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Potential mitigation of midwest grass-finished beef production emissions with soil carbon sequestration in the United States of America

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Beef production can be environmentally detrimental due in large part to associated enteric methane (CH4) production, which contributes to climate change. However, beef production in well-managed grazing systems can aid in soil carbon sequestration (SCS), which is often ignored when assessing beef production impacts on climate change. To estimate the carbon footprint and climate change mitigation potential of upper Midwest grass-finished beef production systems, we conducted a partial life cycle assessment (LCA) comparing two grazing management strategies: 1) a non-irrigated, lightly-stocked (1.0 AU/ha), high-density (100,000 kg LW/ha) system (MOB) and 2) an irrigated, heavily-stocked (2.5 AU/ha), low-density (30,000 kg LW/ha) system (IRG). In each system, April-born steers were weaned in November, winter-backgrounded for 6 months and grazed until their endpoint the following November, with average slaughter age of 19 months and a 295 kg hot carcass weight. As the basis for the LCA, we used two years of data from Lake City Research Center, Lake City, MI. We included greenhouse gas (GHG) emissions associated with enteric CH4, soil N2O and CH4 fluxes, alfalfa and mineral supplementation, and farm energy use. We also generated results from the LCA using the enteric emissions equations of the Intergovernmental Panel on Climate Change (IPCC). We evaluated a range of potential rates of soil carbon (C) loss or gain of up to 3 Mg C ha-1 yr-1. Enteric CH4 had the largest impact on total emissions, but this varied by grazing system. Enteric CH4 composed 62 and 66% of emissions for IRG and MOB, respectively, on a land basis. Both MOB and IRG were net GHG sources when SCS was not considered. Our partial LCA indicated that when SCS potential was included, each grazing strategy could be an overall sink. Sensitivity analyses indicated that soil in the MOB and IRG systems would need to sequester 1 and 2 Mg C ha-1 yr-1 for a net zero GHG footprint, respectively. IPCC model estimates for enteric CH4 were similar to field estimates for the MOB system, but were higher for the IRG system, suggesting that 0.62 Mg C ha-1 yr-1 greater SCS would be needed to offset the animal emissions in this case.
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Research Paper Future of Food: Journal on Food, Agriculture and Society
4 (3) Winter 2016
Potential mitigation of midwest grass-nished beef
production emissions with soil carbon sequestration in the
United States of America
Jason E. RowntREE*1, REbEcca Ryals2, MaRcia s. DElongE3, w. RichaRD tEaguE, MaRilia b. chiavEgato, PEtER byck6,7,
tong wang8 & sutiE Xu1
1 Department of Animal Science, Michigan State University
2 Department of Natural Resources and Environmental Management, University of Hawaii
3 Union of Concerned Scientists, Washington, DC
4 Department of Ecosystem Science and Management, Texas A & M University
5 Departmental de Zootecnia, Universida de de São Paulo
6 School of Sustainability, Arizona State University
7 Walter Cronkite School of Journalism and Mass Communications, Arizona State University
8 Department of Economics, South Dakota State University
* Corresponding author: rowntre1@msu.edu | Tel.: +1-517-974-9539
Data of the article
First received : 30 March 2016 | Last revision received : 28 November 2016
Accepted : 05 December 2016 | Published online : 23 December 2016
URN: nbn:de:hebis:34-2016111451469
Key words
Grass-nishing beef, GHG
emissions, Soil organic
carbon sequestration
Abstract
Beef production can be environmentally detrimental due in large part to associated enteric
methane (CH4) production, which contributes to climate change. However, beef production in
well-managed grazing systems can aid in soil carbon sequestration (SCS), which is often ignored
when assessing beef production impacts on climate change. To estimate the carbon footprint
and climate change mitigation potential of upper Midwest grass-finished beef production sys-
tems, we conducted a partial life cycle assessment (LCA) comparing two grazing management
strategies: 1) a non-irrigated, lightly-stocked (1.0 AU/ha), high-density (100,000 kg LW/ha) system
(MOB) and 2) an irrigated, heavily-stocked (2.5 AU/ha), low-density (30,000 kg LW/ha) system
(IRG). In each system, April-born steers were weaned in November, winter-backgrounded for 6
months and grazed until their endpoint the following November, with average slaughter age of
19 months and a 295 kg hot carcass weight. As the basis for the LCA, we used two years of data
from Lake City Research Center, Lake City, MI. We included greenhouse gas (GHG) emissions as-
sociated with enteric CH4, soil N2O and CH4 fluxes, alfalfa and mineral supplementation, and farm
energy use. We also generated results from the LCA using the enteric emissions equations of the
Intergovernmental Panel on Climate Change (IPCC). We evaluated a range of potential rates of
soil carbon (C) loss or gain of up to 3 Mg C ha-1 yr-1. Enteric CH4 had the largest impact on total
emissions, but this varied by grazing system. Enteric CH4 composed 62 and 66% of emissions for
IRG and MOB, respectively, on a land basis. Both MOB and IRG were net GHG sources when SCS
was not considered. Our partial LCA indicated that when SCS potential was included, each graz-
ing strategy could be an overall sink. Sensitivity analyses indicated that soil in the MOB and IRG
systems would need to sequester 1 and 2 Mg C ha-1 yr-1 for a net zero GHG footprint, respectively.
IPCC model estimates for enteric CH4 were similar to field estimates for the MOB system, but
were higher for the IRG system, suggesting that 0.62 Mg C ha-1 yr-1 greater SCS would be needed
to offset the animal emissions in this case.
Citation (APA):
Rowntree, J. E., Ryals, R., DeLonge, M.S., Teague, W.R., Chiavegato, M.B., Byck, P., Wang,T., Xu, S. (2016). Potential mitigation of midwest grass-nished
beef production emissions with soil carbon sequestration in the United States of America.
Future of Food: Journal on Food, Agriculture and Socie-
ty
, 4(3), 31 -38.
31
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32 UniKassel & VDW, Germany- December 2016
Future of Food: Journal on Food, Agriculture
and Society, 4 (3)
Introduction
There is a growing concern about beef productions
impact on the environment, including contributions to
climate change. However, beef production systems are
variable, ranging broadly from intensive confined feed-
lots to diverse grazing systems. As a result, these sys-
tems contribute differently to climate change through
mechanisms such as animal impacts, off-farm inputs,
and land management. Identifying opportunities to re-
duce climate impacts requires a systematic approach
that considers the larger agroecosystem. This need for
a systems approach has become increasingly urgent,
particularly in light of the fact that one outcome of the
United Nations Conference on Climate Change (COP21)
was a call for greater adoption of regenerative agricul-
tural practices. Specifically, this call includes the “4/1000
Initiative: Soils for Food Security and Climate” and the
Life Beef Carbon Initiative, which recommends greater
adoption of grazing systems that sequester C and re-
duce net GHG emissions from beef production.
Life cycle assessments (LCAs) are important tools that
have been applied to evaluate the costs and benefits of
beef production systems with respect to the environ-
ment and climate change. While LCAs can be insightful,
the outputs are highly sensitive to the methodologies
and boundaries used to develop the analysis. Many ex-
isting beef LCAs have concluded that grazing systems
have a bigger climate footprint than more intensive,
confined systems due to reduced meat yield per unit
land and increased enteric methane (CH4) associated
with greater ruminal fiber digestion (Eshel, Shepon, Ma-
kov, & Milo, 2014; Ripple et al., 2014; Capper, 2012). How-
ever, these assessments have generally not accounted
for the important influence that land management and
soil dynamics can have on the outcome.
Soil is an important pool of C that is sensitive to land
management and can cumulatively have a significant
impact on climate change. Recently, Teague et al. (2016)
indicated agriculturally induced global soil erosion esti-
mates at 1.86 Gt C yr-1, resulting in an annual 0.5 ppm
atmospheric CO2 increase. Because soils can be either a
source or sink of C depending on management practic-
es, soil C is a potentially important component of beef
LCAs (Teague et al., 2016). Soil C has often been unac-
counted for in LCAs (Stackhouse-Lawson, Rotz, Oltjen, &
Mitloehner, 2012; Capper & Bauman, 2013), but has been
found to have a large impact on net GHG footprints
when explicitly included (Liebig, Gross, Kronberg, & Phil-
lips, 2010; Wang, Teague, Park, & Bevers, 2015) or at least
considered (Pelletier, Pirog, & Rasmussen, 2010; Lupo,
Clay, Benning, & Stone, 2013). The availability of experi-
mental data on soil C and GHG effects of grazing systems
has been an obstacle in filling this critical gap in LCAs.
The purpose of this study is to develop a data-driven
partial LCA of upper Midwest grass-finishing beef pro-
duction systems. Our LCA explicitly considers soil C and
GHG dynamics and uses data from localized field exper-
iments. We employ a simple sensitivity analysis to eval-
uate the potential for soil carbon sequestration (SCS) to
offset emissions within grass-finished beef production
systems.
Materials and Methods
LCA components and boundaries
An LCA was constructed to determine net GHG impacts
of two different grazing management practices for beef
production in the upper Midwest, USA. Components of
Figure 1 : Grass-Finishing beef production phase
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Future of Food: Journal on Food, Agriculture
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the LCA include direct and indirect GHG emissions asso-
ciated with the grassland ecosystem, enteric emissions
from cattle, feed production and transportation, and on-
farm energy use. The model boundary was restricted to
the grass-finishing portion of the beef production cycle,
beginning at the time of weaning and ending at slaugh-
ter (Figure 1).
The model quantified the impacts of grazing manage-
ment practices on the net greenhouse gas emissions
(GHGnet) as:
GHGnet = GHGecosystem + GHGfeed + GHGenergy - GHGseq
where GHGecosystem represents biological greenhouse
gas emissions generated on the pasture. This parameter
includes enteric CH emissions from steers (> 1 year old)
and the difference in soil nitrous oxide (N2O) and CH4
emissions relative to an ungrazed control pasture. Emis-
sions associated with the mining, production, and trans-
portation of supplemental feed and minerals are repre-
sented as GHGfeed. Emissions generated from the use of
fossil fuels for on-farm technologies (i.e., irrigation) are
represented as GHGenergy. The change in soil carbon
is shown as GHGseq, where a positive value represents
sequestration (i.e., a sink). All model components are
expressed as GHG fluxes in CO2-equivalents using 100-
year global warming potentials (Intergovernmental Pan-
el on Climate Change, 2006). Positive values represent
a source of GHGs to the atmosphere, whereas negative
values represent a GHG sink. Metrics for comparison of
GHG impacts due to grazing practices were expressed
on a per steer and per area basis.
Study system
Data used for the LCA was derived from two years of on-
farm experiments conducted at the Lake City Research
Center in Lake City, Michigan. The experiments were
composed of grass-finishing beef production systems
that compared two different grazing management strat-
egies. The approaches were: 1) MOB: a non-irrigated,
high-density grazing system stocked at 1.0 animal units
(AU) ha-1 (100,000 kg live weight (LW) ha-1 d-1) and 2) IRG:
an irrigated, low-density grazing system stocked at 2.5
AU ha-1 (30,000 kg LW ha-1 d-1). An AU is considered
one 454 kg cow with or without calf. We define stocking
rate as the number of AUs assigned to the land base for
a given year, while stock density refers to the kg LW/ha
of animal weight assigned to a land base for 1 day. While
our LCA was driven by data specific to the Upper Mid-
west, the management characteristics of the IRG system
are similar to many grazing dairies and beef systems in
New Zealand, parts of Europe, Australia and the United
States. The IRG system is characterized by aggressive
plant defoliation with short (21-45 day) recoveries to
promote a highly vegetative sward. In contrast, MOB is
a grazing system characterized by high stock densities
with a lower stocking rate. The MOB system allows for
longer (> 60 day) plant recovery periods. As a result,
forage is typically more mature when compared to IRG
and has a higher fiber content when compared to other
rotational systems (Chiavegato, Powers, Carmichael, &
Rowntree, 2015b). In each grazing strategy, steers were
born in April, weaned in November, backgrounded on
high quality hay for 6 months, and grazed on pasture
until slaughter the following November, with an average
age at slaughter of 19 months and a 295 kg hot carcass
weight (HCW). Our life cycle model focuses on the peri-
od from weaning to slaughter (Figure 1).
Ecosystem greenhouse gas emissions
Ecosystem GHG emissions included enteric CH and
soil NO and CH fluxes measured at the experimental
site from 2012-13 (Chiavegato, Rowntree, Carmichael, &
Powers, 2015a, Chiavegato et al., 2015b). Emissions were
measured in spring (April/May; Period 1) and late sum-
mer (August/Sept; Period 2) for 2 years. These time pe-
riods were considered to be representative of seasonal
fluxes and were scaled by the numbers of days in each
season. For the base case scenario, soil emissions during
winter months are assumed to be negligible.
Enteric emissions were derived from on-site data from
cow-calf pairs with a mean weight of 555 kg (SE= 20 kg)
using a standard SF tracer gas technique (Johnson, Huy-
ler, Westberg, Lamb, & Zimmerman, 1994). Sampling was
conducted twice daily over 7 days in Periods 1 and 2 in
2012 and 2013. During each sampling period, cattle were
also dosed with chromic oxide to determine dry matter
intake (DMI). There was no management effect on DMI
as cows consumed 2.6 and 2.8% of their body weight
daily during the collection periods for MOB and IRG, re-
spectively. There were no differences between years or
treatments for enteric CH, with emissions ranging from
195 to 249 g CH4 d-1. We used a metabolic body weight
conversion of 0.85 to convert emissions from a mature
cow (555 kg) to a growing steer (454 kg). For both sys-
tems, we estimated winter CH emissions to be 120 g L-1
d-1 on high quality hay, based Stewart et al. (2014). We
also compared our data to enteric CH calculations using
the Tier 1 Methodology of the Intergovernmental Panel
on Climate Change (IPCC):
DayEmit = [GEI XYm ] / [55.65 MJ/kg CH]
where:
DayEmit = emission factor (kg CH head-1 day-1)
GEI = gross energy intake (MJ head-1 day-1)
Ym = CH4 conversion rate, which is the fraction of gross
Eq. 1
Eq. 2
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energy in
feed converted to CH (%)
To complete the IPCC equation, site-specific mean GEI
forage values (Chiavegato et al., 2015a) and the recom-
mended Ym of 6.5% (Mangino, Peterson, & Jacobs, 2003)
were used.
Soil GHG emissions data used for the base case scenario
is detailed in Chiavegato et al. (2015b). Briefly, soil N2O
and CH₄ emissions were measured via the static flux
chamber method and analyzed by gas chromatography.
A 14 day post-graze collection period in both periods in
2012 and 2013 was used.
Greenhouse gas emissions from protein and mineral sup-
plements
The grazed pastures and supplemented feed were pri-
marily alfalfa (Medicago sativa L.). For the supplemental
feed GHG assessment, we used the Farm Energy Analysis
Tool (FEAT ) (Camargo et al., 2013). Assumptions involved
in FEAT indicate a three-year lifespan for the alfalfa, with
an energy use of 9000 MJ input ha-1 y-1 and energy pro-
duction efficiency of 25 MJ output per MJ input (Camar-
go, Ryan, & Richard, 2013). No differences in supplement
consumption were used between the different grazing
systems. The on-farm supplemental feed consumption
per animal for the production cycle was 2044 kg. Half
of the alfalfa was produced on site, while the other half
was brought on farm from an average distance of 24 km.
In each case, a yield of 7490 kg ha-1 y-1 was used based
on USDA harvest estimates (USDA, 2015). All associated
transportation GHG emissions were estimated using die-
sel heavy-duty truck data from the EPA (2008).
Mineral supplement calculations were based on a dai-
ly intake of 77 g head-1 across each grazing treatment
(Buskirk, 2002). Mineral associated emissions were esti-
mated based on Lupo, Clay, Benning, and Stone (2013).
This involves the mining and processing components of
NaCl, CaCO and CaHPO production, along with trans-
port and delivery to the farm.
On-farm energy use
Any associated energy used for alfalfa production and
subsequent feeding is accounted for in the feed compo-
nent. Supplemental irrigation was used in IRG (K-Line Ir-
rigation, St. Joseph, MI) with a goal of providing 2.54 cm
water ha-1 wk-1. The estimated annual usage of irrigation
electricity was 7452 kW yr-1. EPA (2014) emission factors
were used to determine emissions associated with elec-
tricity use.
Soil carbon sequestration
To account for soil C change in each system, we consid-
ered a C-response gradient ranging from -3 Mg C ha-1 yr-1
to 3 Mg C ha-1 yr-1. Grazing lands have the potential to act
as C sinks, but reported rates of SCS due to grazing sys-
tem management vary considerably based on climate,
biome, time of observation, and site-specific conditions.
A review of 81 ranch sites reported SCS rates ranging
from 0.11 to 3.04 Mg C ha-1 yr-1 (Conant, Paustian, & Elli-
ott, 2001). More recent attention to emerging intensive
rotational grazing practices has indicated even greater
potential SCS rates. Teague et al. (2011) reported annual
sequestration rates of 3 Mg C ha-1 yr-1 in a 10 year chron-
osequence study in Texas comparing stocking rate and
grazing management influence on beef production and
ecosystems services. Machmuller et al. (2015) observed
SCS of 8.0 Mg C ha-1 yr-1 in a 7 year chronosequence of
irrigated management-intensive grazing in the south-
eastern USA. Thus, the relatively wide range of SCS rates
used for this LCA provides an opportunity to incorporate
soil C dynamics and uncertainties.
Results and Discussion
LCA results of MOB and IRG systems on a kg CO2-eq ha-1
production cycle and animal basis derived from Eq.1 are
indicated in Figure 2. The MOB system had lower emis-
sions on a land basis when compared to the IRG system
(3.3 vs. 7.1 Mg CO-eq ha-1) due to lower stocking rates.
The IRG farm energy use was 1064 kg CO-eq ha-1 due to
the electricity used for irrigation, compared to no energy
use for the MOB system. For both systems, enteric CH
was the largest contributor to overall emissions, ranging
from 62 to 66% for the IRG and MOB systems, respective-
ly. This finding is lower than results found by Pelletier,
Pirog, & Rasmussen (2010), who estimated enteric CH
emissions to make up 79% of total GHG emissions from
a grass-finishing system.
Enteric emissions ranged from 142 to 268 g CH d-1 (Chi-
avegato et al., 2015a). These results are similar to those
reported by DeRamus, Clement, Giampola, and Dicki-
son (2003), who indicated yearling heifers, first calf heif-
ers and mature cows ranged from emitting 120 to 255
g CH d-1. Similarly, Pavao-Zuckerman, Waller, Ingle, and
Fribourg (1999) reported a range of 150 to 240 g CH d-1.
However, these data fall slightly lower than estimates by
McCaughey, Wittenberg, and Corrigan et al. (1999) and
Pinares-Patiño, Baumont, and Martin (2003), who found
ranges in emissions from 173 to 273 g CH d-1. The lower
stocking rate in MOB also resulted in lower enteric CH4
emissions compared to IRG (2165 vs. 4430 kg CO-eq ha-
1) on a land area basis. However, on a per steer basis, IRG
enteric emissions were 393 kg CO-eq steer-1 less than
MOB. The grazing effect on enteric CH emissions may
be explained by the observed increase in forage crude
protein and reduction in fiber content for IRG compared
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to MOB (Chiavetago et al., 2015a).
The beef production systems used to calculate this LCA
represent improved grazing management as compared
to continuous set stocking strategies, which have been
shown to reduce plant diversity and productivity due to
overgrazing of preferred plants and patches (Murphy,
1998; Gerrish, 2004; Teague, Provenza, Kreuter, Steffens,
& Barnes, 2013). The lower enteric CH emissions in the
observations reported here might be due to the relative-
ly high plant diversity we observed in the well-managed
systems. Both systems included multiple daily to weekly
moves to new pasture, allowing for greater forage resid-
ual biomass and longer recovery periods, feeding back
to the ecosystem by increasing the plant diversity and
forage quality (Chiavegato et al., 2015a). Conceptually,
this agrees with Bannink et al. (2010), who indicated that
forage quality is a primary driver in relative daily enteric
emissions.
Enteric CH emissions were also assessed using Tier 1
IPCC daily enteric emission predictive equations (Eq.1)
(IPCC, 2006), as it is a commonly used methodology
when site- or regionally-specific data are lacking. There
was very little difference between the MOB GHG foot-
print calculated using our field observations compared
to the IPCC approach (3.3 vs 3.5 Mg CO-eq yr-1, respec-
tively) (Figures 2 & 3). However, when evaluating the
IRG system, the IPCC approach generated a greater en-
teric CH4 value and concurrently a larger footprint on a
land and steer basis by 34%. In a review of measured and
simulated enteric emission rates, Stackhouse et al. (2012)
indicated the IPCC overestimated emissions by 16.4% on
average, with a differential range of -0.01 to 55%.
___________Net GHG (Mg C ha-1 yr-1)__________
On-farm IPCC
Soil C Emission MOB IRG MOB IRG
(Mg C ha-1 yr-1)
-3 -2.11 -1.07 -2.05 -0.45
0 0.89 1.93 0.95 2.55
3 3.89 4.93 3.95 5.55
Figure 2 : Life cycle assessment of on-farm data estimated with metabolic body weight
Table 1: Impact of soil C emission gradient on net GHG in two man-
agement systems
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Table 1 denotes overall C footprint balance (in CO2-eq)
based on a plausible gradient of soil C flux, representing
soil C loss or gain ranging from ±3 Mg C ha-1 yr-1. Assum-
ing a sequestration rate of 3 Mg C ha-1 yr-1, all systems
and methods indicate an overall GHG sink ranging from
2.11 to 1.07 (MOB) and 2.0 and 0.45 Mg C ha-1 yr-1 (IRG),
representing on-farm and IPCC calculations, respective-
ly. A soil C flux gradient allows for a greater understand-
ing of soil C influence on the overall environmental foot-
print. As Stackhouse et al. (2012) indicated, LCA’s often
consider soil C to be in dynamic equilibrium. However,
empirical data suggest otherwise (e.g. Machmuller et al.,
2015; Teague et al., 2011). Recent studies such as Ripple
et al. (2014) and Eshel et al. (2014) have reported the
emissions from ruminants in food production without
accounting for the beneficial ecosystem services that
well-managed grazing systems can provide. In our study,
we used 3 Mg C ha-1 yr-1 as a potential C sequestration
figure, which is relatively high (Conant et al., 2001) but
viable based on existing studies (Teague et al., 2011; Del-
gado et al., 2011; Machmuller et al., 2015; Teague et al.,
2016). Importantly, the results presented here suggest
that with appropriately managed grazing, a grass-fin-
ished beef model can not only contribute to food pro-
visioning but also be ecologically regenerative as well.
Conclusions
The recent call for improved management of grazing
systems as part of an international climate change miti-
gation strategy is critical, particularly in light of many ex-
isting beef LCAs that have concluded that beef cattle pro-
duced in grazing systems are a particularly large sources
of GHG emissions. To identify the best opportunities to
reduce GHG emissions from beef production, a systems
approach that considers the potential to increase soil C
and reduce ecosystem-level GHG emissions is essential.
Using a combination of on-farm collected data, litera-
ture values, and IPCC Tier 1 methodology, we generat-
ed an LCA that indicates highly-managed grass-finished
beef systems in the Upper Midwestern United States can
mitigate GHG emissions through SCS while contribut-
ing to food provisioning at stocking rates as high as 2.5
AU ha-1. From this data, we conclude that well-managed
grazing and grass-finishing systems in environmentally
appropriate settings can positively contribute to reduc-
ing the carbon footprint of beef cattle, while lowering
overall atmospheric CO concentrations.
Acknowledgements
The authors express their thanks to the Michigan Animal
Agriculture Alliance and Thornburg Foundation for par-
tial support of this project. Moreover, the authors would
like to thank the anonymous reviewers.
Conict of Interests
The authors hereby declare that there are no conflicts of
interest.
Figure 3 : Life cycle assessment of IPCC data to estimate enteric methane emissions
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Future of Food: Journal on Food, Agriculture
and Society, 4 (3)
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... AMP grazing results in lower N 2 O emissions and is a larger CH 4 sink than continuous grazing (Dowhower et al. 2019) and stores higher levels of soil organic carbon than continuous grazing. In fact, AMP grasslands can store more carbon equivalent units in the soil than is emitted by respiration of soil biota or via ruminant emissions (Liebig et al., 2010;Mosier, 2020;Rowntree et al., 2016;Stanley et al., 2018;Wang et al., 2015). This is a major contributing factor to AMP providing a greater GHG sink because CO 2 emissions are lower from soils with higher carbon content and N 2 O emissions are also decreased at higher levels of soil carbon (Gelfand et al., 2015;Ruser et al., 2006). ...
... Although many scientists have concluded that ruminant production systems are an unusually large source of GHG emissions, others have found it is possible to convert many ruminant-based production chains into net carbon sinks by changing management Teague et al., 2016;Wang et al., 2014;Wang et al., 2015). Previous assessments of capacity for CH 4 uptake in grazed rangeland ecosystems have not considered improved livestock management practices and thus underestimated potential for CH 4 uptake (Delgado et al., 2011;Rowntree et al., 2016;Stanley et al., 2018;Wang et al., 2014). As soils can be a significant sink of carbon depending on management practices (Conant et al. 2001;Liebig et al., 2010;Teague et al. 2011;Machmuller et al., 2015), soil carbon dynamics are an essential component of calculating accurate beef life-cycle-assessments (LCAs) Stanley et al., 2018;Teague et al., 2016;Wang et al., 2015). ...
... In southern tallgrass prairie in Texas, Wang et al. (2015) report a net increased carbon sink of 2.0 Mg carbon ha −1 year −1 when converting from heavily stocked continuous grazing to AMP grazing at the same stocking rate, and net sink of 1.7 Mg C ha −1 year −1 following conversion from heavy to light stocking with continuous, season-long grazing. Similarly, Rowntree et al. (2016), working with beef cattle on cultivated perennial pastures in Michigan, report soil carbon gains of 3 Mg carbon ha −1 year −1 with AMP grazing under rainfed or irrigated conditions. For a net-zero GHG footprint, sensitivity analyses indicated that soil in the rainfed and irrigated AMP grazing systems would need to sequester 1 and 2 Mg carbon ha −1 year −1 , respectively. ...
Chapter
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Historically, nearly 40% of terrestrial ecosystems were grasslands and savannas that co-evolved with grazing animals. Historic wild herd numbers were probably only slightly lower than today's combined global herds of wild ungulates and domesticated livestock. Thus, modern degradation of critical ecosystem services in these ecosystems, including increases in atmospheric greenhouse gases caused by poor grazing and agricultural management, cannot simply be attributed to livestock numbers. Livestock grazing management investigations indicate that emulating the fast and short grazing periods of co-evolved wild herds of native grazers, followed by long recovery periods, can provide significant benefits over continuous grazing in these ecosystems. Such benefits include improved water infiltration, decreased soil erosion, increased soil fertility, vegetative and ecosystem biodiversity, habitat for rare grassland birds, increased vegetation productivity, and increased soil organic carbon stocks, often to a meter depth in many areas.
... AMP grazing results in lower N 2 O emissions and is a larger CH 4 sink than continuous grazing (Dowhower et al. 2019) and stores higher levels of soil organic carbon than continuous grazing. In fact, AMP grasslands can store more carbon equivalent units in the soil than is emitted by respiration of soil biota or via ruminant emissions (Liebig et al., 2010;Mosier, 2020;Rowntree et al., 2016;Stanley et al., 2018;Wang et al., 2015). This is a major contributing factor to AMP providing a greater GHG sink because CO 2 emissions are lower from soils with higher carbon content and N 2 O emissions are also decreased at higher levels of soil carbon (Gelfand et al., 2015;Ruser et al., 2006). ...
... Although many scientists have concluded that ruminant production systems are an unusually large source of GHG emissions, others have found it is possible to convert many ruminant-based production chains into net carbon sinks by changing management Teague et al., 2016;Wang et al., 2014;Wang et al., 2015). Previous assessments of capacity for CH 4 uptake in grazed rangeland ecosystems have not considered improved livestock management practices and thus underestimated potential for CH 4 uptake (Delgado et al., 2011;Rowntree et al., 2016;Stanley et al., 2018;Wang et al., 2014). As soils can be a significant sink of carbon depending on management practices (Conant et al. 2001;Liebig et al., 2010;Teague et al. 2011;Machmuller et al., 2015), soil carbon dynamics are an essential component of calculating accurate beef life-cycle-assessments (LCAs) Stanley et al., 2018;Teague et al., 2016;Wang et al., 2015). ...
... In southern tallgrass prairie in Texas, Wang et al. (2015) report a net increased carbon sink of 2.0 Mg carbon ha −1 year −1 when converting from heavily stocked continuous grazing to AMP grazing at the same stocking rate, and net sink of 1.7 Mg C ha −1 year −1 following conversion from heavy to light stocking with continuous, season-long grazing. Similarly, Rowntree et al. (2016), working with beef cattle on cultivated perennial pastures in Michigan, report soil carbon gains of 3 Mg carbon ha −1 year −1 with AMP grazing under rainfed or irrigated conditions. For a net-zero GHG footprint, sensitivity analyses indicated that soil in the rainfed and irrigated AMP grazing systems would need to sequester 1 and 2 Mg carbon ha −1 year −1 , respectively. ...
Chapter
Full-text available
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... Whether or not including iLUC can have large implications on LCA results. For example, multiple studies proposed land use change for a different grazing strategy (e.g in [389,400,402]). Some of these grazing strategies were more sustainable, although they produced less meat or milk. One could expect that the demand for these products will not change. ...
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... The introduction of barbed wire fences and predator eradication campaigns finally made these horns less important (Elofson, 2004;Netz, 2004). But if consumer demand for "grass-finished beef " leads to animals reared more extensively (Rowntree et al., 2016), and if "rewilding" efforts restore native carnivores to rural . /fsufs. . ...
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There is growing interest in gene editing farm animals. Some alterations could benefit animal welfare (e.g., improved heat tolerance in cattle with the “slick” gene), the environment (e.g., reducing methane emissions from cattle with induced pluripotent stem cells), and productivity (e.g., higher weight gains in cattle with the “double muscling” gene). Existing scholarship on the acceptability of such modifications has used myriad approaches to identify societal factors that shape the ethics and governance of this technology. We argue that integrating historical approaches—particularly from the relatively new and burgeoning field of animal history—offers a form of “anticipatory knowledge” that can help guide discussions on this topic. We conducted a systematic review of the animal history literature in English, German, and Spanish to identify the influence of political, scientific, economic, social, and cultural factors on the development and acceptance of such technologies. We identified analogous structures and fault lines in past debates about farm animals that provide insights for contemporary discussions about gene editing. Those analogous structures include the market power of meatpackers or the racialized precepts in livestock breeding, and fault lines, like the disconnect between states and citizens over the direction of food systems. Highlighting these similarities demonstrates how external forces have shaped—and will continue to shape—the acceptance or rejection of emerging biotechnologies as applied to farm animals.
... Access to heterogeneous vegetation on intact landscapes increases options for wildlife, pastoralists, and their livestock on these landscapes. (Ash et al 2008: 783) 20 In addition, recent soil biology research shows that, in an optimally managed pastoral ecosystem, mobile grazing, especially over vast tracts of land, promotes biodiversity (Endicott 2012: 93, LaCanne and Lundgren 2018, Barnes and Teague 2017 and can contribute to soil carbon sequestration (Beede et al 2018, Apfelbaum et al 2016, Byck et al 2016, Cyle et al 2015. In moving over the landscape, herds shape it, just as their human counterparts do by adapting their lifeway to their herds' needs (Marchina 2019: 24), to seasonal changes and to topographic characteristics -that is, from the perspective of landscape-human-bovine interdependencies and entanglements. ...
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A common response to the current global ecological crisis is the conservation of areas still somewhat spared from anthropogenic damage, in spite of an abundant literature evidencing the social and ecological shortcomings of top-down approaches to nature conservation. As part of the Kailash Sacred Landscape Initiative, the Limi Valley of north-western Nepal is currently under consideration for the establishment of one such area. This paper warns about an understanding of conservation as a segregation of humans and nature, which is at odds with local perceptions of landscape as relational. Through the perspective of pastoral practices in the Limi Valley, I show how the Limey – the people of this Valley – conceive of humans as enmeshed within a network of interacting beings under the guiding principles of ecological ethics of care. This conception is framed by religion (a syncretic mixture of Mahayana Buddhism, Bön religion and Animism), as well as by skills of ecological and spiritual embeddedness which are central to pastoral practice. I also warn against the fallacy of considering locals’ relationship to the environment, informed by Buddhism, as intrinsically more prone to eco-friendly practices. I show how this relationship is dynamic and evolving, and influenced by the economic and political context of the last thirty years. This has led to the progressive obsolescence of pastoralism as the main means of livelihood, with consequences for the local inhabitants’ relationship to landscape and to other-than-human species.
... 3) Lajtha and Silva argue that the impact of grazing on climate would be much higher than for crops due to methane and manure emissions and animal feed in winter. Life-cycle analyses in the north-central United States show that well-managed grazing systems not only can reduce emissions compared to feedlot systems but also can completely offset emissions from grazing cattle (7,8). We focused on the changes in soil C in this paper and therefore did not calculate the C budget related to the animal feed in winter. ...
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Much is discussed about the characteristics, efficiency, and externalities of indoor housing and pasture-based beef production systems, but little is known about how these features influence public attitudes towards beef production. This study aimed to explore Chilean citizens’ attitudes towards beef production systems and their underlying reasons. Citizens (n = 1,084) were recruited to participate in a survey and given information about one beef production system: indoor housing, continuous grazing or regenerative grazing. Participants had more favourable attitudes (from 1 = most negative attitudes to 5 = most positive attitudes) towards pasture-based systems (regenerative grazing = 2.94; continuous grazing = 2.83) than towards indoor housing (1.94), mainly due to concerns with animal welfare and environmental impacts. Productivity was not as important as the other sustainability aspects for participants as they were not willing to do that trade-off. Support for beef production may benefit if production systems adopt characteristics that are perceived by the public as positive for the environment and animal welfare.
Chapter
As the previous chapter lays out, where livestock is raised with regenerative grazing management the net greenhouse gas intensity can be lower than that for industrial production, if soil carbon fluxes are taken into account. And livestock don’t just provide income and food; their manure, hoof action, and periodic grazing appear to play a role in helping soils store carbon. However, we cannot assume that the extraordinary gains in soil carbon that a few farms have seen can be replicated everywhere and sustained indefinitely, especially in the face of warming global temperatures. We also need to acknowledge that there are trade-offs between managing grazing systems to maximize soil carbon and maximizing milk or meat production. Finally, we need far more research on how specific grazing management practices can affect both enteric emissions and soil carbon storage.
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In this chapter, we will discuss the effect of different grassland management practices on greenhouse gas (GHG) emissions and soil organic carbon (SOC) sequestration. This includes comparison of grasslands with arable croplands, the role of N fertilization, and grazing strategies. Special emphasis will be given to grasslands in rotation with cropping systems and integration with timber systems to improve sustainable management and SOC sequestration.
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For more than 10 million years, large, herd forming ruminants have thrived as parts of sustainable grazing ecosystems. Conversely, since their domestication 8,000–11,000 years ago, cattle, sheep, and goats have often exhibited dysfunctional relationships with the ecosystems they inhabit. A considerable literature, developed over decades, documents the negative impacts of animal agriculture and associated activities (e.g., feed production) on grassland ecosystems. Coincident with the accumulating data documenting the impacts of “conventional” animal agriculture, has been a growing interest in restoring functionality to agricultural grazing ecosystems. These “regenerative” protocols often seek to mimic the structure and functions of wild grazing ecosystems. The objectives of this paper were two-fold: First to review the literature describing the structure and some key functional attributes of wild and agricultural grazing ecosystems; and second, to examine these attributes in conventionally and regeneratively managed grazing ecosystems and, assuming the wild condition to be the standard for sustainable grazer-environment relationships, to ascertain whether similar relationships exist in conventionally or regeneratively managed agricultural grazing ecosystems. Not unexpectedly our review revealed the complexity of both wild and agricultural grazing ecosystems and the interconnectedness of biological, chemical, and physical factors and processes within these systems. Grazers may increase or decrease system functionality, depending upon environmental conditions (e.g., moisture levels). Our review revealed that biodiversity, nitrogen cycling, and carbon storage in regenerative grazing systems more closely resemble wild grazing ecosystems than do conventional grazing systems. We also found multiple points of disagreement in the literature, particularly with respect to aboveground primary production (ANPP). Finally, we acknowledge that, while much has been accomplished in understanding grazing ecosystems, much remains to be done. In particular, some of the variability in the results of studies, especially of meta-analyses, might be reduced if datasets included greater detail on grazing protocols, and a common definition of the term, “grazing intensity.”
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There is a lack of information regarding carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2 O) emissions from pasture soils and the effects of grazing. The objective of this study was to quantify greenhouse gas (GHG) fluxes from pasture soils grazed with cow-calf pairs managed with different stocking rates and densities. The central hypothesis was that irrigated low-density stocking systems (SysB) would result in greater GHG emissions from pasture soils than nonirrigated high-density stocking systems (SysA) and grazingexclusion (GRE) pasture sites. The nonirrigated high-density stocking systems consisted of 120 cow-calf pairs rotating on a total of 120 ha (stocking rate 1 cow/ha, stocking density 112,000 kg BW/ha, rest period of 60 to 90 d). The irrigated low-density stocking systems consisted of 64 cow-calf pairs rotating on a total of 26 ha of pasture (stocking rate 2.5 cows/ha, stocking density 32,700 kg BW/ha, rest period of 18 to 30 d). Both systems consisted of mixed cool-season grass-legume pastures. Static chambers were randomly placed for collection of CO2, CH4, and N2 O samples. Soil temperature (ST), ambient temperature (temperature inside the chamber; AT), and soil water content (WC) were monitored and considered explanatory variables for GHG emissions. GHG fluxes were monitored for 3 yr (2011 to 2013) at the beginning (P1) and at the end (P2) of the grazing season, always postgrazing. Paddock was the experimental unit (3 pseudoreplicates per treatment), and chambers (30 chambers per paddock) were considered multiple measurements of each experimental unit. A completely randomized design considered the term year × period as a repeated measure and chamber nested within paddock and treatment as the random term. Generally, SysB had greater CO2 emissions than SysA and GRE pasture sites across years and periods (P < 0.01). Soil temperature, AT, and WC had effects on CO2 emissions. Methane and N2 O emissions were observed from pasture sites of the 3 systems, but the effect of grazing was not constantly significant for CH4 and N2 O emissions. In addition, ST, AT, and WC did not conclusively explain CH4 and N2 O emissions. No clear trade-offs between GHG were observed; generally, GHG emissions increased from 2011 to 2013, which was likely associated with weather conditions, such as higher daily temperature and precipitation events. The central hypothesis that SysB would result in greater GHG emissions from pasture soils than SysA and GRE was not confirmed. © 2015 American Society of Animal Science. All rights reserved.
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Owing to the methane (CH4) produced by rumen fermentation, ruminants are a source of greenhouse gas (GHG) and are perceived as a problem. We propose that with appropriate regenerative crop and grazing management, ruminants not only reduce overall GHG emissions, but also facilitate provision of essential ecosystem services, increase soil carbon (C) sequestration, and reduce environmental damage. We tested our hypothesis by examining biophysical impacts and the magnitude of all GHG emissions from key agricultural production activities, including comparisons of arable- and pastoral-based agroecosystems. Our assessment shows that globally, GHG emissions from domestic ruminants represent 11.6% (1.58 Gt C y-1) of total anthropogenic emissions, while cropping and soil-associated emissions contribute 13.7% (1.86 Gt C y-1). The primary source is soil erosion (1 Gt C y-1), which in the United States alone is estimated at 1.72 Gt of soil y-1. Permanent cover of forage plants is highly effective in reducing soil erosion, and ruminants consuming only grazed forages under appropriate management result in more C sequestration than emissions. Incorporating forages and ruminants into regeneratively managed agroecosystems can elevate soil organic C, improve soil ecological function by minimizing the damage of tillage and inorganic fertilizers and biocides, and enhance biodiversity and wildlife habitat. We conclude that to ensure longterm sustainability and ecological resilience of agroecosystems, agricultural production should be guided by policies and regenerative management protocols that include ruminant grazing. Collectively, conservation agriculture supports ecologically healthy, resilient agroecosystems and simultaneously mitigates large quantities of anthropogenic GHG emissions. Copyright
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The objective of this study was to compare methane (CH) emissions from lactating beef cows grazed with different combinations of stocking rate and density. We hypothesized that a low stocking rate coupled with high-stocking-density grazing management would result in poorer forage quality, thereby increasing enteric CH emissions. System A (SysA) consisted of 120 cow-calf pairs rotating on a total of 120 ha divided into 2-ha pastures (stocking rate 1 cow/ha, stocking density 112,000 kg BW/ha, rest period of 60 to 90 d). System B (SysB) consisted of 16 groups of 4 cow-calf pairs each rotating on a 1.6-ha pasture (stocking rate 2.5 cows/ha, stocking density 32,000 kg BW/ha, rest period of 18 to 30 d). Enteric CH measurements were collected using a sulfur hexafluoride (SF) tracer gas method. Sampling occurred during 2012 and 2013 in 2 periods: the beginning (P1) and end of the grazing season (P2). Cannulated Angus cows were stratified by weight, age, and parity and were assigned to each treatment ( = 6) in a crossover design with a doubly repeated measures design, with period and day as repeated measures (α = 0.05). Dry matter intake was determined using chromic oxide (CrO) as a marker. Forage samples were collected ( = 3) for nutrient composition analyses and total forage mass determination. Forage botanical composition was determined using the dry-weight-rank method. Postgrazing herbage mass was greater for SysA during P2 in 2012 ( < 0.01) and 2013 ( = 0.01). Grasses were predominant and represented 67% to 96% of pastures; legumes contributed 3% to 21% of pastures across periods and treatments. The proportion of legumes tended to be higher in SysB pasture sites in P2 than in P1. There were no treatment effects on DMI. There was a period effect on DMI ( < 0.01); DMI of SysA and SysB cows increased from P1 to P2 (4 and 1.1 kg DMI/d increase, respectively). Cows ingested, on average, 2.6% (SysA) and 2.8% (SysB) of their BW. There was no year effect on CH emissions ( = 0.16). Daily enteric CH emissions did not vary with treatment and ranged from 195 to 249 g CH/d across treatment. Enteric CH emissions per unit GE intake varied with treatment during P1 (6.4% and 3.8% for SysA and SysB, respectively; < 0.01). Across treatments and periods, enteric CH emission per unit GE intake was 4.6%, which could be considered low for grazing lactating beef cows. It is likely that cows in the present study were selecting high-quality forage and produced comparatively lower CH emissions.
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The loss of organic matter from agricultural lands constrains our ability to sustainably feed a growing population and mitigate the impacts of climate change. Addressing these challenges requires land use activities that accumulate soil carbon (C) while contributing to food production. In a region of extensive soil degradation in the southeastern United States, we evaluated soil C accumulation for 3 years across a 7-year chronosequence of three farms converted to management-intensive grazing. Here we show that these farms accumulated C at 8.0 Mg ha(-1) yr(-1), increasing cation exchange and water holding capacity by 95% and 34%, respectively. Thus, within a decade of management-intensive grazing practices soil C levels returned to those of native forest soils, and likely decreased fertilizer and irrigation demands. Emerging land uses, such as management-intensive grazing, may offer a rare win-win strategy combining profitable food production with rapid improvement of soil quality and short-term climate mitigation through soil C-accumulation.
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Simple Summary: The environmental impact of three beef production systems was assessed using a deterministic model. Conventional beef production (finished in feedlots with growth-enhancing technology) required the fewest animals, and least land, water and fossil fuels to produce a set quantity of beef. The carbon footprint of conventional beef production was lower than that of either natural (feedlot finished with no growth-enhancing technology) or grass-fed (forage-fed, no growth-enhancing technology) systems. All beef production systems are potentially sustainable; yet the environmental impacts of differing systems should be communicated to consumers to allow a scientific basis for dietary choices. Abstract: This study compared the environmental impact of conventional, natural and grass-fed beef production systems. A deterministic model based on the metabolism and nutrient requirements of the beef population was used to quantify resource inputs and waste outputs per 1.0 × 10 9 kg of hot carcass weight beef in conventional (CON), natural (NAT) and grass-fed (GFD) production systems. Production systems were modeled using characteristic management practices, population dynamics and production data from U.S. beef production systems. Increased productivity (slaughter weight and growth rate) in the CON system reduced the cattle population size required to produce 1.0 × 10 9 kg of beef compared to the NAT or GFD system. The CON system required 56.3% of the animals, 24.8% of the water, 55.3% of the land and 71.4% of the fossil fuel energy required to produce 1.0 × 10 9 kg of beef compared to the GFD system. The carbon footprint per 1.0 × 10 9 kg of beef was lowest in the CON system (15,989 × 10 3 t), intermediate in the NAT system (18,772 × 10 3 t) and highest in the GFD system (26,785 × 10 3 t). The OPEN ACCESS Animals 2012, 2 128 challenge to the U.S beef industry is to communicate differences in system environmental impacts to facilitate informed dietary choice.
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Simple Summary The environmental impact of three beef production systems was assessed using a deterministic model. Conventional beef production (finished in feedlots with growth-enhancing technology) required the fewest animals, and least land, water and fossil fuels to produce a set quantity of beef. The carbon footprint of conventional beef production was lower than that of either natural (feedlot finished with no growth-enhancing technology) or grass-fed (forage-fed, no growth-enhancing technology) systems. All beef production systems are potentially sustainable; yet the environmental impacts of differing systems should be communicated to consumers to allow a scientific basis for dietary choices. Abstract This study compared the environmental impact of conventional, natural and grass-fed beef production systems. A deterministic model based on the metabolism and nutrient requirements of the beef population was used to quantify resource inputs and waste outputs per 1.0 × 109 kg of hot carcass weight beef in conventional (CON), natural (NAT) and grass-fed (GFD) production systems. Production systems were modeled using characteristic management practices, population dynamics and production data from U.S. beef production systems. Increased productivity (slaughter weight and growth rate) in the CON system reduced the cattle population size required to produce 1.0 × 109 kg of beef compared to the NAT or GFD system. The CON system required 56.3% of the animals, 24.8% of the water, 55.3% of the land and 71.4% of the fossil fuel energy required to produce 1.0 × 109 kg of beef compared to the GFD system. The carbon footprint per 1.0 × 109 kg of beef was lowest in the CON system (15,989 × 103 t), intermediate in the NAT system (18,772 × 103 t) and highest in the GFD system (26,785 × 103 t). The challenge to the U.S beef industry is to communicate differences in system environmental impacts to facilitate informed dietary choice.
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