Key Issue Three:Why are resources reusable?

• 1. Renewing resources• 2. Renewable energy sources• 3. Uses for renewable energy• 4. Recycling resources• 5. Collection • 6. Pollution reduction strategies

Garbage Dump outside

São Paolo, Brazil

Poor children pick through the garbage dump for items that can be sold.

Solar energy• Growth is limitless (Sun’s remaining life estimated at 5

million years), it’s free, and equally distributed, harnessing the Sun’s energy doesn’t damage the environment

• Two types:• 1. Passive solar energy: capturing solar energy without

special devices• EX: greenhouse• 2. Active solar energy: collecting solar energy and

converting it to heat energy or electricity• Using photovoltaic cells

• Drawback? Very expensive to set up infrastructure for active solar energy

Hydroelectricity Production

Fig. 14-16: Percent of electricity from hydroelectric power. Many countries in South America and Africa depend heavily on hydroelectric power.

The Three Gorges Dam

The Three Gorges Dam on the Yangtze River in China will be the world’s largest dam when it is completed. It has had many environmental impacts.

• Three Gorges Impact

U.S. Wind Power Potential

Fig. 14-17: Winds are strong enough to support substantial wind power generation in the U.S. Plains as well as other regions in some of the East and much of the West.

Wind Turbines in Spain

A wind farm in Tarifa, Andalucia, Spain.

Recycling resources

• As a result of recycling, about 79 million of the 238 million tons of solid waste generated by the U.S. in 2005 didn’t have to go to landfills and incinerators.

• Once recycled products are cleaned and separated, they are ready to be manufactured into a marketable product.

• Obstacles:• Especially in recycling plastics, different plastic types can’t be

mixed or it can ruin the melt.• Only certain metals are accepted in recycling, esp. aluminum• Perceived cost of recycling?

• http://www.time.com/time/photogallery/0,29307,1934183_1980312,00.html

Other Pollution reduction strategies• Reducing discharges – • Preferred method • Lowering the amount of pollutants emitted into the air, such

as reducing levels of lead in gasoline (unleaded), and instituting maximum emissions levels.

• Emissions-trading systems – companies can “buy” and “sell” emissions from other companies

• a.k.a. “cap and trade”• EX: Emissions cap set at “Z parts per million”• Company “X” emits Z-100 parts per million, so they have

an extra 100 units that they can sell• Company “Y” emits Z+100 parts per million, so they need

an extra 100 units

Pollution Reduction at a Coking Plant

Fig. 14-18: A coking plant illustrates alternatives for reducing pollution, including: recycling discharges; reducing waste discharges; and increasing environmental capacity.

Other Pollution reduction strategies

• Increasing environmental capacity to absorb waste:

• Ability of the environment to absorb waste varies in different locations and at different times, but is obviously limited.

• Example: a deep, fast-flowing river has a greater capacity to absorb wastewater.

• Problem: Dispersing, rather than reducing waste, so does it really solve the problem?

Key Issue Four:Why can resources be conserved?

• Why can resources be conserved?• Sustainable development

• Sustainability and economic growth• Critics of sustainability

• Biodiversity• Biological and geographic biodiversity• Biodiversity in the tropics

Sustainable development

• Sustainability: development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

• Sustainability and economic growth• Can they happen together?

• As a society increases their level of development, they also usually increase their pollution levels, up to a certain point.

• Critics of sustainability• Some critics claim that the world has already surpassed its

sustainable level• World Wildlife Fund

• Some critics claim that resource availability is unlimited.