GREENHOUSE gas (GHG) accounting takes place at many different levels including State, national, industry and at the farmgate.
It is important to benchmark practices onfarm and carbon emissions are no exception, with several tools available at a farmgate level to support producers understand and give them opportunities to mitigate their GHG product emissions.
That was the message of a presentation given by Department of Primary Industries and Regional Development (DPIRD) senior development officer Mandy Curnow at the virtual Grains Research and Development Corporation (GRDC) Grains Research Updates on Monday.
According to Ms Curnow, it's important to understand the limitations of these tools but also their value in identifying "hotspots" in emissions so that effort can be focussed on areas where the biggest impacts can be made.
"Cropping enterprises in WA generally have higher emissions than Eastern States counterparts, mainly due to higher inputs such as nitrogenous fertilisers," Ms Curnow said.
"Emissions from cropping enterprises are generally higher for canola and lowest for legumes.
"Our opportunities to sequester carbon in low rainfall, high temperature environments are often less than other States, making the task of offsetting emissions more difficult."
However, opportunities to do so do exist and the goal of carbon neutrality for the cropping enterprise is within reach for most grain producers.
Once growers have undertaken a carbon account, which only needs to be an unofficial account using freely available online tools, scenarios for reducing emissions can be investigated and a course of action taken.
That may include identifying and changing practices to become carbon neutral or to have lower emissions intensities to meet market requirements, identifying opportunities for carbon sequestration, either for reserving these to offset emissions from the farm's produce, or to acquire carbon credits to earn income from those activities.
Using one of those online tools, DPIRD calculated the carbon account for four representative farms in WA - eastern Wheatbelt 100 per cent cropping, eastern Wheatbelt mixed farm, Geraldton region 100pc cropping and woolbelt mixed farm -which provided some ballpark emission figures and compositions for different farm enterprises and locations.
"Emissions as well as the composition of these emissions, varied greatly across the different farms," Ms Curnow said.
"While the woolbelt mixed farm was the smallest in hectares, it had the largest number of livestock in the system and the livestock contributed the largest emissions to the farm's total emissions due to the enteric methane generated by rumen fermentation.
"The eastern Wheatbelt 100pc cropping farm had the lowest total emissions, as it was the farm with the lowest intensity of fertiliser and had no livestock."
On that broadacre farm in the eastern Wheatbelt, fertiliser and fuel were the two largest scope one emission contributors and the net farm emissions totalled 2184 tonnes of carbon dioxide equivalent per annum.
The pulse crop gave the least emissions due mainly to the absence of nitrogenous fertiliser application, while most of the emissions produced were by the wheat enterprise, which was to be expected as it is the largest proportion of crop grown.
Scope three emissions were approximately one third of the total emissions, while scope one emissions made up the lion's share and scope two emissions were only 0.2pc of total emissions.
There are several options to decrease emission and sequester carbon onfarm, many of which have the added advantage of boosting productivity and sustainability.
"Decreasing the emissions intensity of produce in tonnes of CO2-e per tonne can be achieved by increasing productivity and efficiency," Ms Curnow said.
"However, it must be remembered that growing more produce more efficiently will not necessarily reduce the farm's overall emission total."
Using an online tool developed by CSIRO, DPIRD estimated carbon sequestration by planting either oil mallees or mixed eucalypts at Merredin was 7.17t CO2-e per hectare per year over a 25 year period.
Given the total farm emissions for the 100pc cropping example in the eastern Wheatbelt was 2184t CO2-e pa, it would take an estimated 305ha of revegetation to completely off-set the farm's emissions.
The farm had 4900ha of arable land out of a total 5100ha.
Assuming little vegetation exists onfarm already, about 120ha of arable land and 180ha of non-arable land would need to be planted if vegetation was the only activity undertaken to reduce emissions.
"Most options to increase efficiency through reduction in inputs, fuel and more efficient use of nitrogenous fertilisers will be incremental contributions to lowering emissions per kilogram, depending on existing practices and the scope for improvement," Ms Curnow said.
"However, small decreases of several factors add up and will lower carbon product intensity.
"Using the online tools allows producers to run some 'what if' scenarios to see the likely impacts these 'tweaks' have on emissions."
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