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

GROUP 2, SESSION A: CARBON OR WATER FOOTPRINTS, SOIL, BIODIVERSITY 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
722
46. Carbon footprint of Irish milk production
Ming-Jia Yan 1 , James Humphreys 2 , Nicholas M. Holden 1,*
1 UCD School of Biosystem Engineering, University College Dublin. Belfield, Dublin 4, Dublin, Rep. of
Ireland, 2 Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, County
Cork, Rep. of Ireland, Corresponding author. E-mail: nick.holden@ucd.ie
The objective of this paper was to calculate the carbon footprint (CF) of Irish milk production on commercial
dairy farms using life cycle assessment (LCA) to estimate the greenhouse gas (GHG) emissions to calculate
CF. LCA of milk production has been carried out on commercial farms in Europe using both national statistics
and ad hoc survey of farm-gate turnover. Most research has focused on comparing production types (e.g.
organic vs. conventional), however relatively little work has examined how detail of farm management may
influence CF.
In this paper, a four stage LCA was implemented following ISO 14040. The foreground data were based on a
survey of specialist dairy farms, and the background data were taken from the Ecoinvent database. The functional
unit was 1 kg energy corrected milk (ECM). Economic allocation was used for concentrate feed ingredients
at the pre-farm stage. Emission factors (EFs) were taken from relevant literature while the EF for enteric
CH4 was determined by estimating net energy for maintenance, lactation, and pregnancy. Global warming
potential of CH4 and N2O were taken as 25 and 298 times CO2 equivalent. The system boundary was set
at the farm gate and included production and transportation of fertiliser and concentrate feed and the on-farm
activity. Infrastructure and machinery, soil carbon sequestration, pesticides, medicine and minor consumables
were not included. In order to exclude on-farm activities not relevant to dairy production a proportioning
rule was devised. This was done by (1) converting all animals into livestock unit (LU) equivalents according
to the ratio of nitrogen excretion compared to a dairy cow as defined in the Irish “Statutory Instrument
(SI) No. 610 (2010)”; (2) assuming the dairy herd consisted of dairy cows + replacement animals +
bulls or suckler cows (if any), deriving the proportion factor of dairy herd as “dairy LU/total LU”; and (3)
excluding from the farm GHG inventory electricity production, which was predominantly used by dairy
herd, and multiply the rest by the proportion factor, and then adding back the electricity contribution to derive
the dairy unit GHG. After proportioning, economic allocation between milk and meat (from surplus
calves and culled cows) was performed based on farm sales records.
Much variation in the tactical management of the farms was found. For example, as much as 1.5-fold difference
in fertiliser N input to support the same stocking density, and up to 2 fold difference in concentrate feed
for a similar milk output per cow. The CF of milk production of the farms averaged 1.23 ± 0.16 kg
CO2 eq/kg ECM. CF was found to be correlated with various tactics using step-wise regression: milk per
cow, economic allocation factor (both P