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.