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Lecture 4

GEOL 1121 Lecture 4: GEOL Final Materials
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Department
Geology
Course
GEOL 1121
Professor
Rice
Semester
Fall

Description
Final Materials November 30, 2015 Fossil Fuels • Primarily the deposition and burial of organic debris is what causes fossil fuels. o Some form of organic carbon is buried and removed from system for a long time • Fossil fuels: Oil, coal, natural gas, oil shale, tar sand o Typical example of combustion: natural gas o CH4 + 2O2 = CO2 + 2H2O + energy • China produces the most CO2 emissions per country from fossil fuel use. The US is number 1 in per capita CO2 emissions from fossil fuels • Our US energy consumption is increasing!! • Fossil fuels are the cheapest and most efficient forms of energy which is why it’s not easy to change our ways to a better form • 1 BTU = amount of energy needed to heat 1 lb. of water 1F o So a coal-burning car would require 100 lbs. of coal for equivalent energy in 10 gallons of gas, which weighs about 60 lbs. o Electric cars are not 100% perfect because we still have to produce energy to for the car to go • Energy Returned on Investment (EROI) = (Energy obtained from resource) / (Energy use to obtain resource) o EROI is now lower than in 1930 and earlier because it takes more energy to access oil now than then because we’ve used up all the easy accessible and therefore are having to dig deeper. o Imported oil EROI is even lower than just obtaining it because it includes transportation costs • Key similarity in origin: anoxic burial of organic remains of plants and animals o It is all in the burial: not too hot, and not too deep Coal • The dirtiest of fossil fuels • Combustible rick composed of compacted plant remains • Typical molecule in coal • (Note: C, H rich, O poor, and some N coals commonly contain S, in pyrite (FES2) • Coal forms from plan material buried in the oxygen poor waters of swamps- like the Okefenokee • With time (youngest coal is about 1 million years), with heat (but not too hot-igneous and metamorphic processes destroy coal), and pressure, coal will form from plant material • Coal is a sediment and forms layers • Coal grade depends on heat and pressure. Increased heat and pressure reduces moisture and volatiles and increases C. The more C the greater the fuel value • Oldest coals 440 Ma  why? o Because maximum coal production occurred when Pangaea straddled the equator. o Why? ▪ Coal formed only after land colonized by plants ▪ Pangaea provided maximum areal extent of equatorial swamps • Reserve: Economically recoverable with existing technology o Coal reserves have a relatively healthy shape • Surface or strip mining: Remove overburden to get a coal. When you do that then they have to put it somewhere. In the Appalachians they have been cutting off mountaintops and putting the sediment in streams, which then pollute the rivers. • Coal commonly contains a sulfide mineral  Acid mine drainage: Oxidation of pyrite, FeS2, 4FeS2 + 15 O2 + 8H20 = Fe2O3 + 8H2SO4 o This reaction produces rust (hematite) and sulfuric acid o Pyrite is common in more rocks including coals, and especially common in ores. Mining increases rock surface area and facilitates acid mine drainage. • Second type of mining is underground mining o Very dangerous o Dangerous to health too ▪ Black Lung Disease: from chronic exposure to coal dust leads to chronic bronchitis and can be fatal ▪ Federal Law: Federal Coal Mine Health and Safety Act of 1969 ▪ Decrease in rate b 90%; currently about 9% of coal miners have more than 25 years of exposure have black lung • Coal burning facilitates acid rain due to oxidation of N (to HNO3- nitric acid, and S (from pyrite; to H2SO4, sulfuric acid)) • Coal fires are difficult to control December 2, 2015 Review: • Fossil Fuels: o Source: Organic Carbon buried in marine sediments (natural gas and petroleum) and in freshwater swamps (coal) ▪ Anoxic burial ▪ No metamorphism/igneous processes ▪ Reserve: recoverable today at a profit ▪ Resource: known but can’t be recoverable at a profit o Example of combustion: CH4 + 2O2 = CO2 + 2h2o + Energy o CO2 emission (2011) China increase, US decrease, European Union decrease, India increase • Fossil fuels account for 85% of US • EROI: Energy from resource divided by energy to obtain resource o Oil and gas (1930) > 100, now because harder to obtain ~30, if we import ~12 o Coal 80 o Tar sands (keystone pipeline) 2-4 o Ethanol .8-10 o Oil scale (fracking) ~5 o Nuclear 5-15 o Hydro >100 o Wind 18 o Solar 2-7 o Biodiesel 1.3 • Coal: o Complex mix of large organic molecules o Commonly contains pyrite FeS2 o Forms from swamp peat layers o Lignite  bituminous  anthracite with higher P,R more C, cleaner  o Coal formation maximized 245-320 Ma when Pangaea straddled equator o US has enough reserves > 100 yrs o Surface Mining: cheaper, more impact (mountain top removal/stream pollution) o Underground: Dangerous, expensive, less impact o Miners: ▪ Black lung (down 90% thanks to MHSA) ▪ Cave-ins ▪ Methane explosions o Environmental impacts: Acid rain, acid mine drainage (H2SO4 + HNO3) Oil/petroleum • Oil petroleum is a fluid and it flows upwards and is extremely versatile • Petroleum: A mix of various hydrocarbons… like butane o Mainly H, C o Minor N, S o Essentially no O • Origin: burial of marine organisms in sediments with limited oxygen • Petroleum production takes time… No oil rocks younger than 1-2 million years old • To make petroleum it can’t be too hot. So igneous and metamorphic processes destroy it. o As T increases, molecules become smaller, and petroleum becomes more gas rich • Petroleum “matures” and then because it is a liquid, it more- like groundwater. o Because lighter than water it floats on top. Also the two don’t mix o “Traditional” petroleum will migrate until trapped and concentrated in a reservoir o Further migration blacked by an impermeable cap rock o Good oil reservoir
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