August 19, 2020, by Andrew Edwards (Ed)

Greenhouse gas emissions from sunflower oil production – by Thomas Alcock

Vegetable oil production around the world

Today, global food systems are responsible for 26% of all of the world’s greenhouse gas (GHG) emissions. Crops grown for vegetable oil and their co-products, such as animal feed, account for 19% of non-pasture, cropped land. They therefore represent a major source of GHG emissions, which are only set to grow as demand for vegetable oil and animal feed continues to increase.

Major sources of vegetable oil around the world include oil palm, soybean, rapeseed and sunflower. Each is associated with its own geographic range and set of production practices. For instance, oil palm is largely produced in South-East Asia, where it is planted once, allowed to establish, and then produces oil-rich fruits for around 25 years. On the other hand, sunflower and rapeseed are cultivated primarily in more temperate climates and require annual sowing and harvest of oil-rich seeds. Due to these differences, each crop system is likely to have its own distinct carbon footprint, with some more environmentally damaging than others.

Sunflower oil production and GHG emissions

My current work with the Future Food Beacon is aiming to quantify variation in GHG emissions produced by each of the world’s major oil crops. This will help to guide future decisions on how to meet growing demand for vegetable oil as sustainably as possible. I have recently completed phase 1 of this project, in which I characterised global variation in GHG emissions from sunflower oil production. This was through harmonised re-analysis of data published around the world, focussing on distinct production practices. Results from this first phase have recently been published online at the bioRxiv preprint server (https://doi.org/10.1101/2020.06.19.161893).

From the sowing of sunflower seeds, through all stages of cultivation, harvest, pressing and refining of seeds to pure vegetable oil, and finally packaging, sunflower oil is associated with between 1.1 and 4.2 kg CO₂ equivalent per kg packaged oil. Of these emissions, over 60% result from agricultural practices, with processing stages contributing a lower proportion. The analysis indicates that diesel and nitrogen-fertiliser use are the two largest sources of GHG emissions across most sunflower production systems. Reducing the use of these inputs, for example by including a nitrogen-fixing legume in the crop cycle to minimise the need for synthetic nitrogen, could help to reduce associated emissions.

Some interesting regional differences jumped out from the study too. Production in Iran, for example, was associated with particularly high GHG emissions. This was largely due to sunflower production in this region being dependent upon large amounts of electricity to power irrigation, since Iran has a particularly dry climate. Production in more temperate regions, where irrigation is not required, was found to have a generally lower carbon footprint.

As this project develops, comparisons between GHG emissions associated with different vegetable oil sources will become possible. By modelling the impacts of meeting increasing demand for vegetable oil using different market mixes of oil crops, we will be in a better position to identify the most environmentally sustainable system for global vegetable oil production to meet growing demand.

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