Environmental Engineering Reference
In-Depth Information
TABLE 9.2
U.S. Federal Vehicle Emission Standards
Light-Duty Vehicles (Auto)
Light-Duty Trucks (Gasoline)
HC
CO
NO x
PM
HC
CO
NO x
PM
Model Year
(g/mi)
(g/mi)
(g/mi)
(g/mi)
(g/mi)
(g/mi)
(g/mi)
(g/mi)
1968
3.2
33
1971 a
4.6
47
4.0
1974
3.4
39
3.0
1977
1.5
15
2.0
1978
1.5
15
2.0
2.0
20
3.1
1979
1.5
15
2.0
1.7
18
2.3
1980
0.41
7.0
2.0
1.7
18
2.3
1981
0.41
3.4
1.0
1.7
18
2.3
1982
0.41
3.4
1.0
0.6
1.7
18
2.3
1985
0.41
3.4
1.0
0.6
0.8
10
2.3
1.6
1987
0.41
3.4
1.0
0.2
0.8
10
2.3
2.6
1988
0.41
3.4
1.0
0.6
0.8
10
1.2
2.6
1994
0.41
3.4
0.4
0.08
0.8
5.5
0.97
0.1
a Test method changed in 1971.
mineral matter in the fuel and on the combustion process. The emission rates of NO x , CO, and PM
would have to be measured at the stack exit.
For mobile sources the U.S. emission standards are given for four major pollutants that are
emitted from these sources: carbon monoxide, hydrocarbons (HC), oxides of nitrogen, and particu-
late matter (PM). Table 9.2 lists the emission standards for mobile sources. The units are grams/mile.
For NO x the units are reckoned in mass of NO 2 . Hydrocarbons include all carbonaceous emissions,
except carbon monoxide and dioxide, coming from the tailpipe and evaporative emissions from
the fuel tank, lines, pump, and injection devices. The hydrocarbon mass unit of measurement is the
molecular fragment HC.
Beginning with the Clean Air Act Amendments of 1977, and continuing with CAAA 1990,
the U.S. Congress required EPA to adopt a completely new way of regulating emission rates from
stationary sources. Instead of defining and measuring emission rates for each industrial category,
what is specified is the control technology that is presumed to achieve the desired emission standard.
Thus, a multitude of acronyms came into being, like BACT (Best Available Control Technology),
MACT (Maximum Achievable Control Technology), and RACT (Reasonable Available Control
Technology). Depending on the industrial category, the pollutant, and the quality of fuel, as well
as on the severity of pollution in an “airshed,” the EPA determines which control technology
needs to be installed on new sources. The CAAA 1990 went even further. For the control of
emissions of toxic pollutants and the precursors of photo-oxidants, the act requires that even
existing sources need the installation of emission control technology. This means retrofitting control
devices on older sources that in previous acts were “grandfathered.” For example, in power plants
that use coal in excess of 0.6% by weight of sulfur the BACT for SO 2 control is a wet limestone
scrubber; for coal with a lower sulfur content, it is a dry sorbent (usually limestone or lime) injection
(see Section 5.2.9.3). For NO x control the present federal BACT is a low-NO x burner (LNB), but
some states require for NO x control selective catalytic reduction or nonselective catalytic reduction
 
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