what is coal ash and how dangerous is it
coal ash refers to the hazardous
byproducts of coal combustion at coal
based power plants
namely fly ash bottom ash and boiler
slag
which contain toxic materials such as
arsenic and lead it is a highly
controversial type of industrial waste
given that the us environmental
protection agency epa
didn't begin regulating its disposal
until 2015.
in its natural state coal is mildly
hazardous
it can emit fine particulate pollution
when sitting uncovered in stockpiles or
being transported by trains
especially during windy weather
conditions but when coal is combusted or
burned
such as in a power plant when coal is
burned in a boiler
heat from the furnace converts boiler
water to steam and the steam spins
turbines to turn generators
it releases a hazardous brew of toxic
pollutants into the air
including sulfur dioxide so2
which contributes to acid rain and
respiratory illnesses
nitrogen oxides nox which contribute to
smog and respiratory illnesses
and carbon dioxide co2
a primary greenhouse gas that
contributes to human-caused global
warming
coal's non-gaseous remnants coal ash
contain arsenic
lead mercury and other heavy metals that
are known to cause cancer
developmental disorders and reproductive
issues
the american coal ash association
estimates that in 2019
nearly 79 million tons of coal ash were
generated
consider this along with the fact that
from 1950 to 2015
coal was the largest fossil fuel-based
source of electricity generation in the
united states
in 2016 it became the second largest
energy source behind natural gas
and you'll have some idea of how much
coal ash currently plagues the planet
according to the epa it's the second
largest waste material in the united
states behind household trash
what are the byproducts of coal ash
coal ash consists of multiple coal
combustion by-products
including fly ash flue gas gypsum bottom
ash and boiler slag which accumulate in
the bellies of coal-fired power stations
fly ash roughly half of coal's
combustion leftovers take the form of
fly ash
a light-colored powdery residue that
resembles wood ash
fly ash is so fine and feather-like that
it flies up into a power plant's smoke
stacks
in the past fly ash was released into
the air this way
but laws now require that fly ash
emissions be captured by filters
flue gas gypsum flue gas gypsum is
produced when emission scrubbers inside
of a coal power plant's exhaust stacks
remove sulfur and oxides from the gas
streams
it is the second most common coal
combustion byproduct
bottom ash as its name suggests bottom
ash is the heavier portion of coal ash
rather than floating into the exhaust
stacks it clumps together and settles at
the bottom of the boiler's furnace
bottom ash comprises about 10 percent of
coal ash waste
boiler slag the portions of coal ash
that melt under the intense heat of
combustion and then cool to form glassy
obsidian-like pellets are called boiler
slag traces of boiler slag can be found
in smokestack filters as well as along
the furnace bottom
exactly how dangerous is coal ash
coal ash is stored near power plants
both in open-air landfills
ash pits and ponds of water or
impoundments ash ponds
the problem with this storage system is
contaminants within coal ash can leach
into the soil
rivers lakes and groundwater this is
especially dangerous for those living
next to the over 310 active coal ash
pits
as well as the over 735 active coal ash
pond disposal sites across the united
states
it's so dangerous in fact that if you
live near a wet ash pond and get your
drinking water from a well
you may have as much as a 1 in 50 chance
of getting cancer from drinking arsenic
contaminated water
notes the epa the december 2008 coal ash
spill in kingston
tennessee which resulted in more than
one billion gallons of coal ash slurry
damaging homes and flowing into
tributaries of the tennessee river
highlighted the environmental and human
health dangers of coal ash
in response the epa proposed that
disposal of coal combustion residuals
from electric utilities
rule for regulating the disposal of coal
ash in june 2010
the epa finalized the rule under the
obama administration in october 2015
but because the rule designated coal ash
is no hazardous solid waste
it wasn't the when environmentalists had
hoped it would be
although the epa still labels coal as
non-hazardous
this doesn't negate the scientific fact
that coal ash contains hazardous
chemical compounds
nor does it void the coal ash rules aim
of protecting communities against coal
ash toxicity
or of holding companies in violation of
coal ash regulations accountable
can coal ash be recycled
one option for reducing the amount of
coal ash that's dumped in ash pits and
ponds is to recycle and reuse it as
other materials
the key to safely recycling such toxic
materials as a process
known as encapsulation which binds the
coal ash on a molecular level and thus
minimizes the leaching of toxic
chemicals
fly ash for example binds together and
solidifies when mixed with water
making it an ideal ingredient for cement
and grout
encapsulated gypsum is commonly used to
create drywall
similarly slag and bottom ash have been
cleared by the epa to be used as filler
during the construction of roadways and
embankments
however these are unencapsulated uses of
coal ash
uses where coal ash still poses some
level of risk to the surrounding
environment
clearly coal ash recycling is an
imperfect science
even so it sometimes offers the least
environmentally problematic
option for coal ash disposal