In 2000, recycling resulted in an annual energy savings of
at least 660 trillion BTUs, which equals the amount of energy
used in 6 million households annually. In 2005, recycling
is conservatively projected to save 900 trillion BTUs, equal
to the annual energy use of 9 million households.

What effects do waste prevention
and recycling have on global warming?

What materials are most commonly
recycled in the United States through collection programs?

US recycling rates for commonly recycled consumer goods in
2006 are listed below:

• Newspapers: 87.9%


• Corrugated Cardboard Boxes: 72.0%


• Steel Cans: 62.9%


• Yard Trimmings: 62.0%


• Aluminum Beer and Soft Drink Cans: 45.1%


• Magazines: 40.5%


• Tires: 34.9%


• Plastic HDPE Milk and Water Bottles: 31.0%


• Plastic Soft Drink Bottles: 30.9%


• Glass Containers: 25.3%

EPA's annually updated report, Municipal
Solid Waste in the US: 2006 Facts and Figures, describes
the national MSW stream based on data collected since 1960.
The historical perspective provided is useful for establishing
trends in the types of MSW generated and the ways in which
it is managed.

In addition to having high global warming
potentials, SF₆ and PFCs have extremely long atmospheric lifetimes,
resulting in their essentially irreversible accumulation in the atmosphere
once emitted (see below).

The definition of a GWP for a particular
greenhouse gas is the ratio of heat trapped by one unit mass of
the greenhouse gas to that of one unit mass of CO₂ over
a specified time period.

While the most current estimates
for GWPs are listed in the IPCC's Third Assessment Report (TAR),
EPA analyses use the 100-year GWPs listed in the IPCC's Second Assessment
Report (SAR) to be consistent with the international standards under
the United Nations Framework Convention on Climate Change (UNFCCC)
(IPCC, 1996

Hydrofluorocarbons (HFCs)

HFCs are man-made chemicals, many of which have been developed as alternatives
to ozone-depleting substances (ODS) for industrial, commercial, and consumer
products.

The atmospheric lifetime for HFCs varies from just
over a year for HFC-152a to 260 years for HFC-23.

The global warming potentials of HFCs range from 140 (HFC-152a)
to 11,700 (HFC-23).

Most of the commercially
used HFCs have atmospheric lifetimes less than 15 years; e.g., HFC-134a, which i sused in automobile air conditioning and refrigeration,
has an atmospheric life of 14 years.

The only significant emissions
of HFCs before 1990 were of the chemical HFC-23

Between 1978 and 1995, HFC-23
concentrations have increased from 3 to 10 parts per trillion (ppt), and
continue to rise. Since 1990, when it was almost undetectable, global
average concentrations of HFC-134a have risen significantly to almost
10 ppt (parts per trillion).

HFC-134a has an atmospheric lifetime of about
14 years and its abundance is expected to continue to rise in line with
its increasing use as a refrigerant around the world.

Perfluorocarbons (PFCs)

Primary
aluminum production and semiconductor manufacture are the largest known
man-made sources of two perfluorocarbons – CF₄ (tetrafluoromethane)
and C₂F₆ (hexafluoroethane).

The GWP of CF₄
and C₂F₆ emissions is equivalent to approximately
6,500 and 9,200 tonnes, respectively. PFCs are also relatively minor substitutes
for ozone-depleting substances (ODSs).

PFCs have extremely stable molecular structures and are largely immune
to the chemical processes in the lower atmosphere that break down most
atmospheric pollutants. Not until the PFCs reach the mesosphere, about
60 kilometers above Earth, do very high-energy ultraviolet rays from the
sun destroy them. This removal mechanism is extremely slow and as a result
PFCs accumulate in the atmosphere and remain there for several thousand
years.

The estimated atmospheric lifetimes for CF₄ and C₂F₆
are 50,000 and 10,000 years respectively.

Sulfur Hexafluoride (SF₆)

The global warming potential of SF₆ is 23,900, making it the
most potent greenhouse gas the IPCC has evaluated.

SF₆ is used for insulation and current interruption in electric power transmission and distribution equipment, in the magnesium industry to protext molten
magnesium from oxidation and potentially violent burning, in semiconductor manufacturing to create circuitry patterns on silicon wafers, and as a tracer
gas for leak detection.

Like the other high GWP gases, there are very few sinks for SF₆, so all man-made
sources contribute directly to its accumulation in the atmosphere. Measurements
of SF₆ show that its global average concentration has increased
by about 7% per year during the 1980s and 1990s, from less 1 ppt in 1980
to almost 4 ppt in the late 1990’s (IPCC, 2001).

In 2005, the weighted average combined fuel economy of cars and light trucks combined was 19.7 miles per gallon (FHWA 2006).

The average vehicle miles traveled in 2005 was 11,856 miles per year.