12
F. Scrucca et al.
determined how the changes in the import demand of raw materials for tempered
glass and polycarbonate production, due to the increase in the market share of polycarbonate, affect the CF of both materials over long term. The results highlighted that
replacing tempered glass with polycarbonate does not produce significant changes
in terms of GHG emissions with ALCA approach, while under the long term consequential scenario, when the import of both materials respond consistently to the
change in demand in Singapore, the replacement causes a substantial increase in
GHG emissions.
In general, the influence of the selected approach on the CF results has been also
demonstrated in other research fields, such as biofuels [67], electric versus internal
combustion engines [10] and milk production [13], revealing that its choice should
be carried out on the basis of the LCA aims and clearly stated.
4.3 Impact of Land Use Change Emissions
In the CF analysis of agricultural and forestry commodities, an important source
of GHG emissions is related to the carbon stock changes due to land use change
(LUC), that is the conversion of land from one use to another use. In particular,
carbon emissions can be released directly (dLUC), accounting the conversion of the
original land use, or indirectly (iLUC), when current agricultural or forest production
is shifted to other areas which causes dLUC there. Since dLUC occurs within the
system boundaries of a given product, it can be included into the ALCA system model
while the inclusion of iLUC effects implies the shift towards the CLCA model. All the
CF standards, ISO/TS 14067, PAS 2050, and the GHG Protocol, are in agreement
that LUC emissions should be accounted for in a product’s CF if they are due to
a change in land management within a studied product system [51]. On the other
hand, none of them provide the accounting of iLUC emissions because of the lack
of a consensus methodology.
As regards the dLUC emissions, in the ISO/TS 14067 the calculation is based on
the IPCC Guidelines [28] which consider the direct changes in four carbon pools
(above ground biomass, below ground biomass, litter and deadwood, and soil carbon
stock); however, estimates of the size of these pools and the related changes typically
involve substantial uncertainty. Furthermore, another critical key hypothesis is the
amortization period used for LUC emissions, that is the period over which the GHG
emissions are linearly distributed for accounting [5]. IPCC Guidelines, as well as the
European Renewable Energy Directive (RED) [18], recommend to assume a time
horizon of 20 years, dividing LUC emissions equally across years. However, this
assumption does not reflect the real dynamics because the LUC disturbance generate
immediate GHG emissions, when associated to above and below ground biomass,
and long term GHG emissions, when associated to the soil [66].
The inclusion of dLUC is essential when the CF analysis concerns food, feed and
bioenergy products because it could deeply change final value of GHG emissions
[65]. Moreover, this remark is more relevant for developing countries than developed
F. Scrucca et al.
determined how the changes in the import demand of raw materials for tempered
glass and polycarbonate production, due to the increase in the market share of polycarbonate, affect the CF of both materials over long term. The results highlighted that
replacing tempered glass with polycarbonate does not produce significant changes
in terms of GHG emissions with ALCA approach, while under the long term consequential scenario, when the import of both materials respond consistently to the
change in demand in Singapore, the replacement causes a substantial increase in
GHG emissions.
In general, the influence of the selected approach on the CF results has been also
demonstrated in other research fields, such as biofuels [67], electric versus internal
combustion engines [10] and milk production [13], revealing that its choice should
be carried out on the basis of the LCA aims and clearly stated.
4.3 Impact of Land Use Change Emissions
In the CF analysis of agricultural and forestry commodities, an important source
of GHG emissions is related to the carbon stock changes due to land use change
(LUC), that is the conversion of land from one use to another use. In particular,
carbon emissions can be released directly (dLUC), accounting the conversion of the
original land use, or indirectly (iLUC), when current agricultural or forest production
is shifted to other areas which causes dLUC there. Since dLUC occurs within the
system boundaries of a given product, it can be included into the ALCA system model
while the inclusion of iLUC effects implies the shift towards the CLCA model. All the
CF standards, ISO/TS 14067, PAS 2050, and the GHG Protocol, are in agreement
that LUC emissions should be accounted for in a product’s CF if they are due to
a change in land management within a studied product system [51]. On the other
hand, none of them provide the accounting of iLUC emissions because of the lack
of a consensus methodology.
As regards the dLUC emissions, in the ISO/TS 14067 the calculation is based on
the IPCC Guidelines [28] which consider the direct changes in four carbon pools
(above ground biomass, below ground biomass, litter and deadwood, and soil carbon
stock); however, estimates of the size of these pools and the related changes typically
involve substantial uncertainty. Furthermore, another critical key hypothesis is the
amortization period used for LUC emissions, that is the period over which the GHG
emissions are linearly distributed for accounting [5]. IPCC Guidelines, as well as the
European Renewable Energy Directive (RED) [18], recommend to assume a time
horizon of 20 years, dividing LUC emissions equally across years. However, this
assumption does not reflect the real dynamics because the LUC disturbance generate
immediate GHG emissions, when associated to above and below ground biomass,
and long term GHG emissions, when associated to the soil [66].
The inclusion of dLUC is essential when the CF analysis concerns food, feed and
bioenergy products because it could deeply change final value of GHG emissions
[65]. Moreover, this remark is more relevant for developing countries than developed