Meat industry responds to AWC report on use of carbon dioxide in pig processing

The AWC, an independent expert committee for DEFRA, was asked to review scientific and practical evidence on the welfare impacts of high-concentration CO₂ gas stunning of pigs, and alternative methods (e.g., inert gases, electrical, and mechanical) in slaughterhouses in Great Britain.

Its members were also asked to compare welfare impacts at various stages (pre-stun handling, induction, and stunning itself), identify knowledge gaps, and propose which methods are best suited for commercial deployment.

In 2024 the Food Standards Agency Slaughter Sector Survey identified that of pigs reared in England and Wales, 90% are stunned by being exposed to high-concentration CO₂ using paternoster Controlled Atmosphere Stunning (CAS) systems.

CO₂ systems became dominant because they allow pigs to be handled in groups (reducing stress from single-file handling), they offer high throughput, and they improve certain meat quality metrics, the report explains.

However, both historical and more recent expert bodies (e.g., FAWC 2003, EFSA 2004/2020) have expressed concern that the high concentration of CO₂ used causes pain, fear, and respiratory distress to pigs and alternatives should be sought.

Report findings

The committee identified three main welfare concerns associated with exposing conscious animals to high CO₂ prior to loss of consciousness: pain/irritation, respiratory distress/‘air hunger’ as well as fear and anxiety.

The report explores several alternative stunning methods and evaluates their pros, cons, and practical constraints. The researchers listed a number of examples, including the use of inert gases/gas mixtures (argon, nitrogen, helium), electrical stunning and penetrating captive bolt.

The researchers pointed out that the welfare of pigs in slaughterhouses does not depend only on the stunning method; factors in the pre-stun handling, movement, social grouping, environmental design, stress during transport, lighting, noise, and operator behaviour are also important.

They stressed that design features and handling protocols can reduce stress, anxieties, and injuries. Monitoring systems (e.g., CCTV inside gas gondolas) should be improved so that pigs can be observed during the entire stunning process and welfare problems detected, they added.

The report also examines whether switching stunning methods would degrade meat quality (appearance, texture, shelf life). The cost as well as the ethical approach have also been considered.

The researchers concluded that high concentrations of CO₂ (alone or combined with inert gases) inevitably cause pain, distress, and fear prior to unconsciousness and should no longer be considered acceptable as a stunning method. The committee said it strongly recommends a prohibition of its use for pigs in the UK.

They also said that operators converting to inert gas systems must carefully calibrate residual oxygen, dwell times, and equipment to ensure irrecoverable unconsciousness with no recovery risk.

Electrical stunning systems should be designed and operated so that restraint is minimal, movement through the system is smooth, and use of coercion (e.g., prods) is avoided, the report reads.

It also recommends that pigs should be kept in small social groups or at least be able to see conspecifics; isolation should be minimised. Slaughter lines should have throughput limits so that pigs have enough time to move without coercion.

Training and certification of staff should require periodic revalidation (not a lifetime qualification).

‘UK industry will only ever use the best and most humane systems available’

The Association of Independent Meat Suppliers (AIMS) said the AWC is actively pressing the industry to move away from what is currently the best and most widely proven method of stunning to one that remains unproven, experimental, and — based on trial data — likely to reduce overall welfare when assessed from start to finish.

Its members said that under current UK practice, pigs are handled calmly in small social groups and moved quietly through a CO₂ chamber, where they lose consciousness rapidly and without restraint. The process is continuously monitored by trained staff and veterinary professionals and operates under some of the strictest welfare legislation anywhere in the world.

The association also claims that the AWC report contains factual inaccuracies and a lack of practical detail on how any transition to alternative methods could be achieved safely or effectively. It fails to address key operational realities such as plant design, gas supply, staff safety, and the handling challenges that would arise in commercial abattoirs.

“The AWC’s recommendation would replace a proven, welfare-led system with one that is untested in practice and, in trials, shows poorer outcomes,” said Dr Jason Aldiss, executive director of AIMS.

“The UK industry will only ever use the best and most humane systems available — and we will vigorously oppose any attempt to reduce welfare standards under the guise of progress,” he continued.

AIMS emphasises that Britain’s pig sector is not out of step with other world-leading nations and that CO₂ stunning, when operated under the UK’s stringent oversight, continues to deliver exceptional welfare outcomes.

The organisation is now calling for DEFRA to correct “misleading impressions” within the report and to engage openly with veterinarians, welfare scientists and industry specialists before considering any regulatory changes.

AIMS reaffirmed its commitment to continuous improvement, supporting ongoing research to refine existing CO₂ systems through better design, monitoring and staff training — but insists that change must be driven by science, not ideology.

“British consumers can be reassured that our pig industry leads the world in humane production,” Dr Aldiss added. “We will not stand by while unfounded claims risk lowering that standard. Welfare comes first — always.”

‘There is still no conclusive best alternative’

National Pig Association (NPA) chief executive Lizzie Wilson said that the NPA acknowledges concerns that the slaughter of pigs could and should be more humane.

“We are part of a UK pig sector group which is committed to exploring alternatives and finding a solution that can deliver on animal welfare at the time of stunning and slaughter.

“Any new approach must be commercially viable to ensure uptake, to ensure quality of meat, and to prevent any unintended consequences for welfare – for example, throughput capacity must be sufficient to ensure that pigs are not held on farm or in lairage for longer than necessary.

“We have awaited the outcomes of the AWC report with interest, and while it has delivered a comprehensive investigation into the welfare aspect of this issue, unfortunately there is still no conclusive ‘best’ alternative due to issues with throughput capacity, meat quality and cost.”

Ms Wilson added that the UK pig industry must now work together to decide how we go forward.”

A spokesperson for DEFRA said: “This government wants to see the highest possible standards of animal welfare at slaughter. We are now carefully considering the findings of this report.”

Read the AWC report here.

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