Improving methane capture, ‘mining’ to help Denton meet standards
Most people probably don’t see a connection between climate change and a week’s worth of household trash.
But scientists do.
Methane has 25 times the global warming potential of carbon dioxide, another greenhouse gas. This week, the Environmental Protection Agency released new rules for landfills, which are the third-largest source of human-produced methane nationwide.
Waste from homes and businesses decomposes in landfills and forms “landfill gas,” which includes carbon dioxide, methane and other toxic emissions. Vance Kemler, the city’s director of solid waste, already knows some of the new rules will apply to Denton’s landfill, although he is still reading through the final document.
New landfills will be required to capture two-thirds of their methane and landfill gas by 2023, about 13 percent more than is required under current rules.
The EPA is also requesting broad public comment on updating the rules to further reduce methane emissions from existing landfills. About 1,000 municipal landfills, such as Denton’s, must follow rules drafted in 1996.
Both federal rules and voluntary programs have helped reduce emissions 30 percent since 1990, according to the EPA. But the agency says methane emissions will continue to increase in the next 15 years unless more steps are taken to reduce them.
Denton voluntarily built a system to capture landfill gas in anticipation of coming requirements, Kemler said.
Denton powers about 1,600 homes with methane captured from the city landfill by a small power plant there.
The plant will eventually be able to triple that output, Kemler said. Researchers at the University of Texas at Arlington are helping to increase the power-generating capacity by studying how to add water to the pile to better control decomposition and the production of gas.
Currently, any excess emissions not burned at the plant are treated and released as carbon dioxide, Kemler said.
In addition, Denton recently opened two new cells for burying waste. The city will be back before the Texas Commission on Environmental Quality within the next three to nine months, Kemler said, to amend its permit further.
The city hopes to be able to “mine” an older part of the landfill for paper, cardboard and other recyclable materials. About 30 years ago, landfills operated under different rules and kept their piles dry. The city has sampled that part of the pile and found many valuable commodities in pristine condition, Kemler said.
One sample pulled up a Denton Record-Chronicle front page from August 1989.
“You could still read every word,” Kemler said.
Because landfill operators in Europe and on both U.S. coasts are already mining their piles, Kemler expects similar operating rules that will help control emissions as Denton begins its own mining program. When the city diverts other recyclables for reuse, such as produce and yard waste for making compost, they follow other state and federal rules to control emissions, he said.
The city may be able to mine other parts of the landfill, after biodegradable items have decomposed, for things like plastics and metals, Kemler said.
“It’s not recycling in that sense,” Kemler said. “But the goal is to make the landfill sustainable and lessen the impact.”
PEGGY HEINKEL-WOLFE can be reached at 940-566-6881 and via Twitter at @phwolfeDRC.