Our trash is filling up DFW landfills. Here’s how some of it can be turned into fuel
In addition to sluggish traffic, there’s at least one more certainty associated with population growth in North Texas: residents and businesses are generating more trash, and landfills are running out of space to store it.
The Dallas Fort-Worth region has about 36 years before existing landfills fill up, said Tamara Cook, the senior program manager of environment and development at the North Central Texas Council of Governments, an organization that brings together officials from 16 counties. Some will run out of room within the next few years, including the Weatherford landfill west of Fort Worth, Cook said.
That’s why researchers at UT Arlington and the council are partnering up to find out if there’s a better way for cities to process food waste, reduce the amount of methane entering the atmosphere and produce alternative fuels in the process.
“When you think about the growth that our region is going to have over the next 20 to 25 years, it really brings into focus the importance of making sure that we have capacity to continue to dispose of the things that we need to dispose of in landfills,” Cook said. “We need to look at alternative long-term options for our region to divert additional materials from those landfills.”
Funded by a $300,000 Environmental Protection Agency grant, the 18-month study will explore the possibility of using anaerobic digesters to turn food waste into biofuel that cities could use to power fleets of trucks or wastewater treatment plants. About 22% of the waste sent to landfills in North Texas is food-related, according to previous studies.
Eight wastewater treatment plants in Dallas-Fort Worth host the costly digesters to treat sewage, including four in Dallas County and one in Tarrant County: the Village Creek facility in Arlington. The machines take advantage of a naturally occurring process where bacteria breaks down organic matter, like manure, without oxygen. In the process, the bacteria generates gas — mostly methane — which the digesters can collect, refine and turn into an energy source, according to the EPA.
Most food waste is sent to landfills and breaks down to produce methane, which contributes to global warming, said Melanie Sattler, a civil engineering professor at UT Arlington who is leading the study. In 2018, municipal landfills were the third largest source of human-caused methane emissions — the equivalent of greenhouse gas emissions from more than 20.6 million cars driven for one year, according to EPA statistics.
While landfill machinery captures some greenhouse gases, much of the landfill is uncovered for two years, allowing methane to escape into the atmosphere, Sattler said.
“With a digester, you’re going to capture 100% of the methane that is coming from the waste,” Sattler said. “There are landfills that use capture and recovery more quickly, so they can go in and recover it, but never at 100% of the landfill. The EPA average is about 75% of natural gas being absorbed by the capture and recovery system, so there’s still 25% of the methane getting out.”
While the environmental benefits are clear, municipal leaders face significant challenges with the high cost and technical expertise required to run food waste through digesters, which are designed to treat sewage.
In the mid-2010s, Fort Worth experimented with processing waste from food manufacturers at the Village Creek plant but discontinued the program because of several issues associated with the types of waste they could accept, said Mary Gugliuzza, the water department’s spokesperson. The organic waste must have a certain oxygen composition to produce biofuel, she said.
“That food waste did not come in at a consistent pace, and that created operational challenges,” Gugliuzza said. “While the anaerobic bacteria loved the liquid food waste, when it didn’t come, for instance, on weekends, it quickly changed the amount of gas produced.”
If the Village Creek treatment plant were to accept food waste again, there would need to be a larger financial incentive and additional capital improvements to make the process more efficient, said Chris Harder, Fort Worth’s water department director.
“One of the biggest items would be some additional storage of the food waste that would allow us to regulate the introduction of food waste into the digesters to be consistent so we don’t have these huge peaks and troughs in terms of methane production,” Harder said. “You can’t effectively utilize that type of gas unless it’s somewhat more uniform.”
Cook stressed that the digester proposal is only one solution to a problem that requires many approaches, including more robust recycling campaigns and initiatives that encourage Texans to compost their organic waste at home.
With the study beginning in earnest early in 2021, Sattler said she understands the reluctance from municipalities to try out the new approach. She and Cook agreed that a pilot facility with governments from across North Texas could help resolve some of those concerns.
“We want to ask our local government partners: Are there ways we could partner and bring in a university, a utility, schools, other partners and share costs on a plant and be more innovative in our approach?” Cook said. “It’s not just one entity having to foot the bill. It’s multiple partners coming together that are interested in the benefits of this.”
While Fort Worth does not plan to accept food waste in the near future, Harder said he is interested in learning more about the gas produced from digesters and how machines designed for wastewater treatment lend themselves to food waste.
“We would like to see the study when it’s completed, especially when it comes to the technical side: chemical composition, generation rights, and especially if they’re looking at the variability amongst the food waste,” Harder said. “The more educated we become on this, the better decisions we can make.”
This story was originally published December 23, 2020 at 6:00 AM.
