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

PARALLEL SESSION 2B: EMISSIONS MODELLING 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
perennial crops) from all calculated emission rates. This value, 0.529 kg N ha -1 yr -1 , is close to the annual
emissions from the native vegetation, i.e. forest (IPCC 2006).
The derived equations for estimating nitrous oxide (N2O) flux from mineral soils for perennial crops (Eq.
1) and for annual spring crops (Eq. 2) are therefore:
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N2O flux (kgN2O-N ha -1 yr -1 ) = 10 (-0.2762 + 0.002848 minN)-0.529 Eq. 1
N2O flux (kgN2O-N ha -1 yr -1 ) = 10 (-0.2762 + 0.002848 minN + 0.58) - 0.529 Eq. 2
These equations can be used to estimate the total emission from the field without dividing it between
emissions from applied N, crop residues and N mineralisation. Indirect nitrous oxide emissions were not
included in the field measurements and therefore need to be calculated separately.
To evaluate the new national method and to understand how it changes the results of Finnish climate impact
studies, comparisons were made at two levels; a simple case study on a potato product and a national
level estimate. Comparison was made with the IPCC 2006 method as it is proposed for use in Finnish carbon
footprinting guidelines (developed in Foodprint-programme). To allow comparisons, all emissions were converted
to CO2 equivalents by using the 100-year global warming potentials of 25 and 298 for CH4 and N2O,
respectively (IPCC, 2007).
The climate impact of packaged raw potatoes was first calculated according to IPCC 2006 method, including
liming, and direct and indirect nitrous oxide emissions from mineral and organic soils. Then the calculation
was repeated with the exception of applying the new national emission factor for nitrous oxide
emissions from applied N and crop residues from mineral soils. The cradle-to-logistic terminal study included
production of agricultural inputs, potato cultivation, processing, packaging, transport and storage. The
activity data were collected from one large Finnish potato marketer. The data from the cultivation stage were
collected from 2008-2010 and the sample covered nearly 60% of the producers. It should be noted that the
nitrogen fertiliser levels in the study were a little lower than average Finnish potato fertiliser levels. This was
likely due to the high level of specialisation of the farmers in potato cultivation. Data from processing (washing,
separation, packing) and transport to logistic terminal from all six producers were collected from 2010.
Neither carbon sequestration nor land use changes were taken into account due to lack of agreed methodology
and data.
The comparisons of national level direct nitrous oxide emissions were made between the new national
method and IPCC 2006 method. National statistics for cultivated area of different crops were used. Average
minimum and maximum total nitrogen fertiliser levels were defined to allow understanding of the magnitude
at low and high fertiliser levels. The levels were based on different farm statistics and the limits of the agrienvironmental
scheme. For cultivation area and fertiliser levels used in national level calculations, specific
data on the 25 most common crops and aggregated data of other crops were used.
It has to be noted that in the national level estimates the crop residues were only included regarding emissions
from mineral soils in national method calculations, as that was done automatically using new emission
factors, but not for the IPCC method calculations. However, the calculations should be comparable as emissions
from crop residues only account for around 5% of direct and indirect nitrous oxide emissions from
agricultural soils in Finland (Statistics Finland, 2012).
3. Results
To demonstrate the impact of the new national method for climate impact studies at product level, a case
study on a potato product was performed. The direct nitrous oxide emissions almost doubled with the new
national method compared with that of IPCC 2006. This means that the greenhouse gas emissions from cultivation
rose 46% and the total climate impact of packaged potatoes rose 25% (Table 1). Compared to the
IPCC default methods, the new national method indicated almost twice as large N2O emissions for many
common annual crops with relatively high fertiliser levels (such as grain crops). The case study shows that
application of the new national method has significant impacts at the product level, especially on low carbon
footprint products.