Carbon anthropogenic emission

The use of coal for electricity generation is responsible for about 32% of anthropogenic carbon dioxide emissions in the U S. 11 As shown by France, it is possible to displace virtually all the coal used in electricity generation. Thus, France in 1997 obtained about 78% of its electricity from nuclear power and only about 5% from coal. Further reductions in carbon dioxide emissions could be made by the electrification of other sectors of the energy economy, including buildings, and eventually perhaps much of transportation. 

Figure 3.12. Longitude-averaged rates of atmospheric C02 assimilation by both land and ocean ecosystems with two scenarios of anthropogenic emissions of carbon 6.26GtC/yr (dashed curve, 2000) and 10.6GtC/yr (solid curve, predicted for 2020). Notation Ha = A//32 I Uh I IIa Hi Hi "<) (GtC yr-1).

Table 6.23. A model estimate of surplus C02 absorption by vegetation in Russia. The anthropogenic emission of carbon is assumed to be 6.5 GtC/yr.

Carbon capture and sequestration is a technology that is being explored to curb the anthropogenic emission of C02 into the atmosphere. With the environmental issues and energy crisis problem associated with greenhouse gas effect being more and more prominent, CO2 capture-fixation-conversion has been a worldwide hot topic for sustainable development [1-12]. 

Trends in atmospheric concentrations and anthropogenic emissions of carbon dioxide. (From Oak Ridge National Laboratory, Carbon Dioxide Information Analysis Center, http //cdiac. 

In the last 150 years the anthropogenic emission of sulfur has increased dramatically, primarily due to combustion processes [1]. In the 1950s anthropogenic emission surpassed natural emission and the atmospheric sulfur cycle is one of the most perturbed biogeochemical cycles [1,2]. The oceans are the largest natural source of atmospheric sulfur emissions, where sulfur is emitted in a reduced form, predominantly as dimethyl sulfide (DMS) and to a much lesser extent carbonyl sulfide (OCS) and carbon disulfide (CS2) [3]. Ocean emitted DMS and CS2 are initially oxidised to OCS, which diffuses through the troposphere into the stratosphere where further oxidation to sulfur dioxide (SO2), sulfur trioxide (SO3) and finally sulfuric acid (H2SO4) occurs [1-4]. 

There are over 70 alcohols in the atmosphere as a result of biogenic and anthropogenic emissions [67]. For example methanol and ethanol [68-70] have been used as fuels additives to reduce automobile emissions of carbon monoxide and hydrocarbons [71], in particular ethanol has been used in Brazil as a fuel for over 20 years [72]. 1-Propanol is widely used as a solvent in the manufacturing of different electronic components. The high volatility of these compounds causes their relative abundance in the troposphere and makes it relevant to determine their degradation pathways. During daytime the major loss process for alcohols is their reaction with OH radicals [68]. Accordingly, several experimental [69,70,73-84] and theoretical [85-88] kinetic studies of alcohols -F OH reactions have been performed. 

Figure 4 Vertical profiles of total dissolved inorganic carbon (TIC) in the ocean. Curve A corresponds to a theoretical profile that would have been obtained prior to the Industrial Revolution with an atmospheric CO2 concentration of 280 ixmol mol The curve is derived from the solubility coefficients for CO2 in seawater, using a typical thermal and salinity profile from the central Pacific Ocean, and assumes that when surface water cools and sinks to become deep water it has equilibrated with atmospheric CO2. Curve B corresponds to the same calculated solubility profile of TIC, but in the year 1995, with an atmospheric CO2 concentration of 360 xmol moPk The difference between these two curves is the integrated oceanic uptake of CO2 from anthropogenic emissions since the beginning of the Industrial Revolution, with the assumption that biological processes have been in steady state (and hence have not materially affected the net influx of CO2). Curve C is a representative profile of measured TIC from the central Pacific Ocean. The difference between curve C and B is the contribution of biological processes to the uptake of CO2 in the steady state (i.e. the contribution of the biological pump to the TIC pool.) (courtesy of Doug Wallace and the World Ocean Circulation Experiment).

Annual emissions of CO2 from fossil fuel combustion are small relative to the natural flows of carbon through terrestrial photosynthesis and respiration (—120 PgC yr ) and relative to the gross exchanges between oceans and atmosphere (—90PgCyr ) (Figure 1). Nevertheless, these anthropogenic emissions are the major contributor to increasing concentrations of CO2 in the atmosphere. They represent a transfer of carbon from the slow carbon cycle (see Chapter 8.09) to the active carbon cycle. 

The extent to which man-made carbon dioxide emissions contribute to global warming is still an issue of considerable debate. Analysis indicates that while the contribution to the total amount of this gas in the atmosphere from anthropogenic sources amounts to 3 to 4 percent, the problem is that carbon dioxide remains in... 

A second possibility for a carbon sink is the world s oceans. At present, there is already some 37 trillion metric tons of carbon, mostly in the form of bicarbonate, dissolved in the oceans of the world. Of the carbon not taken up by terrestrial ecosystems, the oceans will be the eventual repository for about 85 percent of the rest of the carbon emitted to the atmosphere by human activities.2 However, this uptake occurs quite slowly. For example, the oceans are currently taking up only 40 percent (with an uncertainty of 16 percent) of the annual anthropogenic carbon emissions not removed by terrestrial processes. Because of the slow rate of mixing of the world s oceans, it would take many centuries for them to realize most of their uptake capacity, even if anthropogenic emissions were to stop today. 

The transportation sector accounts for 68 percent of all of the petroleum used and one-third of the anthropogenic carbon dioxide emissions in the United States. In addition, the utilization of internal combustion engines for transportation results in a significant amount of nitrogen oxides and particulate emissions. 

According to the results of measurements carried out in the ocean (Seiler, 1974) the carbon monoxide concentration in near surface marine layers is 5 x 10 s mil 1 on an average. This water concentration would be in equilibrium with a surface air CO level of 2.5 ppm. However, the carbon monoxide concentration in air over the ocean surface is between 0.04 ppm and 0.20 ppm, which means that the ocean water is supersaturated with CO. It follows from these data that the ocean is a CO source, the global strength of which is about six times less than the total anthropogenic emission (Table 7). 

Gasolines with added ethers or alcohols, formulated according to the Federal Clean Air Act to reduce carbon monoxide emissions during winter months. PAHs are a suite of compounds with two or more benzene rings. PAHs are found in many petroleum mixtures, and they are predominantly introduced to the environment through natural and anthropogenic combustion processes. 

Today, the anthropogenic emissions of SO, primarily from fossil fuel combustion, largely dominate the sulfur flux into in the atmosphere on the global scale. Climate models have determined the corresponding direct and indirect impacts on radiative forcing, but large uncertainties remain in these estimates. In fact, predictions of future climate need to account not only for the effects of sulfate aerosols, but also for the contributions of mineral dust, black carbon, organic carbon, and sea salt. The current view is that atmospheric particles should be treated as multicomponent, mul-... 

Carbon, nitrogen, and sulfur are essential to the life of animals, plants, and microbes. Interactions between these elements link the internal biogeochemistry of terrestrial ecosystems. Naturally, the availability of these substances is limited in terrestrial ecosystems and this has led to various adaptations of the biota. Nowadays, high anthropogenic emissions of various compounds of carbon, nitrogen, and sulfur have created a new situation for terrestrial ecosystems The surplus (regional) of these three limited elements can affect terrestrial ecosystems in multiple ways and on different time scales (see Table 8). 

---