Jan 20
Electric Arc Furnace (Late-Game Steel Production)
Electric arc furnaces (EAFs) are becoming more ubiquitous, as they allow steel production using less energy and releasing fewer greenhouse gases than the traditional blast furnaces. This could be an interesting alternative source of Steel Bars in the late game (after unlocking Industry).
EAFs cannot produce steel directly from iron ore (iron concentrate) but instead typically use scrap metal or pre-reduced iron from a bloomery. This could give us a recipe like 4 Iron Bars + 2 Quicklime + 4 Charcoal Powder = 4 Steel Bars (improved by Modern Upgrades). While this recipe is more complicated, it is also cheaper, providing a late-game method for mass-producing Steel Bars/Rebar/Corrugated Steel for large construction projects.
The EAF could also have the ability to melt down broken tools/parts into Iron Bars, providing a late-game way to recycle them rather than throwing them in a landfill.
Pending
In addition to this, a DC Electric Arc Furnace could be added as an alternative to the AC EAF shown in the main post. These would use only two electrodes (one at the top and one on the bottom) and require less energy input, whilst making less emissions and slag. The downsides to this compared to the AC EAF is how these would make less metal per cycle (still the same recipe ratios) and are more expensive to make and maintain. The advantages to this would be how it is more efficient at smelting copper and gold, although the iron and steel efficiency doesn't change, these machines would also be faster than the AC EAFs. As for some numbers, the DC EAFs would use 2000w of electrical energy and make around a third of the CO2 emissions.