air pollution, scrubber, biodiesel, solar power, wind power, ambient, baghouses, bioreactor, catalytic converter

1. Clean Air Technologies
Module 13
Earth and Environmental Science

2. There are several inventions that help to
clean air before factories release it back into
the atmosphere.

3. Baghouses
Power plants often use more than one device
to stop pollutants from escaping
smokestacks. Baghouses are filtration
structures such as the one seen here that
have been retrofitted to many power plants
nationwide. They work by catching fine
particulates—tiny clumps of soot, dirt, and
chemicals that can damage lungs and collect
in the atmosphere, creating smog.
Baghouses function as massive vacuum
cleaners. They are lined with many fabric
filter "bags," which plant engineers
periodically clean or replace, carting away
the particulates they collect.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

4. Biodiesel
This relatively new type of alternative fuel is
processed from any vegetable oil—including
used oil from fast-food restaurants—and can
power most diesel-engine vehicles without
modification. Sales of biodiesel are gradually
increasing—75 million gallons were sold in
the U.S. in 2005—and many government
vehicles like these from the USDA use it to fill
up. Though it burns 78 percent cleaner than
petroleum diesel and comes from a
renewable source, it is double the cost and
fueling stations are scattered. Furthermore,
only a fraction of vehicles in the U.S. have
diesel engines, though new fuel-efficient
models on the market have recently gained
in popularity.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

5. Bioreactors
While most antipollution technologies
involve massive, complex equipment, some
scientists are experimenting with tiny, simple
living organisms called cyanobacteria that eat
polluting carbon dioxide (CO2). These algae
can flourish in the blistering temperatures of
chimneys. Researchers have designed
"bioreactors," window-screen-like
membranes teeming with cyanobacteria, for
future installation into power plant
smokestacks. Fiber- optic cables would focus
life-sustaining light across the membranes,
allowing the algae to grow inside chimneys
while feasting on a diet of CO2 exhaust. This
technology has already proved itself in small-scale
demonstrations. A test on a fully
operational power plant is about five years
away, and scientists are also studying the
same algae as a potential source of hydrogen
energy.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

6. NASA envisions clean
energy from algae
Massive algae blooms grow depending on
the amount of light they receive, the
temperature, and the amount of nutrients
available in the water.
http://climate.nasa.gov/news/564/

7. Catalytic Converters
Most cars are sources of pollution, and to
keep up with emissions laws automakers
began refining car engines and fuel systems
in the 1970s. These modifications culminated
in catalytic converters, which treat exhaust
before it leaves a car's tailpipe, converting
toxic combustion by-products such as carbon
and nitrogen monoxides to less-toxic gases.
Catalytic converters have been highly
successful in reducing emissions, but
substantial increases in the distances cars
and trucks travel on average and in the
overall number of vehicles in use have made
up the difference, and cars are still a major
cause of pollution.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

8. Ethanol
Ethanol is a clean-burning alcohol produced
by bacteria that ferment the sugars in corn
and cornstalks. Some environmentalists tout
ethanol as a potential alternative to gasoline.
In the U.S., about five million vehicles already
drive on "flex-fuel." They can use traditional
gas or E85, a mix of 85 percent ethanol and
15 percent gasoline. Converting an
automobile to flex-fuel is inexpensive, but
there are few ethanol pumps in the U.S. In
Brazil, nearly all cars run on a 96 percent
ethanol fuel produced from sugarcane, which
is readily available. Brazilians have seen
benefits: not only is it cleaner burning, it is
half the price of imported gasoline.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

9. Nuclear Power
Nuclear power plants provide about 17
percent of the world's electricity and about
20 percent of the electricity in the U.S. They
are extremely clean compared to coal-fired
plants, which, perhaps surprisingly, release
more radioactivity than a properly
functioning nuclear power plant. Many
experts believe nuclear power such as that
being developed in this Sandia National
Laboratory experiment is an important
option for the U.S. and the world to meet
pollution-free energy needs. But others cite
significant problems with nuclear power. For
example, mining and purifying the uranium
that fuels nuclear plants is not a clean
process; improperly functioning nuclear
plants present environmental and terrorism
risks; spent nuclear fuel remains toxic for
centuries and must be stored; and
transporting nuclear fuel to and from plants
can be hazardous.
http://www.pbs.org/wgbh/nova/sun/clea-nf.html

10. Scrubbers
Since the Clean Air Act was passed by
Congress in 1990, electric generating power
plants in the USA have been required to use
industrial pollution control devices. Toxic
exhaust from power plants creates much of
our air pollution.
Many plants have already added scrubbers to
their chimneys. These industrial pollution
control devices can remove toxic substances
from exhaust streams, or neutralize them so
that they are harmless or even recyclable.
Ironically, the more robust the plume of
smoke rising from a smokestack, the more
likely it is scrubbed exhaust. So-called wet
scrubbers can increase the proportion of
water in waste gases, plumping up smoke
plumes.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

11. Getting free
• So many of our modern conveniences depend on using coal and
petroleum, but we have many pollution problems that result in pollution of
air, water, and land.
• Some of the things that are being done to help get us free of the past fuels
are below.

12. Fuel Cell Cars
Imagine a car that only had one waste
product: water. That is the tantalizing
promise of fuel cell cars, which have not yet
arrived in the commercial marketplace. If it
sounds too good to be true, that's because it
might be. Fuel cell cars produce electricity by
chemically breaking down hydrogen fuel.
When pure hydrogen is used, the only by-product
is water, but pollution is produced in
creating the fuel itself. Also, because
hydrogen is a flammable gas, safety is an
issue. Fuel distribution stations, such as this
proposed northern California hydrogen
pump, and storage solutions are under
development but still rife with kinks. It could
be two or more decades before fuel cell cars
are widely available and adopted by drivers.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

13. Hybrid Cars
Celebrity owners have made them famous,
and drivers' concerns about skyrocketing gas
prices and the environment have made them
a popular new choice. Sales in the U.S. of
hybrid cars such as Toyota's Prius, seen here,
doubled in January 2006 compared to the
year before, with nearly 16,000 cars sold.
Hybrids get their power from small gasoline
engines combined with electric motors and
rechargeable batteries. Their compact
engines deliver excellent gas mileage and
cause much less pollution than those in
conventional cars. Experts estimate that
driving a hybrid for 100,000 miles would
barely fill a teacup with pollutants.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

14. Solar Power
The sunlight that reaches Earth's surface
delivers 10,000 times more energy than we
consume, and solar power aims to harness
this force. Solar technologies use sunlight to
provide heat, electricity, and even cooling for
homes, businesses, and industry by
conducting electrons across an array like the
one at right or like the tiny solar cell in your
calculator. Researchers have optimistically
proposed that if they could cover just 0.1
percent of the Earth's surface with highly
efficient solar cells they could in theory
replace all other forms of energy. At
universities around the world, efforts are
under way to develop the kinds of advanced
solar arrays using nanotechnology and other
cutting-edge science that could perhaps
accomplish this goal in the future.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html

15. Solar Power
The already familiar solar panels

16. Wind Energy
Wind is a renewable energy source that
emits no pollution. It is the fastest-growing
"green" energy in the U.S. and provides light
to the Statue of Liberty. Wind farms—
clusters of huge windmills—produce
electricity by using the motion of their blades
to spin a shaft connected to a generator.
Experts estimate that the electricity created
in 2006 by America's wind farms will displace
some 15 million tons of carbon dioxide. Over
five million acres of forest would be needed
to absorb that much CO2. Some people
oppose wind farms because they occupy
large tracts of land and can sometimes harm
birds, but most agree that their
environmental costs are much lower than
those of fossil fuels.
http://www.pbs.org/wgbh/nova/sun/clea-nf.
html Flikr.com

17. NASA’s MODIS satellite
Terra can send back
photos of pollutants in
the air.
This is a dust storm in the
Sahara on November 5,
2013.
http://lance-modis.eosdis.nasa.gov/cgi-bin/
imagery/gallery.cgi

18. https://earthdata.nasa.gov/labs/worldview/?switch=geographic&products=baselayers,!MODIS_Aqua_CorrectedReflectance_Bands721,!MODI
S_Aqua_CorrectedReflectance_TrueColor,MODIS_Terra_CorrectedReflectance_Bands721,MODIS_Terra_CorrectedReflectance_TrueColor~overla
ys,!Reference_Labels,!Reference_Features,Coastlines&time=2014-11-14&map=-163.786011,54.330688,-160.621948,56.084106

19. https://earthdata.nasa.gov/labs/worldview/?switch=geographic&products=bas
elayers,
!MODIS_Aqua_CorrectedReflectance_Bands721
http://lance-modis.eosdis.nasa.gov/cgi-bin/imagery/gallery.cgi
http://climate.nasa.gov/news/564/
http://www.pbs.org/wgbh/nova/sun/clea-nf.html