State-level trends in the greenhouse gas emission intensity of US milk production

The greenhouse gas emission intensity of US milk production (i.e., greenhouse gas emissions per unit of production) has varied across time and states. However, research has not examined how farm-sector trends af-fect the state-level emission intensity of production. We estimated fixed effects regressions with state-level panel data from 1992 through 2017 to test how US dairy farm-sector changes influenced the greenhouse gas emission intensity of production. We found that increases in per cow milk productivity reduced the enteric greenhouse gas emission intensity of milk production, while it had no statistically significant effect on the manure green-house gas emission intensity of production. In contrast, increases in average farm size and the number of farms reduced the manure greenhouse gas emission intensity of milk production, while they did not affect the enteric greenhouse gas emission intensity of production.