Chapter 18 Fossil Fuels and the Environment

Fossil Fuels Forms of stored solar energy created from incomplete biological decomposition of dead organic matter Crude Oil Natural Gas Coal Also, Oil Shale & Tarsands

Crude Oil and Natural Gas Crude Oil –Naturally occurring petroleum, normally pumped from wells in oil fields. –Refinement of crude oil produces most of the petroleum products we use today Natural Gas –Naturally occurring gaseous hydrocarbon generally produced in association with crude oil or from gas wells –An important efficient and clean burning fuel commonly used in homes and industry

Geology of Oil & Gas Oil & gas found primarily along geologically young tectonic belts at plate boundaries –Source Rock – source material for oil & gas. Fine grained, organic rich sediment, at least 500m deep –High pressure and high temperature, initiates the chemical transformation & upward migration of gas & oil (relatively light) to reservoir rock

Geology Cont’d Reservoir Rock: coarser grain, porous sandstone or limestone. Empty spaces store oil &/or gas. Cap Rock: traps oil or gas in a pocket in the reservoir rock. Usually shale – very fine grained sedimentary tock Two types of Traps: Anticline (arch shape), Fault (fracture in rock

Activity Draw these next slides

Petroleum Production Primary Production – simply pumping –Recovery only 25% of reserve Enhanced Production – steam, water, CO 2 or N 2 are injected into reservoir to puch oil toward the well

Activity Summarize the arguments (on Pg 369 ) that we are heading toward a potential crisis

Natural Gas Only begun to seriously look for natural gas & its’ potential uses. Drawback: transported through piplines Worldwide estimate of recoverable nat.gas is 165 trillion m 3 - could last 70 years Much of it is in the US Considered a clean fuel – less pollutants, less environmental problems

Coal-Bed Methane In the chemical process that converts decomposed organic matter into coal – methane is formed (in large amounts) Currently two areas in our nation are recovering coal-bed methane – Utah & Wyoming Wells are cheap ($100,000 compared to several million for oil wells) Problems: –Lg amounts of water are used to extract the methane – water becomes contaminated and disposal is a problem. –Migration of methane into urban areas (colorless, odorless and highly explosive

Methane Hydrates White ice-like compound made up of molecules of methane gas trapped in “cages” of frozen water in the sediments of the deep seafloor Formed due to microbial digestion of organic matter in sediments on the seafloor. Discovered 30 yrs ago Needs high pressure and low temps. Methane hydrate decomposes rapidly as press. & temp change and releases methane Potential energy source – difficult to mine, bc found along lower continental slopes at greater than 1km in depth

Environmental Effects of Oil and Natural Gas Recovery: –Use of land –Pollution of surface and groundwaters –Air pollutants –Land subsidence ( sinking) –Loss of ecosystems –Release of drilling muds (heavy metals) –Aesthetics (presence of rigs) Refining: soil, water and air pollution – spills & leaks Delivery and Use: energy to power automobiles, produce electricity, etc. Possible spills and air pollution form use

Coal Solid, brittle, carbonaceous rock formed from partially decomposed vegetation buried in a sedimentary environment. Total recoverable resource = 250 billion Metric tons ( 250 yrs )

Coal Composition Classified according to energy content and sulfur content –Anthracitehigh energy –Bituminous –Subbitumious (low sulfur) –Lignite (low sulfur)low energy

Content cont’d Low sulfur coal emits less SO 2. Therefore more desirable fuel High sulfur coal can be treated before, during or after combustion to reduce sulfur content –This is done on the East coast of US. It is more expensive, but more economical than transporting low sulfur coal from the West \

Coal Mining and the Environment Strip Mining –A surface mining process in which the overlying layer of soil and rock is stripped off to reach the coal (Cheap & Easy)

Impacts Acid mine drainage: acid water from mine site is formed from rainwater coming in contact with spoil banks (rock debris) that contains FeS 2 (pyrite – common in sedimentary rock). This forms H 2 SO 4 – sulfuric acid – which infiltrates the surface and groundwater. Good reclamation practices would help 1000’s of km of land have been disturbed by strip mining, but only 50% has gone through reclamation processes

Impacts cont’d Surface Mining Control & Reclamation Act of 1977 –US Gov’t requires that mined land be restored to support its pre-mining use.

Transport of Coal The Future of Coal –Scrubbing: removes sulfur dioxides Allowance Trading –Reduces pollution –EPA grants utility companies tradable allowances for polluting

Underground Mining 40% of coal is mined this way in the US Dangers = collapse, fire, explosions, respiratory illness Environmental Problems: –Acid mine drainage –Land subsidence –Coal fires in mines

Coal & the environment Coal is used to produce lectricity, synthetic oil & synthetic gas Burning coal accounts for 60% of electricity used in US (25% of all energy consumed) Coal is 90% of fossil fuel reserves in US –(enough for several hundred yrs for US population) –PROBLEMS: emissions of SO 2, NO & CO 2 Clean Air Act of 1990 – mandated that sulfur dioxide emissions be reduced vy 70% - 90% This has forced the birth of new technologies

Allowance Trading EPA grants utility companies tradable allowances for polluting 1 allowance = 1 ton of SO2 emissions If you don’t use your allowance you can trade or sell them. Encourages competition for cleaner emissions and reduces pollution.

Oil Shale and Tar Sands Oil Shale –A fine-grained sedimentary rock that must be heated to extract the oil – One tone of oil shale produces 60 l of oil –(Colorado, Utah & Wyoming Tar Sands –Sedimentary rocks or sands impregnated with tar oil, asphalt or bitumen –Wash the sand with hot water to extract oil –Alberta, Canada