During classification and characterization steps, the guidelines
presented below should be taken into consideration [29]:
1. Express LCIA results of different impact categories as equivalent values for midpoint level indicators (such as kg CO 2eq. for
global warming potential—GWP) or as damage values for endpoint level indicators (such as DALYs for human health and
PDF*m
2 *a for ecosystem quality impacts).
(a) It should be noted that the classification and characterization steps of all elementary flows are usually performed in
combined LCI/LCIA database packages or LCA software
and it would not be necessary to carry them out manually
[29]. Nonetheless, under any circumstances, it would still
be the responsibility of LCA practitioners to make sure of
their accuracy.
(b) It should also be noted that the choice of impact categories and the methods used for their evaluation are
regarded as the main sources of inconsistency
[32]. Based on the method used, the impact of a similar
impact category could be assessed in a different way. For
example, for land occupation impact category, terrestrial
area could be measured in dm
2 of occupied land on an
annual basis, i.e., dm
2 .a or in dm
2 of organic arable occupied land without a time range, i.e., dm
2 .org.arable
[31]. Another example would be emissions to air. More
specifically, the European Renewable Energy Directive
(RED) considers three gases, i.e., carbon dioxide, methane, and nitrogen dioxide, while ReCiPe method takes
93 gases into account [36]. In addition to that, it should
also be noted that these different gases are removed from
the atmosphere through chemical and biogenic processes
at different rates as well. For instance, methane has a
GWP100 of 28 CO 2 eq. and a GWP20 of 84 CO 2 eq
[37]. As a result of these differences, it would be difficult
to compare LCA studies for a similar unit process in algal
fuels production/use.
(c) It should be noted that inconsistencies also arise in LCI
owing to different energy sources taken into consideration
in input (such as renewable energy carriers, fossil-oriented
energy carriers, or combined) and output (such as biofuel
or biofuel along with co-products) balances [38]. Moreover, energy input sources such as direct (heat and electricity) and indirect (such as fertilizers, chemicals, and
system construction) energy perimeters on one hand and
the choices concerning the calculation base used (such as
primary or total energy base) on the other hand could
impact the LCA results obtained [39].
Life Cycle Analysis
135
presented below should be taken into consideration [29]:
1. Express LCIA results of different impact categories as equivalent values for midpoint level indicators (such as kg CO 2eq. for
global warming potential—GWP) or as damage values for endpoint level indicators (such as DALYs for human health and
PDF*m
2 *a for ecosystem quality impacts).
(a) It should be noted that the classification and characterization steps of all elementary flows are usually performed in
combined LCI/LCIA database packages or LCA software
and it would not be necessary to carry them out manually
[29]. Nonetheless, under any circumstances, it would still
be the responsibility of LCA practitioners to make sure of
their accuracy.
(b) It should also be noted that the choice of impact categories and the methods used for their evaluation are
regarded as the main sources of inconsistency
[32]. Based on the method used, the impact of a similar
impact category could be assessed in a different way. For
example, for land occupation impact category, terrestrial
area could be measured in dm
2 of occupied land on an
annual basis, i.e., dm
2 .a or in dm
2 of organic arable occupied land without a time range, i.e., dm
2 .org.arable
[31]. Another example would be emissions to air. More
specifically, the European Renewable Energy Directive
(RED) considers three gases, i.e., carbon dioxide, methane, and nitrogen dioxide, while ReCiPe method takes
93 gases into account [36]. In addition to that, it should
also be noted that these different gases are removed from
the atmosphere through chemical and biogenic processes
at different rates as well. For instance, methane has a
GWP100 of 28 CO 2 eq. and a GWP20 of 84 CO 2 eq
[37]. As a result of these differences, it would be difficult
to compare LCA studies for a similar unit process in algal
fuels production/use.
(c) It should be noted that inconsistencies also arise in LCI
owing to different energy sources taken into consideration
in input (such as renewable energy carriers, fossil-oriented
energy carriers, or combined) and output (such as biofuel
or biofuel along with co-products) balances [38]. Moreover, energy input sources such as direct (heat and electricity) and indirect (such as fertilizers, chemicals, and
system construction) energy perimeters on one hand and
the choices concerning the calculation base used (such as
primary or total energy base) on the other hand could
impact the LCA results obtained [39].
Life Cycle Analysis
135