In 2010 we undertook our first analysis of greenhouse gas emissions from our dairy farm. To do this we used the industry developed tool DGAS. DGAS software is intended to give the user an understanding of the greenhouse gases emitted from their enterprise, both in absolute terms and relative to milk solids produced. The gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are multiplied by 1, 21 and 310, respectively, so as to be expressed in tonnes of CO2 equivalents. These are then totalled and compared to the tonnes of milk solids produced by the enterprise. One litre of our milk contains around 8 grams of milk solids. The results are not unlike those from pasture based dairy farms anywhere in southern Australia. According to DGAS, our farm emitted 9T CO2 equivlents per tonne of milk solids produced – the bulk of our emissions (60%) come from methane produced by our animals. At this point in time there is little we can do about this other than ensure the best quality feed is provided to the stock so they have the best chance of converting feed to milk with minimal methane emissions. The graph shows that the key sources of emissions on our farm for the 2008 – 09 year were;
- Methane (60%), from rumen fermentation,
- Nitrous oxide (22%) from fertiliser, dung, urine and indirect sources from leaching and ammonia,
- Embedded emissions (from pre-farm processes) from bought in grain & other inputs accounted for 11,
- Energy from fuel and electricity contributed only 7% of total emissions on farm.
“Of the currently available technologies [for nitrous oxide abatement], nitrification inhibitors, managing animal diets and fertiliser management show the best potential for reducing emissions in the short-term. However, abatement technologies that increase the efficiency of N within the soil–plant system are likely to increase pasture and/or animal productivity, which in turn, is likely to increase methane emissions (e.g. increased stocking rates). It is therefore important that a whole farm system analysis be conducted for individual technologies, to ensure that total GHG abatement is actually achieved.” (De Klein & Eckard, 2008) Richard Eckard from the Primary Industries Climate Challenges Centre suggests that current technologies able to assist with methane reduction on Australian dairy farms include feeding oils (which we do at the moment to improve milker comfort in the shed, ie: less dust) and ensuring that all animals on the farm are productive. So it is very important we continue to breed and feed for highly efficient cows which are able to convert grass to milk.
Catch up with where we are at with the Carbon Tax on Radio National Bush Telegraph this morning in the first of a series of interviews on “Carbon challenge case study #4: The dairy industry“