Environmental Engineering Reference
In-Depth Information
Examples of LCI data
(sources)
Midpoint impact
categories
Endpoint impact
categories
Ammonia (NH
4
)
Climate change
Human health
Carbon dioxide (CO
2
)
Chlorofluorocarbons (CFCs)
Stratospheric ozone
depletion
Hydrochloric acid (HCl)
Hydrochlorofluorocarbons (HCFCs) Acidification
Methane (CH
4
)
Biotic and abiotic
natural environment
Methyl bromide (CH
3
Br) Photochemical smog
Nitrates (NO
3
-
)
Nitrogen oxides (NO
x
)
Eutrophication
Non-methane hydrocarbon (NMHC)
Phosphate (PO
4
-3
)
Terrestrial toxicity
Biotic and abiotic
natural resources
Sulfur oxides (SO
x
)
Quantity disposed of in a landfill
Aquatic toxicity
Quantity of fossil fuels used
Quantity of minerals used
Land use
Releases to air, water, and soil
Water used or consumed
Biotic and abiotic
man-made resources
Water use
Figure 4.6
Impact categories from the life cycle inventory assessment commonly used for food-production
systems with midpoint and endpoint categories. For the purpose of clarity, just few arrows are depicting the
relationship among some sources, midpoints, and endpoint categories.
Adapted from Jolliet et al., 2004, and EPA, 2006.
category to establish relative impacts (EPA, 2006). Impact indicators are calculated using
the following equation:
Impact indicator
=
Inventory data
×
Characterization factor
[4.1]
For instance, different greenhouse gases can be expressed in terms of equivalent carbon
dioxide by multiplying the amount from the inventory data by a characterization factor and
then combining the results in an overall global warming potential (GWP) indicator (EPA,
2006). As an illustration, carbon dioxide (CO
2
) has a GWP of 1 because it is the reference.
In reference to carbon dioxide, methane (CH
4
) has a 100-year GWP of 23 and nitrous oxide
(N
2
O), 296 (IPCC, 2001). Therefore, if the emission per functional unit is 100 kg of methane
and 10 kg of nitrous oxide, then:
CH GWP impact, 23
×
100 kg
=
2,300
4
N O GWP impact, 296
×
10 kg
=
2, 960
2
Total GWP impact
5,260
Step 4: presentation of data after characterization
After the characterization and before the optional elements of steps 5, 6, and 7, data generated
in the previous three steps needs to be compiled and presented as:
an LCIA profile containing category indicator results for different impact categories,
●
an inventory of elementary flows that have not been assigned to impact categories,
or
●
a set of data that does not represent elementary flows.
●
