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

PARALLEL SESSION 3C: SHEEP AND DAIRY PRODUCTION SYSTEMS 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
Greenhouse gas emissions from production of imported and local
cattle feed
Lisbeth Mogensen * , Troels Kristensen, Thu Lan T. Nguyen, Marie T. Knudsen
Dept. of Agroecology, Aarhus University, Blichers Allé 20, Postbox 50, DK-8830 Tjele, Denmark
Corresponding author. E-mail: Lisbeth.Mogensen@agrsci.dk
ABSTRACT
Emissions related to feed production are hotspots in milk production. In this paper, carbon footprint (CF) of different feedstuffs is
estimated, taking into account contribution from growing, processing, transport and land use change (LUC). Subsequently, the effect
of a ‘local’ versus an ‘import’ feeding strategy on the GHG emissions from feed was investigated. There were large variations in CF
of different feedstuffs and between concentrated feed and home grown roughage. When calculating CF of a complete feed ration for
cows by attributional LCA, the main reason for differences was related to contribution from transport, and especially from LUC.
However, if calculated by consequential LCA there was no differences between a ‘local’ and an ‘import’ strategy regarding GHG
emissions from feed production.
Keywords: animal feed, green house gas, transport, land use change, attributional and consequential LCA
1. Introduction
Studies of carbon footprint (CF) of milk have shown that 80-90% of the total greenhouse gas (GHG) emissions
are related to processes before the milk leaves the farm (Hermansen and Kristensen, 2011). On the
farm, methane emission from enteric fermentation gives the highest single contribution to CF of milk followed
by the emissions related to feed production (Kristensen et al., 2011). The hypothesis of the present
study was that by choice of feed, farmers can reduce CF of milk.
2. Methods
The aim of this paper is to 1) estimate carbon footprint (CF) of different feedstuffs for dairy cattle and 2)
compare two feeding strategies for dairy cows regarding GHG emissions from the feed production.
The functional unit (FU) is ‘1 kg dry matter (DM) of feed ready to eat’ (1) and for the comparison of the two
feeding strategies, the FU is ‘amount of feed for production of 1 kg milk (ECM)’ (2). The main system studied
was production of conventional grown fodder crops at dairy farms in Denmark. Besides that, a system
producing soybean from which soybean meal is extracted – assumed to be located in Brazil - was also included.
An attributional life cycle assessment (ALCA) approach has been used, handling co-products by economic
allocation and taking into account LUC which was quantified based on PAS2050 (BSI,2008). For comparison,
a consequential approach (CLCA) was applied, where co-products were handled by system expansion
and contribution from indirect LUC was estimated according to Audsley et al., (2009). The same inventory
data on the production of fertiliser, manure, diesel, and electricity were used for both ALCA and CLCA.
The rate of resource use, energy use and output in relation to growing 1 ha of different crops is presented in
Table 1. Regarding soybean, data related to growing the crop in Brazil were taken from Ecoinvent (2010).
For other crops, data represent Danish average production level.
Crop yield and input of fertiliser and manure
Data for crop yield and input of fertiliser for different crops are the national norms (Plantedirektoratet, 2010)
and correspond to the typical level found at Danish dairy farms (Kristensen et al., 2011). For the roughage
produced at the farm, manure produced at the same farm is used at a rate up to 170 kg total N/ha. The gap
between the input of 170 kg N from manure and N norm was assumed to be filled by supplying fertiliser N.
According to the national rules (Plantedirektoratet, 2010), 70% of N in cattle slurry could be utilised by the
plants. In relation to the issue of allocation of emissions burden created by the two sources, manure spreading
and manure in housing and storage, emissions from the former were fully allocated to crop production,
whereas those from the latter to the milk production. Barley and rape seed were assumed to be imported from
other Danish farms where they are grown without input of manure.
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