The Global Livestock Environmental Assessment Model (GLEAM) is a modelling framework developed within the Animal Production and Health Division of FAO. It simulates the functioning and environmental impacts of livestock production activities. The most relevant characteristics of GLEAM are:
It is based on Life Cycle Assessment (LCA) methodologies. It runs in a Geographic Information System (GIS) environment. It covers upstream, on-farm and downstream impacts.
The current version of GLEAM (1.0) focuses on the quantification of greenhouse gas emissions related to livestock sector supply chains. Future versions of GLEAM,currently under development, will also include other environmental impacts such as nutrient and water use or interactions with biodiversity.
GLEAM generates different data for 11 commodities: meat and milk from cattle, sheep, goats and buffaloes; meat from pigs and meat and eggs from chicken. Ruminant production is differentiated into mixed and grazing systems; pig production into backyard, intermediate and industrial systems and chicken production into backyard, layers and broilers.
Total production is expressed in protein basis to allow comparisons between species and products. Production is calculated on the basis of herd parameters (reproduction, mortality, etc.) and productivity parameters used in the analysis. Therefore, total production may not be consistent with total production in the FAOSTAT database.
Please note that present data does not include emissions from "Other poultry", accounting for 72 million tonnes CO2-eq (see Tackling climate change through livestock report), and emissions allocated to fiber production (wool), draught power and manure use fuel, which accounts for 400 million tonnes CO2-eq.
GHG emissions are split into twelve different sources, as described in the Tackling climate change through livestock (2013) report. Those are the following:
Feed - CO2 CO2 emissions arising from the production, transportation and processing of feed. It also includes emissions arising from the energy use during the manufacture of fertilizers and for field operations such as tillage or fertilizer application.
Feed - CH4 CH4 emissions arising from the anaerobic decomposition of organic matter during rice cultivation. It is only applicable to pigs and chicken, given the use or rice as feed ingredient.
Feed: fertilizer & crop residues - N2O N2O emissions arising from the fertilizer applied to feed crops and from the decomposition of crop residues.
Feed: applied & deposited manure - N2O N2O emissions arising from the manure applied to feed crops as organic fertilizer and from the manure directly deposited by the animals as they graze.
Land Use Change (LUC): soybean - CO2 CO2 emissions arising from the expansion of cropland for feed production. Only the expansion driven by soybean production in Brazil and Argentina was considered. This decision results from the observation of trends in land-use transitions and crop expan- sions: over the 1990-2006 period, which is used as reference for GLEAM data, the main global expansions were for maize and soybean production, but only in Latin America was this expansion directly linked to decrease in forest area. Within Latin America, 90 percent of the soybean expansion took place in Brazil and Argentina.
Land Use Change (LUC): pasture expansion - CO2 CO2 emissions arising from deforestation associated with pasture expansion. Only pasture expansions in Latin America were taken into account. During the 1990-2006 period, significant pasture expansions and simultaneous forest area decrease occurred in Latin America and Africa. However, the link with grazing animals as deforestation driver was not significant enough in Africa.
Enteric fermentation - CH4 CH4 emissions arising from enteric fermentation from both ruminants and monogastrics.
Manure management - CH4 CH4 emissions arising from manure storage and management prior to application.
Manure management - N2O N2O emissions arising from manure storage and management prior to application.
Direct energy - CO2 CO2 emissions arising from the energy use on-farm for heating, ventilation, etc.
Indirect energy - CO2 CO2 emissions arising from the energy use during the production of materials for farm buildings and equipment.
Post-farm - CO2 CO2 emissions arising from energy use for processing and transport of livestock goods after they leave the farm gate.