Environmental impacts of renewable energy technologies

Contents

Introduction     2

Wind Energy 2

Solar Energy     3

Geothermal Energy      4

Biomass     6

Air Pollution    6

Greenhouse Gases 8

Implications for Agriculture and Forestry    8

Hydropower  9

Conclusion  10

Sources     12



Introduction

 To combat global warming and the other problems associated with fossil
fuels, the world must switch to renewable energy sources like sunlight,
wind,  and  biomass.  All  renewable  energy   technologies   are   not
appropriate  to  all  applications  or  locations,  however.  As   with
conventional energy production, there are environmental  issues  to  be
considered. This paper identifies some of the key environmental impacts
associated  with  renewable  technologies  and   suggests   appropriate
responses to them. A study by the Union  of  Concerned  Scientists  and
three other national organizations,  America's  Energy  Choices,  found
that even when certain strict  environmental  standards  are  used  for
evaluating renewable energy projects, these energy sources can  provide
more than half of the US energy supply by the year 2030.
Today the situation in fuel and industrial complexes round the world is
disastrous. Current energy  systems  depend  heavily  upon  fossil  and
nuclear fuels. What this would mean is that we would run out of mineral
resources if we continue consuming non-renewables at the present  rate,
and this moment is not far off. According to some estimates, within the
next 200 years most people, for instance, seize using  their  cars  for
lack of petrol (unless some  alternatives  are  used).  Moreover,  both
fossil and nuclear fuels produce a great amount of polluting substances
when burnt. We are slowly but steadily destroying our  planet,  digging
it from inside and releasing the wastes into the atmosphere, water  and
soil. We have to seize vandalizing the Earth and seek some  other  ways
to address the  needs  of  the  society  some  other  way.  That’s  why
renewable sources are so important for the society. In fact,  today  we
have a simple  choice  –  either  to  turn  to  nature  or  to  destroy
ourselves. I have all reasons to reckon that most of people would  like
the first idea much more, and this is why I’m going to inquire into the
topic and look through some ways of providing a sustainable future  for
next generations.


Wind Energy

It is hard to imagine an energy source more benign to  the  environment
than wind power; it produces no air or  water  pollution,  involves  no
toxic or hazardous substances (other than those commonly found in large
machines), and poses no threat to public  safety.  And  yet  a  serious
obstacle facing the  wind  industry  is  public  opposition  reflecting
concern over the visibility and  noise  of  wind  turbines,  and  their
impacts on wilderness areas.
One of the most misunderstood aspects of wind power is its use of land.
Most studies assume  that  wind  turbines  will  be  spaced  a  certain
distance apart and that all of the land in between should  be  regarded
as occupied. This leads to some quite disturbing estimates of the  land
area  required  to  produce  substantial  quantities  of  wind   power.
According to one widely circulated report from the 1970s, generating 20
percent of US electricity from windy areas in 1975 would have  required
siting turbines on 18,000 square miles, or an area about 7 percent  the
size of Texas.
In reality, however, the wind turbines themselves occupy only  a  small
fraction of this land area, and the rest can be used for other purposes
or left in its natural state. For this reason, wind  power  development
is ideally suited to farming areas. In Europe, farmers plant  right  up
to the base of turbine towers, while in California  cows  can  be  seen
peacefully grazing in their  shadow.  The  leasing  of  land  for  wind
turbines,  far  from  interfering  with  farm  operations,  can   bring
substantial benefits to landowners in the form of increased income  and
land values. Perhaps the greatest potential for wind power  development
is consequently in the Great Plains, where wind is plentiful  and  vast
stretches of farmland could  support  hundreds  of  thousands  of  wind
turbines.
In other settings, however, wind power development can  create  serious
land-use conflicts. In forested areas it may mean  clearing  trees  and
cutting roads, a prospect that is sure to generate controversy,  except
possibly in areas where heavy logging has already  occurred.  And  near
populated areas, wind projects often run  into  stiff  opposition  from
people who regard them as  unsightly  and  noisy,  or  who  fear  their
presence may reduce property values.
In California,  bird  deaths  from  electrocution  or  collisions  with
spinning rotors have emerged as a problem at  the  Altamont  Pass  wind
"farm," where more than  30  threatened  golden  eagles  and  75  other
raptors such as red-tailed hawks died or were injured during  a  three-
year period. Studies under way to determine the cause of  these  deaths
and find preventive measures may have an important impact on the public
image and rate of growth of the wind industry.  In  appropriate  areas,
and with imagination, careful planning, and early contacts between  the
wind industry, environmental groups, and affected  communities,  siting
and environmental problems should not be insurmountable.

Solar Energy

Since solar power systems generate no air pollution  during  operation,
the primary environmental, health, and safety issues involve  how  they
are manufactured, installed, and  ultimately  disposed  of.  Energy  is
required to manufacture and install solar components,  and  any  fossil
fuels used for this purpose will generate emissions. Thus, an important
question is how much fossil energy input is required for solar  systems
compared to the  fossil  energy  consumed  by  comparable  conventional
energy systems. Although this varies depending upon the technology  and
climate, the energy balance is generally favorable to solar systems  in
applications where they are cost effective, and it  is  improving  with
each successive generation of technology. According  to  some  studies,
for example, solar water heaters  increase  the  amount  of  hot  water
generated per unit of fossil energy invested by at least  a  factor  of
two compared to natural gas water heating and by at least a  factor  of
eight compared to electric water heating.
Materials used in some solar  systems  can  create  health  and  safety
hazards for workers and anyone else coming into contact with  them.  In
particular, the manufacturing  of  photovoltaic  cells  often  requires
hazardous materials such as arsenic and cadmium. Even relatively  inert
silicon, a major material used in solar  cells,  can  be  hazardous  to
workers if it is breathed in as dust. Workers involved in manufacturing
photovoltaic modules and components must consequently be protected from
exposure to these materials. There is an additional-probably very small-
danger that hazardous fumes released from photovoltaic modules attached
to burning homes or buildings could injure fire fighters.
None of these  potential  hazards  is  much  different  in  quality  or
magnitude from the innumerable hazards  people  face  routinely  in  an
industrial society. Through effective regulation, the dangers can  very
likely be kept at a very low level.
The large amount of land required for utility-scale solar power plants-
approximately one square  kilometer  for  every  20-60  megawatts  (MW)
generated-poses  an  additional  problem,  especially  where   wildlife
protection is a concern. But this problem is not unique to solar  power
plants. Generating electricity from coal actually requires as  much  or
more land per unit of energy delivered if the land used in strip mining
is taken into account. Solar-thermal  plants  (like  most  conventional
power plants) also require cooling water, which may be costly or scarce
in desert areas.
Large central power plants are  not  the  only  option  for  generating
energy from  sunlight,  however,  and  are  probably  among  the  least
promising.  Because  sunlight  is  dispersed,  small-scale,   dispersed
applications are  a  better  match  to  the  resource.  They  can  take
advantage of unused space on the roofs of homes and  buildings  and  in
urban  and  industrial  lots.  And,  in  solar  building  designs,  the
structure itself acts as the collector, so there is  no  need  for  any
additional space at all.

Geothermal Energy

Geothermal energy is heat contained below the earth's surface. The only
type  of  geothermal  energy  that  has  been   widely   developed   is
hydrothermal energy, which consists of  trapped  hot  water  or  steam.
However, new technologies are being developed to exploit hot  dry  rock
(accessed  by  drilling  deep  into   rock),   geopressured   resources
(pressurized brine mixed with methane), and magma.
The various geothermal resource types differ in many respects, but they
raise a common set of environmental issues. Air and water pollution are
two leading concerns, along with the safe disposal of hazardous  waste,
siting, and land subsidence. Since these resources would  be  exploited
in a highly centralized fashion, reducing their  environmental  impacts
to an acceptable level should be relatively easy. But it will always be
difficult  to  site  plants  in  scenic  or  otherwise  environmentally
sensitive areas.
The method used to convert geothermal steam or hot water to electricity
directly affects the amount of waste generated. Closed-loop systems are
almost totally benign, since gases or fluids removed from the well  are
not exposed to the atmosphere and are usually injected  back  into  the
ground after giving up their heat. Although  this  technology  is  more
expensive than conventional open-loop systems, in  some  cases  it  may
reduce scrubber and solid waste disposal  costs  enough  to  provide  a
significant economic advantage.
Open-loop systems, on the other hand, can  generate  large  amounts  of
solid wastes as well as noxious  fumes.  Metals,  minerals,  and  gases
leach out into the geothermal steam or hot water as it  passes  through
the rocks. The large amounts  of  chemicals  released  when  geothermal
fields are  tapped  for  commercial  production  can  be  hazardous  or
objectionable to people living and working nearby.
At The Geysers, the largest geothermal development, steam vented at the
surface contains  hydrogen  sulfide  (H2S)-accounting  for  the  area's
"rotten egg" smell-as well as ammonia, methane, and carbon dioxide.  At
hydrothermal plants carbon dioxide is expected  to  make  up  about  10
percent of the gases trapped in geopressured brines. For each kilowatt-
hour of electricity generated, however, the amount  of  carbon  dioxide
emitted is still only about 5 percent of the amount emitted by a  coal-
or oil-fired power plant.
Scrubbers reduce air emissions but produce  a  watery  sludge  high  in
sulfur  and  vanadium,  a  heavy  metal  that  can  be  toxic  in  high
concentrations. Additional sludge is generated when hydrothermal  steam
is condensed, causing the dissolved solids  to  precipitate  out.  This
sludge is generally  high  in  silica  compounds,  chlorides,  arsenic,
mercury, nickel, and other toxic heavy metals.  One  costly  method  of
waste disposal  involves  drying  it  as  thoroughly  as  possible  and
shipping it to licensed hazardous waste sites. Research  under  way  at
Brookhaven National Laboratory in New York points to the possibility of
treating these wastes with microbes designed  to  recover  commercially
valuable metals while rendering the waste non-toxic.
Usually the  best  disposal  method  is  to  inject  liquid  wastes  or
redissolved solids back into a porous stratum  of  a  geothermal  well.
This technique is especially important  at  geopressured  power  plants
because of the sheer volume of wastes they  produce  each  day.  Wastes
must be injected well below fresh water aquifers to make  certain  that
there is no communication between  the  usable  water  and  waste-water
strata. Leaks in the  well  casing  at  shallow  depths  must  also  be
prevented.
In addition to providing safe waste disposal, injection may  also  help
prevent land subsidence. At Wairakei, New  Zealand,  where  wastes  and
condensates were not injected for many years, one  area  has  sunk  7.5
meters since 1958. Land subsidence  has  not  been  detected  at  other
hydrothermal plants in long-term operation. Since  geopressured  brines
primarily are found along the Gulf of Mexico coast, where natural  land
subsidence is already a problem, even slight settling could have  major
implications for flood control and hurricane damage. So  far,  however,
no settling has been detected at any of the  three  experimental  wells
under study.
Most geothermal power plants will require a large amount of  water  for
cooling or other purposes. In places where water is  in  short  supply,
this need could raise conflicts with other users for water resources.
The development of hydrothermal energy faces a  special  problem.  Many
hydrothermal reservoirs are located in  or  near  wilderness  areas  of
great natural beauty such as Yellowstone National Park and the  Cascade
Mountains. Proposed developments in such  areas  have  aroused  intense
opposition. If hydrothermal-electric  development  is  to  expand  much
further in the United States, reasonable compromises will  have  to  be
reached between environmental groups and industry.

Biomass

Biomass power, derived from the burning of plant  matter,  raises  more
serious environmental issues than any other renewable  resource  except
hydropower. Combustion of biomass and  biomass-derived  fuels  produces
air pollution; beyond this, there are concerns  about  the  impacts  of
using land to grow energy crops. How serious  these  impacts  are  will
depend on how carefully the resource is managed. The picture is further
complicated because there is no single biomass technology, but rather a
wide variety of production and conversion methods, each with  different
environmental impacts.

Air Pollution

Inevitably,  the  combustion  of  biomass  produces   air   pollutants,
including carbon monoxide, nitrogen oxides, and  particulates  such  as
soot and ash. The amount  of  pollution  emitted  per  unit  of  energy
generated varies widely by technology,  with  wood-burning  stoves  and
fireplaces generally the worst offenders. Modern,  enclosed  fireplaces
and wood stoves pollute much less than traditional, open fireplaces for
the simple reason that they are more efficient.  Specialized  pollution
control  devices  such  as  electrostatic  precipitators   (to   remove
particulates) are available, but without specific regulation to enforce
their use it is doubtful they will catch on.
Emissions from conventional biomass-fueled power plants  are  generally
similar to emissions from coal-fired power  plants,  with  the  notable
difference that biomass facilities produce very little  sulfur  dioxide
or toxic metals  (cadmium,  mercury,  and  others).  The  most  serious
problem is their particulate emissions, which must be  controlled  with
special devices. More advanced technologies,  such  as  the  whole-tree
burner  (which  has  three  successive  combustion  stages)   and   the
gasifier/combustion turbine combination,  should  generate  much  lower
emissions, perhaps comparable  to  those  of  power  plants  fueled  by
natural gas.
Facilities that burn raw municipal waste present  a  unique  pollution-
control problem. This waste often contains  toxic  metals,  chlorinated
compounds, and plastics, which generate harmful emissions.  Since  this
problem is much less severe in facilities burning  refuse-derived  fuel
(RDF)-pelletized or shredded paper and other waste with most  inorganic
material removed-most waste-to-energy plants built in  the  future  are
likely to use this fuel. Co-firing RDF in coal-fired power  plants  may
provide an inexpensive way to reduce coal emissions without  having  to
build new power plants.
Using biomass-derived methanol and ethanol as vehicle fuels, instead of
conventional  gasoline,  could  substantially  reduce  some  types   of
pollution from automobiles. Both methanol and  ethanol  evaporate  more
slowly than gasoline, thus helping to reduce evaporative  emissions  of
volatile organic compounds (VOCs), which react with heat  and  sunlight
to generate ground-level ozone (a  component  of  smog).  According  to
Environmental  Protection  Agency  estimates,  in   cars   specifically
designed to burn pure methanol  or  ethanol,  VOC  emissions  from  the
tailpipe could be reduced 85  to  95  percent,  while  carbon  monoxide
emissions could be reduced 30 to  90  percent.  However,  emissions  of
nitrogen oxides, a source  of  acid  precipitation,  would  not  change
significantly compared to gasoline-powered vehicles.
Some studies have indicated that the  use  of  fuel  alcohol  increases
emissions of formaldehyde and other aldehydes, compounds identified  as
potential carcinogens. Others counter that these results consider  only
tailpipe  emissions,  whereas  VOCs,  another  significant  pathway  of
aldehyde formation, are much  lower  in  alcohol-burning  vehicles.  On
balance, methanol  vehicles  would  therefore  decrease  ozone  levels.
Overall, however, alcohol-fueled cars  will  not  solve  air  pollution
problems in dense urban  areas,  where  electric  cars  or  fuel  cells
represent better solutions.

Greenhouse Gases

A major benefit of substituting biomass for fossil fuels  is  that,  if
done in a sustainable fashion, it would  greatly  reduce  emissions  of
greenhouses gases. The amount of carbon dioxide released  when  biomass
is burned is very nearly the same as the amount required  to  replenish
the plants grown to produce the biomass. Thus, in  a  sustainable  fuel
cycle, there would be no net emissions of carbon dioxide, although some
fossil-fuel  inputs  may  be   required   for   planting,   harvesting,
transporting, and processing biomass. Yet, if efficient cultivation and
conversion processes are used, the resulting emissions should be  small
(around 20 percent of the emissions created by fossil fuels alone). And
if the energy needed to produce and process biomass came from renewable
sources in the first place, the  net  contribution  to  global  warming
would be zero.
Similarly, if biomass wastes such as crop residues or  municipal  solid
wastes are used for energy, there should be few or  no  net  greenhouse
gas emissions. There would even be a slight greenhouse benefit in  some
cases,  since,  when  landfill  wastes  are  not  burned,  the   potent
greenhouse gas methane may be released by anaerobic decay.

Implications for Agriculture and Forestry

One surprising side effect of growing trees and other plants for energy
is that it could benefit soil quality and farm economies. Energy  crops
could provide a steady supplemental income for farmers  in  off-seasons
or allow them to work unused land  without  requiring  much  additional
equipment. Moreover, energy crops could be used to  stabilize  cropland
or rangeland prone to erosion and flooding. Trees would  be  grown  for
several years before being harvested, and their roots and  leaf  litter
could help stabilize the soil. The  planting  of  coppicing,  or  self-
regenerating, varieties would minimize the need for disruptive  tilling
and planting. Perennial grasses harvested like hay could play a similar
role; soil losses with a crop such as switchgrass, for  example,  would
be negligible compared to annual crops such as corn.
If improperly managed,  however,  energy  farming  could  have  harmful
environmental impacts. Although energy crops could be grown  with  less
pesticide and fertilizer  than  conventional  food  crops,  large-scale
energy farming could nevertheless lead to  increases  in  chemical  use
simply because more land would be  under  cultivation.  It  could  also
affect  biodiversity  through  the  destruction  of  species  habitats,
especially if forests are more intensively managed. If agricultural  or
forestry wastes and residues were used for fuel, then  soils  could  be
depleted of organic content and nutrients  unless  care  was  taken  to
leave enough wastes behind.  These  concerns  point  up  the  need  for
regulation and monitoring of energy crop development and waste use.
Energy farms may present a perfect opportunity  to  promote  low-impact
sustainable  agriculture,  or,  as  it  is  sometimes  called,  organic
farming. A relatively new federal effort for food crops emphasizes crop
rotation, integrated pest  management,  and  sound  soil  husbandry  to
increase profits and  improve  long-term  productivity.  These  methods
could be adapted to energy farming. Nitrogen-fixing crops could be used
to provide natural fertilizer, while crop diversity  and  use  of  pest
parasites  and  predators  could  reduce  pesticide  use.  Though  such
practices may not produce as high a yield as  more  intensive  methods,
this penalty could be offset by reduced energy and chemical costs.
Increasing the amount of forest wood harvested for  energy  could  have
both positive and negative effects. On one hand, it  could  provide  an
incentive for the forest-products industry to manage its resources more
efficiently, and thus improve forest health. But it could also  provide
an  excuse,  under  the  "green"  mantle,  to  exploit  forests  in  an
unsustainable  fashion.  Unfortunately,  commercial  forests  have  not
always been soundly managed,  and  many  people  view  with  alarm  the
prospect of increased wood  cutting.  Their  concerns  can  be  met  by
tighter government controls on forestry practices and by following  the
principles of "excellent" forestry. If such principles are applied,  it
should be possible to extract energy from forests indefinitely.

Hydropower

The development of hydropower has become  increasingly  problematic  in
the United States. The construction of large dams has virtually  ceased
because most suitable undeveloped sites are under federal environmental
protection. To some extent, the slack has been taken up by a revival of
small-scale development. But small-scale hydro development has not  met
early expectations. As of 1988, small hydropower plants  made  up  only
one-tenth of total hydropower capacity.
Declining fossil-fuel prices and reductions  in  renewable  energy  tax
credits are only partly responsible  for  the  slowdown  in  hydropower
development. Just as significant have been  public  opposition  to  new
development and environmental regulations.
Environmental regulations affect existing projects as well as new ones.
For example, a series of large facilities  on  the  Columbia  River  in
Washington will probably be forced to reduce their peak output by 1,000
MW to save  an  endangered  species  of  salmon.  Salmon  numbers  have
declined rapidly because the young  are  forced  to  make  a  long  and
arduous trip downstream through several  power  plants,  risking  death
from turbine blades at each stage. To ease this trip, hydropower plants
may be required to divert water around their turbines at those times of
the year when the fish attempt the trip. And in  New  England  and  the
Northwest, there is a  growing  popular  movement  to  dismantle  small
hydropower plants in an attempt to  restore  native  trout  and  salmon
populations.
That environmental concerns would constrain hydropower  development  in
the United States is perhaps ironic, since these plants produce no  air
pollution or greenhouse gases. Yet, as the salmon example makes  clear,
they affect the environment. The impact of very large dams is so  great
that there is almost no chance that any  more  will  be  built  in  the
United States, although large projects continue to be pursued in Canada
(the largest at James Bay in Quebec) and in many developing  countries.
The reservoirs created by such projects frequently inundate large areas
of forest, farmland, wildlife habitats, scenic areas, and  even  towns.
In addition, the dams can cause radical  changes  in  river  ecosystems
both upstream and downstream.
Small hydropower plants using reservoirs can  cause  similar  types  of
damage, though obviously on a smaller scale. Some  of  the  impacts  on
fish can be mitigated by installing "ladders" or other devices to allow
fish to migrate over dams, and by maintaining minimum river-flow rates;
screens can also be installed to keep fish away from turbine blades. In
one case, flashing underwater lights placed in the Susquehanna River in
Pennsylvania direct night-migrating American shad around turbines at  a
hydroelectric station. As environmental regulations  have  become  more
stringent, developing cost-effective mitigation measures such as  these
is essential.
Despite  these  efforts,  however,  hydropower  is   almost   certainly
approaching the limit of its potential in the United  States.  Although
existing hydro facilities can be upgraded with more efficient turbines,
other plants can be refurbished, and  some  new  small  plants  can  be
added, the  total  capacity  and  annual  generation  from  hydro  will
probably not increase by more than 10 to 20  percent  and  may  decline
over the long term because of increased demand on water  resources  for
agriculture and drinking water, declining rainfall (perhaps  caused  by
global warming), and efforts to protect or restore endangered fish  and
wildlife.


Conclusion

So, no single solution can meet our society's future energy needs.  The
solution  instead  will  come  from  the  family  of   diverse   energy
technologies that do not deplete our natural resources or  destroy  our
environment. That’s the final decision that the nature  imposes.  Today
mankind’s survival directly depends upon how quickly we can  renew  the
polluting  fuel  an  energy  complex  we  have  now  with   sound   and
environmentally friendly technologies.
Certainly, alternative sources of energy have their own drawbacks, just
like everything in  the  world,  but,  in  fact,  they  seem  minor  in
comparison with the hazards posed by conventional sources. Moreover, if
talking about the dangers posed by new energy technologies, there is  a
trend of localization. Really, these have  almost  no  negative  global
effect, such as air pollution.
Moreover, even the minor effects posed by geothermal  plants  or  solar
cells can be overseen and prevented if  the  appropriate  measures  are
taken. So, when using alternatives, we operate a  universal  tool  that
can be tuned to suit every purpose. They reduce the terrible impact the
human being has had on the environment for the years of his  existense,
thus drawing nature and technology closer than ever before for the last
2 centuries.

Sources

1. "Biomass fuel." DISCovering Science. Gale Research, 1996.  Reproduced  in
   Student Resource Center College Edition. Farmington  Hills,  Mich.:  Gale
   Group. September, 1999;
2. "Alternative energy sources." U*X*L Science; U*X*L, 1998;
3. Duffield, Wendell A., John H. Sass, and Michael L. Sorey,  1994,  Tapping
   the Earth’s Natural Heat: U.S. Geological Survey Circular 1125;
4. Cool Energy: Renewable Solutions to Environmental  Problems,  by  Michael
   Brower, MIT Press, 1992;
5.  Powerful  Solutions:  Seven  Ways  to  Switch   America   to   Renewable
   Electricity, UCS, 1999;



	

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