Energy Energy production and consumption, Agriculture and Chemical Manufacturing underlie most environmental issues freons-stratospheric O 3 depletion CO 2 -global warming Agricultural run off contaminating water ways Urban smog and aerosols PCB contamination of the Great Lakes in the US Acid rain and acid aerosols

 Of this ~30% is reflected back to into space (albedo)  One Joule = 4.2 calories. It takes ~2000 K- calories to feed a human each day  What fraction of the earth’s energy striking the earth, if turned into food, could feed the planet Sun earth 54.4x10 20 kJoules of the sun’s energy strikes the earths surface each year Energy from the earth

SO what is a joule?? Force = mass x acceleration f = m x a a =  velocity /  time = dv/dt velocity =  distance /  time a=  distance /  time 2 Work = force x distance W = f x d W= m x a x d and W = m x d 2 /t 2 Work and energy have the same units (The First Law U 2 - U 1 = q - w ) a joule is defined as accelerating 1 kg of mass at 1 meter/sec 2 for a distance of 1 meter A watt is a unit of power = 1 joule/second or energy/time

 54.4x10 20 kJoules of the sun’s energy strikes the earths surface each year  # of kJ striking the earth/year, minus reflection ( albedo = 0.3)= total energy 54.4x10 20 x 0.7= 38.1x10 20 kJoules  what fraction of total sun’s energy absorbed by the earth is used by human activity ?  people use 3.7 x10 17 kJoules/year  3.7 x10 17 / 38.1x10 20 = = 0.1%  so if we harnessed 1/1000 th of the sun’s energy we could supply all of our needs What is the total human energy utilization compared to the Sun’s energy striking the earth?

Worldwide energy use and how do we use fuels Oil34.1% (44%) Coal24.1% (25%) natural gas 17.4% (26%) Biomass14.7% (0.2%) Hydro 5.5% (2.4%) Nuclear 4.1% (2.2%) energy use/yPopulation (1993) world 382 x10 18 joules 4.87x10 9 Indust. world 347 x10 18 joules 1.22x10 9 Developing world 35 x10 18 joules 3.65x10 9

Where are the global energy reserves Figure 1.5 Spiro page 10 oil Middle East Asia and Australia including China Former USSR

Fraction of US oil reserves compared to the global total (British petroleum web site, 2007)

BP 2007 OIL RESERVES IN BILLIONS OF BARRELS

Where are the global energy reserves Natural gas Middle East Asia and Australia including China Former USSR

Where are the global energy reserves Coal China Australia Former USSR

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Earth’s nonrenewable energy resources (1980) estimated stockconsumption (world)/year x J x10 18 J petroleum10135 Natural gas1060 coal oilshale2,0000 uranium (non-breading water reactors) Thorium and 10,000 0 Uranium (in breeder react) Deuterium and Li in sea water for fusion

how long will the oil last?? 1980 estimate of reserves Oil 1x10 22 J Proved reserves of oil are generally taken to be those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and geological conditions. Where does a number like this come from?

how long will the oil last?? Let’s look at a 2004 Christian Science Monitor article: World wide proven Oil reserves = 1.1 to 1.3 x10 12 barrels BP 2007 estimate was 1238 billion barrels = 1.24 x barrel of oil = 42 US gallons or 159 liters If hydrocarbons have a density of 0.9 kg/liter 1 barrel = 159 x 0.9 x 1000 grams = 1.43x10 5 grams oil /barrel

We will see later that one gram of oil gives off 44 kJoules/g when it is burned We said there were 1.2x10 12 barrels known reserves This means that we have 1.43x10 5 x 1.24x10 12 x 44 x1000 joules of oil= ~0.8x10 22 joules WE SAID THE 1980 ESTIMATE 1x10 22 joules

1x10 22 joules in reserves 1980 estimate of oil usage /year 1.35x10 20 J/year Estimate the # years of oil left if we used at the above rate from 1980 to 1990 and 2x’ s the 1980 rate after 1990 = ??

Newer data WE use globally (2004)about 30x10 9 barrels/year If we have 1.2 x10 12 in reserve or 1200 x 10 9 in reserve Others say World wide oil reserves have grown 15% between 1999 and 2004 and have grown by a factor of 5 since WWII

These estimates place the global reserves at ~3x10 12 barrels and suggest that we have only used 25% of the total oil on the planet What we know is that major importers are not waiting around to see who is right!!! The US, China, Japan are scrambling to tie down interests in Russia, West Africa, Iraq, Iran and Libya

What happens to the fuel we burn  Burning “old” carbon: fossil fuels add CO 2 to the atmosphere that has been buried as carbon under the earths surface eons ago.  Burning “new”: biomass fuels puts CO 2 in the atmosphere that has just recently been remove from the atmosphere by plants. These kinds of fuels would be considered green house neutral.green house neutral.  Given the exponential increase in our use of fossil fuels, one must ask, how much longer this can go on?  Some people in the automotive industry said in 2000 (conversation of Kamens with D. Schuetzle of Ford) we will see significant shortages by 2015

Carbon cycle

Oil  Petroleum and gas deposits come from the seas.  Oceans produce billion tons of reduced carbon annually.  Most is recycled to the atmosphere as CO 2. A very small fraction settles to the bottom where oxidation is negligible  here it is compacted with clay and sand particles  Anaerobic bacteria digest the bacterial digestible matter, releasing O 2 and N 2.  The hydrocarbons most resistant are the hydrocarbon based lipids and these persist and are found in their cell membranes indicating that bacteria process organic debris in the oceans and over the eons turned it into oil

oil

 As the sediment becomes buried deeper, the pressure and temperature rise.  Bacterial action decreases and organic reactions occur.  These reactions release large quantities of methane and light volatile hydrocarbons and these become trapped in impermeable rock (natural gas)  Oil results from continued organic reactions and as pressure increases the water is squeezed out of the sediment  This process spans 100s of millions of years and in the short period from 1900 through the 21 st century we may deplete most of the known reserves

Coal  Coal formation is land or terrestrial based Woody plants 200 million years ago, as they are now, are composed of cellulose and lignins. Bacteria can digest the cellulose over time but lignins are resistant In swamps the lignins accumulate under water and are compacted into peat Crustal upheavals buried the peat and subjected it to huge pressures and temperatures peat   coal over time

Coal formation In swamps the lignins accumulate under water and are compacted into peat   coal over time

Coal formation

Fuel energy  When we burn a fuel where does the energy reside?  Let s take hydrogen in water as an example. If we were to react H 2 with O 2 to form water, we would 1 st have to break the hydrogen bonds and the oxygen bonds  This takes energy; in the case of H 2 it takes 432 kJ/mole (~100,000 calories/mole) for H 2  2H.  100,000 calories will supply you with many minutes of food energy??  To break O 2 to O. (O 2  2O.) requires 494 kJ/mol  When when water forms, however, we get energy back from the formation of H 2 O because new bonds are formed. Which ones??

Fuel energy  The equation for the combination of hydrogen and oxygen if say we were to burn hydrogen would be  2H 2 + O 2  2H 2 O  To break a mole of H 2 bonds requires 432 kJ/mole  We need 2 moles of H 2 so this requires 864 k joules/mole  To break a mole of O 2 requires 492 kJ/mol; so the total energy required to break 2H 2 and O 2 apart is 1356 kJ  To form water we need to form two O-H bonds. When one OH bond forms it releases 460 kJ/mole  But there are two water molecules that from = 2x 460x2= 1840 kJ/mole  So how much energy is released?

Energy from breaking other bonds (enthalpy) kJ/mole H-H432 O=O492 O-H460 C-H360 C=O799 C-C347 C-C aromatic519 N=O632

Fuel energy  Let’s do the same thing for burning methane gas; the reaction is methane + oxygen  CH 4 + 2O 2  CO 2 + 2H 2 O  We calculated before that to form one mole of H 2 O we get 920 kJ, so for two moles we get 1840 kJ/mole; to form CO 2, which also releases energy, we need to form two C=O bonds {O=C=O} or 2x 799kJ. This gives a total formation energy of kJ  But for this process, we 1 st have to break 4 carbon- hydrogen bonds; why?? This requires 410 kJ/mole/bond or 1640 kJ  The total energy release is the energy forming bonds - break bonds  3438kJ – 2628kJ = 810 kJ excess energy

Combustion energies from different fuels (kJ) react.perperper moles heatmolemolegramCO2 per kJO 2 fuelfuel1000kJ hydrogen H 2 +O 2  2H 2 O Gas CH 4 + 2O 2  CO 2 +2H 2 O Petroleum (-CH 2 -)+ 3O 2  2CO 2 +2H 2 O Coal (-CH-)+ 5O 2  4CO 2 +2H 2 O Ethanol C 2 H 5 OH + 3O 2  2CO 2 +3H 2 O wood (-CHOH-) + O 2  CO 2 +2H 2 O

A Homework problem Assume as students, that you each use 1000 Watts of power for 12 hours each day (lights, computers, class room air conditioning, etc, travel). Much of this energy in Thailand and China is generated from coal. Assume that the process is only 50% efficient, and if you use 1000 Watts it really requires 2000 Watts of coal power. Calculate how much CO 2 is going into the atmosphere to maintain you at this level of energy consumption for each year and put your answer in metric tonnes/year CO 2.

Hint 1 watt = 1 joule/sec Estimate the total number of joules used per year if you are using 2000 watts for 12 hours each day The combustion table gives you the mole of CO2 evolved from burring 1000 kJ of coal. Convert this to the total moles of CO2 given off per year for 2000 watts at 12 hours each day Convert to metric tonnes of CO2 per year One metic tonne equals 1000kg Much of this energy in Thailand and China is generated from coal. Assume that the process is only 50% efficient, and if you use 1000 Watts it really requires 2000 Watts of coal power. Calculate how much CO 2 is going into the atmosphere to maintain you at this level of energy consumption for each year and put your answer in metric tones/year CO 2.