Climate mitigation by dairy intensification depends on intensive use of spared grassland.

David Styles,James Gibbons,Jon Moorby,Alejandra Gonzalez‐Mejia,Andreas Foskolos

doi:10.1111/gcb.13868

Abstract

Milk and beef production cause 9% of global greenhouse gas (GHG) emissions. Previous life cycle assessment (LCA) studies have shown that dairy intensification reduces the carbon footprint of milk by increasing animal productivity and feed conversion efficiency. None of these studies simultaneously evaluated indirect GHG effects incurred via teleconnections with expansion of feed crop production and replacement suckler-beef production. We applied consequential LCA to incorporate these effects into GHG mitigation calculations for intensification scenarios among grazing-based dairy farms in an industrialized country (UK), in which milk production shifts from average to intensive farm typologies, involving higher milk yields per cow and more maize and concentrate feed in cattle diets. Attributional LCA indicated a reduction of up to 0.10kg CO2 e kg-1 milk following intensification, reflecting improved feed conversion efficiency. However, consequential LCA indicated that land use change associated with increased demand for maize and concentrate feed, plus additional suckler-beef production to replace reduced dairy-beef output, significantly increased GHG emissions following intensification. International displacement of replacement suckler-beef production to the "global beef frontier" in Brazil resulted in small GHG savings for the UK GHG inventory, but contributed to a net increase in international GHG emissions equivalent to 0.63kg CO2 e kg-1 milk. Use of spared dairy grassland for intensive beef production can lead to net GHG mitigation by replacing extensive beef production, enabling afforestation on larger areas of lower quality grassland, or by avoiding expansion of international (Brazilian) beef production. We recommend that LCA boundaries are expanded when evaluating livestock intensification pathways, to avoid potentially misleading conclusions being drawn from "snapshot" carbon footprints. We conclude that dairy intensification in industrialized countries can lead to significant international carbon leakage, and only achieves GHG mitigation when spared dairy grassland is used to intensify beef production, freeing up larger areas for afforestation.

Highlights

Milk and beef production currently contribute 9% of global greenhouse gas (GHG) emissions (Gerber, 2013)
Reasons to expect dairy intensification supported by concentrate feed to reduce the GHG intensity of milk production include: (i) reduced enteric methane (CH4) emissions owing to increased ratio of highly digestible starch-based concentrate feed in cattle diets (Hristov et al, 2013); (ii) more feed energy going into milk production rather than animal maintenance at higher yields per cow (Capper, Cady & Bauman, 2009); (iii) sparing of grassland (Burney et al, 2010; Lamb et al, 2016) (Figure 1)
Such intersystem consequences are at best only partially captured by carbon footprints based on attributional life cycle assessment (LCA), in which dairy system emissions are allocated between milk and beef (BSI, 2011), and may not be reflected in national GHG inventories (Figure 1)

Summary

| INTRODUCTION

Milk and beef production currently contribute 9% of global greenhouse gas (GHG) emissions (Gerber, 2013). Higher milk yields per cow result in fewer dairy calves being exported to beef farms, leading to more suckler beef production with larger land and carbon footprints (Nguyen, Hermansen & Mogensen, 2010). Such intersystem consequences are at best only partially captured by carbon footprints based on attributional LCA, in which dairy system emissions are allocated between milk and beef (BSI, 2011), and may not be reflected in national GHG inventories (Figure 1). We apply cLCA to specific pathways of dairy intensification to investigate the major direct and indirect consequences for GHG emissions that arise when milk production shifts to more intensive farm types (Figure 1), and compare results against simple carbon footprints for milk produced on these farm types pre- and post-intensification

| MATERIALS AND METHODS

| RESULTS

| DISCUSSION

Findings

| Limitations and future work