The primary execution method in Alabama is lethal injection, though the electric chair is an option for people convicted prior to 2002. The method of gas executions has never been used in Alabama. And heck, out of every execution in 2020 all of them were via injection, not gas. Is gassing really any more or less moral than the electric chair or injections? Plus, just because the infrastructure for gassing exists doesn’t mean it will be used, as the people facing the death penalty may very well choose a lethal injection.
Also, here are the sources for the statistics:
https://deathpenaltyinfo.org/state-and-federal-info/state-by-state/alabama
https://deathpenaltyinfo.org/executions/2020