Windy cows make the production of butter three-and-a-half times as damaging to the environment as plant-based spreads, according to a new study.

Scientists compared the amount of carbon dioxide (CO2) generated during the production of 212 plant-based margarines with 21 popular dairy butters.

They found that for each kg of product, the 'mean average' CO2 equivalent for plant-based spreads was 3.3kg - compared to 12.1kg for dairy-based products.

The main source of greenhouse gases comes from the production of milk, the key ingredient in dairy butter.

Nearly 40 per cent of this comes from 'enteric emissions' - methane caused by cows burping and breaking wind.

In fact, just one 250g pack of dairy butter equates to 1 kilogram of cow emissions (kg CO2 eq).

And while carbon dioxide regularly gets the bad publicity, methane is about 80 times more powerful than its greenhouse gas cousin when it comes to trapping heat and is responsible for 25 per cent of global warming.

The report, published in The International Journal of Life Cycle Assessment, was based on products made by Upfield.

Sally Smith, head of sustainability at Upfield, said: "In order to achieve emissions targets designed to limit global warming to 1.5° by 2050, there needs to be a fundamental transformation of our food system.

"In Western countries especially, we currently rely too heavily on meat and dairy.

"It is our responsibility as a forward-thinking company to understand and act to address the impact of our plant-based products on the environment.

"A shift to regenerative agricultural practices will be key for both arable and dairy farmers.

"Robust life cycle assessments help ensure that our approach is data driven and grounded on the latest scientific evidence.

"As our products generally have a significantly lower carbon footprint, use less water and less land, we have an opportunity to help people understand the impact that food choices have on the environment and therefore help them to make a more informed choice that is better for the planet."

The 212 plant-based spreads and margarines analysed by scientists ranged from 0.98 to 6.93 kg CO2 equivalent for every kg produced to compared to 8.08 to 16.93kg CO2 equivalent for every kg of the 21 butter products.

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Researchers considered the full life cycle of the products, including production stages such as crop cultivation, oil extraction and refining, transport of oils, production of all other ingredients, blending into final products, packaging, distribution, refrigeration at retail and at the consumer home and end-of-life treatment of packaging.

The study revealed cattle feed production and livestock rearing - including cow-related burps, farts and manure management - contributed significantly to climate change impacts, with a higher impact than most other factors.

Packaging for plant-based spreads makes up eight per cent of its emissions compared to one per cent for butter, with the latter often wrapped in a lightweight foil or paper parchment compared to a tub.

The life cycle assessment of Upfield's margarines and spreads is in line with growing consumer attitudes towards meat, dairy and plant-based alternatives, which continue to prompt debate.

It follows separate research by Dr Hannah Ritchie, from the University of Oxford, who concluded the 'eating local' mantra was a 'misguided piece of advice' when discussing climate change.

Her study revealed transport emissions are often a very small percentage of food's total emissions - only six per cent globally.