At the Atascocita Landfill, located between Interstate 69 and the Sam Houston Tollway, some 20 miles north of downtown Houston, acres of pipeline wind among trash mounds. Through the piles of discarded banana peels and leftover supper, a gas produced by the years-old waste rises to the surface. The gas is gathered and cleaned at the top before being pumped out to the main gas pipes of CenterPoint Energy.
Across 2,600 landfills, there are currently over 500 landfill-to-energy operations in operation in the United States. According to the state Environmental Project Agency, there are 29 active in Texas and an additional 44 being considered. As of September 2024, these include Harris County’s Atascocita and McCarty.
This is because methane gas emissions from landfills are among the highest in the world. A powerful greenhouse gas that traps heat in the atmosphere and speeds up global warming is methane, which is colorless, odorless, and combustible. But methane can also provide us with energy.
How is methane connected to trash?
As organic matter, including plants and animals, decomposes over time, methane is naturally produced. garbage accumulates on top of garbage at a landfill until the discarded cheese and old bread at the bottom are oxygen-suffocated. The garbage is then consumed by microscopic bacteria, which releases methane gas.
As a result, the third-largest source of methane emissions in the US is organic municipal solid waste landfills, such as Atascocita or McCarty. An estimated 100.9 million metric tons of methane, or 14.4% of all methane emissions in the United States, were released into the atmosphere by these landfills in 2022.
Texas is the nation’s biggest methane emitter, and the US is the second-largest emitter in the world, after China.
According to a 2024 estimate, 78 percent of Harris County’s methane emissions come from Atascocita, McCarty, and the Baytown Landfill. Dallas and Houston are among the top ten cities with the greatest levels of urban methane emissions.
But according to Dan Cohan, a professor of civil and environmental engineering at Rice University, methane is also the primary component of natural gas. Drilling oil wells or fracking releases natural gas into the environment, which is used to heat or power homes. According to Cohan, the gas derived directly from decomposing waste materials can be used to augment these natural sources of renewable energy.
Instead of allowing methane to escape directly into the environment, there are several advantages to trapping it and using it as fuel, according to Cohan. No matter how many landfills and garbage we have, we ought to be collecting as much of the methane that is produced as we can.
This methane can be collected by landfill firms and sent via a network of pipelines to an on-site renewable energy facility. There, the gas is either purified for natural gas distribution or burned in engines to generate electricity.
How does your trash become energy?
Your garbage starts to break down as soon as it is picked up from the street or delivered to your apartment building.
Your waste is transferred to one of Houston’s six garbage landfills, where it is disposed of and continues to break down alongside everyone else’s old ham, pants, and pizza boxes. According to Melanie Sattler, chair of the University of Texas at Arlington’s civil engineering department, the decomposing garbage does not initially release methane as it lies at the top of the pile.
According to Sattler, the garbage at the top of the pile is exposed to oxygen, which microorganisms will use to break down the waste. However, these tiny microbes reduce the oxygen until only 1% or 2% remains when the garbage is buried beneath an increasing number of rubbish heaps. That is in contrast to our atmosphere’s 21 percent oxygen content.
Landfill gas is created when new microbes activate in these oxygen-poor circumstances, producing roughly 50% carbon dioxide and 50% methane. In contrast, methane makes up around 90% of natural gas.
After rising to the landfill’s surface, this gas mixture is headed toward the atmosphere. However, gas collection wells are positioned throughout the landfill at different depths for waste-to-energy operations. To allow gas to enter, these pipelines have holes in them. According to Sattler, the gas is blown up from the waste and into a duct system by the interior fans.
Through the ducts, the landfill gas is transported to a plant on the property where it is transformed into natural gas or energy.
There are 394 gas collectors spread out around the Atascocita dump, often ten feet or so below the trash pile’s bottom. After being transported to a facility, the landfill gas undergoes cleaning or scrubbering, ultimately changing from roughly 55% methane to 90–99% methane.
According to Keith Sharon, gas operations manager for Waste Management in Texas and Oklahoma, the gas will be used in CenterPoint’s natural gas general pipelines to heat homes, turn on stoves, and power our landfill’s natural gas fleet. It can be used and transported to many different locations.
Atascocita will generate enough renewable natural gas to power roughly 10,000 homes in the Houston region for every 1,000 standard cubic feet per minute of landfill gas, or the flow rate of gas processed at the plant.
What about electricity?
Certain landfills will turn their on-site landfill gas into electricity that will be distributed throughout the CenterPoint grid as a whole.
The procedure is essentially the same at Waste Management landfill Coastal Plains, which is located just south of Houston. The facility generates energy by burning the landfill gas. According to Sharon, the byproducts, which include sulfur dioxide, nitrogen oxides, and carbon dioxide, are released into the atmosphere. However, only around 2% of the landfill gas is flared out after the remaining 98% of the gas is burned to produce energy.
Instead, just recycle
Methane conversion is not the answer, despite these advantages. Methane gas leaks from landfills continue to occur daily.According to satellite data, methane emissions from the Fort Bend Regional Landfill, Blue Ridge Landfill, and McCarty Road Landfill in the greater Houston area are among the highest in Texas.
In 2022, Fort Bend Regional Landfill released 1.5 million metric tons of carbon dioxide emissions. According to the EPA, these emissions are equivalent to around 336,777 passenger automobiles operating for a year.
In 2022, Texas produced 31 million metric tons of carbon dioxide equivalent to 7 million automobiles annually.
Carbon Dioxide Equivalent, or CO2e. The impact of various greenhouse gases on the climate is compared using this metric. In other words, the amount of carbon dioxide emissions that would have the same global warming potential as one metric ton of another greenhouse gas.
In Harris County and throughout the United States, waste is a significant environmental problem. Houston generates about 4.2 million tons of solid waste a year, with that number expected to increase to 5.4 million tons by 2040. At the same time, some of the biggest landfills have less than 20 years before they reach capacity.
It s not as simple as we get energy from trash so that s it, said Cohan. There s a lot of energy that goes into growing your food, trucking it to the grocery store, tracking your trash. This is a matter of capturing the methane that is being produced anyway.
With the amounts of natural gas we consume daily. cleaner methods of producing energy, such as landfill gas, remain a fraction of the total energy used in the U.S., said Cohan. The real solution: be mindful of what is thrown out and what you can recycle or compost instead.
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