No other issue related to global warming is perhaps more misunderstood or misrepresented
than the relationship between the stated global warming potential (GWP) value of a substance
from automobiles, power generation, the exhalation of living creatures
and other sources. As a result, the impact (GWP x emissions)
of CO2 emissions on global warming is very high—despite a very
low GWP value.
Likewise, does a large GWP value always mean that the impact
of that gas on global warming is high? Not always. HFC-227ea
(CF3CHFCF3, 1,1,1,2,3,3,3-heptafluoropropane) is the most
widely employed clean fire protection agent worldwide. It has a
GWP value of 3220—does that mean that the use of HFC-227ea
in fire protection has a large impact on global warming? The facts
provide a clear answer of “No,” as evidenced by data from the
EPA1 and the EEA2 that indicates that the relative contribution
to global warming of the use of HFC-227ea in fire protection
applications is 0.04% and 0.06%, respectively. The volume in use
and the emissions of HFC-227ea in fire protection applications
are extremely low, and hence the impact on global warming is low,
despite the relatively high GWP of HFC-227ea.
The preceding two examples clearly show that GWP values
alone cannot be simply extrapolated as an indication of the relative
impact of a gas on global warming. Any attempt to regulate
global warming must consider the global market size and mass
of the compound released into the atmosphere, as well as the
compound’s GWP value.
Regulatory agencies should take into consideration this balance
between GWP value and the global market applications when
crafting regulatory decisions and in the rulemaking process. Regulatory
decisions are not based solely on the consideration of product
GWP values, but include consideration of the active use of a
product around the world, global market size, emissions in target
uses, product performance, safety and cost, as well as sustainability.
Today’s GWP regulations are an exercise in balancing many
competing factors to achieve the most beneficial environmental
results. GWP regulations are not the only environmental directives
in play, particularly for the aerosol propellants industry.
Volatile Organic Compounds
From an environmental perspective, ozone (O3), as described in
EPA literature,3 “can be good or bad, depending on where it is
found.”
In the stratosphere—the region of the atmosphere extending
from about six to 31 miles above the ground—ozone forms a
protective layer that absorbs potentially damaging ultraviolet (UV)
radiation. Depletion of this beneficial stratospheric ozone is what
created the “ozone hole” in the Antarctic.
In the troposphere—the region of the atmosphere extending
from ground level up to about six miles—ozone is a harmful air
pollutant and the main ingredient of photochemical smog. Tropospheric,
or ground level, ozone is formed by the chemical reaction
of nitrogen oxides (NOx) and Volatile Organic Compounds
(VOC) in the presence of heat and sunlight. VOCs are organic
chemicals with high vapor pressures at room temperature, allowing
them to readily vaporize; the term “volatile” refers to a substance
that vaporizes readily. Within the aerosol industry, many of the
most common ingredients of aerosol packaging are VOCs, including
fragrances, solvents and hydrocarbon-based propellants. HFC
aerosol propellants are not classified as VOCs.
HFC aerosol propellants
HFC aerosol propellants provide enhanced solubility, high chemical
and thermal stability, high material compatibility and low toxicity,
making them useful formulating tools for the aerosol industry.
The HFC aerosol propellants include HFC-227ea, HFC-134a and
HFC-152a, and their properties are compared in Table 1.
Table 1: HFC Aerosol Propellants
Propellant Chemical Boiling Vapor Pressure
Structure Point (oF) at 70 oF (psig) GWP
HFC-152a CH3CF2H -13 63 124
HFC-134a CF3CH2F -15 71 1300
HFC-227ea CF3CHFCF3 2.6 44 3220
HFC-227ea is employed as a propellant in pharmaceutical metered
dose inhalers (MDIs), and has limited, if any, uses in consumer
aerosol products. Current global warming regulations allow the
use of HFC-227ea as a propellant in MDIs and, despite the robust
GWP value, this application is expected to continue into the
foreseeable future.
While HFC-134a is primarily employed as a propellant in
MDIs, it has also been used in some consumer aerosol products.
The EPA Significant New Alternatives Policy (SNAP) Rules 20 and
21 proposed to restrict the use of HFC-134a in aerosol products,
except for certain critical uses, including MDIs. Although Rules
20 and 21 were partially vacated in the courts, California, Vermont
and Washington State each have legislation prohibiting the
use of HFCs consistent with the Federal SNAP Rules 20 and 21.
Additionally, as of Jan. 1, 2019, Canadian regulations prohibited
the use of HFCs with a GWP greater than 150, also limiting
the use of HFC-134a in aerosol propellants to critical uses. The
aerosol industry has been successful in reformulating many of the
products previously using HFC-134a.
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and its actual impact on global warming...
Depletion of beneficial stratospheric ozone is what created the “ozone hole”
in the Antarctic.