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Unformatted text preview: UCSD Physics 12 Fossil Fuels
Our fantastic flash in the pan UCSD Physics 12 A brief history of fossil fuels Here today, gone tomorrow What will our future hold? Will it be back to a simple life? Or will we find new ways to produce all the energy we want? Or will it be somewhere in the middle Spring 2010 2 UCSD Physics 12 Finding Oil Oil is trapped in special (rare) geological structures Most of the oil in the world comes from a few large wells About one in ten exploratory drillings strike oil and this in places know to be oil-rich: get nothing in most of world Spring 2010 Q 3 UCSD Physics 12 The Oil Window Organic material must be deposited without decomposing oxygen-poor environment: usually underwater with poor flow Material must spend time buried below 7,500 feet of rock so that molecules are "cracked" into smaller sizes But must not go below 15,000 feet else "cracked" into methane: gas, but no oil So there is a window from 7,500 to 15,000 feet Additional circumstances must be met existence of "caprock" to keep oil from escaping: even a drop per second depletes 20 million barrels per million years source rock must be porous and permeable to allow oil flow Spring 2010 4 UCSD Physics 12 The hydrocarbons All fossil fuels are essentially hydrocarbons, except coal, which is mostly just carbon Natural Gas is composed of the lighter hydrocarbons (methane through pentane) Gasoline is hexane (C6) through C12 Lubricants are C16 and up Spring 2010
55 kJ per gram 48 51 48 50 48 46 48 48 48 5 UCSD Physics 12 Hydrocarbon Reactions Methane reaction: CH4 + 2O2 CO2 + 2H2O + energy 1g 4g 2.75 g 2.25 g 55 kJ Octane reaction: 2C8H18 + 25O2 16CO2 + 18H2O + energy 1g 3.51 g 3.09 g 1.42 g 48 kJ For every pound of fuel you burn, you get about three times that in CO2 one gallon of gasoline ~20 pounds of CO2 occupies about 5 cubic meters (1300 gallons) of space Spring 2010
Q 2 6 UCSD Physics 12 Aside: Carbohydrate Reactions Typical carbohydrate (sugar) has molecular structure like: [CH2O]N, where N is some integer refer to this as "unit block": C6H12O6 has N=6 Carbohydrate reaction: [CH2O]N + NO2 NCO2 + NH2O + energy 1g 1.07 g 1.47 g 0.6 g 17 kJ Less energy than hydrocarbons because one oxygen already on board (half-reacted already) For every pound of food you eat, exhale 1.5 lbs CO2 Actually lose weight this way: 0.5 to 1.0 lbs per day in carbon Must account for "borrowed" oxygen mass and not count it Spring 2010 7 UCSD Physics 12 So where does our petroleum go? Each barrel of crude oil goes into a wide variety of products Most goes into combustibles Some goes to lubricants Some goes to pitch and tar Some makes our plastics 40% of our energy comes from petroleum Spring 2010 8 UCSD Who's got the crude oil resources? Physics 12 Spring 2010 9 UCSD Physics 12 Let's get our barrels straight An oil barrel (bbl) is 42 gallons, or 159 liters In the U.S., we use about 24 bbl per year per person average person goes through a barrel in 15 days recall: 60 bbl/yr oil equivalent in all forms of energy: oil is 40% of our total energy portfolio That's 7.2 billion bbl/yr for the U.S. 20 million bbl/day For the world, it's 30 billion bbl/year 85 million bbl/day Spring 2010 10 UCSD Physics 12 Oil in the World (older data) Spring 2010 11 UCSD Physics 12 Excerpts from current Table 2.2 in book
Country Saudi Arabia Russia U.S. Iran China Mexico Norway U.A.E. Canada Kuwait Prod (Mbbl/day) 9.03 7.98 5.73 3.74 3.41 3.34 2.86 2.35 2.24 2.18 Reserves (Gbbl) 262.7 69.1 29.4 130.7 23.7 16.0 10.1 97.8 16.9 96.5 54,061 790 833 No. Prod. Wells 1,560 41,192 521,070 1,120 72,255 years left 80 24 14 96 19 13 10 114 21 121 Spring 2010 12 UCSD Physics 12 Notes on Table 2.2 Not a single country matching U.S. demand of 20 Mbbl/day Reserves: Non-OPEC proved reserves: 173 Gbbl OPEC reserves: 882 Gbbl Total: 1055 Gbbl To maintain current production of 85 Mbbl/day... this will last 34 years means entries in previous table with longer timescales than this would have to step up production, if they can may not be possible to extract oil fast enough for demand Saudi Arabia used to produce at less than 100% capacity, now running full-out Spring 2010 13 UCSD Physics 12 How long will the world oil supply last? Not as long as you might think/hope We'll be spent before the century is done, but we'll have to scale down oil usage before then (in the next few decades) Spring 2010 14 UCSD Physics 12 How about the U.S. Supply? The estimated total U.S. supply is 230324 billion bbl We've used >60% of this, leaving 130 billion barrels Production is already down to 60% of peak At current rate of production, will be exhausted before 2070 If we used only U.S. supply, we'd run out in 18 years!! includes bet that we find 105 billion barrels more in U.S. Spring 2010 Q 15 UCSD Physics 12 Discovery must lead production There must be a lag between the finding of oil and delivery to market In the U.S., discovery peaked around 1950, production peaked in 1970 Spring 2010 16 UCSD Physics 12 Various Estimates of Oil Remaining To date, we've used about 1000 billion barrels of oil worldwide We seem to have about this much left halfway through resource There will be some future discovery still, but not likely any new Saudi Arabia ANWR: 510 Gbbl 1 years' worth at U.S. consumption rate In any case, production unlikely to increase appreciably from this point forward will soon fail to pump as fast as today's demand Spring 2010
Q 17 UCSD Physics 12 Worldwide Discovery and Production discovery peaked before 1970; production peak soon to follow Spring 2010we've been using oil faster than we find new oil since 1983 18 UCSD Physics 12 The Hubbert Peak Idea Hitting new oil field must precede assessment of oil capacity Discovery peak (numerical assessment) must follow hits Production peak follows discovery (assessment) Area under three curves the same (total oil resource) Deffeyes estimates that we've hit 94%, discovered 82%, and produced 50% as of about 2005 graphic attribution: Deffeyes Spring 2010 19 UCSD Physics 12 rate of growth exponential Logistic ("S") curves
Logistic curves result from growth limited by a finite resource: at first exponential, but unable to sustain exponential once resource limits kick in logistic resource Qmax production rate marks half-way point time Qmax resource Spring 2010 20 time UCSD Physics 12 Rate plot for U.S. Can plot rate of production (P: annual production) divided by resource (Q: total produced to date) against total resource, Q P/Q is like an interest rate: fractional increase per year
Peak Production; half consumed 1970 graphic attribution: Deffeyes Spring 2010 A "logistic" or S-curve would follow a straight line sloping down U.S. oil production does so after 1958 When you get to zero P/Q, you've hit the end of the resource: no more growth 21 UCSD Physics 12 Same fit, in rate history plot The best-fit line on the previous plot produces a decent fit to the rate history of oil production in the U.S. Supports the peak position well, and implies a total resource of about 225 Gbbl Spring 2010 graphic attribution: Deffeyes 22 UCSD Physics 12 World Data After 1983, world data follows logistic curve Spring 2010 23 graphic attribution: Deffeyes shows us halfway along 2,000 Gbbl at 2005 (now-ish) implies the peak is imminent
Q UCSD gasliquid deep-water arctic tar sands Physics 12 all others EU Russia mid-east USA USA was "Saudi Arabia" of world until about 1960 Spring 2010 http://www.oilposter.org/ 24 UCSD Physics 12 Discouragement of Oil Usage In this country, there is no such thing U.S. taxes on gasoline are 6.5 times lower than in most industrialized countries (about 32 cents per gallon in the U.S.) The Frito Lay attitude: Burn all you want--we'll pump more Efforts on the part of the U.S. to keep oil prices low have lead to numerous questionable actions on the international scene
Spring 2010 25 2 Q UCSD Physics 12 Natural Gas Extracted as oil-drilling byproduct was once burned off at well head as means of disposal Mostly methane, some ethane, and a little propane, butane 2 times cheaper than electricity per energy content, comparable gasoline per joule this is recent: when I taught the class (2004), it was 3.5 times cheaper than electricity, 3 times cheaper than gas Well-suited to on-the-spot heat generation: water heaters, furnaces, stoves/ovens, clothes dryers more efficient than using fossil-fuel-generated electricity Spring 2010 26 UCSD Physics 12 Distribution of natural gas Impractical to ship: must route by pipe 1.3 million miles of pipe (250,000 miles of mains) Spring 2010 27 UCSD Physics 12 How much do we use, and where do we get it? In 2003, we used 21.8 tcf (Tera-cubic feet, or 1012ft3); about 23 QBtu (23% of total) Out of the 21.8 tcf used, 88% was domestic 11.8% from Canada 0.08% from Algeria (shipped in liquefied form) 0.03% from Mexico Have used about 1,100 tcf to date Spring 2010 Q 28 UCSD Physics 12 How much do we have left? Estimated recoverable amount: 871 tcf 40 years at current rate Estimates like this do account for future discoveries Spring 2010 present proven reserves provide only 8 years' worth 29 UCSD Physics 12 Coal Coal is a nasty fuel that we seem to have a lot of Primarily carbon, but some volatiles (CO, CH4) Reaction is essentially C + O2 CO2 + energy Energy content varies depending on quality of coal, ranging from 47 Cal/g Highly undesirable because of large amounts of ash, sulphur dioxide, arsenic, and other pollutants Also ugly to remove from the ground Spring 2010 30 UCSD Physics 12 Coal types and composition
Natural Graphite Anthracite Bituminous Bituminous subbituminous Lignite Peat Wood volatile matter moisture content ash fixed carbon kJ/g 34 29 35 31 27 25 21 20 Spring 2010 31 UCSD Physics 12 Use of Coal 88% of the coal used in the U.S. makes steam for electricity generation 7.7% is used for industry and transportation 3.5% used in steel production 0.6% used for residential and commercial purposes 0.1% used on Halloween for trick-or-treaters Spring 2010 32 UCSD Physics 12 Estimated Worldwide Coal Reserves
Country United States Russia Europe China Australia Africa South America North America Total Amount (109 tonne) 250* 230 138 115 82 55 22 7.7 984 Percentage of Total 25 23 14 12 8.3 5.6 2.2 0.8 100 *1st edition of book had U.S. at 1500 billion tons. What happened to all that coal? 1st edition of book had Russian coal at 4300 billion tons. Gross overestimates? Spring 2010 33 UCSD Physics 12 U.S. Coal Production History Spring 2010 34 UCSD Physics 12 When will coal run out? We use 109 tonnes of coal per year, so the U.S. supply alone could last as long as 250 (1500) years at current rate Using variable rate model, more like 75100 (400600) years especially relevant if oil, gas are gone This assumes global warming doesn't end up banning the use of coal Environmental concerns over extraction also relevant Spring 2010 35 UCSD Physics 12 Shale Oil Possibly 6002000 billion barrels of oil in U.S. shale deposits compare to total U.S. oil supply of 230 billion bbl Economically viable portion may only be 80 billion bbl 8 times less energy density than coal lots of waste rock: large-scale disposal problem Maximum rate of extraction may be only 5% of our current rate of oil consumption limited by water availability: requires 3 as much water as oil Spring 2010 36 UCSD Physics 12 Tar Sands Sand impregnated with viscous tar-like sludge Huge deposit in Alberta, Canada 300 billion bbl possibly economically recoverable It takes two tons of sands to create one barrel of oil energy density similar to that of shale oil In 2003, 1 million bbl/day produced grand hopes for 5 Mbbl/day; or 6% of world oil production 2002 production cost was $20 per barrel, so economically competitive Spring 2010 37 UCSD Physics 12 References and Assignments Hubbert's Peak: The Impending World Oil Shortage, by Kenneth Deffeyes Beyond Oil, by same author Out of Gas: The end of the Age of Oil, by David Goodstein The Party's Over, by Richard Heinberg Read Chapter 2 in book Read Chapter 3 for next lecture HW2 available on website, due Friday 4/16 Quiz 2 due by Friday, 4/16 at midnight on WebCT
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