New York City on Tuesday filed an $8.5 million lawsuit against a biodiesel vendor, arguing that the company violated its contract with the city by failing to pass along a biofuels tax credit.

According to the complaint, which was filed in the Eastern District of New York, the New Hampshire-based energy company Sprague Operating Resources was awarded several contracts with the city in recent years for various kinds of fuel. As part of the contracts for biodiesel, Sprague agreed to remit a $1 per gallon tax credit to the city when the Biodiesel Blender’s Tax Credit was in effect.