As a factorio player, by the time I'm upgrading steel production I'm wondering whether I even care about pollution. The #1 benefit of electric smelters is that

As a factorio player, by the time I'm upgrading steel production I'm wondering whether I even care about pollution. The #1 benefit of electric smelters is that I can beaconize and fill it with prod mods, to get 140% the output at only the minor cost of a fuckton of pollution and electricity use. In fact, the real score for reducing pollution here is efficiency mods - electric smelters plus steam engines apparently produce the exact same amount of pollution as just using lv2 smelters directly so you'll need those efficiency mods anyway (unless you've already switched to solar+nuclear), but you're better off putting your initial efficiency mods into your miners and oil. Solar and nuclear are both a pain in the ass to switch to, though - nuclear takes stacks and stacks of copper to build and is a PITA to set up centrifuges and pipe down hydrochloric acid to uranium, and solar needs bots to place with any speed. It's just easy to slap down steam engines fed by either coal or solid fuel. So if you prioritize player-time over strict efficiency then the quickest way of reducing pollution is almost certainly efficiency mods into pre-existing buildings (i.e. miners and oil), and building electric furnaces will in-practice force you to build more power plants anyway. At least, in my experience. But maybe that's due to the prod-mods and beacons.