Why did the train cross the border 24 times and never unload?

Apparently there's lots of money to be made off of US taxpayers, for importing "renewable fuels", even if you're not actually importing anything at all.

The companies “made several million dollars importing and exporting the fuel to exploit a loophole in a U.S. green energy program.” Each time the loaded train crossed the border the cargo earned its owner a certain amount of Renewable Identification Numbers (RINs), which were awarded by the US EPA to “promote and track production and importation of renewable fuels such as ethanol and biodiesel.” The RINs were supposed to be retired each time the shipment passed the border, but due to a glitch not all of them were. This enabled Bioversal to accumulate over 12 million RINs from the 24 trips, worth between 50 cents and $1 each, which they can then sell on to oil companies that haven’t met the EPA’s renewable fuel requirements.