Per the 2011 IRS Instructions for Form 4136
The credits for alcohol fuel mixtures, biodiesel mixtures, renewable diesel mixtures, alternative fuels (except liquefied hydrogen), and alternative fuel mixtures (except liquefied hydrogen) expired December 31, 2011.
The current IRS Instructions for Form 4136
provide information on the credits still available. See IRS Publication 510 Excise Taxes (Including Fuel Tax Credits and Refunds)
for definitions and information on nontaxable uses.