By Peter Stevenson OBE, Chief Policy Adviser, Compassion in World Farming  

As the new documentary film Pignorant (Prime Video) so vividly portrays, the use of CO2 gas to slaughter pigs is totally inhumane. 

In what can only be described as highly distressing scenes, the film captures for the first time in the UK, undercover footage of pigs being gassed with CO2 at a facility in Manchester. They can be seen hyperventilating, struggling for breath and trying to escape from the gas chamber for some time before being rendered unconscious. Their suffering is unimaginable and is confirmed by scientific research. 

For many years, scientists have raised strong animal welfare concerns over the use of CO2 to slaughter pigs. A recent Scientific Opinion on pig slaughter by the European Food Safety Authority (EFSA) stressed that “there are no preventive or corrective measures to the pain, fear and respiratory distress caused by the exposure to high CO2 concentrations, as this is inherent to the stunning method.” As long ago as 2003, the Government’s Farm Animal Welfare Council concluded that the use of high concentrations of CO2 to stun and kill pigs was not acceptable and urged the practice to be phased out in five years. 

Yet this has been ignored by both government and industry. Why? Because it’s cheaper to use CO2 than other more humane methods such as well-designed electrical stunning systems. The UK pig sector and the UK Government have failed to take any effective steps to develop a humane alternative. Compassion in World Farming and other NGOs have repeatedly highlighted this issue but there has been no appetite for change.  

Indeed, the number of British pigs slaughtered by this inhumane method has even increased, from 52% in 2013 to 88% today – that’s over nine and a half million individual, sentient pigs killed annually in this inhumane way. These are staggering statistics, yet the public remains largely unaware of the process involved in getting their pork to their plate.  

In 2022, the cost of CO2 tripled and three factories that produced the gas closed down, creating a crisis for the meat industry and adding more pressure to already inflated food costs. You might think that this threat to the supply chain alone would provide a strong enough incentive to industry to find more humane and reliable alternatives to CO2, yet still nothing has changed.  

Most UK chickens are also slaughtered with gas, but with much lower concentrations of CO2 than for pigs. Permitted levels for chickens are on the cusp of what is regarded as causing distress and the process is preferable to the electric water-bath method of stunning chickens.  Nevertheless, the European Food Safety Association (EFSA) clearly points out that “a certain level of respiratory distress” is inherent in gas stunning and it is not without problems that may go unnoticed in large abattoirs which can stun 9,000 chickens per hour.  

It is imperative that the UK Government urgently reviews slaughter methods used to kill millions of pigs every year and brings forward a cut-off date for use of high levels of CO2 to kill pigs of 1 January 2026. The EU is currently funding research to find alternatives – the PigStun Project aims to encourage EU pig slaughterhouses using high carbon dioxide concentration to convert to more welfare-friendly systems. Why isn’t the UK Government doing the same? 

Pignorant will no doubt help to raise awareness of this widespread yet largely hidden cruelty issue. The hope is that, as awareness grows, momentum will build until the UK government, and other governments around the world, are compelled to act to end this inhumane practice without further delay. Until then, consumers will have to decide for themselves whether their bacon sandwich is worth the terrible suffering it inflicts on pigs.