In 2011 I began melting Canadian copper pennies (those minted 1996 and before) because it became profitable to do so. Paradoxically, copper pennies are worth more for their material than their face value. Even after subtracting the cost of the fuel, a profit can be achieved.
However, destroying currency in Canada is illegal. So I petitioned the Ministry of Finance for special permission for the project, and was eventually granted a one-time unique licence from the Minister of Finance, Jim Flaherty.
With license, I melted 25,000 coins into bars of ‘Good Delivery’ proportions — the same dimensions used for trading bars of precious metals on international exchanges.
A version of the economic model I used to petition the Ministry of Finance can be found here, and further documentation of the project is forthcoming.