Fossil Fuels and the Environment

1. Fossil Fuels and the Environment

2. Fossil Fuels • Fossil fuels are forms of stored solar energy • Plants convert solar energy to chemical energy through photosynthesis • Incomplete decomposed organic matter then covered up • Converted to oil, natural gas, and coal • Provide 90% of energy consumed

6. Crude Oil and Natural Gas • 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

7. Crude Oil and Natural Gas • Source rock is fine grained, organic-rich sediment • 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

8. Crude Oil and Natural Gas • Reservoir rock is coarser grained and relatively porous • 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

11. Petroleum Production • Primary production • Involves simply pumping the oil from wells • Recovers only 25% of petroleum in reservoir • Enhanced recovery • Increase the amount recovered to about 60% • Steam, water, or chemicals injected into the reservoir to push oil towards wells

12. Petroleum Production • 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 • Domination of energy use in North America but not reserves. • Leads to trade imbalance

16. Oil in the Twenty-First Century • Recent estimates of proven oil reserves suggest that oil and natural gas will last only a few decades. • When will we reach peak production? • Likely to be between 2020-2050 • Will have to adjust to potential changes in lifestyle and economies in a post-petroleum era

17. Oil in the Twenty-First Century • 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.

18. Oil in the Twenty-First Century • 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.

19. Oil in the Twenty-First Century • 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

20. Natural Gas • Only begun to utilize this resource • Transported by pipelines • Worldwide estimates of recoverable gas will last about 70 years. • 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

21. Coal-Bed Methane • The process of coal formation also produces a lot of methane that is stored within coal • Estimated amount is about five-year supply • Promising energy source however there are several environmental concerns • Disposal of large volumes of salty water • Migration of methane, which may contaminate surrounding areas

22. Coal-Bed Methane • Environmental benefits • Produces a lot less carbon dioxide than does burning coal or petroleum. • Reduces the amount of methane released into the atmosphere

23. Methane Hydrates • 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

24. Methane Hydrates • Found in ocean where deep, cold seawater provides high pressure and low temperatures. • Not stable at lower pressure and warmer temperatures • Documented cases of releases seen off coast of Norway • Potential energy source but currently no way to mine or transport the gas

25. Environmental Effects of Oil and Natural Gas • Recovery, refining, and use of oil and natural gas cause well documented environmental problems. • Air and water pollution, acid rain, and global warming

26. 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 waters 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.

27. Recovery • 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.

28. 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.

30. 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.

31. Delivery and Use • 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

37. Coal • Partially decomposed vegetation, when buried in a sedimentary environment, may be slowly transformed into the solid, brittle, carbonaceous rock. • Most abundant fossil fuel • At current consumption rate could last 250 years

40. Coal • Classified according to its energy and sulfur content • Anthracite • Bituminous • Subbituminous • Lignite • Energy content greatest in anthracite and lowest in lignite • Lower sulfur coal emits less sulfur dioxide

43. Coal 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 by reforming the surface and replanting vegetation.

44. Strip Mining • 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

45. Strip Mining • 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

47. Strip Mining • 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

49. Strip Mining • 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

50. Strip Mining • 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