Somewhere deep inside a dark building, four large pigs enter a small metal cage that’s only just large enough to accommodate them. Shot from above, a video shows the pigs to be apparently relaxed and at ease, until the cage – called, in the industry, a gondola – starts to descend.
At this point, a hoarse screaming can be heard, and the pigs back into one end of the container as if trying to get away from something monstrous. One pig sticks its snout up in the air, desperately trying to poke it through the thick bars at the top as a thin white froth forms around its mouth.
By this stage, all the pigs are scrabbling around, twitching and looking distressed. After about 30 seconds, the pigs lie down, having inhaled a sufficient quantity of carbon dioxide (CO2) for them to be stunned. From here, they will be taken out of the gondolas and ‘stuck’ – effectively bled to death.
It’s harrowing, upsetting footage. But this is how the vast majority of pigs in the UK, Europe and Australia are slaughtered.
This video was taken in Australia by Chris Delforce, executive director of an organisation called the Farm Transparency Project, and aired in 2023 on ABC. Chris illegally entered the abattoir and risked both his life and prison to film the process while waiting above the gondola system, where the pigs are stunned, for 10 hours.
Similar footage from a UK abattoir was obtained by an animal activist for a film called Pignorant that also came out in 2023.
“Almost all pigs killed in Australia and increasingly around the world are stunned in these gas chamber systems,” Delforce told ABC at the time. “People still don’t know this is happening.”
The science supports what can be seen in Delforce’s video. Scientists say the acidic gas irritates mucous membranes in the pigs’ eyes, lungs and nose, causing a burning sensation before they are rendered unconscious after about 30 seconds. “When CO2 comes into contact with their eyes and snout, it forms carbonic acid which is believed to be painful,” says Kate Parkes, the RSPCA’s pig welfare specialist.
Watch the video - warning: the footage contains distressing images of animal suffering.
Warnings repeated
It’s been known for many years that the use of CO2 to stun pigs in abattoirs in the UK and Europe has negative welfare outcomes for pigs, but nothing has changed. As long ago as 2004, the European Food Safety Authority noted the use of CO2 elicited “hyperventilation and gasping before loss of consciousness”.
In 2021, the Department for Environment, Food & Rural Affairs (DEFRA) also produced a report saying more humane methods of stunning pigs should be researched and adopted.
Now, the Animal Welfare Committee (AWC), an advisory panel of independent experts that was established by the Government in 2011, has published a report stating use of CO2 to stun pigs should be discontinued – this will be difficult for DEFRA to ignore. A consultation exercise on the use of CO2 is expected to begin, probably in 2026.
Pigs used to be stunned by an electrical discharge, but, as Katie Jarvis, chief policy advisor for the National Pig Association (NPA) explains, because the mechanism had to be fitted to each individual animal’s head there was room for human error that could have resulted in compromised welfare.
“The pincers have to be in the right place for the right amount of time to ensure the pig is properly stunned,” she says. “And then you don’t have long before it regains consciousness.”
Using the electrical system, the pigs also see other pigs being stunned, whereas with CO2, they go quietly in groups into the gondolas.
It’s also worth noting that a major EU project called PigStun, which aimed to find the best “non-aversive” stunning method, found in 2024 that facilities using CO2 reported nearly a 100% efficiency rate (between 0 and 0.05% “inefficiently stunned”), while one using the electrical method reported 0.8% inefficiency.
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Speed and safety
The consensus appears to be that some kind of gas – just not CO2 – is the best solution for slaughtering pigs in a humane way. This would also reduce the need for major alterations to the way abattoirs function and maintain the extraordinary levels of throughput in major processing units.
Just to give an idea, in 2023, more than 10 million pigs were slaughtered for their meat in the UK. In a single week, that can translate to around 200,000 pigs, with more than 80% of them passing through just eight major abattoirs.
One of these large units might handle 18,000 pigs in a week, or more than 3,500 a day. That’s a lot of pigs, and the need to keep the throughput steady and streamlined is paramount if productivity is to be maintained.
These figures roughly tally with official statistics in Europe in terms of throughput – for example, a single Spanish abattoir would expect to process around 650 pigs an hour.
So, the idea being considered by experts is to replace CO2 with another gas; argon, helium and nitrogen are all being considered.
At the moment, argon is considered the best option. “Though this hasn’t been tested at a commercial scale, the experience so far with argon is that the pig is quite calm and quietly loses consciousness,” says Jarvis. “It’s slower to work, however, so you’ve got a period of a good couple of minutes in which the pig is breathing in this high concentration of argon.”
The length of time it takes to act – between two and three times longer than CO2, according to Jarvis – is a problem. As already shown, the throughput of pigs in an abattoir is huge – up to 3,500 a day in the biggest ones in the UK – and any drop in that would impact overall productivity and profits.
“Moving away from CO2 would slow down operations to such an extent that it would render processors completely un-competitive,” says Nick Allen, chief executive of the British Meat Processors Association (BMPA). “It would decimate the domestic pigmeat industry and be a severe blow to UK food security.”
Allen argues that the only trial using argon was very small-scale and threw up as many questions as it answered. And while he accepts there are some issues with the use of CO2, he says there is no guarantee argon would be any better from a welfare point of view.
While DEFRA hasn’t fully committed the Government to taking on the recommendations of the AWC report, everyone expects a consultation paper to be issued at some point. “We are now carefully considering the findings of this report,” is as much as DEFRA would say when contacted by BBC Countryfile Magazine.
Allen says the BMPA would support the process of finding an alternative to CO2 under two main conditions – the first is that the Government accepts there is a need for more research to be carried out on alternatives such as argon and the second is that any move to stop using CO2 is synchronised with Europe.
Though Europe’s PigStun project reported in 2024, there is no sign of the EU progressing things further at this stage. But according to Allen, if the UK were to change the stunning system independently, it would merely result in us importing more pork products from our European competitors as costs increased here.
“Things happen quite slowly in Europe,” he points out. “And they will come under huge pressure from countries that are big players in the pork industry, such as Denmark, the Netherlands, Spain and Germany who will all defend the status quo.”
Both Allen and Katie Jarvis of the NPA say a move to more electrical stunning would be worse from a welfare point of view. “The problem with pigs is that you can’t trap their necks,” Allen argues.
“You can’t hold them still and they panic a lot when they are separated. Electronic stunning is really difficult to do [with pigs] – you end up with people chasing them around, trying to get the last one. There is a reason everyone moved to CO2.”
When it comes to other livestock, electronic stunning is used for sheep, while cattle are stunned by firing a steel bolt into their brains and (as with pigs), both are then bled out so that death happens quickly. Figures vary, but nearly 30% of all sheep slaughtered in the UK are done so under Halal rules, which means they are not stunned first.
Whatever happens next, it does seem likely that this time change is, if not inevitable, then hard to avoid. The RSPCA’s Kate Parkes says the momentum for making progress is now strong. “It feels like the impetus is building for change, and we will be really pushing for it,” she says. “Due diligence will need to be done in terms of understanding the costs.”
And while any public outcry over the shortcomings of using CO2 has been relatively muted, there is little doubt that millions of pigs every year experience a short, perhaps 30-second period of pain and distress while being stunned. Shouldn’t a humane society attempt to reduce or even eliminate that?
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How slaughter standards compare
– Standards for the slaughter of pigs in the UK and EU countries are currently largely the same.
– UK rules are governed by the Welfare of Animals at the Time of Killing (WATOK) regulations, which are derived from a time when we were in the EU.
– In both the EU and UK, the process is the same – render the pig unconscious before bleeding it to death.
– This can be done either by using electrical stunning or through exposure to CO2. Smaller abattoirs may use a mechanical stunning device called a ‘captive bolt’.
– Stunning without slaughter is permitted in the UK under Halal rules and most (but not all) EU countries.
Pork in numbers
– In 2024, about 10.5 million pigs were slaughtered for their meat in the UK. The total quantity of pig meat produced was 920 thousand tonnes, an increase of about 3.9% on 2023.
– This represents a reduction compared with figures for 2022 and 2021 (both more than 11 million pigs), but on a par with, or an increase on, most of the years in the past decade.
– We eat approximately 1.3 million tonnes of pork products in the UK every year, with cuts of meat such as joints for roasting and chops and processed products including bacon, ham and sausages all popular.
– Pork consumption per UK consumer is around 25.6kg a year, which is lower than some European countries; in France, this figure is 32.3kg, and in Austria it’s 51.8kg.
Top image: UK pig farm. Credit: Getty
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