Scrap metals are not cleaned, they are melted. For steel; Zn, Sn, Pb, and others vaporize or oxidize. The most problematic is Zn as the oxide in the slag can deteriorate the refractory. Aluminum is similar except scrape with Cu and Si will be segregated as much as possible, used for certain alloys. Copper scrap, being more valuable is separated according to ...
Oh, that's really not a problem.
Recycling metal involves pre-processing. They are concerned with contaminants like paint and plating getting into the batch. What they use to remove paint and galvanization will certainly remove grease.
If every citizen in the world had an average carbon footprint of 16.1 Mg (1 Mg = 1 metric ton) per year, the global average temperature would likely rise more than 6.0º C by 2050.
However, there are some important caveats to this answer which I will detail below.
Per capita vs. Globalization
The question you stated might be slightly different from the ...