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
results published by Arrouays et al., (2002), this method proposes emission factors: -500 kg C/ha/yr for permanent
grassland up to 30 years old; -200 kg C/ha/yr for permanent grassland more than 30 years old. For
temporary grassland, the calculation considers a cycle of 5 years of grassland that emits -500 kg C/ha/yr,
followed by two years of annual crops that emit 1000 kg C/ha/yr. In this method emissions for annual crops
are 0 kg C/ha/yr. This method could not be implemented in Agri-BALYSE because it is in conflict with
IPCC recommendations, as it considers that permanent grassland (i.e. not resulting from LUC) sequesters C
under constant management.
Measured emission factors for permanent grassland and annual crops are also available in the literature
(Schulze et al., 2009; Soussana et al., 2009). We chose not to use them for two reasons: i) differences in the
methodologies used to determine them, which is contrary to the desired consistency for the Agri-BALYSE
LCI database; ii) difficulties to accurately identify the cause of this CO2 emission (LUC, management
change, increased atmospheric CO2 content,...).
In this paper, we focus on soil carbon dynamics resulting from direct LUC in mainland France. In Agri-
BALYSE, soil carbon dynamics for areas without LUC, i.e. resulting from changes in management practices,
could not be taken into account, as insufficient data on management of crops and grassland were available.
2. Methods
In collaboration with CITEPA, the French Interprofessional Technical Centre for Studies on Air Pollution
which is in charge of reporting French national greenhouse gas emissions, and ARVALIS, a technical institute
involved in Agri-BALYSE, two methods for estimating soil C dynamics from direct LUC were developed.
Both are based on the mass balance method described in IPCC 2003. The basics of these methods are
to compare soil C stocks at two dates (corresponding to two land use types) and allocate the carbon emissions
/ absorptions over the period between the two dates. IPCC gives a transition period of 20 years as a
standard. C flows can be estimated from LUC area and estimations of soil C stocks for the initial and final
land-use. Soil C dynamics are considered to be linear over the transition period. One important hypothesis of
the method is that temporary grassland is considered as an annual crop.
2.1. Construction of matrices
The first step of the calculation is the construction of matrices for LUC between permanent grassland and
annual crops.
In France, the Ministry of Agriculture implements a very large annual survey to monitor land use changes
over time. This program, named TerUti and TerUti-Lucas since 2005, provides the land cover and the land
use of more than 300,000 fields sampled across mainland France. The survey contains a detailed nomenclature
to characterise the land use of each field (Table 1), this nomenclature is based on two parameters: the
land cover which is strictly the physical occupation (grass, trees, etc.), and the land-use which describes human
activities. These definitions can differ from common understanding of grassland and cropland.
Table 1. Nomenclature for permanent grasslands and annual crops for the survey TerUti-Lucas.
Land cover codes Land-use codes
Annual crops
2110 (wheat) to 2530 (annual hay)
All
2730 (crop nursery) to 2742 (other crops)
All
6030 (bare soil)
111 to 114 (agriculture)
9999 (unknown)
111 to 112 (cultivation)
Permanent grass- 4020 (lands with bush and trees