Where have all the steel wheels gone?
They went around smaller steel wheels:
I wish it was pure iron dust wearing off that steel, but no. The flying drone idea seems good, but for harvesting?
Exhaust gas is poison.
The relatively high amount of metal contents emitted from diesel engines strongly suggests that the measurement on the control of metal contents in diesel fuel should be taken in the future.
https://www.sciencedirect.com/science/article/abs/pii/S1352231003006241
As, Hg and Se exhaust emissions were dominated by fuel combustion while Cd, Cr, Cu, Ni, Pb, and Zn exhaust emissions were dominated by lubricant oil combustion.
https://www.sciencedirect.com/science/article/abs/pii/S1352231012006942
https://www.quora.com/How-do-I-know-if-I-have-heavy-metals-in-my-organs/answer/Harri-K-Hiltunen