CO2 stunning of pigs is widely used but causes significant distress. Research into more humane alternatives is progressing, with welfare implications for billions of animals.
CO2 gas stunning is the dominant method for pig slaughter globally despite decades of evidence that pigs find CO2 exposure intensely aversive - they experience acute panic, gasping, and distress during the 30 to 40 seconds before unconsciousness. Given that over a billion pigs are slaughtered annually, even a 30-second reduction in pre-slaughter suffering would represent an enormous welfare gain. Nitrogen-argon mixtures cause rapid loss of consciousness with minimal aversion. The welfare case for transitioning away from CO2 is scientifically robust; the barrier is predominantly economic.