By Emma Betuel
March 5, 2019 - First, the bad news: An analysis by Earth Justice and the Environmental Integrity Project found that hundreds of coal plants across the country are leeching dangerous toxins into surrounding groundwater. But scientists at North Carolina State University may have already found a solution to a pressing and dangerous problem.
The report, issued Monday, analyzed publicly available data from coal ash disposal sites at 265 coal plants and found that 91 percent of them are leeching dangerous toxins like arsenic, lead, or radium into the surrounding environment. At the same time, a paper released online Monday ahead of print in the Journal of Geotechnical and Geoenvironmental Engineering shows a way that scientists might be able to tackle this problem using a bacterial biocement.
The contamination report was co-authored by Abel Russ, a senior attorney at the nonprofit watchdog organization the Environmental Integrity Project (EIP), and the biocement paper was first-authored by Brina Montoya, Ph.D., an associate professor of civil engineering at North Carolina State University.
In Montoya’s research, her team shows that mixing the coal waste slurry into a biocement may help stop toxins present in coal ash from roaming astray. But to understand how this biocement might solve the problem, it’s important to know a bit about how coal plants operate
How Do Toxins From Coal Ash End Up in Groundwater?
Once coal is burned for energy, that coal becomes a heap of ash that contains dangerous chemicals, some of which are known carcinogens — think: arsenic. That ash is then deposited in special landfills or, sometimes, ponds where it is mixed with water to form a slurry. Sometimes, this slurry spills over the top — as it did when Hurricane Florence struck North Carolina in September, leaking the toxic slurry into the Cape Fear River.
Russ explains that once this ash sits around in a landfill or a pond for a number of years, those toxins start to leach out into the surrounding underground environment — including into groundwater if it is nearby. The EPA estimates that in 2012, 470 coal plants in the US produced 110 million tons of ash — so the stuff just keeps piling up.
The EPA — as well as members of the coal industry — is aware that toxins can leech from landfills or ponds into surrounding groundwater, says Russ, which is why it mandates that these depositories be lined with an impermeable substance that is supposed to keep the nasty stuff in the hole — sort of like a plastic liner on a swimming pool.
Some ash ponds are lined to prevent toxins from leaking out into groundwater, but leakage can still occur over time.
Earth Justice’s map of the report’s data suggests the 95 percent of coal ash ponds are unlined, but Russ says that even those that do have liners still face a problem:
“It’s fairly common for landfills and ponds to be built in a way that they’re touching groundwater,” Russ tells Inverse. “In a situation like that, even if you do put an impermeable cap over the landfill or pond, the water will be washing through the ash all the time and leeching out those toxic pollutants and carrying them off into the environment.”
But even ponds that are capped still face a problem. The report analyzed landfills and groundwater supplies separately, and it showed that 76 percent of landfills had unsafe levels of coal ash pollutants nearby. Ponds were worse: 92 percent of the ponds had unsafe levels of pollutants nearby. For instance, groundwater near a plant northwest of Pittsburgh had arsenic contents 372 times higher than safe levels. Nineteen miles southeast of Washington, D.C., the report shows that ash from three coal power plants has leaked dangerous levels of eight different pollutants into groundwater.
“We were consistently seeing multiple pollutants above safe levels,” says Russ. “More than half have at least four pollutants present at unsafe levels. When it rains, it pours.”
What Solutions Are on the Table?
In 2015, the passage of the Coal Ash Disposal Rule required that plants release data on nearby groundwater so the public can monitor pollutants that may originate from landfills and ponds. It also issued guidelines for liners at new plants.
Montoya’s paper specifically applies to surface water — they were concerned with spilling — but in principle, her paper indicates that biocement could change the consistency of the coal ash slurry to help keep it solidly in the pond, even when liners are absent.
Working under a grant from the Electric Power Research Institute, Montoya’s team looked the nature of the coal ash slurry itself by mixing it with the soil bacteria Sporosarcina pasteurii, as well as urea and calcium. When she combined those ingredients with a coal ash slurry in a series of lab experiments, that runny coal ash slurry became thicker.
“The resulting biocement wouldn’t make the coal ash completely solid, but it would be a lot more viscous than the existing coal ash slurry,” Montoya said. “Our goal with this work was to see whether we could use bacteria to create a biocement matrix in coal ash ponds, making the coal ash stiffer and easier to contain.”
Russ has heard of similar solutions, but prefers a simple approach that would induce a sweeping change across the coal industry. “I’m a little suspicious because, anything in contact with water will break down over time,” he adds. “I think the best thing to do still, is to dig the ash out of areas where it is vulnerable to escaping into the environment.”
He would rather see these plants dug up and moved to areas where there is no chance that they’ll come into contact with groundwater — just in case something goes wrong. This, he adds, would also give plants the opportunity to create better liners in safer locations.
When coal plants are concerned, there is rarely good news — at least from an environmental perspective. Whichever way the EPA and the coal industry agree to go, it’s promising at least that there is more than one viable way to mitigate the damage.