A federal subsidy that allows businesses to reduce their taxable income dollar for dollar based on specific types of fuel costs. There are several types of fuel credits. For example, a 2005 fuel credit to companies that produce biofuels provided a tax credit to companies that combined diesel derived from biomass with diesel derived from petroleum to create an alternative fuel mixture.

Watch: Tax Deduction Vs. Tax Credit

The black liquor tax credit, once part of the alternative fuel credit, was a tax loophole allowed to companies for using black liquor - a paper production byproduct that the paper and pulp companies were already using - mixed with diesel as a fuel source. The paper and pulp companies began adding diesel to their black liquor so they could claim a tax credit. This achieved the reverse of what the bill intended, increasing the use of fossil fuels and reducing the use of biofuels.