34 research outputs found
A case study of the carbon footprint of milk from high-performing confinement and grass-based dairy farms
Life cycle assessment (LCA) is the preferred methodology to assess carbon footprint per unit of milk. The objective of this case study was to apply a LCA method to compare carbon footprints of high performance confinement and grass-based dairy farms. Physical performance data from research herds were used to quantify carbon footprints of a high performance Irish grass-based dairy system and a top performing UK confinement dairy system. For the USA confinement dairy system, data from the top 5% of herds of a national database were used. Life cycle assessment was applied using the same dairy farm greenhouse gas (GHG) model for all dairy systems. The model estimated all on and off-farm GHG sources associated with dairy production until milk is sold from the farm in kg of carbon dioxide equivalents (CO2-eq) and allocated emissions between milk and meat. The carbon footprint of milk was calculated by expressing the GHG emissions attributed to milk per t of energy corrected milk (ECM). The comparison showed when GHG emissions were only attributed to milk, the carbon footprint of milk from the IRE grass-based system (837 kg of CO2-eq/t of ECM)¬ was 5% lower than the UK confinement system (877 kg of CO2-eq/t of ECM) and 7% lower than the USA confinement system (898 kg of CO2-eq/t of ECM). However, without grassland carbon sequestration, the grass-based and confinement dairy systems had similar carbon footprints per t of ECM. Emission algorithms and allocation of GHG emissions between milk and meat also affected the relative difference and order of dairy system carbon footprints. For instance, depending on the method chosen to allocate emissions between milk and meat, the relative difference between the carbon footprints of grass-based and confinement dairy systems varied by 2-22%. This indicates that further harmonization of several aspects of the LCA methodology is required to compare carbon footprints of contrasting dairy systems. In comparison to recent reports that assess the carbon footprint of milk from average Irish, UK and USA dairy systems, this case study indicates that top performing herds of the respective nations have carbon footprints 27-32% lower than average dairy systems. Although, differences between studies are partly explained by methodological inconsistency, the comparison suggests that there is potential to reduce the carbon footprint of milk in each of the nations by implementing practices that improve productivity
Performance of novel VUV-sensitive Silicon Photo-Multipliers for nEXO
Liquid xenon time projection chambers are promising detectors to search for
neutrinoless double beta decay (0), due to their response
uniformity, monolithic sensitive volume, scalability to large target masses,
and suitability for extremely low background operations. The nEXO collaboration
has designed a tonne-scale time projection chamber that aims to search for
0 of \ce{^{136}Xe} with projected half-life sensitivity of
~yr. To reach this sensitivity, the design goal for nEXO is
1\% energy resolution at the decay -value (~keV).
Reaching this resolution requires the efficient collection of both the
ionization and scintillation produced in the detector. The nEXO design employs
Silicon Photo-Multipliers (SiPMs) to detect the vacuum ultra-violet, 175 nm
scintillation light of liquid xenon. This paper reports on the characterization
of the newest vacuum ultra-violet sensitive Fondazione Bruno Kessler VUVHD3
SiPMs specifically designed for nEXO, as well as new measurements on new test
samples of previously characterised Hamamatsu VUV4 Multi Pixel Photon Counters
(MPPCs). Various SiPM and MPPC parameters, such as dark noise, gain, direct
crosstalk, correlated avalanches and photon detection efficiency were measured
as a function of the applied over voltage and wavelength at liquid xenon
temperature (163~K). The results from this study are used to provide updated
estimates of the achievable energy resolution at the decay -value for the
nEXO design
Temporal and inter-specific variations in forage fish feeding conditions in the NW Mediterranean : lipid content and fatty acid compositional changes
We describe the total lipid content, lipid class composition and fatty acid profiles of
adult forage fishes (anchovy, sardine and sprat) sampled in the NW Mediterranean Sea in 2010
and 2011. Inter- and intra-species differences were mostly related to sampling period with limited effect of gender or total length. As an assemblage, total lipid content and relative levels of triacylglycerols and fatty acids 16:1n7, 20:5n3 and 14:0 in forage fish were highest in summer and autumn, indicating better feeding conditions and a more pronounced diatom-supported food web.
In contrast, total lipid content was lowest at the end of winter and spring, and coincided with high
levels of 22:6n3, indicating a more herbivorous diet based on dinoflagellates. Resource partitioning
and niche separation, as inferred from fatty acid profiles, were apparent between species. Sardine
showed a more diverse, temporally separated feeding strategy than anchovy, and dietary
overlap was higher in winter than summer with sardine having higher markers of copepods,
22:1n11 and 20:1n9. Sprat collected in winter occupied a separate niche area to both sardine and anchovy with higher total lipid content and carnivory biomarker 18:1n9. Our results show that the lipid dynamics of forage fishes can be used to gain quantitative insights into sub-system level
changes in species interactions, including prey and predator productivity