Some UK social media users have been pouring milk down their sinks and toilets in protest at the trial of a new feed additive that claims to significantly reduce the emission of methane gas in dairy cows.

Arla Foods, a Danish-Swedish company which owns the UK’s biggest dairy cooperative, announced last week that 30 of its farms across the country would test the additive, named Bovaer.

The company behind Bovaer – which is added in small quantities to cow feed – says it could reduce cow methane emissions by between 30-45%.

It has been approved for use by UK regulators, and several major supermarkets will stock milk produced by cattle eating feed with the additive.

Some online users have raised concerns around the use of Bovaer, citing issues around the safety of certain compounds used in it.

However, experts have told the BBC that the additive “does not pose any food safety issues”.

Other consumers have been threatening to boycott products from leading supermarkets in anger over the trial, while multiple farmers have taken to social media to inform consumers that they don’t use Bovaer.

Meanwhile, baseless claims of it being part of a “depopulation” plot have swirled online alongside misinformation about its links to US-billionaire Bill Gates.

The manufacturer, DSM-Firmenich, says “mistruths and misinformation” have been spread about its product. It says it is “totally safe” for use, and has been tested over many years in many countries.

Methane is a much more potent greenhouse gas than carbon dioxide and is helping drive climate change.

Cows produce it when their stomachs are breaking down hard fibres like grass for digestion. This fermentation process creates methane gas which is then mostly belched out again.

Bovaer works to suppress the enzymes in a cow’s stomach that create the gas. The National Farmers Union (NFU) says when the additive is used as recommended it breaks down in the cow’s digestive system and as such is not found in milk or meat.

According to DSM-Firmenich, the additive is available for sale in 68 countries around the world.

As part of its trial, Arla Foods is working with some of the UK’s largest supermarkets, including Tesco, Morrisons and Aldi, who will stock products produced by cows which have eaten the additive.

Since Arla announced the trial, Bovaer has been subjected to a huge range of claims online.

Among those raising concerns has been Reform UK MP Rupert Lowe, who said on X that he had asked the Department for Environment Food and Rural Affairs to carry out an urgent review of the additive.

Meanwhile, some dairy farmers have said they will not use the feed, citing concerns over some of the compounds used to make the additive.

Bovaer is made using silicon dioxide, propylene glycol and organic compound 3-nitrooxypropanol (known as 3-NOP).

Opponents of the additive have pointed to a report by the FSA last year, which found that “3-NOP “should be considered corrosive to the eyes, a skin irritant, and potentially harmful by inhalation” to humans handling it.

But experts emphasised that no traces of Bovaer or the compounds contained within it would be found in milk or other produce, as it is broken down in a cow’s stomach.

“It has gone through a series of regulatory processes around the world and all are satisfied that it actually does what’s claimed around methane emissions and does not pose any food safety issues,” Professor Chris Elliott – an expert in food safety and microbiology at Queens University Belfast – told the BBC.

Other opponents have pointed to claims that 3-NOP could cause cancer, but UK regulators dismissed the concerns after carrying out an assessment which concluded “that the additive is not carcinogenic at the recommended inclusion rate”.

The FSA told the BBC in a statement: “Milk from cows given Bovaer, a feed additive used to reduce methane emissions, is safe to drink.

“Bovaer has undergone rigorous safety assessments and is approved for use in Great Britain.”

In a statement to the BBC, Arla said safety concerns being spread online were “completely false”.

A spokesman for DSM-Firmenich said: “We are grateful for independent, third-party experts, farmers and farmers’ organisations who have come out to counter this misinformation.”

Some of those posting online have alleged that Microsoft founder Bill Gates is involved in the development of Bovaer, a claim which the additive’s developer flatly denies.

In a strongly worded statement on 2 December, DSM-Firmenich said it had “fully developed” Bovaer and emphasised that the company had “no other investors”.

“Bill Gates is not involved in the development of Bovaer,” the statement added.

The US-based billionaire has instead invested in a rival start–up, Rumin8, which develops a similar methane reducing product.

Mr Gates has long been the subject of multiple conspiracy theories – the most extreme of which claim that he is part of an effort to depopulate the world.

Some online activists have sought to link Bovaer to such claims, pointing to a past approval letter from US regulator the FDA which found that the additive could lead to male infertility.

However, the letter was referring to precautions that must be taken when handling the product in its pure form – rather than when it is added to animal feed.

Jack Bobo of the University of Nottingham Food Systems Institute told the BBC that the concerns appeared to stem “from a misunderstanding of the FDA approval letter”.

“The letter highlights precautions related to the handling of Bovaer due to its active ingredient, 3-nitrooxypropanol. However, it’s important to note that this active ingredient does not remain in the final dairy product.”

Debates about Bovaer appear to have started to spread almost immediately after Arla announced its planned trial on 26 November.

Its post on X announcing its partnership with Tesco, Aldi and Morrisons has nearly 6 million views and attracted thousands of comments as of 3 December.

Users with a history of spreading conspiracy theories latched onto the trial within hours. Some of those posting have in the past shared anti-vaccine and climate-change denying content.

Other users, however, appear to be sharing posts about the additive out of genuine concern.

According to the social media analysis firm Brandwatch, mentions of Bovaer on X rose from virtually zero to over 71,000 in the days after the trial was announced.

Meanwhile, on TikTok clips attacking the product have received up to 1.8m views each.

Some of the most popular have seen users disposing of packets of Arla’s Lurpak butter and pouring cartons of milk away, with one captioned: “Not in my house.”

The National Farmers Union says 15 years of trials have proved there is no risk to consumers or animals – that Bovaer breaks down in a cow’s digestive system and is not present in milk or meat.

Graphics by Christine Jeavans.