Average values for carbon footprint of sheep milk production
systems in Northern Spain ranges from 2.0 to 5.2 kg CO2eq/kg
FPCM, when soil carbon sequestration is not taken into account.
Results show that more intensive farms with higher amount of milk
production per sheep have lower carbon footprint values than more
traditional farms with less efficiency per animal (statistically significant). However, when soil carbon sequestration is included in
the assessment, the carbon footprint values decrease much more in
the lower productive farms due to highest C sequestration from
grazing practices. Carbon footprint values per kg FECM are still
higher, but there is no longer a statistically significant difference
between groups.
So far, there is no commonly accepted methodology to include
contribution from soil carbon sequestration in LCA. When different
methods were compared, the approach by Petersen et al. (2013),
based on actual data on C inputs and a 100 years' time perspective
as for GWP, seems to give more precise and realistic results and
allows for designing mitigation strategies with higher precision.
This study shows the importance of including soil carbon
sequestration in LCA, especially in farming systems where grasslands are a substantial resource for animal feeding with high potentials of carbon sequestration. Nevertheless, there is a need to
continue the development of strategies for a correct use and
improvement of grasslands. Higher inputs from crop residues and
manure increase the soil carbon sequestration. This study also indicates that grasslands used by extensive sheep farms plays an
important role as carbon sinks.