Publikationsdatenbank

Modelling the downstream impact of diet and manure management on whole farm greenhouse gas and nitrogen emissions in cattle farming systems (2025)

Art

Hochschulschrift

Autor

Ouatahar, Latifa (WE 10)

Quelle

Berlin, 2025 — vi, 85 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/50036

Kontakt

Institut für Tier- und Umwelthygiene

Robert-von-Ostertag-Str. 7-13
14169 Berlin
+49 30 838 51845
tierhygiene@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Feed management decisions play an essential role in reducing greenhouse gas (GHG) and nitrogen (N) emissions from ruminant farming systems. However, evaluating the downstream effects of diet on emissions in dairy production is challenging. This is due to the complex interplay among interconnected components such as animals, housing, manure storage, and soil. Consequently, a comprehensive assessment that considers both direct and indirect GHG and N emissions and accounts for the underlying processes and drivers of carbon (C) and nitrogen within the system is necessary. Static emission factors (EFs) and empirical models often fail to capture the spatial and temporal variability of these systems. This limits their utility for site-specific assessments and targeted mitigation strategies. This thesis addresses this problematic by applying PB modelling approaches that simulate the underlying biogeochemical processes driving emissions, thereby offering a more dynamic and comprehensive perspective. The research begins with a comprehensive review (the first Paper) of modelling the influence of feed management on GHG and N emissions in cattle farming systems. It contrasts statistical and empirical models, with mechanistic PB models. The former are useful for inventory applications, whilst the latter capture dynamic interactions between feed composition, microbial fermentation, and downstream emissions. This review establishes the scientific rationale for integrating PB approaches into whole-farm emission assessments. By identifying the limitations of simpler methods, it sets the stage for a more sophisticated modelling approach. Building on this foundation, the second paper introduces an innovative PB modelling framework. This framework creates links across the manure management chain. It integrates the Dutch Tier 3 model for animal emissions with the Manure-(DNDC) model for manure storage and a soil biogeochemistry model. This study evaluates the downstream impact of dietary factors on whole-farm emissions. The methodology was rigorously applied to two contrasting dairy systems: a confined system in Germany and a pasture-based system in New Zealand. The differences in production systems between them demonstrated significant differences in C and N emission. This highlights the critical role of feeding and manure management practices in shaping the environmental footprint. This application showed the framework's adaptability and its capacity to reveal system-specific dynamics. The third paper further advances the research by comparing the dynamic PB Tier 3 modelling approach with IPCC Tier 1 and Tier 2 methods. This comparative analysis showed substantial differences between PB Tier 3 dynamic EFs and IPCC Tier 1 and 2 EFs. This reveals that PB models can capture interannual and system-specific GHG emission variability more accurately, leading to more precise and adaptable emission estimates. The housing component of the Manure-DNDC model was validated against field measurements, confirming its effectiveness in simulating ammonia and methane barn emissions, a key source of uncertainty in GHG assessments. This validation underscores the reliability of the PB approach for capturing complex emission processes that generic EFs may overlook. Collectively, these studies demonstrate that integrating PB models into whole-farm emission assessments enables a more nuanced understanding. It shows how feeding and manure management practices impact GHG and N emissions. These models offer a more wholistic and accurate picture of on-farm emissions by simulating the underlying processes and considering the interactions between different farm components. This integrated modelling approach has significant implications. It can help develop of targeted mitigation strategies and improve the C accounting in the context of Carbon-farming and monitoring, reporting and verification (MRV) in agricultural systems. It can also inform future policies aimed at reducing the environmental footprint of cattle farming. The PB models represent a step towards more precise and adaptable tools for researchers and policymakers. They facilitate evidence-based decision-making in sustainable agriculture and pave the way for more environmentally responsible livestock production.