General
The problems associated with fossil fuels are widely understood and have begun to drive a shift in urban energy and environmental policy making towards sustainable energy. To meet the rising global energy demand, several energy sources have been exploited over the years. The distribution of the energy sources over the total primary energy use of the world can be found in Figure 51 including the projection for the reference scenario for 2035. In Figure 52 the distribution can be found of the different types of consumption per sector. Figure 51: World primary energy demand over 1980‐2008 and the projected primary energy demand over 2008‐2035 according to the 3 scenarios as devised by the International Energy Agency (IEA) in World Energy Outlook 2010. [1] 1 Mtoe (million tonnes of oil equivalent) = 4.1868*104 TJ Figure 52: World energy consumption by fuel and sector in the Reference Scenario of the IEA [45] From these figures follows that a major part of our energy demand (82% in 2007) is met with fossil fuels, i.e. oil, coal and gas. A relatively small part (12 % in 2007) of our total energy demand is met by renewables, i.e. hydro, biomass and others. The remaining 6% is covered by nuclear energy. The figures for 2030 in the reference scenario are comparable with respectively 80, 14 and 6 %. [45] The use of fossil fuels causes two main problems: the amount of fossil fuels that can be used is finite and the use of these fuels causes harmful emissions. Other problems include geographic distribution of availability and associated political and social problems, resulting in large fluctuations in prices [46].
The finiteness of fossil fuels
Fossil fuels are the product of typically millions of years of formation in the earth’s crust. At present, the extraction of these fuels causes the amount of discovered reserves to drop. Although at the same time new reserves are being discovered, eventually the increase in demand will surpass the discovery of new reserves and existing reserves will become exhausted [47]. In Figure 53 the ratios between reserves and consumption are depicted for oil, gas and coal in the period 1980‐2006 and in 2009 specified per region. Figure 53: Ratios between reserves and consumption for oil, coal and gas in the period 1980‐2006 [47] (left) and the same ratios for the year 2009 specified per region [48] (right, OECD = Organisation for Economic Co‐operation and Development). This ratio describes the amount of years a certain fuel could technically still be used at a certain moment if the consumption would stay constant and no extra reserves would be discovered. These figures cannot be used as predictions at what moment fossil fuels will be exhausted however. As fossil fuels become less abundant, the price of these fuels will rise. The basic law of supply and demand applies, but will be heavily influenced by geographic availability, politics and local markets. With an increasing price for fossil fuels, the economic viability of other fuels will also increase. This means that the economic limit of the use of fossil fuels presents itself before the technical limit of the resources and other energy sources will become economically viable. Studies have been conducted in the field of econometrics studying the fossil fuel depletion times which take the economic aspects into account. The predicted depletion time differs between studies. However, they all agree that the economic end of fossil fuels will occur. In table 16 the predicted depletion times for fossil fuels are given for several studies.
Table 16: Predicted fossil fuel reserves depletion time for different studies [years]
Study Oil Coal Gas
World Energy Outlook 2006 [49] 39‐43 164 64
World Energy Outlook 2009 [45] N/A 130 (WEO
2009)
N/A
Lior [50] 40 60 150
Shafiee & Topal 2008 ‐ Klass model [47] 34 106 36
Shafiee & Topal 2008 ‐ New model [47] 35 107 37
As mentioned before, the result of the uncertainty about fossil fuel availability causes the market price of these commodities to fluctuate. This effect has already been visible on the energy market before and will be more pronounced when the resources become less abundant [46]. These temporary effects might also induce a market response to shift towards alternative
Figure 54: The yearly historical trend of nominal fossil fuel prices from 1950 to 2008 [46].
In Figure 54 the yearly historical trend of nominal fossil fuel prices from 1950 and 2008 are depicted. This figure illustrates the fluctuations in price and it shows an escalation from 2000 to 2008. This steep incline in fossil fuel prices has had a major part in the economic crisis and shows the influence of energy on global systems and the dependence of mankind on this commodity [46].
The environmental impact of fossil fuels
The second problem associated with the use of fossil fuels is the harmful emissions: CO2, NOx,
SOx, Volatile Organic Compounds (VOCs) and heavy metals. These emissions are formed during
the combustion of fossil fuels and are in many cases directly emitted into the atmosphere. The most well‐known emission is CO2, which
is a greenhouse‐gas as well as most of the VOCs. The characterisation greenhouse‐gas means that the excretion of this gas into the atmosphere contributes to the greenhouse effect (see frame). The Intergovernmental Panel on Climate Change (IPCC) stated in 2007 in their fourth assessment that the change in global temperature since mid‐20th century is very likely (>50 % certain) caused
by anthropogenic (caused by man)
greenhouse gases. [42] This in temperature increase is related to many adverse effects on the environment, i.e. rise of the sea level, tropical cyclones, windstorms, floods, tornadoes and droughts. These natural
events have a large influence on food and water supply, and ecology [51, 52]. Another way the use of fossil fuels contributes to the greenhouse effect is through particulate matter excreted during combustion, including dust, soot, smoke and other suspended matter. This particulate
Figure 55: Atmospheric concentration of CO2 over the last 10,000 years in ppm (parts per million) [51].
matter enters the atmosphere and absorbs solar energy, causing the atmosphere to heat up, just like green‐house gases. Another effect of particulate matter is that it reduces the natural reflecting capabilities (albedo) of the earth due to its deposition on snow and ice. Black carbon, a collective term for various forms of carbon in particulate form, is estimated to have 60% of the impact that CO2 has on the greenhouse effect which makes it the second largest contributor
after CO2 to this effect. In the global atmosphere it is estimated that 25‐35 % of the black carbon
comes from China and India [52].
The second problem with fossil fuel emissions are the sulphuric and nitrous acids. These acids are airborne in the flue gas and fall back to earth with rain. While in the air, these pollutants appear in the air above cities as yellowish brown clouds and contribute to smog. The acid rain enters surface water and the soil, potentially killing plants (deforestation), fish and wildlife [52]. Another concern of acid rain is the damage it does to buildings, statues and other man‐made structures. The acids erode the building materials, especially materials like marble and lime stone which contain high amounts of calcium carbonate.
The emissions caused by the combustion of fossil fuels also cause various health problems as clean air is essential to life and good health. The emissions present in the atmosphere can cause many kinds of cardiovascular and respiratory problems. The World Health Organization states: “Air pollution is a major environmental risk to health and is estimated to cause approximately 2 million premature deaths worldwide per year” [53].
The last down‐side to the usage of fossil fuels is the risks related to the extraction of these fuels. A recent example of this is the oil‐spill in the Gulf of Mexico with the Deep Water Horizon drilling platform. The platform exploded on 20 April 2010 and continued spilling oil into the sea until 15 July 2010. This pollution has a disastrous effect on the ecology in the sea itself and on the shore. Apart from ecological damage, the fish industry has been put on halt, causing financial damage. Former example illustrates the damage the extraction of fossil fuels can do the environment and economy. Many other examples of fossil fuel related accidents exist e.g. leaking oil tankers, collapsing coal mines, explosions in refineries etc. The greenhouse effect
In short: greenhouse‐gases, present in the earth’s atmosphere, cause energy to become trapped in this atmosphere.
The cause of this effect is the difference in wavelength of the radiation from the sun and the radiation from the earth. A large part of the wide spectrum radiation energy from the sun passes through the atmosphere and ‘hits’ the earth’s surface. Here it is converted into thermal energy and together with energy from the earth itself causes the earth to emit long‐wave energy. This long‐wave energy is partly absorbed by the gases in the atmosphere and causes the temperature to rise. This temperature rise causes an increase in atmospheric water vapour which is a greenhouse‐gas.