The niche alternative energy industry that generates power from hazardous piles of coal waste that litter the U.S. is facing an environmental Catch-22.
The torrent of coal mined and processed in the U.S. since the mid-1700s—first sorted by the little, raw fingers of “breaker boys” (Figure 1) and, later, by machinery—has produced hundreds of millions of tons of coal “refuse” that was discarded for its very low heat content. This waste coal—also known as culm, gob, or boney, and often mixed in with rock, shale, slurry, slate, clay, and other materials—has been randomly stockpiled high on thousands of acres of abandoned mine lands (AML), scattered across landscapes in coal country, sometimes filling up entire valleys with dark gray moonscape-like formations.
But over the years, the environmental impact of these dumps has also crested. Refuse mounds, toxic to plant life, are barren and therefore highly erosive. Unstable coal refuse piles can collapse, becoming potential disasters. And bituminous piles, in particular, can leach concentrated levels of acid mine drainage. “The cost of reclaiming these piles using conventional AML techniques is high, and the extremely poor water quality is often beyond the reach of current passive treatment technology,” noted ARIPPA, a trade organization that started as the Anthracite Region Independent Power Producers Association but that has since adopted its acronymic name, along with a broader mission to produce power from all varieties of the nation’s coal refuse.
In Pennsylvania alone, where coal miners have extracted about 16.3 billion short tons of anthracite and bituminous coal since commercial mining began in 1800, the state is scarred by more than 5,000 abandoned, unreclaimed mining areas that cover 184,000 acres. Coal refuse piles at these mines undulate over an aggregate area of 8,500 acres and contain a total volume of more than 200 million cubic yards. And that’s a conservative estimate: ARIPPA guesses the amount of coal refuse in the state is actually about 2 billion cubic yards, split equally between the anthracite and bituminous coal regions. The Pennsylvania Bureau of Abandoned Mine Reclamation (PBAMR), meanwhile, estimates that a complete cleanup of AML sites will cost about $16.1 billion.
Then, there’s the ever-present, exorbitant risk of fire. In 2014, PBAMR paid (using emergency funds in a trust partially funded by the coal industry via fees paid per ton of mined coal) Pennsylvania firm Minichi Inc. $2.2 million to snuff out a stubborn blaze at the 100-foot-high, 4-acre bank of the Simpson Northeast coal refuse pile. The fire, which started out smoldering and ignited into flames at the periphery of a vastly larger coal refuse area, took nearly six months to extinguish, requiring material excavation, millions of gallons of water, and thousands of gallons of firefighting foam (Figure 2).
That’s just one example. At least 40 other coal refuse piles—not including underground mine fires—are currently burning just in Pennsylvania and will need to be addressed at some point, the state agency says.
There’s not much the commonwealth can do, beyond reclamation—which is a complicated task that requires addressing water pollution from run-off and acid mine drainage discharges, site stabilization, covering the pile with soil, and planting vegetation. In 1968, Pennsylvania became the first state to pass a law to address air pollution associated with coal refuse disposal.
On a federal level, it’s a similar struggle, ARIPPA noted. “Laws were enacted in the late 1970s that now require coal mining companies to reclaim the sites that they currently mine. But by the time these laws were enacted, a billion tons of coal refuse had been stockpiled, thousands of mine sites were abandoned—and the former legally responsible parties had vanished,” it explained.
From Refuse to Resource
That’s why, ARIPPA says, its solution to use coal refuse as fuel at power plants sited near piles across the nation is indispensable.
In its simplest sense, the process entails re-mining coal refuse piles in accordance with surface mining regulations, and then processing that material at the mine site by screening to remove rock and other inert materials. The finer material—typically 75% or more of the coal refuse—is used as fuel in a fluidized bed combustion boiler or circulating fluidized bed (CFB) boiler. Combustion ash from the boiler—which meets beneficial use criteria—is then returned to the mine site and mixed with unusable coal refuse material as a way of neutralizing any remaining acidic materials. The materials are then compacted in place to contours as described in the surface mining permit. “As such the concentration of the acidity as well as the metals such as iron, aluminum, and manganese in surface and groundwater releases are significantly reduced,” says ARIPPA.
The coal refuse–to-power solution was conceived in the aftermath of the oil embargo of the 1970s. Just as Congress was preparing to vote for the Public Utility Regulatory Policies Act (PURPA) in 1978, CFB technology was being developed and showing a capability to convert low–heating value carbonaceous material (such as coal refuse) into energy.
The first CFB plant designed to convert large quantities of coal refuse into power—the 30-MW Westwood Generating Station in Schuylkill County, Pa.—came online in 1987. Eighteen more projects have since been grid-connected, 13 in Pennsylvania alone (Figure 3); two are in West Virginia, one in Montana, one in Utah, and one in Illinois.
The plants are owned by a diverse mix of companies, including NRG Energy, Exelon, Olympus Power, Babcock & Wilcox Co., Foster Wheeler, Northern Star Generation, Pacific Gas and Electric, Kimberly Clark, Cogentrix Energy, Olympus Power, Schuylkill Energy Resources, Waste Management, Southern Illinois Power Cooperative, and Colstrip Energy. Most power produced is sold in the PJM wholesale and capacity markets. Today, these plants—with a total capacity of 1,767 MW (see https://www.powermag.com/plants-that-turn-coal-refuse-to-power/ for a slideshow of the plants)—have removed a purported 214 million tons of coal refuse from the environment at no expense to taxpayers.
But the sector that has been the darling of most coal-producing states—and lauded even by the Environmental Protection Agency (EPA)—for its potential to eradicate coal refuse piles and reclaim thousands of disfigured acres is facing new, debilitating challenges.
Lucrative power purchase agreements signed under PURPA are beginning to expire, forcing plants to compete in the open market. Then, as Vincent Brisini, director of environmental affairs at Olympus Power, recently told congressional lawmakers, because coal refuse piles close to existing coal refuse plants have been successfully removed, generators must source coal refuse from piles at ever-greater distances, which has added to transportation costs. And, as with conventional coal plants, the economics of existing coal refuse plants have suffered in the advent of “abnormally low natural gas prices,” and a “sluggish economy [that is] stifling electricity demand,” the trade group told POWER.
An Environmental Muddle
Lately, that economic burden has gotten even heavier owing to “federal regulatory policies that dramatically and unnecessarily increase environmental compliance costs,” ARIPPA said.
For the coal refuse generation sector, air pollution in particular poses an environmental Catch-22 with no resolution in sight. The EPA emphasized, when questioned by POWER in May, that coal refuse piles are a marked environmental worry for their acid seepage and leachate production, spontaneous combustion, and low soil fertility. It also acknowledged that “[u]nits that burn coal refuse provide multimedia environmental benefits by combining the production of energy with the removal of coal refuse piles and by reclaiming land for productive use.” However, the agency underscored, they are still coal-fired power plants. They still emit hazardous air pollutants that the agency has determined are “significant” public health disadvantages.
Critics of the niche industry, like the Pennsylvania arm of the Energy Justice Network project, contend that coal refuse plants aren’t just inefficient, they also are far more polluting than new coal plants. “The large new waste coal burning power plants planned for western [Pennsylvania] were granted permits in 2005 to release higher levels of [sulfur dioxide (SO2) and nitrogen oxides (NOx)] and other air pollutants than the normal pulverized coal power plant proposed near Morgantown, W.Va.,” the group pointed out. Also, “If 100 tons of waste coal are burned, 85 tons will remain as waste coal ash,” it said.
A better solution to the coal refuse problem would be to plant beach grass, which it says, citing research from the Natural Resources Conservation Service, “has been shown to bring life back to long-dead waste coal piles for only 6-10% of the cost of conventional methods. Within a few years, beach grass enabled native plants to take over, allowing organic matter to accumulate around plants, forming a plant layer that stopped erosion, held water, cooled the surface, and looked better.”
ARIPPA contests the air pollution charge, saying its members take precautions to control emissions of SO2, NOx, air toxics, filterable particulate matter, and total particulate matter. Coal refuse power plants use CFB boilers, which use limestone injection for acid gas control, and they are also equipped with fabric filter systems to control filterable particulate matter emissions, it explained.
The nation’s coal refuse plants are also the lowest emitters of mercury of all coal generation facilities, even though coal refuse may be higher in mercury content, ARIPPA said, noting that multiple coal-refuse units were included in the EPA’s Maximum Achievable Control Technology (MACT) floor calculations (top 12% performing units) used to establish the emission standards for mercury and non-mercury metals as outlined in its Mercury and Air Toxics Standards (MATS).
Meanwhile, the emissions of greenhouse gases (GHGs) from these units can be considered as offset due to the eventual in-place burning of coal refuse piles, ARIPPA said. “Coal refuse fires also result in the uncontrolled release of the same pollutants that these plants control with high removal rates. Because these units provide electricity to the grid they also reduce emissions from other fossil fuel–fired [electric generating units (EGUs)] which otherwise would be operating. The reclamation and re-vegetation of coal refuse sites also results in the expansion of green spaces which aids in the sequestration of GHGs,” it said.
The EPA told POWER that it has considered and requested comment on separate emission standards for coal refuse generators for various proposals. “In fact, EPA has established subcategory SO2 and NOx emission standards for new, modified and reconstructed coal refuse-fired EGUs,” it said.
However, in the final MATS rule, the EPA noted that the waste coal hazardous air pollutant emissions are not sufficiently different from other coal-fired generators to warrant further subcategorization. “There are EGUs firing bituminous, subbituminous, and coal refuse among the top performing units for mercury emissions. EGUs firing bituminous, subbituminous, lignite, and coal refuse are also all among the top performers for the acid gas and non-mercury metallic emissions. This indicates that the MACT floor limits established based on these units are achievable by units burning all ranks of coal,” it said.
This approach, the EPA noted, was upheld by the D.C. Circuit’s April 2014 decision in White Stallion v. EPA. The court, in that case, said that the “EPA reasonably decided that separate standards for coal-refuse-fired CFBs were not warranted.”
Looking to Congress for a Resolution
Underscoring its message that “one regulation does not fit all plants the same,” the industry has continued its fight to keep afloat amid the deluge of environmental rules targeting coal plants. Its cause has now been taken up in Congress.
Rep. Keith Rothfus (R-Pa.) last October introduced the Satisfying Energy Needs and Saving the Environment (SENSE) Act, legislation that would modify the EPA’s Cross-State Air Pollution Rule (CSAPR) by allocating additional SO2 allowances for coal refuse generators (but reducing allowances elsewhere so the overall program cap does not change). The bill also creates an alternative means of demonstrating compliance with the hydrochloric acid (HCl) standard under MATS by assuming that a 93% reduction in SO2 demonstrates compliance with the HCl standard.
But the Obama administration has threatened to veto the bill, raising concerns that it chooses “winners and losers” because it favors coal refuse generators over other facilities. At a House Subcommittee on Energy and Power hearing on the bill this February, speaking on ARIPPA’s behalf, Brisini refuted that argument, underscoring that coal varieties have unique characteristics.
Anthracite refuse plants can meet the CSAPR alternative 2.0 standard because sulfur content in coal refuse from the anthracite region is lower, but bituminous plants cannot, he said. “It is not because the technology is different or they have anything special and it is part of the problem when you lump all of these things together not recognizing the [technical differences] in these kinds of fuels.” Meanwhile, he noted, only two bituminous coal refuse plants can meet the HCl requirements under MATS. “No other plants, whether they are bituminous coal refuse [or] anthracite coal refuse, they don’t do it,” he said.
The bill continues its course through Congress and is currently under consideration by the Senate. Brisini remains hopeful that the acid gas issue is resolved by the SENSE Act or other regulatory amendments.
If all fails, “the measures that would have to be taken by bituminous coal refuse–fired electric generating units to allow them to meet the acid gas limit would likely prevent them from successfully participating in the PJM wholesale electric market, with the exception of the last coal refuse fired facility built,” he noted. ■
—Sonal Patel is a POWER associate editor.