1
1. History
Carbon dioxide (CO2) emissions are the main driver of climate
change. CO2 is released into the atmosphere primarily from the
combustion of fossil fuels.Time series on CO2 emissions from fossil
fuels go back remarkably far in history. National estimates of annual
emissions have been made possible by commercial records on the
use of fossil fuels. „This is because carbon emissions are exactly
proportional to the amount of fuel burned based on their chemical
properties. As a culmination of statistical compilations, Boden et al.
(2011) have collected time series on annual carbon emissions going as
far back as 1751 in some cases.”
„Countries differ considerably in levels and in trendsof carbon
emissions.This has formed a key challenge in the international
climate negotiations.United States, Australia and Canada have
relatively high levels of per capita emissions reflecting their energy-dependent
economies
and
produce
more
pollution,
striking
even
when
like
Germany
countries
fuel-efficient
economies.
reliance
like
coal.
compared
and
to
Japan,
Moreover,
the
on
The
fuels
difference
other
which
gap
ger compared to less developed countries like India.”
which
developed
have
is
is
even
more
lar-
2
2. Causes
Since the Industrial Revolution, human activities such as the
burning of oil, coal and gas, as well as deforestation have greatly
increased CO2 concentrations in the atmosphere. As we can see from
figure 1, almost all CO2 emissions (about 96.5%) come from fossil fuels
use. The 3 types of fossil fuels that are used the most are coal, natural
gas and petroleum. When fossil fuels are combusted, the carbon stored
in them is emitted almost entirely as CO2.
The main human activity that emits CO2 is the combustion of fossil
fuels (coal, natural gas, and oil) for energy and transportation, although
certain industrial processes and land-use changes also emit CO2.
2.1 Transportation and Utilities
„Virtually all human activities have an impact on our environment, and
transportation is no exception. While transportation is crucial to our
economy and our personal lives, as a sector it is also a significant
source of greenhouse gas (GHG) emissions.”
Based on current GHG emission reporting guidelines, the
transportation sector directly accounted for about 28 percent of total U.S.
GHG emissions in 2006, making it the second largest source of GHG
emissions, behind only electricity generation (34 percent). Nearly 97
3
percent
of
transportation
GHG
emissions
came
through
direct
combustion of fossil fuels, with the remainder due to carbon dioxide
(CO2) from electricity (for rail) and Hydrofluorocarbons (HFCs) emitted
from vehicle air conditioners and refrigerated transport. Transportation is
the largest end-use sector emitting CO2, the most prevalent greenhouse
gas. Estimates of GHG emissions do not include additional "lifecycle"
emissions related to transportation, such as the extraction and refining of
fuel and the manufacture of vehicles, which are also a significant source
of domestic and international GHG emissions.
2.2 Industrial Production
The Industry sector produces the goods and raw materials we use
every day. The greenhouse gases emitted during industrial production
are split into two categories: direct emissions that are produced at the
facility, and indirect emissions that occur off site, but are associated with
the facility's use of energy.
Direct emissions are produced by burning fuel for power or heat,
through chemical reactions, and from leaks from industrial processes or
equipment. Most direct emissions come from the consumption of fossil
fuels for energy. A smaller amount, roughly a third, come from leaks from
natural gas and petroleum systems, the use of fuels in production (e.g.,
4
petroleum products used to make plastics), and chemical reactions
during the production of chemicals, iron and steel, and cement.
Indirect emissions are produced by burning fossil fuel at a power
plant to make electricity, which is then used by an industrial facility to
power industrial buildings and machinery.
2.3 Electricity
The Electricity sector involves the generation, transmission, and
distribution of electricity. Carbon dioxide (CO2) makes up the vast
majority of greenhouse gas emissions from the sector, but smaller
amounts of methane (CH4) and nitrous oxide (N2O) are also emitted.
These gases are released during the combustion of fossil fuels, such as
coal, oil, and natural gas, to produce electricity. Less than 1% of
greenhouse gas emissions from the sector come from sulfur hexafluoride
(SF6), an insulating chemical used in electricity transmission and
distribution equipment.
The total electricity generation by electric power plants in the
United States, net of internal uses, was about 4.2 gigawatt-hours (GWh,
billion watt-hours) in 2007, as shown in Table 3. Three major fuel groups
were used by electric power plants to generate electricity: coal, at over
48 percent, or more than 2 billion watt-hours; natural gas and propane, at
over 21 percent, or nearly 900 million watt-hours; and nuclear energy, at
5
19 percent, or more than 800 million watt-hours. Renewable sources of
energy, such as solar, geothermal, water, and wind, generated a total of
291 million watt-hours, or 7 percent of total electricity, and biomass
generated 64 million watt-hours, or 1.5 percent, to the net electricity
generation in the United States in 2007 (Table 3).
„Trends in electricity generation for each energy source during the 2003–
2007 period are summarized in Table 3, and charted for major fuel
groups in Figure 1. Total electricity generation increased by about 7
percent between 2003 and 2007. Generation from natural gas and
propane showed a significant increase of more than 37 percent during
this time. Generation from all non-biomass renewable energy sources,
such as solar, water, wind, and geothermal, which result in no or
minimal emissions of carbon dioxide, actually decreased during this
period. However, use of solar energy to produce electricity increased
by more than 13 percent during the 2003–2007 period. Wind is now
the fastest growing source of electricity due to substantial
investments, particularly in the Great Plains region of the United
States, with generation increasing by almost threefold over the last
five years. Major efforts to promote greater use of biomass fuels for
electricity generation have resulted in this source increasing by over 7
percent. It should be noted that biomass is considered carbon neutral
6
because the carbon released during combustion is recaptured through
plant growth. Woody biomass captures carbon from the atmosphere,
whereas fossil fuels transfer underground carbon to the atmosphere
(Biomass Energy Resource Center 2008). Higher petroleum prices
have negatively affected the use of this fuel for generating electricity,
decreasing its share by 51 percent since 2003, and it now represents
only a little more than 1 percent of all fuel types used for electricity in
2007.”
3. Global Warming Effects
The effects of global warming are the ecological and social changes
caused by the rise in global temperatures. There is a scientific
consensus that climate change is occurring, and that human activities
are the primary driver. Evidence of climate change includes the
instrumental temperature record, rising sea levels, and decreased snow
cover in the Northern Hemisphere. „According to the Intergovernmental
Panel on Climate Change (IPCC), most of the observed increase in
global average temperatures since the mid-20th century is very likely due
to the observed increase in human greenhouse gas concentrations.”
3.1 Sea Level Rise
7
Projections of future climate change suggest further global
warming, sea level rise, and an increase in the frequency and severity of
some extreme weather events.[4] Parties to the United Nations
Framework Convention on Climate Change (UNFCCC) have agreed to
"stabilize greenhouse gas concentrations in the atmosphere at a level
that would prevent dangerous anthropogenic interference with the
climate system."
„Core samples, tide gauge readings, and, most recently, satellite
measurements tell us that over the past century, the Global Mean
Sea Level (GMSL) has risen by 4 to 8 inches (10 to 20
centimeters). However, the annual rate of rise over the past 20
years has been 0.13 inches (3.2 millimeters) a year, roughly twice
the average speed of the preceding 80 years.”
Over the past century, the burning of fossil fuels and other human
and natural activities has released enormous amounts of heat-trapping
gases into the atmosphere. These emissions have caused the Earth's
surface temperature to rise, and the oceans absorb about 80 percent of
this additional heat. The rise in sea levels is linked to three primary
factors, all induced by this ongoing global climate change:
8
Thermal expansion: When water heats up, it expands. About half of
the past century's rise in sea level is attributable to warmer oceans
simply occupying more space.
Melting of glaciers and polar ice caps: Large ice formations, like
glaciers and the polar ice caps, naturally melt back a bit each summer.
But in the winter, snows, made primarily from evaporated seawater, are
generally sufficient to balance out the melting. „Recently, though,
persistently higher temperatures caused by global warming have led to
greater-than-average summer melting as well as diminished snowfall due
to later winters and earlier springs.” This imbalance results in a
significant net gain in runoff versus evaporation for the ocean, causing
sea levels to rise.
Ice loss from Greenland and West Antarctica: As with glaciers and
the ice caps, increased heat is causing the massive ice sheets that cover
Greenland and Antarctica to melt at an accelerated pace. Scientists also
believe meltwater from above and seawater from below is seeping
beneath Greenland's and West Antarctica's ice sheets, effectively
lubricating ice streams and causing them to move more quickly into the
sea. Moreover, higher sea temperatures are causing the massive ice
shelves that extend out from Antarctica to melt from below, weaken, and
break off.
9
„When sea levels rise rapidly, as they have been doing, even a small
increase can have devastating effects on coastal habitats. As
seawater reaches farther inland, it can cause destructive erosion,
flooding of wetlands, contamination of aquifers and agricultural
soils, and lost habitat for fish, birds, and plants. When large storms
hit land, higher sea levels mean bigger, more powerful storm
surges that can strip away everything in their path.”
In addition, hundreds of millions of people live in areas that will
become increasingly vulnerable to flooding. Higher sea levels would
force them to abandon their homes and relocate. Low-lying islands could
be submerged completely.
3.2 Reduction of the Ozone Layer
Ozone depletion describes two distinct but related phenomena
observed since the late 1970s: „a steady decline of about 4% per decade
in the total volume of ozone in Earth's stratosphere (the ozone layer),
and a much larger springtime decrease in stratospheric ozone over
Earth's polar regions.” The latter phenomenon is referred to as the ozone
hole. In addition to these well-known stratospheric phenomena, there are
also springtime polar tropospheric ozone depletion events.
The details of polar ozone hole formation differ from that of midlatitude thinning, but the most important process in both is catalytic
10
destruction of ozone by atomic halogens. The main source of these
halogen atoms in the stratosphere is photodissociation of man-made
halocarbon refrigerants (CFCs, freons, halons). These compounds are
transported into the stratosphere after being emitted at the surface. Both
types of ozone depletion were observed to increase as emissions of
halo-carbons increased.
„FCs and other contributory substances are referred to as ozonedepleting substances (ODS). Since the ozone layer prevents most
harmful UVB wavelengths (280–315 nm) of ultraviolet light (UV
light) from passing through the Earth's atmosphere, observed and
projected decreases in ozone have generated worldwide concern
leading to adoption of the Montreal Protocol that bans the
production of CFCs, halons, and other ozone-depleting chemicals
such as carbon tetrachloride and trichloroethane. It is suspected
that a variety of biological consequences such as increases in skin
cancer, cataracts,damage to plants, and reduction of plankton
populations in the ocean's photic zone may result from the
increased UV exposure due to ozone depletion.”
3.3 Ecosystem Change
Climate changes affect each biome and each species individually.
Different species and populations migrate, begin, and become extinct at
11
different rates, climate changes, could cause the extinction of existing
ecosystems and the formation of new ecosystems.
„Ecological changes in climate (temperatures, flooding, warming, and
freezing) will probably eliminate some species, and these species
losses may cause the elimination of entire ecosystems.”
For example we could lose cold-adapted systems such as arctic and
alpine communities to global warming, and low laying areas or islands to
be flooded by the sea level rising. All of these changes could have a
disastrous effect on the ecology of earth and its ecosystems, as we know
it today. All climate changes affect each species way of life, the way they
eat, sleep, and survive and interact with each other.
4. Solutions
Finding a comprehensive solution to the issue of the emission of CO2
from power plants means finding a solution for the entire chain, from the
CO2 capture itself, through the transport of the captured CO2, up to its
storage, or possible industrial use. From the point of view of mastering
the technology of the entire chain in an economically acceptable manner,
the weakest link in the solution is CO2 capture. So far research and
development of capture technology has not reached the point of
12
commercial utilization under the conditions of power plant units having
regular outputs.
„In addition to power engineering research, the extraction industry is also
devoting its eff orts to the problem of CO2 storage, mainly in
connection with the utilization of CO2 to increase the yields of oil
fields. CO2 storage technology, similarly to CO2 capture technology,
before commercial implementation in power engineering, will have to
undergo equipment demonstration and pilot project phases, which will
verify the feasibility and functionality of the designed solution and will
provide the foundation for the more realistic assessment of the
economic impacts of the implementation of the new technology. The
problem of CO2 transport can be considered as technically feasible.”
4.1 Evolution of Technology
Hydroelectric reservoirs emit fewer greenhouse gases than the
amount previously attributed to them, says an international team of
scientists.
Reservoirs used to generate hydroelectric power emit 48 million
metric tonnes of carbon annually, according to a new study of 85
reservoirs published in this week's online version of Nature Geoscience.
That is very small compared to a previous estimate of emissions from all
13
man-made reservoirs, including hydroelectric reservoirs, of 321 million
metric tonnes.
"Our analysis indicates that hydroelectric reservoirs are not major
contributors to the greenhouse gas problem," Jonathan Cole, a
limnologist at New York State's Cary Institute of Ecosystem Studies, said
in a release.
"But there are some caveats," he warned. "To date, only 17 per
cent of potential hydroelectric reservoir sites have been exploited, and
impacts vary based on reservoir age, size, and location."
In particular, emissions are correlated with latitude and the amount
of vegetation being flooded.
4.2 People's Contribution to Reducing CO2 Emissions
„Citizens can put pressure on their governments to take
responsible actions. There is a lot that governments can do to contribute
to the efforts to reduce carbon dioxide emissions”. To begin with, they
can impose stricter regulations on those engaged in activities that
contribute to the problem. This includes requiring factories to curb their
emission rates. It also includes restricting all sorts of transportation
manufacturers from selling their goods if those goods do not meet certain
standards.
14
Governments can also invest in cleaner technology that will help
people meet their needs. For example, countries that rely heavily on coal
to produce electricity can begin to invest in renewable energy resources,
such as solar, wind, and hydro power.
Putting a halt to deforestation is another way to reduce carbon
dioxide emissions. Like humans inhale oxygen to live, trees consume
carbon dioxide. Yet millions of acres of trees are cut down every year to
make room for other purposes such as urban development and cattle
grazing. If this trend were reversed, and replanting projects were
undertaken, it would help because the trees would soak up some of the
emitted carbon dioxide.