Fossil Fuels and the Environment
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
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
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
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
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
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
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
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.
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.
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
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
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
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
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
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
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
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.
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.
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.
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.
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
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
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
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.
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
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
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
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
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
Underground 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 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.
Transport of Coal
Transporting coal from mining areas to large population centers where energy is needed. Significant environmental issue Freight trains and slurring pipelines have
been used
The 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 dioxide
The Future of Coal 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
The Future of Coal
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
The Future of Coal 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.
Allowance Trading
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
Oil shale
Fine grained sedimentary rock containing organic matter (kerogen). When heated to 500oC oil shale yields
oil Destructive distillation The oil from shale called synfuel
Tar Sands
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. Most in Alberta, Canada
Strip mined Similar problem as with shale, greater volume
Oil shale
Recovery done both surface and subsurface Disposal of waste a problem because shale
must be retorted Volume of waste 20-30% greater than original
volume. Despite this oil shale may developed as oil
prices rise.