Biodiesel is a completely renewable, American-made replacement for diesel fuel. It is made the same way Bioheat is (in fact, just like diesel and fuel oil, they are the same fuel, just taxed differently, and fuel oil is dyed to show that the road tax has not been assessed).
Like Bioheat, Biodiesel can be used in your vehicle with absolutely no modifications. It contains no sulfur, so emissions are clean. But because it is produced from oils and fats, its lubricity is actually higher than petroleum diesel was before the current ultra-low sulfur diesel standards went into place.
The result is a cleaner fuel, with better emissions, that runs at higher efficiency, wears your engine less and is completely renewable.