Current Status of Greenhouse Gas Emissions

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Industrial activities, especially related to the burning of fossil fuels, are major contributors of global greenhouse gas emissions. Climate change due to anthropogenic greenhouse gas (GHG) emissions is a growing concern for the global society. In the third assessment report, the Intergovernmental Panel on Climate Change (IPCC) provides the strongest evidence so far that the global warming of the last 50 years is due largely to human activity and the C02 emissions that arise when burning fossil fuels (Farahani et al. 2004).

It has been reported that the C02 level now is at the highest point in 125,000 years (Service 2005). Approximately 30 billion tons of C02 are released from fossil fuel burning each year. The C02 concentration level in the atmosphere traced back to 1750 was reported to be 280 ± lOppm (IPCC, 2001). It has risen continuously since then, and the COz level reported in 1999 was 367 ppm. The present atmospheric C02 concentration level has not been exceeded during the past 420,000 years (IPCC 2001; Houghton et al. 2001; Houghton 2004).

The latest 150 years have been a period of global warming (Figure 7.1). Global mean surface temperatures have increased 0.5-1.0°F since the late 19th century. The 20th century's 10 warmest years all occurred in the last 15 years of the century. Of these, 1998 was the warmest year on record. Sea level has risen 4-8 inches globally over the past century, and worldwide precipitation over land has increased by about one percent.

The industrial emissions of C02 consist of process emissions and production emissions. Coal mining, oil refining, gas processing, petroleum fuel combustion, pulp and paper, ammonia, petroleum refining, iron and steel, aluminum, electricity generation, and cement production are the major industries responsible for producing various types of greenhouse gases. Besides these industrial sources, the transportation sector also contributes a large share of greenhouse

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Year

Figure 7.1 Global temperature changes froml880 to 2000 (Modified after EPA Global Warming site: US National Climate Data Center 2001).

gas emissions. Greenhouse gas emissions from bio-resources are also significant. However, the National Energy Board of Canada does not consider C02 from biomass as contribution to greenhouse problems (Hughes and Scott 1997). The justification emerges from the fact that greenhouse gas emissions from bio-resources, such as fuel wood, agricultural waste, and charcoal, are carbon neutral because plants synthesize this C02. However, if various additives are added during the production of fuel, such as pellet making and charcoal production, the C02 produced is no longer carbon neutral. For instance, pellet making involves the addition of binders such as carbonic additives, coal, and coke breeze, which all emit carcinogenic benzene as a major aromatic compound (Chhetri et al. 2006). The C02 contaminated with such chemical additives is not favored by plants for photosynthesis, and, as a result, C02 will accumulate in the atmosphere. Moreover, deforestation, especially the unsustainable harvesting of biomass due to urbanization or so as to fulfill the industrial biomass requirement, also results in net C02 emission from bio-resources.

The worldwide COz emissions from the consumption of fossil fuels amounted to 24,409 million metric tons in 2002, and it is projected to reach to 33,284 million metric tons in 2015 and 38,790 million tons in 2025 (IEO 2005). The worldwide C02 production from consumption and flaring of fossil fuels in 2003 was 25,162.07 million metric tons. The U.S. alone had a share of 5802.08 million tons of C02 emission in 2003 (IEA 2005). Current C02 emission levels are expected to continue increasing in the future as fossil fuel consumption is sharply increasing (WEC 2006). The projection shows that emissions from all sources are expected to grow by 36% in 2010 (to 18.24 Gt/y) and by 76% in 2020 to 23.31 Gt/y (compared to the 2000 base level). The variation of COz concentrations at different time scales is presented in Figure 7.2 This figure shows the increase in C02 emissions exponentially after 1950. However, present methodology does not classify C02 based on its source. Industrial activities during this period also went up exponentially. Because of this industrial growth and extensive use of fossil fuels, the level of "industrial" C02 emissions increased sharply. The worldwide supply of oil in 1970 was approximately 49 million barrels per day, but the supply has increased to approximately 84 million barrels per day (EIA 2006). At the same time, the level of "natural" C02, which comes by burning biomass, went down due to deforestation. However, researchers, industry, and governments are focused on the total C02, which

-— COj Mauna Loa

COj South Pole

1970 1980 Year

1990

1950

1960

1970 1980 Year

1990

2000

Figure 7.2 Variation in atmospheric C02 concentration (IPCC 2001).

is not correct in terms of its impacts on global warming. NOAA (2005) defined the annual mean growth rate of C02 as the sum of all C02 added to and removed from the atmosphere by human activities and natural processes during a year. Natural C02 cannot be the same as that of industrial C02 and should be examined separately (See Chapter 5, section 5.17 for more details).

Some recent studies reported that the human contribution to global warming is negligible (Khilyuk and Chilingar 2004). The global forces of nature, such as solar radiation, outgassing from the ocean and the atmosphere, and microbial functions, are driving the Earth's climate (Khilyuk and Chilingar 2006). These studies showed that the COz emissions from human-induced activities are far less in quantity than the natural C02 emissions from ocean and volcanic eruptions. Others use this line of argument to demonstrate that the cause of global warming is, at least, a contentious issue (Goldschmidt 2005). These studies fail to explain the differences between natural and human-induced C02 and their impacts on global warming. Moreover, the COz from the ocean and natural forest fires were a part of the natural climatic cycle even when no global warming was noticed. All the global forces mentioned by Khilyuk and Chilingar (2006) are also affected by human interventions. For example, more than 70,000 chemicals used worldwide for various industrial and agricultural activities are exposed, in one way or another, to the atmosphere or ocean water bodies, therefore contaminating the natural C02. The C02 produced from fossil fuel burning is not accepted by plants for their photosynthesis, and for this reason, most organic plant matters are depleted in carbon ratio 8,3C (Farquhar et al. 1989; NOAA 2005). Finally, the notion of "insignificant" has been used in the past to allow unsustainable practices, such as the pollution of harbors, commercial fishing, and the massive production of toxic chemicals that were deemed to be "magic solutions" (Khan and Islam 2006). Today, banning chemicals and pharmaceutical products has become almost a daily affair (Globe and Mail 2006; New York Times 2006). None of these products were deemed "significant" or harmful when they were introduced. Khan and Islam (2006) have recently catalogued an array of such ill-fated products that were made available in order to "solve" a critical solution (Environment Canada 2006). In all these engineering observations, a general misconception is perpetrated; that is, if the harmful effect of a product can be tolerated in the short-term, the negative impact of the product is "insignificant."

According to Thomas and Nowak (2006), human activities have already demonstrably changed the global climate, and further, much greater changes are expected throughout this century. The emissions of COz and other greenhouse gases will further accelerate global warming. Some future climatic consequences of human induced C02 emissions, sea-level rise, for example, cannot be prevented, and human societies will have to adapt to these changes. Other consequences can perhaps be prevented by reducing C02 emissions.

Figure 7.3 shows the pathway of crude oil. Crude oil is refined to convert into various products including plastics. More than four million tons of plastics are produced from 84 million barrels of oil per day. It has been further reported that burning plastics produces more than 4,000 toxic chemicals, 80 of which are known carcinogens (Islam 2004).

In addition to C02, various other greenhouse gases have contributed to global warming. The concentration of other greenhouse gases has increased significantly in the period between 1750 and 2001. Several classes of halogenated compounds, such as chlorine,

Crude oil -» Gasolene + Solid residue + diesel + kerosene + volatile HC + numerous petroleum products

Solid residue + hydrogen + metal (and others) -» plastic

Plastic + Oxygen -> 4000 toxic chemicals (including 80 known carcinogens)

Figure 7.3 The crude oil pathway (Islam 2004).

bromine, and fluorine, are also greenhouse gases and are the direct result of industrial activities. None of these compounds existed before 1750 but are found in significant concentrations in the atmosphere after that period (Table 7.1). Chlorofluorocarbons (CFCs) and hydrohloroflorocarbons (HCFCs), which contain chlorine and halocarbons such as bromoflorocarbons (contains bromine), are considered potent greenhouse gases. The sulfur hexafluoride (SF6) that is emitted from various industrial activities, such as aluminum production, semi-conductor manufacturing, electric power transmission and distribution, magnesium casting, and nuclear power generating plants, is also considered a potent greenhouse gas. Table 7.1 shows that the concentration of these chemicals has significantly increased in the atmosphere after 1750. For example, CFC-11 was not present in the atmosphere before 1750. However, the concentration after 1750 reached 256 ppt after 1750. It is important to note here that these chemicals are totally synthetic in nature and cannot be manufactured under natural conditions. This would explain why the future pathway of these chemicals is so rarely reported.

The transportation sector consumes a quarter of the world's energy and accounts for about 25% of the total C02 emissions, 80% of which is attributed to road transportation (EIA 2006). Projections for Annex I countries indicate that, without new C02 mitigation measures, C02 emissions from road transportation might grow from 2,500 million tons in 1990 to 3,500 to 5,100 million tons in 2020. The transportation sector's fossil fuel consumption is also sharply increasing in the Non Annex I countries, as well. Thus, the total greenhouse gas emissions from transportation will rise in the future. It is also reported that as much as 90% of global biomass burning is human-initiated and that such burning is increasing with time (NASA 1999). Forest products are the major source of biomass, along with agricultural and household wastes. C02 from biomass has long been considered to be the source of feedstock during photosynthesis by plants. Therefore, the increase in COz from biomass burning cannot be considered unsustainable, as long as the biomass is not contaminated through "processing" before burning. C02 from unaltered biomass is distinguished from COz emitted from processed fuels. To date, any processing involves the addition of toxic chemicals. Even if the produced gases do not show detectable concentrations of toxic products, it is conceivable that the associated COz will be different from C02 of organic origin. COz emissions from biomass that is contaminated with various chemical additives during processing

Table 7.1 Concentrations, global warming potentials (GWPs), and atmospheric lifetimes of GHGs.

Gas

Pre-1750 concentration

Current topo-spheric concentration

GWP (100-yr time horizon)

Life time (years)

carbon dioxide (C02)

280 ppm

374.9

1

varies

methane (CH4)

730 ppb

1852ppb

23

12

nitrous oxide (N20)

270

319 ppb

296

114

CFC-11 (trichlorofluo-romethane) (CC1JF)

0

256 ppt

4600

45

CFC-12 (dichlorodi-fluoromethane) (CC12F2)

0

546 ppt

10600

100

CFC-113 (trichloro-trifluoroethane) (C2C1,F3)

0

80 ppt

6000

85

carbon tetrachloride (CC14)

0

94 ppt

1800

35

methyl chloroform (CH3CC1,)

0

28 ppt

140

4.8

HCFC-22 (chlorodi-fluoromethane) (CHC1F2)

0

158 ppt

1700

11.9

HFC-23 (fluoroform) (CHF3)

0

14ppt

12000

260

perfluoroethane (C2F6)

0

3 ppt

11900

10000

sulfur hexafluoride (SF6)

0

5.21 ppt

22200

3200

trifluoromethyl sulfur pentafluoride (SF5CF3)

0

0.12 ppt

18000

3200

Source: (1PCC 2001)

Source: (1PCC 2001)

has been calculated and deducted from the C02 that is good for the photosynthesis and does not contribute to global warming.

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Responses

  • birgit
    What share of global greenhouse emissions comes from human activity?
    1 year ago
  • Zula
    What is the current status of green house gases?
    9 months ago

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