© CSIRO 2015. Australian agriculture generated 15% of national greenhouse gas emissions (GHGE) in 2011, with CH4 and N2O accounting for 12 and 3% of national emissions, respectively. In 2011, the Australian government introduced a voluntary carbon offset scheme called the Carbon Farming Initiative, which enables farmers to earn carbon credits by lowering GHGE or sequestering carbon. One way of reducing emissions is to decrease the number of replacement animals required on-farm and increase the amount of product that animals produce across their lifetime. This study explores two options for reducing GHGE over an animal's lifetime: (1) changing from an annual calving system to extended lactation system on dairy farms; and (2) increasing the longevity of ewes on wool enterprises to produce an extra year of wool and offspring. The biophysical models DairyMod and GrassGro were used to simulate the dairy and wool enterprises, respectively, and GHGE were calculated using the Australian National Inventory methodology. Extended lactation produced lower total emissions and emissions intensity (t CO2e/t milk fat plus protein) than annual calving and also resulted in higher operating profits. The GHGE from increasing longevity on sheep enterprises was similar to the baseline scenario, largely as a result of similar stocking rates. Extended lactation had greater potential of reducing emissions than increasing longevity on wool enterprises because there was a larger increase in the production of milk fat plus protein across cows' lifetimes, as well as greater reductions in the number of replacement animals required on the enterprise. This research demonstrated that the profitability of farm enterprises would be driven more by productivity than claiming carbon offsets from these management changes.