Variability in greenhouse gas emission intensity of semi-intensive suckler cow beef production systems

Paul Crosson,Karen A Beauchemin,Laila Aass,Stine Samsonstuen,Bente A Åby,Helge Bonesmo,Marit S Wetlesen

doi:10.1016/j.livsci.2020.104091

Abstract

Emission intensities from beef production vary both among production systems (countries) and farms within a country depending upon use of natural resources and management practices. A whole-farm model developed for Norwegian suckler cow herds, HolosNorBeef, was used to estimate GHG emissions from 27 commercial beef farms in Norway with Angus, Hereford, and Charolais cattle. HolosNorBeef considers direct emissions of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) from on-farm livestock production and indirect N2O and CO2 emissions associated with inputs used on the farm. The corresponding soil carbon (C) emissions are estimated using the Introductory Carbon Balance Model (ICBM). The farms were distributed across Norway with varying climate and natural resource bases. The estimated emission intensities ranged from 22.5 to 45.2 kg CO2 equivalents (eq) (kg carcass)−1. Enteric CH4 was the largest source, accounting for 44% of the total GHG emissions on average, dependent on dry matter intake (DMI). Soil C was the largest source of variation between individual farms and accounted for 6% of the emissions on average. Variation in GHG intensity among farms was reduced and farms within region East, Mid and North re-ranked in terms of emission intensities when soil C was excluded. Ignoring soil C, estimated emission intensities ranged from 21.5 to 34.1 kg CO2 eq (kg carcass)−1. High C loss from farms with high initial soil organic carbon (SOC) content warrants further examination of the C balance of permanent grasslands as a potential mitigation option for beef production systems.

Highlights

The agricultural sector accounts for 10-12% of greenhouse gas (GHG) emissions (Tubiello et al, 2014) with livestock production contributing a significant portion
Soil C balance accounted for 6% of the total emissions and had the largest variation across farms, ranging from -2.7 to 14.1 CO2 eq-1 depending on location
Our study investigated the GHG emissions from commercial Norwegian farms from different geographical regions, compared with simulated farms used in other studies (e.g. Mogensen et al, 2015; White et al, 2010) with different management practices, cattle breeds, and natural resources

Summary

Introduction

The agricultural sector accounts for 10-12% of greenhouse gas (GHG) emissions (Tubiello et al, 2014) with livestock production contributing a significant portion. There is substantial variation in emission intensities among countries (Gerber et al, 2013), and among farms within a country (Bonesmo et al, 2013) This variation in GHG intensity is partly due to methodological differences among studies, but fundamental differences in natural resource availability and farm management practices contribute significantly (Alemu et al, 2017a; White et al, 2010). Exploring differences between farm systems in GHG intensity may help identify beef production systems and practices that are more efficient, which could lead to the development of mitigation options at farm level. Hristov et al, (2013) reviewed different management practices such as diet formulation, feed supplements, manure management, improved reproductive performance, and enhanced animal productivity to reduce GHG emissions from ruminant production and showed potential long term mitigating effects

Objectives

Methods

Results

Discussion

Conclusion