LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 3A: LAND USE CHANGE 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
which were directly allocated to a specific crop, based on the area additionally cultivated with the respective
crop relative to the overall expansion of agricultural land. It also includes estimated indirect LUC effects for
the replaced crops with an allocation based on expansion rates of replaced crops relative to the respective
national agricultural area (see also Ponsioen and Blonk, 2012).
Accounting (depreciation) periods for LUC can be either derived from isolated areas with LUC-emission
or from a global carbon view. For derivation of accounting periods, information on soil carbon cycling was
collected during a literature review; in order to obtain sound accounting periods which reflect the dynamics
in atmospheric carbon cycles, Hörtenhuber et al., (2011a) simulated the development of CO2 concentration
by using elements of an established method (Bern Carbon cycle model, Bern2.5CC; Joos et al., 2001).
Hörtenhuber et al., (2011a) suggested that 10 or 20 years may be used as suitable default values for accounting
periods for overall LUC-related emissions. The 10 year period includes the majority of LUC-related
emissions released from biomass and soils as well as of emissions remaining in the atmosphere, especially
for tropical regions with quicker processes. Twenty years are more feasible for temperate conditions with
their lower rates of CO2-release (Hörtenhuber et al., 2011a).
The productive period of farmland which originated from LUC is usually greater than one year, probably
at least within the magnitude of the duration which is needed to find a new equilibrium state of soil organic
carbon. Consequently and for the sake of simplification, we allocate CO2 which is rapidly released from
cleared biomass not only to the crops of the first year following LUC, but to the same time period accounted
for CO2 emissions from soil after LUC (see Hörtenhuber et al., 2011a). This constitutes an exemption to our
definition of restricting GHG accounting to physical fluxes. This is nevertheless justifiable, as it does not
create a new accounting period and is also in line with most CF standards (e.g. BSI, 2011). Thereby, punctually
emitted fluxes from above-ground biomass are distributed over a representative period of land use by
allocating the sum of emissions from cleared above- and below-ground biomass together with SOC losses to
the overall emitting period.
For exemplary model calculations following different approaches concerning LUC (see Fig. 1), a 20 years
period was used. GHG emission factors for the applied 20 years accounting period are derived from Hörtenhuber
et al., (2011b; Table 1). Emission from LU are estimated according to Hörtenhuber et al., (2010) for
Austrian average barley and based on Hörtenhuber et al., (2011a) for an average of Brazilian soybeans (no
specifical value for certified soybeans; for certification criteria see ProForest, 2004).
For classification and comparison of our product-specific LUC results, we use average global LUC emissions
according to Vellinga et al., (2011) and values for LUC (land transformation) and LU (land occupation)
derived from the land use impact method by Müller-Wenk and Brandão (2010), both presented in Table
1.
Vellinga et al., (2011) calculated global CO2-eq emission from LUC (5.8 Gt per year) per total agricultural
land used (4.9 * 10 9 hectare). This translates into 1,180 kg CO2-eq per ha and per year or 1.18 kg CO2eq
per kg crop if yield is 1,000 kg per ha.
For comparison of the method presented herein with the method of Müller-Wenk and Brandão (2010), we
introduced a few assumptions to the latter, which are based on Hörtenhuber et al., (2011b): emissions from
land transformation (LUC) are evaluated only for areas converted within the last 20 years with 39% and 10%
from tropical forest, 9% and 2% from savannah for average conventional and for certified Brazilian soybeans,
respectively (Hörtenhuber et al., 2011b). For Austrian barley this land transformation can be neglected
(Hörtenhuber et al., 2010, 2011b). Emissions from land occupation (defined as land use, which prevents
atmospheric CO2 to be sequestrated again) are fully counted as described in Müller-Wenk and Brandão
(2010). The land occupation results following Müller-Wenk and Brandão (2010) in Table 1 take into account
that soybean production is partially taking place on previous tropical forest land and partially in previous
grassland areas (we assumed three quarters of overall farmland for soybeans coming from savannahs/grasslands,
one quarter from tropical forests, but no difference between average Brazilian and certified
soybeans). For the case of previous (Brazilian) tropical forest areas converted to cropland, Müller-Wenk and
Brandão (2010) calculated 46.2 tons of C emitted from land transformation (LUC) over the whole time series,
resulting in 0.961 kg C per kg dry matter (DM) soybeans (with the assumption of a 20 years allocation
period). Analogous, for (Brazilian) crop land converted from tropical savannahs, they reported 18.0 tons of C
from LUC (0.374 kg C per kg DM soybean, assuming a 20 years period). Additionally, Müller-Wenk and
Brandão (2010) reported 1.48 and 0.37 tons C for land occupation (LU) per ha and year from previous tropical
forest and grassland, respectively.
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