Comparative life cycle environmental impacts of three beef production strategies in the Upper Midwestern United States

Previous studies on beef systems that included soil organic carbon used fixed values based on literature, measured data over limited periods, or modelled soil carbon fluxes.

“Previous studies on beef systems that have included SOC have used fixed values based on literature data (e.g.Pelletier et al., 2010), relied on measured data during a limited period of time (e.g.Stanley et al. (2018) used data from soil measurements on-site over four years) or used modelled soil carbon fluxes (Alemu et al., 2017).”

Studies have identified gaps and called for more robust research and inclusion of soil carbon in future life cycle assessment models.

“Studies have identified these gaps and have called for more robust research and inclusion of soil C in future LCA models”

On-farm energy use per head of cattle was taken from Ryan and Tiffany (1998) in the absence of current or on-farm data.

“As Pelletier et al. (2010) did, on-farm energy use per head of cattle was taken from Ryan and Tiffany (1998) in the absence of current or on-farm data.”

Different assumptions about fertilization rates on pasture have resulted in a 5-fold difference in N2O emissions.

“For example, different assumptions about fertilization rates on pasture have resulted in a 5fold difference in N 2 O emissions”

Average finishing weights for the feedlot steers were similar to those reported by others.

“Average finishing weights for the FL steers (Table 2) were similar to those reported by others”

Compared to the grass-finishing model of Pelletier et al. (2010), GHG emissions from finishing with AMP grazing in this study were about 45% lower.

“Compared to results of the grass-finishing model of Pelletier et al. (2010), GHG emissions from finishing with AMP grazing in our study were about 45% lower.”

GHG emissions (per kg CW) were within the range of those reported in other studies for the Northern Great Plains, Upper Midwest, and California within the U.S.

“Generally, GHG emissions (per kg CW) were within the range of those reported in other studies for the Northern Great Plains (Lupo et al., 2013), Upper Midwest (Pelletier et al., 2010), andCalifornia (Stackhouse-Lawson et al., 2012) within the U.S.”

Feed production emissions in the FL finishing scenario were slightly greater than those reported by Lupo et al. (2013) and Pelletier et al. (2010).

“Feed production emissions in the FL finishing scenario were slightly greater than those reported by Lupo et al. (2013) and Pelletier et al. (2010), likely because our FL ration included only a small proportion of legume forages and a larger proportion of DDGS and corn grain which have greater emissions per kg than other feedstuffs (Camargo et al., 2013).”

Manure CH4 and N2O for the FL scenario estimated in this study were greater than those in other studies (Lupo et al., 2013; Pelletier et al., 2010).

“Manure CH 4 and N 2 O for the FL scenario estimated in this study were greater than those in other studies (Lupo et al., 2013;Pelletier et al., 2010).”

In beef LCA studies from the Northern Great Plains and the Upper Midwest in which soil C dynamics were estimated, hypothetical C sequestration rates of 0.41 and 0.12 Mg C ha-1 yr-1 reduced emissions from continuous grass-fed beef production by 24% and 30%, respectively.

“In beef LCA studies from the Northern Great Plains and the Upper Midwest in which soil C dynamics were estimated, hypothetical C sequestration rates of 0.41 and 0.12 Mg C ha -1 yr -1 reduced emissions from continuous grass-fed beef production by 24% and 30%, respectively (Lupo et al., 2013;Pelletier et al., 2010).”

Most farm-level LCAs either exclude SOC from net emissions or extrapolate literature estimates due to the lack of on-farm data or reliable SOC models for grazing systems.

“Most farm-level LCAs either exclude SOC from net emissions (Cusack et al., 2021) or extrapolate literature estimates (Pelletier et al., 2010) due to the lack of on-farm data or reliable SOC models for grazing systems that adequately capture management complexity (Gerber et al., 2013).”

Attempts to measure grazing-induced changes in SOC and incorporate them into LCAs have been sparse in the literature and have yielded widely variable results.

“Attempts to measure grazing-induced changes in SOC and incorporate them into LCAs have been sparse in the literature and have yielded widely variable results (Lupo et al., 2013;Mehre et al., 2024;Pelletier et al., 2010;Rowntree et al., 2020; see SI Section A.3.4 for a direct comparison with these studies).”

Our AMP-GF footprint was ~15% lower than the value reported for a conventionally grazed cow-calf to grass-finishing system in the Upper Midwest using the same IPCC methodologies (Pelletier et al., 2010).

“our AMP-GF footprint was ~15% lower than the value reported for a conventionally grazed cowcalf to grass-finishing system in the Upper Midwest using the same IPCC methodologies (Pelletier et al., 2010)”

Our study indicates that incorporating AMP grazing either partially (AMP-FL) or entirely (AMP-GF) leads to significantly improved ecological outcomes compared to conventional grazing and grass-finishing systems, and maintains production levels comparable to current systems in our region.

“Our study indicates that incorporating AMP grazing either partially (AMP-FL) or entirely (AMP-GF) not only leads to significantly improved ecological outcomes compared to conventional grazing and grass-finishing systems, but also maintains production levels comparable to current systems in our region (Asem-Hiablie et al., 2016;Lindquist, 2014;Pelletier et al., 2010).”