A UK-based study has found canola oil is by far the most environmentally friendly vegetable oil in terms of greenhouse gas emissions per litre of oil produced.
In good news for Australia's booming canola sector, the oilseed was ranked far more efficient than other leading oils such as soybean oil, sunflower oil and palm oil.
The University of Nottingham study also threw up a curveball in that palm oil, traditionally vilified for its poor environmental credentials, was actually a lower GHG emitter than soybean oil per litre, even allowing for the added emissions associated with deforestation as well as ongoing production emissions.
Scientists from the University of Nottingham's Future Food Beacon carried out their analysis into emissions used to produce vegetable oil.
This new study encompassed almost 6000 producers in 38 countries, and is representative of over 71 per cent of global vegetable oil production.
Across all oil crop systems, median GHG emissions were 3.81 kg carbon dioxide equivalent (CO2e) per kg refined oil.
By crop type, emissions varied from 2.49 kg CO2e for rapeseed (canola) oil all the way up to 4.25 kg CO2e for soybean oil per kg refined oil.
The researcher found that land use made a significant contribution to GHG emissions, generally making up half of the total overall emissions.
Thomas Alcock, Future Food Beacon research fellow said the work was important in identifying better systems for the future.
"The strength of having lots of different production systems included in this study is that we can identify the most sustainable systems for each crop type, and push for these to be adopted more widely," Dr Alcock said.
"The results, particularly around land use, show that we should target production on low carbon storage potential land, although we also need to consider other sustainability indicators such as biodiversity."
"Most previous studies only considered recent land use change, but in this study we considered the impacts of continuing to grow crops on an area of land as well, instead of setting it aside for regeneration of forests."
He said farmers were faced with a difficult balancing act into the future where they looked to improve sustainability within current production systems, including through increasing yields whilst limiting application of inputs with high carbon footprints, such as reducing synthetic fertiliser application.
"On-farm, fertiliser is generally the biggest source of GHG emissions."
"This is tricky, as crops need a lot of nitrogen to be productive, but there are ways to reduce this, such as through choosing crop cultivars that are more nitrogen-use efficient, and by including leguminous plants in the crop rotations, as these provide nitrogen to the soil more naturally."
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