Invited review: A position on the Global Livestock Environmental Assessment Model (GLEAM)
MacLeod, M.J. ; Vellinga, T. ; Opio, C. ; Falcucci, A. ; Tempio, G. ; Henderson, B. ; Makkar, H. ; Mottet, A. ; Robinson, T. ; Steinfeld, H. ; Gerber, P.J. - \ 2018
Animal 12 (2018)2. - ISSN 1751-7311 - p. 383 - 397.
climate change - environmental assessment - life-cycle analysis - livestock - models
The livestock sector is one of the fastest growing subsectors of the agricultural economy and, while it makes a major contribution to global food supply and economic development, it also consumes significant amounts of natural resources and alters the environment. In order to improve our understanding of the global environmental impact of livestock supply chains, the Food and Agriculture Organization of the United Nations has developed the Global Livestock Environmental Assessment Model (GLEAM). The purpose of this paper is to provide a review of GLEAM. Specifically, it explains the model architecture, methods and functionality, that is the types of analysis that the model can perform. The model focuses primarily on the quantification of greenhouse gases emissions arising from the production of the 11 main livestock commodities. The model inputs and outputs are managed and produced as raster data sets, with spatial resolution of 0.05 decimal degrees. The Global Livestock Environmental Assessment Model v1.0 consists of five distinct modules: (a) the Herd Module; (b) the Manure Module; (c) the Feed Module; (d) the System Module; (e) the Allocation Module. In terms of the modelling approach, GLEAM has several advantages. For example spatial information on livestock distributions and crops yields enables rations to be derived that reflect the local availability of feed resources in developing countries. The Global Livestock Environmental Assessment Model also contains a herd model that enables livestock statistics to be disaggregated and variation in livestock performance and management to be captured. Priorities for future development of GLEAM include: improving data quality and the methods used to perform emissions calculations; extending the scope of the model to include selected additional environmental impacts and to enable predictive modelling; and improving the utility of GLEAM output.
A framework to assess life cycle nitrogen use efficiency along livestock supply chains
Uwizeye, U.A. ; Tempio, G. ; Gerber, P.J. ; Schulte, R. ; Boer, I.J.M. de - \ 2014
In: Proceedings of the Life Cycle Assessment Food Conference (LCA Food 2014). - - p. 1398 - 1407.
to the significant contribution of the livestock sector to nitrogen (N) losses, improving N use efficiency (NUE-N) along the life cycle of livestock products is one of the important step towards increasing production performance and reduction of its environmental impacts. We developed a comprehensive framework and novel metrics to assess NUE-N along the livestock supply chain (i.e. -to-primary- ). Our framework was illustrated for the case study of mixed dairy production in Western Europe. Metrics developed included the life cycle NUE-N; total N losses to the environment per unit of N in the final co-products; and the N hotspot index (NHI-N), defined as the relative evenness of the N losses along the supply chain. Averaged across countries, the life cycle NUE-N was 36¿3.1%, N losses were 6.6¿1.8 g N per g N in the final animal co-products, and NHI-N of 1.0¿0.1. The N losses and NHI-N also revealed large differences in hotspots across supply chains, and allowed to identify priority areas where improvement actions are necessary to enhance the efficiency. We show that the combination of life cycle NUE-N, N losses and NHI-N gives valuable information to guide N management in livestock supply chains
Feed-milk-manure nitrogen relationships in global dairy production systems
Powell, J.M. ; Macleod, M. ; Vellinga, Th.V. ; Opio, C. ; Falcucci, A. ; Tempio, G. ; Steinfeld, H. ; Gerber, P. - \ 2013
Livestock Science 152 (2013)2-3. - ISSN 1871-1413 - p. 261 - 272.
dietary-protein - nutrient management - use efficiency - urea nitrogen - farms - cows - excretion - cycle - performance - emissions
Nitrogen (N) inputs from fertilizer, biologically-fixed N, feed, and animal manure sustain productive agriculture. Agricultural systems are limited however in their ability to incorporate N into products, and environmental N losses may become local, regional and global concerns. The anticipated increases in global demand for food, especially for animal products, necessitate an urgent search for practices that enhance N use efficiency (NUE) and reduce environmental N loss. The objectives of this study were to determine feed-milk-manure N relationships for the global dairy herd, and to evaluate how well regional and production system determinations of these relationships correspond to measurements made under experimental conditions and on commercial dairy farms. Data on dairy cattle populations, feed and milk production from 142 countries were used in a Life Cycle Assessment (LCA) model to determine dry matter intake (DMI), N intake (NI), the percentage of NI secreted as milk N (NUE-milk), the percent of NI used by the whole-herd (NUE-herd), and manure N excretion (Nex). On a global basis, an average lactating cow weighs approximately 420 kg; per animal unit (AU = 1000 kg live weight) daily DMI and NI are 21.0 kg and 477 g, respectively; annual milk production is 5000 kg/AU; and NUE-milk and NUE-herd are 16.0% and 15.6%, respectively. Approximately 37% of global lactating cows have NUE-milk of <10% and these low efficient cows account for 10% of the milk production and 33% of Nex globally. Approximately 30% of global lactating cows have NUE-milk between 21% and 25% and these cows account for 53% of the milk production and 35% of Nex globally. Estimates of NUE-milk and Nex corresponded well to measurements under experimental and commercial farm conditions. Study determinations of Nex were however 3-50% lower than IPCC Tier 1 values of Nex for Africa, Middle East, Latin America and Asia. The apparent accuracy of LCA model calculations of Nex should enhance regional, production system and global determinations of dairy Nex loss during collection, storage, and land application, and the amounts of Nex actually recycled through crops and pastures. Published by Elsevier B.V.