scholarly journals How does soil carbon sequestration affect greenhouse gas emissions from a sheep farming system? Results of an life cycle assessment case study

Author(s):  
Pasquale Arca ◽  
Enrico Vagnoni ◽  
Pierpaolo Duce ◽  
Antonello Franca

Highlights Extensification of dairy sheep systems provides an environmental benefit when soil C sequestration is considered. Extensification of dairy sheep systems determines lower environmental impact per hectare of utilized agricultural area. Enteric methane emissions are the main source of GHG emissions of the sheep milk life cycle. Carbon sequestration in permanent grasslands can considerably contribute to climate change mitigation.   Abstract A life cycle assessment (LCA) study of a transition from semi-intensive to semi-extensive Mediterranean dairy sheep farm suggests that the latter has a strong potential for offsetting greenhouse gas (GHG) emissions through the soil C sequestration (Cseq) in permanent grasslands. The extensification process shows clear environmental advantage when emission intensity is referred to the area-based functional unit (FU). Several LCA studies reported that extensive livestock systems have greater GHG emissions per mass of product than intensive one, due to their lower productivity. However, these studies did not account for soil Cseq of temporary and permanent grasslands, that have a strong potential to partly mitigate the GHG balance of ruminant production systems. Our LCA study was carried out considering the transition from a semi-intensive (SI) towards a semi-extensive (SE) production system, adopted in a dairy sheep farm located in North-Western Sardinia (Italy). Impact scope included enteric methane emissions, feed production, on-farm energy use and transportation, infrastructures as well as the potential C sink arising from soil Cseqwith respect to the emission intensity. In order to provide a more comprehensive analysis, we used the following FUs: 1 kg of fat and protein corrected milk (FPCM) and 1 ha of utilised agricultural area (UAA). We observed that the extensification of production system determined contrasting environmental effects when using different FUs accounting for soil Cseq. When soil Cseq in emission intensity estimate was included, we observed slightly lower values of GHG emissions per kg of FPCM in the SI production system (from 3.37 to 3.12 kg CO2 equivalents – CO2-eq), whereas a greater variation we observed in the SE one (from 3.54 to 2.90 kg CO2-eq). Considering 1 ha of UAA as FU and including the soil Cseq, the emission intensity in SI moved from 6,257 to 5,793 kg CO2-eq, whereas values varied from 4,020 to 3,299 kg CO2-eq in SE. These results indicated that the emission intensity from semi-extensive Mediterranean dairy sheep farms can be considerably reduced through the soil Cseq, although its measurement is influenced by the models used in the estimation.

2021 ◽  
Author(s):  
Sylvia Vetter ◽  
Michael Martin ◽  
Pete Smith

<p>Reducing greenhouse gas (GHG) emissions in to the atmosphere to limit global warming is the big challenge of the coming decades. The focus lies on negative emission technologies to remove GHGs from the atmosphere from different sectors. Agriculture produces around a quarter of all the anthropogenic GHGs globally (including land use change and afforestation). Reducing these net emissions can be achieved through techniques that increase the soil organic carbon (SOC) stocks. These techniques include improved management practices in agriculture and grassland systems, which increase the organic carbon (C) input or reduce soil disturbances. The C sequestration potential differs among soils depending on climate, soil properties and management, with the highest potential for poor soils (SOC stock farthest from saturation).</p><p>Modelling can be used to estimate the technical potential to sequester C of agricultural land under different mitigation practices for the next decades under different climate scenarios. The ECOSSE model was developed to simulate soil C dynamics and GHG emissions in mineral and organic soils. A spatial version of the model (GlobalECOSSE) was adapted to simulate agricultural soils around the world to calculate the SOC change under changing management and climate.</p><p>Practices like different tillage management, crop rotations and residue incorporation showed regional differences and the importance of adapting mitigation practices under an increased changing climate. A fast adoption of practices that increase SOC has its own challenges, as the potential to sequester C is high until the soil reached a new C equilibrium. Therefore, the potential to use soil C sequestration to reduce overall GHG emissions is limited. The results showed a high potential to sequester C until 2050 but much lower rates in the second half of the century, highlighting the importance of using soil C sequestration in the coming decades to reach net zero by 2050.</p>


2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 147-148
Author(s):  
Jason Rowntree ◽  
Paige Stanley ◽  
David Beede ◽  
Marcia DeLonge ◽  
Michael Hamm

Abstract Using life cycle analysis (LCA), several studies have concluded that grass-finished beef systems have greater GHG intensities than feedlot-finished (FL) beef systems. These studies evaluated only one grazing management system– continuous grazing – and assumed steady-state soil carbon (C), to model the grass-finishing environmental impact. However, by managing for more optimal forage growth and recovery, adaptive multi-paddock (AMP) grazing can improve animal and forage productivity, potentially sequestering more soil organic carbon (SOC) than continuous grazing. To examine impacts of AMP grazing and related SOC sequestration on net GHG emissions, a comparative LCA was performed of two different beef finishing systems in the Upper Midwest, USA: AMP grazing and FL. We used on-farm data collected from the Michigan State University Lake City AgBioResearch Center for AMP grazing. Impact scope included GHG emissions from enteric methane, feed production and mineral supplement manufacture, manure, and on-farm energy use and transportation, as well as the potential C sink arising from SOC sequestration. Across-farm SOC data showed a 4-year C sequestration rate of 3.59 Mg C ha−1 yr−1 in AMP grazed pastures. After including SOC in the GHG footprint estimates, finishing emissions from the AMP system were reduced from 9.62 to −6.65 kg CO2-e kg carcass weight (CW)−1, whereas FL emissions increased slightly from 6.09 to 6.12 kg CO2-e kg CW−1 due to soil erosion. This indicates that AMP grazing has the potential to offset GHG emissions through soil C sequestration, and therefore the finishing phase could be a net C sink. However, FL production required only half as much land as AMP grazing. This research suggests that AMP grazing can contribute to climate change mitigation through SOC sequestration and challenges existing conclusions that only feedlot-intensification reduces the overall beef GHG footprint through greater productivity.


Author(s):  
Meng Na ◽  
Xiaoyang Sun ◽  
Yandong Zhang ◽  
Zhihu Sun ◽  
Johannes Rousk

AbstractSoil carbon (C) reservoirs held in forests play a significant role in the global C cycle. However, harvesting natural forests tend to lead to soil C loss, which can be countered by the establishment of plantations after clear cutting. Therefore, there is a need to determine how forest management can affect soil C sequestration. The management of stand density could provide an effective tool to control soil C sequestration, yet how stand density influences soil C remains an open question. To address this question, we investigated soil C storage in 8-year pure hybrid larch (Larix spp.) plantations with three densities (2000 trees ha−1, 3300 trees ha−1 and 4400 trees ha−1), established following the harvesting of secondary mixed natural forest. We found that soil C storage increased with higher tree density, which mainly correlated with increases of dissolved organic C as well as litter and root C input. In addition, soil respiration decreased with higher tree density during the most productive periods of warm and moist conditions. The reduced SOM decomposition suggested by lowered respiration was also corroborated with reduced levels of plant litter decomposition. The stimulated inputs and reduced exports of C from the forest floor resulted in a 40% higher soil C stock in high- compared to low-density forests within 8 years after plantation, providing effective advice for forest management to promote soil C sequestration in ecosystems.


2008 ◽  
Vol 38 (2) ◽  
pp. 168-173 ◽  
Author(s):  
Alan L. Wright ◽  
Frank M. Hons ◽  
Robert G. Lemon ◽  
Mark L. McFarland ◽  
Robert L. Nichols

2013 ◽  
Vol 31 (3) ◽  
pp. 169-176 ◽  
Author(s):  
Dewayne L. Ingram ◽  
Charles R. Hall

Life cycle assessment (LCA) was utilized to analyze the global warming potential (GWP), or carbon footprint, and associated costs of the production components of a field-grown, spade-dug, 5 cm (2 in) caliper Cercis canadensis ‘Forest Pansy’ in the Lower Midwest, U.S. A model production system was determined from interviews of nursery managers in the region. Input materials, equipment use and labor were inventoried for each production system component using international standards of LCA. The seed-to-landscape GWP, expressed in kilograms of carbon dioxide emission equivalent (CO2e), was determined to be 13.707. Equipment use constituted the majority (63%) of net CO2-e emissions during production, transport to the customer, and transplanting in the landscape. The model was queried to determine the possible impact of production system modifications on carbon footprint and costs to aid managers in examining their production system. Carbon sequestration of a redbud growing in the landscape over its 40 year life, weighted proportionally for a 100 year assessment period, was calculated to be −165 kg CO2e. The take-down and disposal activities following its useful life would result in the emission of 88.44 kg CO2e. The life-cycle GWP of the described redbud tree, including GHG emissions during production, transport, transplanting, take down and disposal would be −63 kg CO2e. Total variable costs associated with the labor, materials, and equipment use incurred in the model system were $0.069, $2.88, and $34.81 for the seedling, liner, and field production stages, respectively. An additional $18.83 was needed for transport to the landscape and planting in the landscape and after the 40 year productive life of the tree in the landscape, another $60.86 was needed for take-down and disposal activities.


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