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Ways are being sought to reduce the environmental impact of ruminant livestock farming. Integration of trees into farming systems has been advocated as a measure to deliver ecosystem services, inter alia climate regulation and adaptation, water quality regulation, provisioning of fibre, fuel and habitats to support biodiversity. Despite the rapid expansion of cattle farming in the tropics, notably in Latin America, there is little robust evidence on the extent to which trees are able to mitigate the effects of cattle farming in this ecological zone. This article describes a case study conducted on a large, specialised dairy farm in Costa Rica, where two-thirds of the field boundaries are live tree fences. For the first time, this study quantifies the offset potential of trees by estimating rate of carbon sequestration in a silvopastoral system (SPS) in the tropics. It was found that over a 30-month interval, trees sequestered 1.43 Mg C ha-1 year-1 above and below ground. Attributional life cycle assessment (LCA) (cradle to farm gate) was applied to calculate the carbon footprint of milk produced on the farm for the years 2016 to 2018. Trees in live fences offset 21-37% of milk footprints, resulting in residual net footprints of 0.75±0.25 to 0.84±0.26 kg CO2 eq. kg-1 milk. Exclusion of life cycle emissions that may not fall within national emission inventory accounting (e.g. fertiliser manufacture and feed production) increased the mean offset from 27 to 34% of gross milk footprint. Although based on temporally limited data (30 months), our findings indicate that a live fence SPS could play an important role in short- to medium-term climate mitigation from livestock production, buying time for deployment of long-term mitigation and adaptation planning. Supplementary Information: The online version contains supplementary material available at 10.1007/s13593-022-00834-z.
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The study reviewed carbon footprint (CF) analyses for milk production in Latin America from cradle to farm gate. The objective was to estimate (1) the effect of feeding management (zero-grazing, semi-confinement, and pasture), (2) cattle system (specialized dairy vs. dual-purpose), and (3) region (tropical vs. temperate) on milk production (kg/cow/day) and CF (kg CO2eq/kg fat and protein corrected milk (FPCM)). A systematic literature review was conducted, and for the final analysis, a total of 32 individual CF (from 11 studies) were used. Studies included in the final analysis allowed to calculate CF per kg FPCM, included upstream emissions calculations, and used the IPCC's tier 2 approach for enteric methane emissions. The range of the CF observed in the region was from 1.54 to 3.57 kg CO2eq/kg FPCM. Feeding management had a significant effect on milk production, but not on CF. Zero-grazing compared with pasture systems had a 140% greater milk production (20.1 vs. 8.4 kg milk/cow/day), but numerically greater CF for pasture systems (2.6 vs. 1.7 kg CO2eq/kg FPCM). Compared with specialized dairy cattle, dual-purpose cattle produced less milk (P < 0.001) and higher CF (P < 0.05). Compared with temperate regions, tropical region systems produced less milk and higher CF. In conclusion, in Latin America, the cattle system and region have a significant impact on CF, whereas the feeding management (zero-grazing, semi-confinement, and pasture) does not impact the CF of milk produced.
Assuntos
Pegada de Carbono , Indústria de Laticínios , Animais , Bovinos , Dieta , Feminino , Lactação , América Latina , Metano/análise , Leite/químicaRESUMO
Agriculture is the largest source of ammonia (NH3) emissions. As NH3 is an indirect greenhouse gas, NH3 measurements are crucial to improving greenhouse gas emission inventory estimates. Moreover, NH3 emissions have wider implications for environmental and human health. Only a few studies have measured NH3 emissions from pastures in the tropics and subtropics and none has compared emissions to inventory estimates. The objectives of this study were to (1) measure NH3 emissions from dairy pastures in tropical and subtropical regions; (2) calculate NH3 emissions factors (EF) for each campaign; and (3) compare measured EF with those based on the 2006 Intergovernmental Panel on Climate Change (IPCC) Tier 1, 2019 Refinement to the 2006 IPCC Tier 1, and the European Monitoring and Evaluation Programme/European Environmental Agency (EMPE/EEA) Tier 2 inventory estimates. Pasture NH3 emissions were measured on 3 dairy farms in Costa Rica. On each dairy, NH3 emissions were measured twice during the wet season and once during the dry season using a micrometeorological integrated horizontal-flux mass-balance method. Emissions were measured from excreta (dung and urine) deposited by grazing cattle and the subsequent application of organic (slurry) or synthetic fertilizer (ammonium nitrate or urea). Measured EF for all campaigns [from grazing cattle excreta and any subsequent slurry or fertilizer application; 4.9 ± 0.9% of applied nitrogen (mean ± SE)] were similar to those of the EMEP/EEA Tier 2 approach (6.1 ± 0.9%; mean ± SE) and 4 times lower than 2006 IPCC and 2019 Refinement to 2006 IPCC Tier 1 default estimates (17.7 ± 1.4 and 18.2 ± 0.9%, respectively; mean ± SE). Measured EF for excreta deposited on pasture and excreta both deposited on pasture and slurry application [3.9 ± 2.1 and 4.2 ± 2.1% (mean ± 95% CI), respectively] were 5 times lower than default EF assumed by 2006 IPCC and 2019 Refinement to 2006 IPCC methodology (both 20 and 21%, respectively), whereas EMEP/EAA estimates were similar [6.0 and 4.6 ± 0.3% (mean ± 95% CI), respectively]. This suggests an overestimation of EF from excreta deposited on pasture and slurry applications in tropical and subtropical regions by IPCC methodologies. Furthermore, rainfall, which is not included as a parameter in the current EMEP/EEA Tier 2 methodology, appeared to reduce NH3 emissions, suggesting that accounting for this in the inventory methodologies could improve inventory estimates.