Energy Sources: Tar Sands and Coal Formation

Chapter 7 Fundamentals of Energy Fossil Fuels and Nuclear Energy

Tar Sand Tar sands, also referred to as oil sands or bituminous sands, are a combination of clay, sand, water, and a solid, tar-like petroleum, called bitumen Most of the remaining 15% is found in Venezuela and Russia, but these deposits will probably never be economical to mine The bitumen is far too thick to flow out of the rock 85% of all tar sand deposits occur in Canada

Tar Sand About 88% of Canada’s known petroleum reserves are tar sands

Tar Sand Fortunately, the Canadian tar sand are concentrated in three regions in the state of Alberta This concentration means that some of these deposits are currently economic to mine In fact, serious tar sand mining began before WWII

Tar Sand There are about 174 billion barrels of crude bitumen which are economically recoverable from the three Alberta oil sands areas at current prices using current technology This is equivalent to about 10% of the estimated 1,700 and 2,500 billion barrels of bitumen in place

Tar Sand It takes two tons of tar sand to produce one barrel of oil

Tar Sand Note the processing plant in the distance

Tar Sand The oil sands after surface removal are further broken up and then extracted from the rock pores by subjecting the material to hot water and other chemicals, such as sodium hydroxide The oil-bearing sand is piped into a large settling tank where the heavy sand settles to the bottom, water settles above that, and the oil floats to the top, where it can be removed for refining

Tar Sand For every barrel of oil produced from tar sands in Alberta, more than 80 kg of greenhouse gases are released into the atmosphere and between 2 and 4 barrels of waste water are dumped into tailing ponds that have flooded about 50 square kilometers of forest and bogs

Tar Sand Critics contend that measures taken to minimize environmental and health risks posed by large-scale mining operations are inadequate, potentially causing damage to archaeological sites and natural resources

Tar Sand The open-pit mining of the Alberta oils sands destroys the boreal forest, the bogs, the rivers as well as the natural landscape The mining industry believes that the boreal forest will eventually colonize the reclaimed lands, yet 30 years after the opening of the first open pit mine in the region no land is considered as having been "restored“

Coal

Coal Coal currently provides 23% of the total U.S. energy needs Now that oil and gas are dwindling, many energy producers and users are looking again at the potential of coal

Formation of Coal Deposits Unlike petroleum, coal is not formed from marine organisms, but from the remains of land plants A swampy setting, in which plant growth is lush and where there is water to cover fallen trees, dead leaves and other plant debris, is ideal for the initial stages to create coal

Formation of Coal Deposits The formation of coal from dead plant matter requires burial, pressure, heat and time The process works best under anaerobic conditions (no oxygen) since the reaction with oxygen during decay destroys the organic matter It is the carbon content of the coal that supplies most of its heating value The greater the carbon to oxygen ratio the harder the coal, the more reduced the state of the carbons and the more potential energy it contains

Formation of Coal Deposits The products of coalification are divided into four major categories based on the carbon content of the material Peat Lignite Bituminous Anthracite

Peat Peat is an accumulation of partially decayed vegetation matter and is the first stage in the formation of coal Peat forms in wetlands, variously called bogs, moors, muskegs, pocosins, mires, and swamps It contains a large amount of water and must be dried before use Historically, it has been used as a source of heat and burns with a long flame and considerable smoke

Peat Peat deposits are found in many places around the world, notably in Russia, Ireland, Finland, Scotland, Poland, northern Germany, the Netherlands and Scandinavia, and in North America Approximately 60% of the world's wetlands have peat

Peat Peat is still mined as a fuel in Ireland and England The peat is stacked to slowly dry out

Lignite Lignite is the second step in the formation of coal and is formed when peat is subjected to increased vertical pressure from accumulating sediments Lignite, often referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for steam-electric power generation It has a high inherent moisture content, sometimes as high as 66 percent, and very high ash content compared to bituminous coal

Lignite Because of its low energy density, brown coal is inefficient to transport and is not traded extensively on the world market compared to higher coal grades It is often burned in power stations constructed very close to the mines

Bituminous Bituminous Coal is the third stage of coal formation Additional pressure over time has made it compact and virtually all traces of plant life have disappeared It is of higher quality than lignite coal but of poorer quality than anthracite coal It is greatly used in industry as a source of heat energy

Bituminous Bituminous coal is usually black, sometimes dark brown, often with well-defined bands of bright and dull material It is a relatively hard coal containing a tar-like substance called bitumen

Bituminous Bituminous coal is a complex molecular mix of 60-80% carbon, plus oxygen, hydrogen and nitrogen, plus some occasional impurities like sulfur

Coking Coal When used for many industrial processes, bituminous coal must first be "coked" to remove volatile components Coking is achieved by heating the coal in the absence of oxygen, which drives off volatile hydrocarbons such as propane, benzene and other aromatic hydrocarbons, and some sulfur gases and a considerable amount of the contained water of the bituminous coal Coking coal is used in the manufacture of steel, where carbon must be as volatile-free and ash-free as possible

Anthracite Anthracite is formed during the forth stage of coal formation It is the most valuable and highest grade of coal, and has a carbon content of 92-98% Physically, anthracite differs from bituminous coal by its greater hardness and higher density Plus, it burns far more efficiently with less smoke

Fuel Efficiency As the coals becomes harder, their carbon content increases, and so does the amount of heat released Anthracite produces twice the energy (BTUs) of lignite

U.S. Coal Reserves The U.S. possesses 25% of all the known coal in the world

U.S. Coal Reserves U.S. coal reserves represent about 50 times the energy remaining in proven oil reserves and 40 times the energy in proven natural gas reserves

U.S. Coal Reserves The U.S. has consumed half of our oil reserves, but only a few percent of our coal reserves Our coal reserves could meet current U.S. energy needs for 200 years (compared to 50 years for oil)

World Coal Reserves 46% of the U.S. reserves are bituminous and anthracite The remaining 54% is lignite

Coal-bed Methane During the formation of coal deposits, quantities of methane-rich gas are also formed Historically, methane has been considered as a hazardous nuisance In fact, currently it is usually burned off rather than recovered It is estimated that 100 trillion cubic feet of methane can be economically recovered from existing U.S. coal beds

Coal-bed Methane U.S. coal deposits are already mapped, so there would be no exploration cost Waste water is a potential pollution problem Coal-bed methane is already being produced in Utah

Coal Gasification One of the most advanced - and cleanest - coal power plants in the world is Tampa Electric's Polk Power Station in Florida It uses a coal gasification process that turns coal into a gas that can be cleaned of almost all pollutants

Coal Gasification The coal is heated inside a large oven and blasted with steam The coal is converted into carbon monoxide and hydrogen gas Hydrogen gas burns very easily

Coal Gasification This 2544-ton-per-day coal gasification demonstration pilot plant in Pennsylvania, will have energy conversion efficiencies 20 to 35% higher than those of conventional pulverized-coal steam power plants

Coal Liquefaction Coal can also be converted into liquid fuels like gasoline or diesel by several different processes This is an attractive technology because it is well developed and thus could be implemented fairly rapidly and there are relatively large quantities of coal reserves

Coal Liquefaction Estimates of the cost of producing liquid fuels from coal suggest that domestic U.S. production of fuel from coal becomes cost-competitive with oil priced at around $35 US per barrel (currently over $100 per barrel) A coal liquefaction test plant in Japan

Coal & Environment A major problem with coal is the pollution associated with its mining and use Coal is a major source of the greenhouse gas, carbon dioxide In fact, coal releases more carbon dioxide per unit energy burned than natural gas or oil

Coal & Sulfur The pollutant of special concern with coal is sulfur The sulfur content of coal can be as high as 3%, with some in the form of the iron sulfate mineral pyrite (FeS2) and some bound in the remaining organic matter When a coal containing sulfur is burned, sulfur gases, notably sulfur dioxide (SO2), are emitted These gases are poisonous and are extremely irritating to both eyes and lungs

Acid Rain These sulfur gases also react with water in the atmosphere to produce sulfuric acid, which is a very strong acid This acid falls to earth as acid rain These trees near coal-fired power plants have been killed by acid rain

A Hard Rain’s A-gonna Fall Acidity in rain is measured by collecting samples of rain and measuring its pH The areas of greatest acidity (lowest pH values) are located in the Northeastern U.S.

A Hard Rain’s A-gonna Fall This pattern of high acidity is caused by the large number of cities, the dense population, and the concentration of power and industrial plants in the Northeast

A Hard Rain’s A-gonna Fall Acid rain can acidify soil, stunting plant growth It can kill fish and other aquatic life, dissolve rocks, destroy the surface of building facades and monuments Most coal-burning power plants have scrubbers in the smoke stacks that remove most, but not all of the sulfur gas emissions Low sulfur coal, less than 1%, is the coal of choice

Ash Coal also produces a tremendous amount of solid waste The ash residue left after coal is burned is typically 5-20% of the original volume It is primarily composed primarily of non-combustible silicate minerals, but also contains toxic metals

Ash If released with emission gases, the ash fouls the air When dumped onto the surface, the fine-grained ash weathers very rapidly, releasing toxic metals, such as selenium, creating a serious water-pollution threat The average coal-fired power plant produces one million tons of ash per year, which is usually buried

Ash On December 22, 2008, there was a catastrophic collapse of the dyke around an ash retention pond at the TVA coal-powered electricity generating facility at Kingston, Tennessee

Ash TVA estimated that 5.4 million gallons of wet fly ash had escaped thru the breach

Ash About 40 private homes, buildings and other structures were damaged or destroyed by the ash flow Some residents were forced to leave their homes forever

Ash TVA denies that the fly ash is dangerous to the environment or to human health However, TVA’s own records revealed that the 5.4 million gallons of fly ash contained 44,000 pounds of arsenic 49,000 pounds of lead 142,000 pounds of manganese 1.4 million pounds of barium compounds

Energy Sources: Tar Sands and Coal Formation