Energy Energy production and consumption, Agriculture and Chemical Manufacturing underlie most environmental issues freons-stratospheric O3 depletion CO2-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

Energy from the earth 54.4x1020 kJoules of the sun’s energy strikes the earths surface each year Sun earth 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

SO what is a joule?? Work = force x distance Force = mass x acceleration f = m x a a = D velocity / D time = dv/dt velocity = D distance / D time a= D distance / D time2 Work = force x distance W = f x d W= m x a x d and W = m x d2 /t2 Work and energy have the same units (The First Law U2 - U1 = q - w ) a joule is defined as accelerating 1 kg of mass at 1 meter/sec2 for a distance of 1 meter A watt is a unit of power = 1 joule/second or energy/time

What is the total human energy utilization compared to the Sun’s energy striking the earth? 54.4x1020 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 54.4x1020 x 0.7= 38.1x1020 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 / 38.1x1020 = 0.001 = 0.1% so if we harnessed 1/1000th of the sun’s energy we could supply all of our needs

Worldwide energy use and how do we use fuels (1993) Oil 34.1% Coal 24.1% natural gas 17.4% Biomass 14.7% Hydro 5.5% Nuclear 4.1% energy use/y Population (1993) world 382 x1018 joules 4.87x109 Indust. world 347 x1018 joules 1.22x109 Developing world 35 x1018 joules 3.65x109

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

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

Where are the global energy reserves Coal Former USSR China Australia

Earth’s nonrenewable energy resources (1980) estimated stock consumption (world)/year x 1021 J x1018J petroleum 10 135 Natural gas 10 60 coal 250 90 oilshale 2,000 0 uranium 20 6.3 (non-breading water reactors) Thorium and 10,000 0 Uranium (in breeder react) Deuterium and Li 1010 0 in sea water for fusion

Worldwide energy use and how do we used fuels

how long will the oil last?? 1980 estimate of reserves Oil 1x1022 J Where does a number like this come from? Let’s look at a 2004 Christian Science Monitor article: World wide proven Oil reserves = 1.1 to 1.3 x1012 barrels 1 barrel of oil = 42 US gallons or 158.99 liters If hydrocarbons have a density of 0.9 kg/liter 1 barrel = 158.99x 0.9x1000 grams = 1.43x105 grams oil /barrel

~0.8x1022 joules 1x1022 joules = 1.43x105 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 1.2x1012 barrels known reserves This means that we have 1.43x105 x 1.2x1012 x 44 x10000 joules of oil= ~0.8x1022 joules WE SAID THE 1980 ESTIMATE 1x1022 joules

1x1022 joules in reserves 1980 estimate of oil usage /year 1.35x1020 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 = ??

1200 x 109 in reserve New data WE use globally (2004)about 30x109 barrels/year If we have 1.2 x1012 in reserve or 1200 x 109 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 ~3x1012 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 CO2 to the atmosphere that has been buried as carbon under the earths surface eons ago. Burning “new”: biomass fuels puts CO2 in the atmosphere that has just recently been remove from the atmosphere by plants. These kinds of fuels would be considered 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 25- 50 billion tones of reduced carbon annually. Most is recycled to the atmosphere as CO2. 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 O2 and N2. 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

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 21st 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 temperatuers 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 H2 with O2 to form water, we would 1st have to break the hydrogen bonds and the oxygen bonds This takes energy; in the case of H2 it takes 432 kJ/mole (~100,000 calories/mole) for H2 2H. 100,000 calories will supply you with many minutes of food energy?? To break O2 to O. (O2  2O.) requires 494 kJ/mol When when water forms, however, we get energy back from the formation of H2O 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 2H2 + O2  2H2O To break a mole of H2 bonds requires 432 We need 2 moles of H2 so this requires 864 joules To break a mole of O2 requires 492 kJ/mol; so the total energy required to break 2H2 and O2 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-H 432 O=O 492 O-H 460 C-H 360 C=O 799 C-C 347 C-C aromatic 519 N=O 632

Fuel energy Let’s do the same thing for burning methane gas; the reaction is methane + oxygen CH4 + 2O2  CO2 + 2H2O We calculated before that to form one mole of H2O we get 920 kJ, so for two moles we get 1840 kJ/mole; to form CO2, 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 1840 + 1598kJ But for this process, we 1st 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. per per per moles heat mole mole gram CO2 per kJ O2 fuel fuel 1000kJ hydrogen 482 482 241 120 0 2H2+O2 2H2O Gas 810 405 810 52 1.2 CH4 + 2O2CO2 +2H2O Petroleum 2120 407 610 44 1.6 2 (-CH2-)+ 3O22CO2 +2H2O Coal 4332 409 512 39 2.0 4 (-CH-)+ 5O24CO2 +2H2O Ethanol 1257 419 1257 27 1.6 C2H5OH + 3O22CO2 +3H2O wood 447 447 447 15 2.2 (-CHOH-) + O2CO2 +2H2O

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 CO2 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 CO2.

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 CO2 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 CO2.