Waste and Recycling

Alexis Aberle

CBE 555

Spring 2008

Outline

• Overall recycling information

• Recycling regarding– Plastics– Glass – Aluminum – Steel– Paper

General Recycling

• Americans generated 251 million tons of trash and recycled 81 tons of materials, at rate of 32.5% (2006)

• This saved the energy equivalent of more than 10 billion gallons of gasoline

• Of the generation rate of 4.6 pounds per person per day, 1.5 pounds was recycled

• 2.4 million tons more than 2005 was recycled in 2006• 3 pounds per person per day was thrown away excluding

composting• By recycling 7 million tons of metals, greenhouse gas

emissions were eliminated close to 6.5 million metric tons of carbon equivalent (MMTCE).– Equivalent to removing 5 million cars from the road for a year!

2006 MSW Figures

Sources of Waste

MSW Generation

Number of Landfills

Solid waste

Two types of plastics

• Thermoplastics– Characterized as meltable– Have repeat units as unit cells– Hydrocarbons make monomers and then monomers are joined

to make polymers– Hydrocarbons are separated from natural gas, petroleum, or

coal into pure streams of chemicals– Benzene and xylene can be isolated from petroleum and reacted

to form monomers for polystyrene– Polymerization

• Addition reactions: catalyst added, usually peroxide, causing one monomer to link to next. No byproducts

• Condensation reaction: catalysts make monomers react with other monomers. Creates byproduct, usually water

Thermoset plastics

• When the connection of carbon atoms forms two and three dimensional networks

• Not meltable• Created by user mixing two chemicals and immediately

using mixture before it “sets up”

Plastics

• PET: Polyethylene Terephthalate

• HDPE: High density polyehtylene

How plastics are recycled• 1. Inspection

– Plastic is inspected for contaminants like rocks, glass, and plastics that cannot be recycled

• 2. Chopping and washing– The plastic is washed and chopped into flakes. If the plastic is

mixed, they are put into a flotation tank, where some float and others sink

• 3. Drying– The plastic flakes are dryed in a tumble dryer. The flakes are fed

into an extruder, where heat and pressure are used to melt the plastic.

• 4. Filtering– The molten plastic is put through a screen to remove any

contaminants that made it through the washing• 5. Pelletizing

– The strands are cooled in water and chopped into uniform pellets.

Using Waste Effectively

• Waste-to-energy plants: like coal-fired power plants

• Garbage is burned to produce heat, then heat is used to make steam. The steam turns blades of turbine generator to produce electricity

• 2000 pounds waste reduced to 300-600 pounds of ash

• 600 plants in 35 countries• US: 14% of waste is burned• It takes 2000 lbs of waste to

equal the heat energy in 500 lbs of coal

How Long to Disappear?

Diaper 500-600 years

Sock 5-6 months

Styrofoam cup 106 years

Glass bottle 106 years

Leather belt 40-50 years

Wooden block 10-20 years

Paper box 1-2 months

Aluminum can 200-500 years

Water bottle growth: Increased recycling?• Only 12% of “custom” plastic

bottles, dominated by water bottles, were recycled in 2003

• About 40 million bottles a day thrown as trash

• Soft drink bottles recycle rate ~30%

• Recycling would reduce the amount of petroleum consumed

Recycling law?

• Four out of five bottles are recycled in states with recycle laws

• 11 states have bottle bills but only 3 include water bottles

• MI: 95% recovery rate for deposit containers

• Cargill and Dow Chemical: invented water bottles from biodegradable plastic from corn starch – degrades in 80 days

Recycling Plastic Bags

• 40% less energy to manufacture than paper bags• For 1 truck to deliver plastic bags, 7 are needed to

deliver paper bags, reducing emissions• 91% less energy to recycle plastic than paper bags• Generate 80% less waste than paper• Consumes less than 4% of the water needed to make

paper bags• 65% of Americans reuse plastic bags for waste disposal• 80% of polyethylene is produced from natural gas• Grocery stores have collection programs for bags

Household Waste

• Glass: 7% in 2001. 2.5 million tonnes was land filled

• 8.6*109 kWh of energy consumed

• CO2 emissions 1.8 million tonnes from fossil fuels burnt in factories

Glass

• Accounts for 5% of MSW stream• Recycling glass to make new glass requires 40% less energy• Crushed glass, called cullet, melts at lower temperature than raw

materials to make glass, reducing energy• New glass raw materials:

– Soda ash

– Limestone

– Sand

• Recycled glass can be made into new glass or fiberglass insulation• Colored glass protects food and beverages from sunlight but the

colors must be separated before recycling

Some glass not recyclable

• Light bulbs • Ceramics • Glass mirrors• Windowpanes

• Dishes • However, these items are

not problematic because they do not make up our trash like glass bottles do!

Why Recycle?

• Recycling two glass bottles saves enough energy to boil water for five cups of tea

• For every ton of recycled glass used, 1.2 tons of raw materials are preserved

• Reduces the amount of waste put in landfills• Reduces demand for raw materials• Most bottles and jars contain 25% recycled glass• Over a ton of resources saved for every ton glass

recycled:– 1330 pounds of sand– 433 pounds soda ash– 433 pounds limestone– 151 pounds feldspar

More facts…

• A ton of glass produced from raw materials produces 384 pounds mining waste. Using 50% recycled glass cuts this by 75%. 27.8 pounds of air pollution produced for every ton new glass made

• Recycling reduces that pollution by up to 20%• Saves 25-32% of energy • The average American can save 6 pounds glass per

month• States with bottle deposit laws have 35-40% less litter by

volume

Aluminum production process

• Aluminum only exists in combination with other elements, usually oxygen, forming alumina

• To free the aluminum, the alumina must be stripped of oxygen

• Alumina is put into large pots and dissolved in molten salt

• An electric current is run through the liquid to separate the aluminum from oxygen

• Molten aluminum sinks to the bottom of the pots• Making a pound of aluminum from bauxite ore takes 7.5

kWh of electricity• When made from recycled aluminum scrap takes only

4% of the energy.

Recycling Aluminum

• Saves 95% of energy needed to make aluminum from bauxite ore

• 1500 cans recycled every second in America. 90 billion aluminum cans used in 2003. 65% was recycled

• Cuts air pollution by 95%• Americans throw away enough aluminum every three

months to rebuild our entire commercial air fleet.• Paper grocery bag holds 1.5 pounds empty cans• Recycling 4 aluminum cans saves as much energy as

the energy in 1 cup of gasoline• 1 ton of aluminum cans conserves 207 million BTUs

– Equivalent of 36 barrels of oil, or 1655 gallons of gasoline

Steel

• Avg. US family uses 90 pounds of steel a year• Recycling would save:

– 144 KWh of electricity– 63 pounds of coal– 112 pounds of iron– 5.4 pounds limestone

• Steel made from iron ore much like aluminum in that it must be stripped of oxygen

• Takes 60% less energy to make steel from recycled materials than from scrap

How it is recycled

• Special magnetic belts are used to separate steel from solid waste stream

• After collected from homes, recycling centers, or waste-to-energy plants, it is shipped to a company that buys steel

• Steel is then melted in a furnace and poured into casters that continuously roll and flatten steel into sheets

• Recycled steel can be made into new cars, girders for buildings, or new food cans

• In US, steel cans are at least 25% of recycled steel

Paper

• The number one waste!• For 100 pounds of trash, 35

pounds is paper• More than a third of all paper

recovered in the world is done so in the US

• 50% of all paper recovered in 2003

• Corrugated containers account for 50% of recovered paper

• 50% of energy to make paper is from wood scraps leftover

Recycled paper

• Recycled paper must be deinked– Removes fillers, clays, and fiber fragments

• If paper is waxed, gummed, or pasted it is usually not recycled because the process is too expensive

• Old newspapers: made into newsprint, egg cartons, or paperboard

• Office paper can be made into any paper product• New paper is usually mixed with recycled paper. Cannot

be made purely from recycle because the fibers get too weak

• Cardboard boxes: usually 50% new and 50% recycled

Conservation

• Recycling a ton of paper from recycled fiber instead of virgin fibers saves:– 7000 gallons of water– 17-31 trees– 4000 KWh of electricity– 60 pounds of air pollutants– 450 gallons of oil– 3 cubic yards of landfill space

Resources

• http://www.eia.doe.gov• http://

www.americanchemistry.com/s_plastics/doc.asp?CID=1102&DID=4665

• http://www.cityofinglewood.org/pdfs/pw/recycling_facts.pdf

• http://www.gpi.org/recycling/• http://www.vitalgraphics.net/waste/html_file/24-25_munic

ipal_trashbin.html• http://www.epa.gov/garbage/pubs/msw06.pdf