Growing decarbonsiation and the decline of fossil fuels poses a threat to fertiliser supply and global food security, a University College London (UCL) study has found.

Published in The Geographical Journal, the study revealed that farmers could struggle to source phosphorous fertilisers, as the shift towards a greener economy will expose weaknesses in current methods of producing sulphuric acid.

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The researchers at UCL are concerned that “as green technology booms and agriculture intensifies, global demand for sulphuric acid is set to rise significantly by 2040.

“At the same time, the major present-day source of sulphur for these industries will rapidly diminish with the decline in production of oil and gas.”

Increasing demand

At present, more than 80% of global sulphuric acid supply is derived as a by-product from the desulphurisation of fossil fuels, and current demand is around 246m tonnes – but, this is expected to soar to more than 400m tonnes by 2040.

Sulphur, which is converted to sulphuric acid, is instrumental in making fertiliser as it is used to dissolve phosphate from its rock form.

But, the agricultural industry could soon find itself in competition with the rapidly expanding green-tech industries producing lithium-ion batteries, as sulphuric acid is used to remove rare earth elements from their ores.

Prof Mark Maslin, UCL lecturer and co-author of the study, said: “We think that the sulphur crisis will occur sometime in the next 10 years.

“Supplies [of sulphuric acid] are relatively healthy at the moment, but this will change once fossil fuels begin to be phased out. The war in Ukraine is likely to accelerate this because Europe is trying to move to renewables as quickly as possible.

“The demand is increasing every year because of the need for sulphuric acid to create phosphate fertilisers and also because of the increased mining required for the rare metals that are used in electric cars and solar panels.”

Bidding wars

The study raises concerns that a dwindling supply could lead to a transition period when green tech outbids the fertiliser industry for the limited, more expensive sulphur supply, creating an issue with food production, particularly in developing countries.

Researchers at UCL have suggested repurposing human sewage as a solution to the looming crisis, as it has been proven to be a good source of both phosphate and nitrogen, making it suitable for use as a fertiliser. 

This, Prof Maslin suggests, is a feasible and attainable solution. “Repurposing sewage will also stop the phosphate from getting into our rivers and coasts. Why not create a circular economy where you are not only removing the sewage, but creating something good from it?”