Fossil Fuels Notes - Nhvweb

1/29/2013Chapter 17: Fossil Fuels and theEnvironment17.1 Fossil Fuels Fossil fuels are forms of stored solar energy Form from prehistoric plants and animals that lived hundreds ofmillions of years ago. Since plants store solar energy, fossil fuels are also stored solarenergy How do they form? Dead plants and animals were covered up and decomposed intoorganic 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 whatcombination of animal and plant debris was present, how longthe material was buried, and what conditions of temperature andpressure existed when they were decomposing.Oil and Natural Gas (Methane) Formation Organisms that lived in the water and were buried under oceanor river sediments After the great prehistoric seas and rivers vanished, heat,pressure and bacteria combined to compress and "cook" theorganic material under layers of silt Oil formed first, but in deeper, hot regions underground, thecooking process continued until natural gas was formed Over time, some of this oil and natural gas began working its wayupward through the earth's crust until they ran into rockformations called "caprocks" that are dense enough to preventthem from seeping to the surface.17.2 Crude Oil and Natural Gas Most geologist accept the hypothesis that these derived fromorganic 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 sedimentCrude Oil and Natural Gas 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 orblocked 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 thechemical transformation Elevated pressure causes sediment to be compressed This initiates upward migration to lower‐pressure reservoir rock1

1/29/2013Petroleum Production Primary production Involves simply pumping the oil from wells Recovers only 25% of petroleum in reservoir (roughly one barrelrecovered for every 3 discovered) Enhanced recovery Increase the amount recovered to about 60% Steam, water, saline, or chemicals injected into the reservoir topush 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 hasbeen identified and can be extracted now at a profitDrilling Terms:Refining Crude Oil through distillation:Oil is distilled into the following petrochemicals Peak Production: the point at which the pressure within an oilwell starts to decline Known Reserves: Resources that have been identified but notthroroughly mapped Proven reserves: Resources which have been mapped,measured and shown to be recoverable2

1/29/2013Oil in the Twenty‐First Century Recent estimates of proven oil reserves suggest that oil andnatural gas will last only a few decades. (US reserves until2035) When will we reach peak production? Likely to be between 2020‐2050 Will have to adjust to potential changes in lifestyle andeconomies in a post‐petroleum era Argument that we are head toward a potential crisis We are approaching the time when approximately 50% of thetotal crude oil available from transitional oil fields will have beenconsumed. Proven reserves are about 1.2 trillion barrels. World consumptionis quickly using what is left.Natural Gas Mostly methane Can be purified from NG and transported under low temp and highpressure to form liquified natural gas (LNG) Only begun to utilize this resource Transported by pipelines Used to heat homes, produce electricity, cook, and fuel carsOil in the Twenty‐First Century For every three barrels of oil we consume, we are finding only onebarrel. Forecasts that predict a decline in production of oil are based on manyassumptions 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. Worldproduction 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 powerEnvironmental Effects of Oil andNatural Gas Recovery, refining, and use of oil and natural gas cause welldocumented environmental problems Air and water pollution, acid rain, and global warming Worldwide estimates of recoverable gas will last about 70years. (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 energyRecovery Possible environmental impacts on land include: Use of land to construct pads for wells, pipelines, andstorage tanks and to build a network of roads and otherproduction facilities. Pollution of surface water and groundwater from: leaksfrom broken pipes or tanks containing oil or otherchemicals and salty water (brine) that is brought to thesurface in large volumes with the oil. Accidental release of air pollutants, such as hydrocarbonsand 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/ oilproduction in marine environment: Oil seepage into the sea from normal operations orlarge spills from accidents. Release of drilling muds containing heavy metals, suchas barium, that may be toxic to marine life. Aesthetic degradation from the presence of offshoreoil drilling platforms, which some people think areunsightly.3

1/29/2013Refining At refineries, crude oil is heated so that its components can beseparated and collected Fractional distillation Accidental spills and slow leaks Over years large amount of hydrocarbons released, polluting soiland ground water Variety of chemicals used in the industrial process which havethe potential to pollute.Delivery and Use Crude oil mostly transported on land by pipelines and acrossthe ocean in tankers Both have danger of oil spill Air pollution most serious impact associated with use(burning) Contributes to urban smogCoal‐Bed Methane The process of coal formation also produces a lot of methanethat is stored within coal Estimated amount is about 5 year supply Promising energy source however there are severalenvironmental concerns 1. Disposal of large volumes of salty water 2. Migration of methane, which may contaminate surroundingareas Environmental benefits Produces a lot less carbon dioxide than does burning coal orpetroleum. Reduces the amount of methane released into the atmosphereMethane Hydrates Beneath the seafloor there exist deposits known as methanehydrates White, ice like compound made up of molecules of methane gasmolecular “cages” of frozen water Forms as a result of microbial decomposition on the sea floor andthen trapped in ice Also found on land in permafrost Found in ocean where deep, cold seawater provides highpressure and low temperatures.17.3 Coal Most abundant fossilfuel At currentconsumption ratecould last 250 years 85% used forelectricity 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 ortransport the gas4

1/29/2013Coal Formation 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 otherplants that lived 300 to 400 million years ago In some areas, such as portions of what‐is‐now the easternUnited States, coal was formed from swamps covered by seawater. The sea water contained a large amount of sulfur, and as theseas dried up, the sulfur was left behind in the coal. Clean Coal: Attempts to get rid or lower the sulfur contentSome coal deposits, however, were formed from freshwaterswamps 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)5

1/29/2013Coal Mining and the Environment In US thousands of sq miles disturbed by coal mining Only about half reclaimed The process of restoring and improving disturbed land, often byreforming the surface and replanting vegetation.Strip Mining A surface process in which overlying layers of soil and rock isstripped 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 spoilbanks Water reacts with sulfide minerals to produce sulfuric acid. The acid then pollutes streams and groundwaterStrip Mining In arid and semiarid regions the land may be more sensitive toactivities 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/ miningwaste Flood hazard increases as valleys filled w/ mine waste and toxicwaste water is stored behind coal waste sludge dams Also produces voluminous amounts of coal dustStrip Mining Surface Mining Control Act of 1977 US government has required that mined land restored to supportpre‐mining use Prohibit mining on prime ag land Reclamation includes Disposing of wastes Contouring the land Replanting vegetation6

1/29/2013Underground Mining Accounts for 40% of coal mined in the US Some of the environmental problems: Acid mine drainage from the mines and waste piles has pollutedthousands of kilometers of streams. Land subsidence can occur over mines. Coal fires in underground mines may be either naturally causedor deliberately set.Transport of Coal Transporting coal from mining areas to large populationcenters where energy is needed. Significant environmental issue Freight trains and slurring pipelines have been usedThe Future of Coal 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 dioxideThe Future of Coal Clean Air Amendments of 1990 mandate reducingthese emissions. Option for cleaner coal include: Chemical and/or physical cleaning of coal prior tocombustion. New boiler designs that permit lower temp of combustion. Injection of material rich in calcium carbonate into the gasesfollowing 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 toreduce the demand for energy. Development of zero emissions coal‐burning electric power plantsThe Future of Coal Clean Coal technology would reduce CO2, SO2,NOx and Mercury As oil and gas reserves dry up more pressure puton coal. Increased use of coal will have significantenvironmental impact. More land strip mined. Burning coal produces large amounts of air pollutants Handling of large quantities of coal through all stageshas potentially adverse environmental effects. include aesthetic degradation, noise, dust, and release ofharmful or toxic trace elements into the water, soil, and air7