How is controlled atmosphere stunning in europe different the what take place in american slaughterhousss

Controlled atmosphere stunning is a slaughter method where small groups of animals are placed in a container with an atmosphere that consists of an asphyxiant gas, typically argon, nitrogen or carbon dioxide, causing them to lose consciousness and the environmental effect is pretty major due to slaughtering animals because it contributes to land and water degradation, biodiversity loss, acid rain, coral reef degeneration and deforestation. Livestock farming contributes 18% of human produced greenhouse gas emissions worldwide. This is more than all emissions from ships, planes, trucks, cars and all other transport put together.

because they were not just any seashells they were sally's seashells

can you give me a hint