Here's a weird and slightly off-topic story that perhaps one of you can help me understand better:
A friend of mine lives in South Portland near one of the tank farms and his house has a front-row view of several tanks in the Turner's Island neighborhood. All of the tanks are painted white, and one of the tanks is covered in black gunk and looks pretty ugly. He was wondering what the black gunk was, and wondering why it was just on that one particular tank. He called someone at city hall, and that person gave him the phone number of the company that owns and operates that particular tank. He called the number and spoke to a guy who said (I'm paraphrasing) "Yes, I know which tank you're referring to. That tank holds ethanol. What you see on the outside of the tank is mildew [or fungus or mold, can't remember for sure what he called it] and the reason it only grows on that one tank is because that's the only tank that holds ethanol and the mildew [or whatever] is attracted to it." I was there for the phone conversation (it was on speakerphone) and I heard the whole thing. My friend asked "So does that mean ethanol is leaking from the tank?" and the guy said "no, absolutely not, nothing is leaking."
Can anyone help me understand 1) why ethanol would attract or promote mildew, and 2) why it would grow on the outside walls of the tank?
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