It is different from carbon credits. I don’t think you get a rebate from not emitting. If the cost is passed onto the consumer when there are good alternatives with less carbon, they will be out-competed. One thing with few alternatives is transportation, which low-income households tend to spend more on.
I was able to enable it on stable by toggling browser.urlbar.showSearchTerms.featureGate
Edit: Nevermind, it doesn’t work for custom engines, which suggests that it’s a separate implementation from mobile?