Environmental impacts along intensity gradients in Norwegian dairy production as evaluated by life cycle assessments
Introduction
Food production represents a significant contribution to the global environmental burden, and impacts from ruminant husbandry are of special concern (e.g. Janzen, 2011, Lesschen et al., 2011). The relationship between the production intensity and the environmental impacts per unit of milk and beef produced has recently been widely analyzed and debated in the international scientific literature, mostly in terms of the global warming potential (GWP) of the production (e.g. Crosson et al., 2011, Hermansen and Kristensen, 2011, Weiss and Leip, 2012, Bellarby et al., 2013). When using the cowshed as the system boundary, high yields per animal and high feed efficiency lower the burden (per unit produce) from enteric methane production. However, expanding the boundaries to include also the feed production chains, may change the picture, since large emissions related to the production of energy- and protein-rich feed for the high yielding animals may undermine the benefits of high animal yields. Few recent studies of dairy production have included all processes and inputs to the forage production chain (Baldini et al., 2017).
In life cycle assessment (LCA) studies, emissions related to the production and acquisition of all major inputs in a production are normally accounted for, such as the feedstuffs used in dairy production. In LCA and other modelling work based on real farm data, the relation between GWP per unit milk and the production intensity, expressed as the average herd milk yield, appears, however, to be ambiguously negative. Gerber et al. (2011) and Vellinga et al. (2011) found no significant relationship above milk yields of 6000–7000 kg energy corrected milk (ECM) per year and head, and in the study of Bonesmo et al. (2013), the measures were not correlated at all. On the other hand, in a recent LCA of intensive dairy farms in Italy (Guerci et al., 2013), animal efficiency expressed as milk yield per cow and milk production per unit of dry matter (DM) intake, accounted for more than 80% of the variance in GWP in the population of farms. In their study, animal efficiency was clearly separated from farming intensity, expressing livestock units and amounts of milk produced per area farm land, nutrient balances, feed self-sufficiency and N-input from purchased feed. Farming intensity was, in contrast to animal efficiency, not significantly related to GWP. These findings were supported by a study of Dutch farms (Thomassen et al., 2009), in which the authors concluded that high annual milk production per cow and efficient use of feed per kg milk produced at moderate stocking density would be the best option for reducing GWP per kg milk.
The studies by Guerci et al. (l.c.) and Thomassen et al. (l.c.) also covered other impact categories as well as GWP. In brief, their findings showed that animal efficiency was significantly and negatively correlated to environmental acidification, eutrophication and both energy and land use per unit of milk, whereas farming intensity was positively correlated to the acidification and eutrophication burdens. None of these studies included the use of on-farm capital goods in the inventories, and they did not investigate or separate consequences of different forage production strategies as options for intensification.
In a previous LCA of combined dairy and beef production in Norway (Roer et al., 2013), we did include capital goods, and hypothesized that their inclusion would add to the environmental burden associated with the small-scale Norwegian production. The hypothesis was only correct for the toxicity indicators. Here, large (on a per unit produce base) investments in capital goods such as buildings, indoor mechanization and machinery accounted for more than 20% of the environmental burden of milk and meat production. By contrast, these investments accounted for less than 10% of the total impact for GWP, acidification and eutrophication. In terms of intensification, this study of Norwegian dairy farms appeared to support the findings for Italian and Dutch dairy farms, as moderate yields per animal and low forage yields (relative to N-fertilizer inputs) were identified as the two main bottlenecks for the environmental performance (i.e. they affected several impact categories negatively). However, the actual effects of increasing the level of intensity were not tested by Roer et al. (2013). The data gathered from this study did not allow for exploration of effects of intensity in forage production, although they revealed that forage production amounted to 50% or more of the environmental impact score for nine out of twelve investigated categories.
The intensity of Norwegian dairy production, expressed as yearly milk yield per cow has gradually increased over the last decade, to the present average of 7900 kg ECM (TINE Rådgiving, 2014). In some herds with Norwegian Red cattle, average yields up to 12,000 kg ECM per cow (l.c.) are found and single cows have been reported to produce 16,000 kg/year, indicating that there is a genetic potential to increase milk yields on a national basis. Hence, a thorough study is required of the environmental effects of the observed intensification in Norway, which is similar to that found in most comparable countries. It is also of interest to explore and compare the effects of different production strategies, since higher animal yields may be obtained by a range of means, including different combinations of feed, concentrates and several other factors.
In the present study, we explore whether and how the intensification of Norwegian dairy production, in terms of higher animal yields, may contribute to more environmentally friendly production, using recently improved LCA methodology (Goedkoop et al., 2012). We have envisaged farms representing intensive production strategies in three regions of the country, and included all capital goods and machinery investments regarded as necessary in a cost-effective and modern production with a long indoor housing season. Further, we have constructed and analyzed scenario farms, which are either intensified or extensified through management principles and options that we regard as likely to be implemented under northern temperate conditions, with similar farm size and structure as that found in Norway. In all these comparisons, we have used as base case a medium/normal intensity level dairy farm envisaged and analyzed in the previous study (Roer et al., 2013).
Section snippets
Case description
Three farms representing intensive combined milk and meat production were selected from a defined population for further inventory and analysis. The basis and procedure for the definition and selection process have been outlined in Section 2.2. The farms were located in the counties Rogaland (‘southwest intensive’; SWI), Oppland (‘central southeast intensive’; CSEI) and Nord-Trøndelag (‘central intensive’; CI). Figures for farm and herd characteristics, inputs and outputs have been listed in
Results
For the functional units 1 kg ECM and 1 kg carcass weight, total impacts for the categories Global warming potential (GWP), Agricultural land occupation (ALO), Fossil depletion (FD), Terrestrial acidification (TA), Terrestrial ecotoxicity (TE) and Freshwater eutrophication (FE) have been assigned to the sub-processes concentrate production, on-farm forage production (including field emissions), direct emissions from cattle and other inputs representing production of buildings, machinery,
Discussion
Achieving higher animal yields than medium and low levels appeared to reduce the environmental impacts from milk production in five out of the six evaluated categories. For GWP, this was the case when higher milk yields were obtained by using either a high forage energy concentration (SWI, scenario F) or a high proportion of concentrates in the diet (CSEI), and also when higher yields per head resulted in higher milk yields and higher nitrogen inputs per area land. These results were not in
Conclusions
Our results indicated that an intensification of Norwegian dairy production by means of higher yields per animal would contribute to more environment-friendly production. For GWP this was also the case when higher yields per head resulted in higher milk yields and higher N inputs per area of land, irrespective of the composition of diets and forage production strategies.
Also for impact categories TA, FD and FE, the milk from farms with high-yielding animals scored more favourably. This was not
Conflict of interest statement
No actual or potential conflict of interest including any financial, personal or other relationships with other people or organizations.
Acknowledgements
The authors gratefully acknowledge the contribution from the Norwegian Agricultural Extension Service, TINE Extension service and the three farmers. TINE is acknowledged for EK-data and Felleskjøpet for concentrate feed data, and we thank Hugh Riley for critically reading the manuscript. The research was funded by The Research Council of Norway (Program: Sustainable Innovation in Food and Bio-based Industries; BIONAER)
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