Global agriculture could be carbon-negative, says analysis

Agriculture is responsible for roughly a quarter of the world’s total greenhouse gas emissions, but a new analysis says it could become not only carbon neutral, but carbon negative – removing billions of tonnes of CO₂ each year – by 2050.

The study, published in PLOS Climate, estimates that changes to agricultural technology and management could result in an annual removal of 13 billion tonnes of CO₂ by 2050. For context, the world currently emits about 50 billion tonnes of CO₂-equivalent each year.

“Our study recognizes the food system as one of the most powerful weapons in the battle against global climate change,” says co-lead author Professor Benjamin Houlton, dean of the College of Agriculture and Life Sciences at Cornell University, US.

“We need to move beyond silver-bullet thinking and rapidly test, verify and scale local solutions by leveraging market-based incentives.”

The researchers used a global food systems model to chart different scenarios for the agricultural industry by 2050, when it will need to feed an estimated 10 billion people.

“Our study examines both dietary change and agricultural technologies, as various options for slashing emissions,” says co-lead author Dr Maya Almaraz, associate research scholar at Princeton University, US.

“This included an analysis of carbon sequestration.”

The researchers examined what would happen if everyone in the world adopted a flexitarian diet – defined here as the EAT-Lancet’s Planetary Health diet, which emphasises plant-based foods and has only a small amount of meat and dairy.

They found that flexitarianism would reduce greenhouse gas emissions by 8.2 billion tonnes of CO₂-equivalent in total.

Changing agricultural technologies and practices had a much larger impact, according to the analysis. Seaweed farming, for instance, could remove up to 10.7 billion tonnes of CO₂ annually, while planting trees on unused farmland could remove up to 10.3 billion metric tons of carbon a year.

“We only looked at about a dozen technologies,” says Almaraz. “But there are even more under development, which hold a lot of promise for the food system.”

These technologies included things like soil carbon sequestration, enhanced rock weathering, and hydrogen-powered fertilisers.

“If people choose to switch to healthier diets, as suggested by EAT-Lancet – and if they can afford it – great,” says Houlton.

“But to get the world to net negative greenhouse gas emission – a global imperative to avoid the most dangerous climate impacts – we need to rely heavily on agricultural technology and management techniques.”

These technologies are very context dependent. For instance, enhanced rock weathering, which involves putting crushed silicate rocks on soil to absorb carbon, could dramatically improve the UK’s sequestration. But most of Australia’s agricultural soil is too dry for it to be highly effective.

The researchers emphasise changes at a regional level as being the most effective.

“We need a portfolio of solutions that are effective locally but have global impact,” says Houlton.