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Characterisation Method Information
Characterisation Method Name:
Contributions to EF(po)
Version:
1997
Date Completed:
1997
Principal Method Name:
EDIP: photochemical ozone formation
Method Description:
When solvents and other volatile organic compounds are released to the atmosphere, they are often degraded within a few days. The reaction involved is an oxidation, which occurs under the influence of light from
the sun. In the presence of oxides of nitrogen (NO,), ozone can be formed. The oxides of nitrogen are not consumed during ozone formation, but have a catalyst-like function. This process is termed photo-chemical ozone formation.
The volatile organic compounds or VOCs are broken down especially in the troposphere, the lowest region of the atmosphere, to which they are emitted. The most significant man-made sources of VOCs are road transport with its emission of unburnt petrol and diesel and the use of organic solvents, e.g. in paints.
Ozone is an unstable gas with a half-life in the troposphere of a few weeks, and ozone formed in the troposphere thus cannot rise to the stratosphere and there counteract the depletion of the ozone layer, Despite ozone's short life, the ozone concentration in the troposphere rises by about 1% a year over most of the northern hemisphere, where
most VOC and N0x emissions occur. In the southern hemisphere, however, the ozone concentration in the troposphere is practically constant.
Ozone attacks organic compounds in plants and animals or materials exposed to air. This leads to an increased frequency of problems of the respiratory tract in humans during periods of photochemical smog in cities. For agriculture it causes a reduction in yield which for Denmark is
conservatively estimated to be about 10% of total production.
Photochemical ozone formation is an impact which affects the environment on both local and regional scales.


1 Deteimine which substances contribute to photo-chemical ozone formation

Crude oil contains hundreds of compounds which fulfil these criteria
The use of crude oil products can therefore lead to emission of very many different substances with a potential for photochemical ozone formation. The list of equivalency factors in right side is not exhaustive and therefore cannot be used alone as a basis for deciding which correspounds contribute to photochemical ozone formation.
The presence of oxides of nitrogen can be equally as important a man-made factor in photochemical ozone formation as emission of
VOCs. Despite this, a contribution from oxides of nitrogen to photo-chemical ozone formation cannot be calculated because the equivalency factor system used for calculation of ozone formation potentials does not facilitate calculation of an equivalency factor for NOx.
The significance of NO, for ozone formation is, however, reflected in the fact that two sets of equivalency factors are used - one for emissions of VOCs occurring in areas with a low background concentration of
NO, and one for emissions occurring in areas with a high background concentration of N0x.

2 Calculate the photochemical ozone formation potential

UNECE, the United Nations Economic Council for Europe, has established a committee to investigate transnational air pollution. For use in mapping the most significant sources of the rising ozone concentration ;
the troposphere and the increasingly more frequent episodes of photochemical smog, this committee applies factors which, for each individual compound, express the potential contribution to photochemical ozone
formation. These factors are called Photochemical Ozone Creation Potentials (POCPs). In the same way as the GWP values for global warming and the ODP values for stratospheric ozone depletion, the
POCP values express the ozone formation potential as an equivalent emission of a chosen reference substance. For photochemical ozone formation the reference substance is the gas ethylene (C2H2).

EF(po)=Contributions to ozone formation from gas(i)/contribution to ozone formation from C2H2

There is no international panel of experts for the environmental impact of photochemical ozone formation such as there is for global environmental impacts. Agreement among participating countries in the UNECE on using the POCP factor system is therefore the closest approximation to international recognition of any equivalency factor system for photochemical ozone formation.
The POCP values are calculated with the aid of atmospheric chemical models and a series of assumptions must be made on climatic conditions and the magnitude of the simultaneous emissions of a number of other VOCs and of Nox. The assumptions underlying the POCP values correspond to typical situations in areas with low and high background concentrations of Nox. The assumptions are discussed in the references presenting these POCP values (Andersson-Skold et aL,1992; Derwent &Jenkin, 1990).
A time scale must also be chosen for ozone formation in model calculations of POCP values. A POCP value for a short time scale of 24 hours describes the photochemical ozone formation immediately surrounding the place of emission corresponding to potential contribution to episodes of photochemical smog. For a longer time scale of e.g. a week,
most of the VOCs will be broken down and the POCP value provides a better expression of the total ozone formation potential. The right side presents POCP factors calculated for an intermediate time scale of 4-5 days.

In the references cited, POCP values have been calculated only for the individual VOCs of greatest significance for total photochemical ozone formation in Europe. But these are not necessarily the compounds of
greatest significance for the ozone formation potential in an LCA. For example, styrene will give a significant contribution to the ozone formation potential in the LCA of the polymer polystyrene, but none of the
references gives a POCP value for styrene. It can therefore be an advantage to be able to make an estimation of missing POCP values. Hauschild & Wenzel (1997a) describe various methods of estimating POCP values. As an example, a POCP value for styrene is estimated.
Emissions of VOCs will often figure in the inventory for a product system, without an indication of which individual compounds they are composed of. The composition can vary greatly for different sources, but
if the source of the VOC emission is known (e.g. "exhaust from petrolengined cars"), it may be possible in the right side list to find an average POCP value which is representative for the VOC mixture in question.

The average POCP values are calculated as a weighted average for the VOC mixture which is characteristic of the type of source in question. Weighted average POCP values can be calculated for other types of sources if the average composition of the source's VOC emission is known. For example, a weighted POCP for the aggregated VOC "source" "polystyrene production from oil to final polystyrene polymers" is calculated in Hauschild & Wenzel (1997a).
Literature Reference:
Henrik Wenzel, Michael Hauschild and Leo Alting (1997 ): Environmental assessment of products Vol. 1 Methodology, tools and case studies in product development London Chapman & Hall
Methodological Range:
Geographical range is Europe and Low NOx concentration is the precondition
Notes:

Existing Characterisation Factors of Contributions to EF(po)
Characterisation Parameter Category Indicator Impact Indication Principle Aspect Substance Quantity Unit Notes
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Methyl i-butyl ketone 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
O-xylene 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
M-xylene 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
P-xylene 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
1,2,3,-tri-metylbenzene 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
1,2,4,-tri-metylbenzene 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
O-ethyltoluene 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
M-ethyltoluene 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
P-ethyltoluene 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Methanol 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Butanol 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
1-pentene 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Propionaldehyde 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Butyraldehyde 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Valeraldehyde 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Dimethylether 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Propylene glycol methylether 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-butylacetate 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-heptane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-oktane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-propylbenzene 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-butane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Propylene 0.6 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Isobutane 0.6 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
CH4 0.007 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
CO 0.04 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Trichloroethylene 0.1 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Acrolein 0.8 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Benzene 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Isopropanol 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Isoprene 0.6 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Acetone 0.1 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-pentene 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-pentane 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-nonane 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-metylokane 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-decane 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-methylnonane 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-undecane 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-dodecane 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
1-butene 1 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2,2-dimethyl butane 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Toluene 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Methyl ethyl ketone 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-methylheptane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from food industry 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from surface coating 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from chemical cleaning of clothes 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from oil refining and distribution 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from natural gas leakage 0.02 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from coal mining 0.007 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from farming 0.04 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from power plant 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-butene(trans) 1 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from Diesel powered car, exhaust 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Acetaldehyde 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Acetylene 0.4 kg/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Chloroform 0.004 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Ethanol 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Ethylbenzene 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Ethylene 1 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Formaldehyde 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Propane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Ethyl acetate 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from controlled landfilling 0.007 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-methylbut-1-ene 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Ethane 0.1 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2,3-dimethyl butane 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-methyl hexane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
3-methyl hexane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
3-methyl pentane 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Methyl acetate 0.1 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-methyl pentane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Isopentane 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from combustion of wood or twigs 0.6 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Methylcyclohexane 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Methyl chloroform 0.002 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
2-methylbut-2-ene 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
3-methylbut-1-ene 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
1,2,5-trimethylbenzene 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Isopropyl acetate 0.2 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Isobutyl acetate 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Tetrachloroethylene 0.01 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
Isobutyraldehyde 0.3 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from petrol powered car, exhaust 0.5 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
VOC from petrol powered car, vapour 0.4 g/g
CFactor EF(po) EDIP/1997
Type = Emission
Direction = Output
Media = Air
Geography = *
N-hexane 0.5 g/g