Life Cycle Assessment of Greenhouse Gas Emissions from Dairy Production in a Central New York State Watershed

Cumulative greenhouse gas emissions related to dairy production in the Fall Creek watershed of central New York State were calculated using a life-cycle approach for the period 1975-2001. Expressed as CO2 equivalents (CO2e), emissions include CO2, CH4 and N2O related to fertilizer manufacture and transport, bovine metabolism, volatilization and leaching losses from applied fertilizer, nitrogen dynamics in crop residues, among a myriad of sources. During the 1975-2001 period, dairy N production in the study area increased by over 20%, although crop N production in the watershed declined by 33%. This change was driven by consolidation within the dairy industry that also led to a six-fold increase in N in feed imports into the watershed during the same period. Cumulative GHG emissions related to dairy production in Fall Creek rose by about 20% over 1975-2001 to about 14,000 tons CO2e per year for the 326 km2 watershed by 2001. In 1975, about 90% of CO2e emissions related to dairy production in the Fall Creek watershed were emitted within the watershed. However, by 2001 over 50% of emissions were generated outside of the watershed, primarily as N2O emissions related to fertilizer used in the production of feed subsequently imported into Fall Creek watershed.