Earth’s Changing Environment Lecture 4 Improving Air Quality.

Earth’s Changing Earth’s Changing EnvironmentEnvironment

Lecture 4Lecture 4

Improving Air QualityImproving Air Quality

Emission of PollutantsEmission of Pollutants

Point Source Point Source Non-point SourceNon-point Source

Emissions From AutomobilesEmissions From Automobiles(non-point source)(non-point source)

Automobile Emission Automobile Emission StandardsStandardsSet by EPASet by EPA

(g/mile)(g/mile)

PollutanPollutantt

19751975 19901990 19981998

VOCVOC 3.43.4 0.410.41 0.250.25NOxNOx 3.13.1 1.01.0 0.400.40COCO 3434 3.43.4 3.43.4

How are emission standards How are emission standards achieved?achieved?

Catalytic ConverterCatalytic Converter

Converts VOC, CO, NOx -> H2O, N2, O2, CO2Converts VOC, CO, NOx -> H2O, N2, O2, CO2 Catalysts are platinum, palladium, rhodium or Catalysts are platinum, palladium, rhodium or

a ceramic.a ceramic. Add $500 to cost of car.Add $500 to cost of car.

Mathematical Example 1Mathematical Example 1 There are 220 million cars, light trucks, There are 220 million cars, light trucks,

vans, and SUVs on the road in the US.vans, and SUVs on the road in the US. Estimate the approximate national Estimate the approximate national

investment in catalytic converters.investment in catalytic converters.

2.2 x 102.2 x 1088 vehicles x 5.0 vehicles x 5.0 x 10x 1022 $/vehicles $/vehicles = 11 x = 11 x 10108+28+2 $ = 11 x $ = 11 x 10101010 $ = 110 x $ = 110 x 101099 $ $ = $110 billion (Compare to trillions in vehicles)= $110 billion (Compare to trillions in vehicles)

Mathematical Example 2Mathematical Example 2 There are 220 million cars, light trucks, vans, and There are 220 million cars, light trucks, vans, and

SUVs on the road in the US.SUVs on the road in the US. Each vehicle travels an average of 13,000 Each vehicle travels an average of 13,000

mi/year.mi/year. By what amount were NOx emissions reduced by By what amount were NOx emissions reduced by

switching from the 1975 to the 1998 standard?switching from the 1975 to the 1998 standard?

2.2 x 102.2 x 1088 vehicles x 1.3 x 10 vehicles x 1.3 x 1044 mi/vehicle x (3.1-0.4) g/mi mi/vehicle x (3.1-0.4) g/mi = 7.7 x = 7.7 x 10108+48+4 g = 7.7 x g = 7.7 x 10101212 g = 7.7 x g = 7.7 x 101099 kg kg = 7.7 x = 7.7 x 101066 MT (metric tons)MT (metric tons) Would still emit 1.1 million metric tons. Would still emit 1.1 million metric tons.

Command and Control Command and Control StrategyStrategy

Automobile emission standards are an Automobile emission standards are an example of the “Command and example of the “Command and Control” strategy. Emission standards Control” strategy. Emission standards are set and enforced by EPA.are set and enforced by EPA.

Tailpipe Emissions Tailpipe Emissions TestingTesting

in San Antonioin San Antonio     Tailpipe Emissions Testing is still being Tailpipe Emissions Testing is still being

considered for SA.considered for SA. $40 per vehicle annually.$40 per vehicle annually. Strongly opposed by the local community.Strongly opposed by the local community.

Mathematical Example 3Mathematical Example 3 There are 1 million cars in SA.There are 1 million cars in SA. Each vehicle travels an average of 13,000 mi/year.Each vehicle travels an average of 13,000 mi/year. Assume 90% of cars meet the 1998 NOx standard, but Assume 90% of cars meet the 1998 NOx standard, but

10% only meet the 1975 standard.10% only meet the 1975 standard. How many tons of NOx does each group of cars emit?How many tons of NOx does each group of cars emit?

0.90 x 1 x 100.90 x 1 x 1066 vehicles x 1.3 x 10 vehicles x 1.3 x 1044 mi/vehicle x 0.4 g/mi mi/vehicle x 0.4 g/mi = 0.46 x = 0.46 x 10106+4 6+4 g = 4.6 x g = 4.6 x 101099 g = 4.6 x g = 4.6 x 101033 metric tonsmetric tons 0.10 * 1 x 100.10 * 1 x 1066 vehicles x 1.3 x 10 vehicles x 1.3 x 1044 mi/vehicle x 3.4 g/mi mi/vehicle x 3.4 g/mi = 0.44 x = 0.44 x 10106+4 6+4 g = 4.4 x g = 4.4 x 101099 g = 4.4 x g = 4.4 x 101033 metric tonsmetric tons So, 10% of the cars emit half the pollution.So, 10% of the cars emit half the pollution.

Have EPA Strategies Worked for Have EPA Strategies Worked for

Pollution Emission by cars?Pollution Emission by cars?

PollutanPollutantt

19701970 20012001

VOCVOC 16.9 (41*)16.9 (41*) 4.94.9NOxNOx 11.5 (28*)11.5 (28*) 8.28.2COCO 163 163

(400*)(400*)7575

Emission by On-Road Vehicles ( million short Emission by On-Road Vehicles ( million short

tons)tons)

• Estimate of current value with no pollution control program, business as usual. Estimate of current value with no pollution control program, business as usual.

Assuming 143 percent increase in vehicle miles. Assuming 143 percent increase in vehicle miles.

Emissions From Power PlantsEmissions From Power Plants(point sources)(point sources)

Power Plant EmissionsPower Plant Emissions

• 1970 power plant emission 17 million tons1970 power plant emission 17 million tons• Acid Rain Program set 9.0 million ton cap Acid Rain Program set 9.0 million ton cap by 2010by 2010 • Use Cap and Trade strategy.

Cap and TradeCap and Trade

• To reduce SO2 emissions from 3,208 Electric To reduce SO2 emissions from 3,208 Electric Utilities.Utilities.• Utilities are assigned allowances - permission Utilities are assigned allowances - permission to emit a ton of sulfur dioxide to emit a ton of sulfur dioxide • Utilities can sell unused allowances or carry Utilities can sell unused allowances or carry them over into the next year.them over into the next year.

ScrubbersScrubbers

• Flue-gas desulfurization passes exhaust gas Flue-gas desulfurization passes exhaust gas through slurries of limestone (calcium through slurries of limestone (calcium carbonate) to form calcium sulfates and carbonate) to form calcium sulfates and removing the SO2. Disposing of the calcium removing the SO2. Disposing of the calcium sulfates is a problem.sulfates is a problem.

Other TechniquesOther Techniques

• Tall ChimneysTall Chimneys• Using Low-Sulfur coalUsing Low-Sulfur coal• Fluidized Bed Combustion – mixes limestone in Fluidized Bed Combustion – mixes limestone in the boilerthe boiler

EconomicsEconomics

• Cost of Scrubber: $50 to $80 per installed kWCost of Scrubber: $50 to $80 per installed kW• San Antonio’s Electric Utility, CPS, has 1,425 San Antonio’s Electric Utility, CPS, has 1,425 MW capacity in coal-burning plantsMW capacity in coal-burning plants• Assuming $50 per installed kW, estimated the Assuming $50 per installed kW, estimated the cost of scrubbers for this total capacitycost of scrubbers for this total capacity..

• $50 x 1,425,000 kW = $70 million$50 x 1,425,000 kW = $70 million

New Source ReviewNew Source Review NSR states that if a plant makes any NSR states that if a plant makes any

modifications to its operation that increases its modifications to its operation that increases its pollution emissions, it must install state of the pollution emissions, it must install state of the art or best available emissions control art or best available emissions control equipment. equipment.

The Bush Administration has recently asked for The Bush Administration has recently asked for changes in EPA policy that would make it easier changes in EPA policy that would make it easier for power plants to make modification in older for power plants to make modification in older plants without installing new equipment.plants without installing new equipment.

An appeals court ruled in favor of An appeals court ruled in favor of environmental groups and 14 states. These rule environmental groups and 14 states. These rule changes have been blocked.changes have been blocked.

The Clean Air Act Worked!The Clean Air Act Worked!

Emissions have declined.Emissions have declined.

Air Quality has improved.Air Quality has improved.

But, ozone improvements have But, ozone improvements have leveled off.leveled off.

Because VOCs declines have Because VOCs declines have slowed.slowed.

50% of NOx emissions are from autos and 50% of NOx emissions are from autos and this has leveled off.this has leveled off.

22% of NOx emissions are from power plants 22% of NOx emissions are from power plants and this has declined by 22%.and this has declined by 22%.

What about Acid Rain?What about Acid Rain?

SO2 emissions have SO2 emissions have declined.declined.

NOx emissions from power plants have NOx emissions from power plants have declined, but emissions from other declined, but emissions from other sources have not declined as much.sources have not declined as much.

Sulfate Deposition has decreased Sulfate Deposition has decreased dramatically.dramatically.

Nitrogen Deposition has changed little.Nitrogen Deposition has changed little.

ConclusionsConclusions

Clean Air Act has been very Clean Air Act has been very successfulsuccessful

But, Ozone problems persist.But, Ozone problems persist. Acid rain problems persist.Acid rain problems persist. NOx emission from autos is a major NOx emission from autos is a major

contributor to these problemscontributor to these problems