Energy and coal

Environmental ScienceMr. Wasley

How do we get our energy?

The US consumes 28% of the world’s energy sources

How do we get our Energy?• 28% of the world’s oil supply is used by the US. Does the US have 28% of the world’s oil?

• What three energy sources are most widely used used in both the US and in the world?

• What do these three energy sources have in common?

How do we Use Energy?Transportation

•light-duty vehicles•freight trucks•air transport•marine•rail

Residential & Commercial

•space heating•space cooling•water heating•lightingIndustrial

•refining•pulp & paper•chemicals, rubber, & plastics•metals

Historical Energy USe• ancestors relied on renewable sources of energy like

photosynthesis• Burned wood from fallen trees• Used wind to move ships• 1700‘s- Steel making: need lots of wood. Many forests were cut

down. Used for heating homes too. • 1800‘s- Coal: railroads were developed, so it could be transported

easily• 1920’s- Oil and natural gas: cleaner, easier, cheaper. Became

popular at the end of World War II. • Presently? Oil and natural gas are coming to an end. Nuclear is

increasing, coal is coming back.

Fossil Fuels• current sources of energy are dominated by fossil fuels• These include:

• Oil• Natural Gas• Coal

• formed eons (10,000) years ago by the compression, decay, and heating of plant and animal matter buried in mud and sand

• only can form if oxidation does NOT occur to the plant or animal

Wood

• 1850’s: Settlers cut lots of forests down to build their homes, heat their homes, build ships, etc.

• 90% of energy used was wood• A family would use 17.4 cords a year.

• One cord is 4000 lbs (4 x 4 x 8 area)• How many lbs of wood would a family use in a year?

Coal• ranks 2nd as a source of energy in the world• Chemical equation for burning coal:

• coal + oxygen CO2 + H20 + heat + waste• Wastes of coal include: sulfur dioxide (SO2), nitrogen oxides (NOx), Carbon Monoxide (CO), soot (unburned coal), fly ash, and bottom ash (impurities in coal)

• Coal is almost three times more efficient than wood

Origin of Coal• occurs in strata along with other sedimentary rocks like shale

and sandstone• If you look at coal through a magnifying glass you can see bits

of fossilized wood, bark, leaves, root, etc.• It’s organic: contains primarily carbon but also hydrogen,

oxygen, nitrogen, and sulfur• Coal was created in ancient swamps and marshes along

equatorial regions• Stagnant water has low oxygen, only anaerobic bacterial can

live there. They break down the dead plants in the swamp. • Carbon from the plants do not get consumed by the bacteria.

Eventually, the bacteria get killed by acids being released from the decaying plants.

OriGin of Coalpeat

• After the destruction of bacteria, the plant matter becomes peat

• looks like decayed wood• very smoky when burned because it contains some water

• Peat will become buried beneath more plant matter and accumulating sand, silt, and clay - increases temperature + pressure

Origin of CoalLignite

• As peat is compressed H20 and CH4 gets squeezed out, concentration of carbon increases (25 to 35%) - forms lignite

• Also known as brown coal• Easy to convert to a liquid or gas for energy BUT it produces more pollutants and carbon dioxide than other forms of coal

Origin of coalBituminous

• under more heat and pressure, lignite will become bituminous coal. Carbon concentration increases to 60 to 80%

• also known as black coal• better for burning than lignite, less harmful wastes like fly ash and sulfur dioxide are produced

Origin of coalAnthracite

• technically, a metamorphic rock. Carbon content is 92 to 98%

• also known as stone coal• Used to heat homes because it burns clean and produces a small amount of soot.

• Power-plants do not use it because it is too expensive. 2-3 times more expensive than bituminous coal.

U.S. Coal Deposits

Obtaining Coal• Underground mining: pillars are left in these mines to support the roof. Miners now use machines like the continuous mining machine to loosen and collect 12 tons of coal a minute

• In the past, 50% of coal was recovered from areas. Now we can recover 80 to 90% of coal in an area

• Longwall mining: A machine provides roof support while the cutter shaves coal off the wall and dumps the coal onto a conveyer belt

• Surface mining: If coal is 200 ft or less below the surface they can dig the coal out. It’s the cheapest way to mine.

Open Pit Mining

Strip MiningAfter the process,

the land is restored to it’s prior condition.

But it isn’t always the case

Cons to Coal• We are running out (300 years?)• Creates air pollutants and greenhouse gases• SPECIFICALLY, it makes sulfur dioxide (SO2)- SO2 in the air decreases the pH of rainwater- creating ACID RAIN!