of about 8 million gallons of diesel fuel a year. And in 2020, South Side Landfill prevented 19,000 tons of methane from being released into the atmosphere, Publow said.

“I think that this type of an operation where we can take something that historically was thought of as potentially a nuisance and turn it into an actual drop-in energy source,” Publow said. “I think that that’s a really good way to use a resource that we have.”

This, of course, is just an overview to get you thinking. If you want more specifics, that’s a perfect opportunity to ask the Scrub Hub. 

Submit a question through our Google form below. Can’t see the form? Click here.

Call IndyStar reporter Sarah Bowman at 317-444-6129 or email at sarah.bowman@indystar.com. Follow her on Twitter and Facebook: @IndyStarSarah. Connect with IndyStar’s environmental reporters: Join The Scrub on Facebook.

IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.