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Chapter17:FossilFuelsandthe
Environment
17.1FossilFuels
• Fossil fuels are forms of stored solar energy
• Form from prehistoric plants and animals that lived hundreds of millions of years ago.
• Since plants store solar energy, fossil fuels are also stored solar energy
• How do they form?
• Dead plants and animals were covered up and decomposed into organic compounds slowly
• Under the conditions of extreme heat and pressure
• Converted into oil, natural gas and coal
• Different types of fossil fuels were formed depending on what combination of animal and plant debris was present, how long the material was buried, and what conditions of temperature and pressure existed when they were decomposing.
OilandNaturalGas(Methane)Formation
• Organisms that lived in the water and were buried under ocean or river sediments
• After the great prehistoric seas and rivers vanished, heat, pressure and bacteria combined to compress and "cook" the organic material under layers of silt
• Oil formed first, but in deeper, hot regions underground, the cooking process continued until natural gas was formed • Over time, some of this oil and natural gas began working its way upward through the earth's crust until they ran into rock formations called "caprocks" that are dense enough to prevent them from seeping to the surface.
17.2CrudeOilandNaturalGas
• Most geologist accept the hypothesis that these derived from organic matter
• Buried in what are known as depositional basins
• Oil and gas primarily found along plate boundaries
• Exceptions to this include Texas, Gulf of Mexico and the North Sea
• Source rock is fine grained, organic‐rich sediment
CrudeOilandNaturalGas
• Reservoir rock is coarser grained and relatively porous
• E.g. sandstone and porous limestone
• Trap
• Natural upward migration of the oil and gas is interrupted or blocked
• Rock that helps form a trap known as cap rock, often shale
• At a depth at least 500 m
• Subjected to increased heat and pressure that initiates the chemical transformation
• Elevated pressure causes sediment to be compressed
• This initiates upward migration to lower‐pressure reservoir rock
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PetroleumProduction
• Primary production
• Involves simply pumping the oil from wells
• Recovers only 25% of petroleum in reservoir (roughly one barrel recovered for every 3 discovered)
• Enhanced recovery
• Increase the amount recovered to about 60%
• Steam, water, saline, or chemicals injected into the reservoir to push oil towards wells
• Next to water, oil is the most abundant fluid in the upper crust
• Concentrated in a few fields
• Proven oil reserves are the part of the total resource that has been identified and can be extracted now at a profit
DrillingTerms:
RefiningCrudeOilthroughdistillation:
Oilisdistilledintothefollowingpetrochemicals
• Peak Production: the point at which the pressure within an oil well starts to decline
• Known Reserves: Resources that have been identified but not throroughly mapped
• Proven reserves: Resources which have been mapped, measured and shown to be recoverable
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OilintheTwenty‐FirstCentury
OilintheTwenty‐FirstCentury
• Recent estimates of proven oil reserves suggest that oil and natural gas will last only a few decades. (US reserves until 2035)
• When will we reach peak production?
• For every three barrels of oil we consume, we are finding only one barrel.
• Forecasts that predict a decline in production of oil are based on many assumptions but most expert agree it is coming in the next few decades.
• In the US production of oil as we know it now will end by 2090. World production by 2100.
• Before shortages we need to planning and appropriate action to avoid
• Military confrontation
• Food shortages
• Social disruption
• Need to develop alternative energy sources
• Solar energy
• Wind power
• Nuclear power
• Likely to be between 2020‐2050
• Will have to adjust to potential changes in lifestyle and economies in a post‐petroleum era
• Argument that we are head toward a potential crisis
• We are approaching the time when approximately 50% of the total crude oil available from transitional oil fields will have been consumed.
• Proven reserves are about 1.2 trillion barrels. World consumption is quickly using what is left.
NaturalGas
• Mostly methane • Can be purified from NG and transported under low temp and high pressure to form liquified natural gas (LNG)
• Only begun to utilize this resource
• Transported by pipelines
• Used to heat homes, produce electricity, cook, and fuel cars
EnvironmentalEffectsofOiland
NaturalGas
• Recovery, refining, and use of oil and natural gas cause well documented environmental problems
• Air and water pollution, acid rain, and global warming
• Worldwide estimates of recoverable gas will last about 70 years. (Majority in Russia)
• In US about 30 years
• Considered a clean fuel
• Produces fewer pollutants than burning oil or coal
• Could be a transition fuel to alternative energy
Recovery
• Possible environmental impacts on land include:
• Use of land to construct pads for wells, pipelines, and storage tanks and to build a network of roads and other production facilities.
• Pollution of surface water and groundwater from: leaks from broken pipes or tanks containing oil or other chemicals and salty water (brine) that is brought to the surface in large volumes with the oil.
• Accidental release of air pollutants, such as hydrocarbons and hydrogen sulfide (a toxic gas).
• Land subsidence (sinking) as oil and gas are withdrawn.
• Loss or disruption of and damage to fragile ecosystems, such as wetlands or other unique landscapes.
Recovery
• Environmental impacts associated w/ oil production in marine environment:
• Oil seepage into the sea from normal operations or large spills from accidents.
• Release of drilling muds containing heavy metals, such as barium, that may be toxic to marine life.
• Aesthetic degradation from the presence of offshore oil drilling platforms, which some people think are unsightly.
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Refining
• At refineries, crude oil is heated so that its components can be separated and collected
• Fractional distillation
• Accidental spills and slow leaks
• Over years large amount of hydrocarbons released, polluting soil and ground water
• Variety of chemicals used in the industrial process which have the potential to pollute.
DeliveryandUse
• Crude oil mostly transported on land by pipelines and across the ocean in tankers
• Both have danger of oil spill
• Air pollution most serious impact associated with use (burning)
• Contributes to urban smog
Coal‐BedMethane
• The process of coal formation also produces a lot of methane that is stored within coal
• Estimated amount is about 5 year supply
• Promising energy source however there are several environmental concerns
• 1. Disposal of large volumes of salty water
• 2. Migration of methane, which may contaminate surrounding areas
• Environmental benefits
• Produces a lot less carbon dioxide than does burning coal or petroleum.
• Reduces the amount of methane released into the atmosphere
MethaneHydrates
• Beneath the seafloor there exist deposits known as methane hydrates
• White, ice like compound made up of molecules of methane gas molecular “cages” of frozen water
• Forms as a result of microbial decomposition on the sea floor and then trapped in ice
• Also found on land in permafrost
• Found in ocean where deep, cold seawater provides high pressure and low temperatures.
17.3Coal
• Most abundant fossil fuel
• At current consumption rate could last 250 years
• 85% used for electricity
• Not stable at low pressure and warm temperature.
• Documented cases of releases seen off coast of Norway
• Potential energy source but currently no way to mine or transport the gas
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CoalFormation
• Heat content and hardness increase
• Typical Sulfur Content in Coal
• Same types of forces created • Coal formed from the dead remains of trees, ferns and other plants that lived 300 to 400 million years ago
• In some areas, such as portions of what‐is‐now the eastern United States, coal was formed from swamps covered by sea water. • The sea water contained a large amount of sulfur, and as the seas dried up, the sulfur was left behind in the coal.
• Clean Coal: Attempts to get rid or lower the sulfur content Some coal deposits, however, were formed from freshwater swamps which had very little sulfur in them
• Anthracite Coal : 0.6 ‐ 0.77 weight % (High Demand)
• Bituminous Coal : 0.7 ‐ 4.0 weight % (Largest Supply)
• Lignite Coal : 0.4 weight % (AKA: Brown Coal)
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CoalMiningandtheEnvironment
• In US thousands of sq miles disturbed by coal mining
• Only about half reclaimed
• The process of restoring and improving disturbed land, often by reforming the surface and replanting vegetation.
StripMining
• A surface process in which overlying layers of soil and rock is stripped off to reach the coal.
• Over half of the coal in US mined this way
• One serious problem is acid mine drainage
• The drainage of acidic water from mine sites
• Happens in eastern US where there is abundant rain fall
• Acid mine drainage occurs where surface water infiltrates spoil banks
• Water reacts with sulfide minerals to produce sulfuric acid.
• The acid then pollutes streams and groundwater
StripMining
• In arid and semiarid regions the land may be more sensitive to activities related to mining
• Exploration and road building
• Soils thin and water scarce
• Makes reclamation more difficult
• Reclamation can minimize damage
• Laws vary by site
• Appalachian Mountain’s of West Virginia
• Technique known as “mountaintop removal”
• Strip‐mining levels tops of mountains and fills valleys w/ mining waste
• Flood hazard increases as valleys filled w/ mine waste and toxic waste water is stored behind coal waste sludge dams
• Also produces voluminous amounts of coal dust
StripMining
• Surface Mining Control Act of 1977
• US government has required that mined land restored to support pre‐mining use
• Prohibit mining on prime ag land
• Reclamation includes
• Disposing of wastes
• Contouring the land
• Replanting vegetation
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UndergroundMining
• Accounts for 40% of coal mined in the US
• Some of the environmental problems:
• Acid mine drainage from the mines and waste piles has polluted thousands of kilometers of streams.
• Land subsidence can occur over mines.
• Coal fires in underground mines may be either naturally caused or deliberately set. TransportofCoal
• Transporting coal from mining areas to large population centers where energy is needed.
• Significant environmental issue
• Freight trains and slurring pipelines have been used
TheFutureofCoal
• Burning of coal • produces 60% of electricity used and • 25% of total energy consumed in US
• Coal 90% of our energy reserves
• However coal power plants emit
• 70% of sulfur dioxide
• 30% of nitrogen oxides
• 35% of carbon dioxide
TheFutureofCoal
• Clean Air Amendments of 1990 mandate reducing these emissions.
• Option for cleaner coal include:
• Chemical and/or physical cleaning of coal prior to combustion.
• New boiler designs that permit lower temp of combustion.
• Injection of material rich in calcium carbonate into the gases following burning.
• Scrubbers‐removes sulfur dioxides
• Conversion of coal at power plants into gas before burning.
• Convert coal to oil.
• Consumer education about energy conservation and efficiency to reduce the demand for energy.
• Development of zero emissions coal‐burning electric power plants
TheFutureofCoal
 Clean Coal technology would reduce CO2, SO2, NOx and Mercury
 As oil and gas reserves dry up more pressure put on coal.
 Increased use of coal will have significant environmental impact.
 More land strip mined.
 Burning coal produces large amounts of air pollutants
 Handling of large quantities of coal through all stages has potentially adverse environmental effects. ○ include aesthetic degradation, noise, dust, and release of harmful or toxic trace elements into the water, soil, and air
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AllowanceTrading
• EPA grants utility companies tradable allowances for polluting
• 1 allowance good for 1 ton of sulfur dioxide
• Could then be traded and sold by brokers
• Idea is to reduced overall pollution through economic market forces
17.4Oilshale
• Fine grained sedimentary rock containing organic matter (kerogen).
• When heated to 500oC oil shale yields oil
• Destructive distillation
• The oil from shale called synfuel
TarSands
• Sedimentary rocks or sands impregnated with tar oil, asphalt, or bitumen. • Recovered by
• mining the sands and then washing the oil out with hot water.
• Steam extraction
• Most in Alberta, Canada
• Strip mined
• Similar problem as w/ shale, greater volume
Oilshale
• Recovery done both surface and subsurface
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Disposal of waste a problem because shale must be retorted
Volume of waste 20‐30% greater than original volume.
Large amounts of water are necessary for processing
Extensive environmental damage is done in extraction
Synfuels
• Liquid fuels that are produced from nonpetroleum hydrocarbon sources like coal
• More info on clean coal…
• Despite this oil shale may developed as oil prices rise.
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CarbonSequestration
• Decreasing CO2 from burning fossil fuels by
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Pumping CO2 into oil reservoirs
Injecting CO2 into aquifers
Pumping into the bottom of the ocean
Storing in depleted oil and gas wells
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