Three Solutions for Legacy Coal Ash Disposition
When coal combustion residuals (CCR), such as coal ash, fly ash, bottom ash, gypsum and other solids produced by coal-fired power plants are improperly stored, they can contaminate surrounding soil and ground and surface water, causing a host of environmental problems.
The most expedient way to deal with legacy CCR stored in outdoor ponds has been “cap in place,” which involves covering it where it lies. This is deemed “safe under certain conditions” by EPA regulations, but environmentalists and the public have become more savvy to the inherent drawbacks and consider cap in place a non-solution.
No one intentionally wants to harm the environment, so utilities that have legacy CCR, environmentalists, legislators and energy end users do share common goals for its proper disposition. Foremost is the desire to recycle as much as possible to keep the coal ash out of landfills, but the simple fact is that the quantity of legacy CCR far outstrips current capacity and requires innovation to solve it.
For instance, in Virginia, legacy coal ash is estimated to be 30 million tons or 27 million cubic yards. Indiana is wrestling with what to do with 60 million cubic yards. These are examples of only two states dealing with legacy CCR.
Microencapsulation is a simplified process for beneficiation or recycling and the federal CCR rule defines this as “a beneficial use of CCR that binds the CCR into a solid matrix that minimizes its mobilization into the surrounding environment.” So, CCR is repurposed to create building/construction products such as brick or aggregate, and as Portland cement (PC) substitute in concrete.
We support CCR microencapsulation as the preferred method of CCR recycling, but it currently faces production and market limitations. For utilities, it’s a race to get processing plants online to prepare coal ash for recycling by end-product manufacturers who have finite production capacity and accept conditioned CCR on a first-come, first-served basis.
Macroencapsulation is another, often simpler, solution for beneficial use that deals with the remaining legacy coal ash. For years, using CCR, rather than earth, as fill material to construct embankments for landfills, highways, dikes and levees has proven itself a virtually foolproof and comprehensive beneficial use.
Coal ash is transferred and encapsulated into berms or bunkers designed with the land’s eventual reuse in mind. They’re lined with the same geosynthetic material used in modern landfills that blocks seepage into surrounding earth and groundwater. As these structures are completed, they’re fully entombed in liner. This method is an accepted reuse by engineering firms and utilities which has been used for land redevelopment, solar farming or any project that beneficially reuses materials that would otherwise be disposed of; offsetting the use of other natural resources.
Macroencapsulation, in most cases, is a large-volume beneficial use. It’s the most practical solution for constructing berms or bunkers near the coal ash source because roadway logistics, transportation costs and risks are all minimized. In addition, no time is spent, as with microencapsulation, in locating and negotiating terms with end-product manufacturers, building processing plants or guessing what the construction market will do. Once the initial macroencapsulated bunker is lined, coal ash removal can begin, efficiently and immediately.
Disposal – environmentally, the last resort – has historically been the first choice of utilities across the U.S. after cap in place efforts have been exhausted because disposal is relatively easy. However, it’s the last resort because the number of U.S. landfills is dwindling and they tend to be in remote locations.
Additionally, current projections for landfills’ remaining “air space” (waste capacity) don’t include coal ash. So, to begin adding coal ash to an existing landfill’s waste stream maxes out that landfill’s capacity years sooner and creates the need for expansion.
Using landfills also comes with the drawbacks of trucking coal ash over public roadways, exacerbating congestion and risk of spills, as well as increased transportation costs to reach landfills in remote rural areas.
Therefore, disposal as a disposition method for legacy CCR should only be considered after ALL other methods have been exhausted.
No matter what method is chosen, project costs matter in all CCR disposition. Next, we’ll discuss the time factors and financial pros and cons of each solution.