When NRM North Carbon Farming extension officer Adrian James attended a Tasmanian Institute of Agriculture field day at the Brock's farm in April, he approached Mr Brock and asked if he could run the farm's data through the dairy greenhouse gas calculator.

Mr James said he believed that if the Brock's production was so efficient and profitable, it must also produce less greenhouse gas per litre of milk than the average dairy.

"Based on the 2006-07 year - farms that participated in the TasMilk 60 project - the Tasmanian average dairy farm emissions were 1.04 kilograms of carbon dioxide equivalent per kilo of fat-and- protein-corrected milk (CO2- e/kg FPCM)," Mr James said.

"The Brock's emission results from the 2012-13 year were at the lower end of the scale at 0.89kg CO2-e/kg FPCM, much lower than average."

The result came as a surprise to Mr Brock, as the farm had not been managed specifically to reduce emissions.

"It's great to put a comparative figure on our emissions and know that we are performing efficiently with our current dairy practices," Mr Brock said.

"It is easy to get swallowed up in the hype surrounding greenhouse emissions, but knowing exactly where we stand gives us confidence that we are producing milk in a sustainable way."

Mr James said the result showed that highly productive farming was better for more than just the farm balance sheet.

"Many factors can influence a farm's greenhouse gas emissions, (so) it can be worthwhile comparing several years to confirm that a farm has practices in place that can result in a long term reduction in greenhouse gas emissions compared to industry averages," he said.

"Efficiently converting nitrogen fertiliser into palatable grass makes good business sense and reduces nitrous oxide emissions and efficiently turning pasture and other feeds into milk reduces methane emissions while making more profit.

"The Brock's cows, which produced 95 per cent of their bodyweight in milk solids in a year, are really efficient at converting inputs into milk."