A new global study has revealed the extent of greenhouse gas (GHG) emissions caused by vegetable oil production, emphasizing the need for more sustainable agricultural practices. Scientists from the University of Nottingham's Future Food Beacon conducted the first study to examine GHG emissions from almost all possible systems used to produce palm, soybean, rapeseed, and sunflower oil around the world.
The research was a meta-analysis of all relevant studies on the environmental impact of oil production published between 2000 and 2020. The findings were published today in the journal Science of the Total Environment.
Findings of Study:
This new study includes nearly 6,000 producers from 38 countries, accounting for more than 71% of global vegetable oil production. The median GHG emissions from all oil crop systems were 3.81 kg CO2e per kg of refined oil. Per kg refined oil, crop-specific median emissions ranged from 2.49 kg CO2e for rapeseed oil to 4.25 kg CO2e for soybean oil.
Despite receiving more negative attention, soybean oil had higher median emissions than palm oil. However, median rapeseed and sunflower oil systems produced fewer emissions than both palm and soybean oil, making them appear to be more environmentally friendly options.
When a forest is cleared to make way for agriculture, the carbon stored in the trees and vegetation is released into the atmosphere in the form of CO2. Much of the carbon stored in the soil is frequently released. The researchers looked into the effects of this type of deforestation on crop sustainability.
They also took into account the carbon costs of agricultural land occupation, even in cases where deforestation occurred more than a century ago (as is likely the case for most of Europe). This is because, even if no land-use change carbon is released today as a result of using the land for agriculture, the opportunity to store carbon, such as through re-growing trees, is lost. The researchers discovered that land use had a significant impact on GHG emissions, generally making up half of the total overall emissions.
The study was led by Dr. Thomas Alcock, a Future Food Beacon research fellow and Postdoctoral Researcher at the Technical University of Munich. "The strength of including so many different production systems in this study is that we can identify the most sustainable systems for each crop type and push for them to be adopted more widely," he says.
The findings, particularly in terms of land use, indicate that we should prioritize production on low carbon storage potential land, though we must also consider other sustainability indicators such as biodiversity.
The study emphasizes the need and opportunity to improve sustainability within current production systems, such as increasing yields while limiting the use of inputs with high carbon footprints, and, in the case of palm oil, more widely adopting methane capture technologies in processing stages.
Dr. Alcock elaborates: "This entails using as little synthetic nitrogen as possible on crops. On-farm, this is typically the most significant source of GHG emissions. This is difficult because crops require a lot of nitrogen to be productive, but there are ways to reduce this, such as selecting crop cultivars that are more nitrogen-use efficient and including leguminous plants in crop rotations, which provide nitrogen to the soil more naturally."
(Source: University of Nottingham)
