You don't know how lucky you are to have this available near you already! Its possible that Biodiesel in very low concentrations will be the additive used across the US to deal with the lower lubricity of ULSD, whenever we get it. So you are definitely ahead of the crowd.
It seems to be petro-diesel with soy-based biodiesel used as an additive. It would be good to know what is the concentration of BD in that blend. For example, Soypower BD "Diesel Fuel Lubricity Additive" recommends on the label: 32 ounces per 100 gals of regular #2 diesel, or 12 ounces per 100 gals of premium diesel. I suppose that US Soy Field Diesel is using such a low concentration of BD.
The offer two varieties: US Soy Field Diesel ("typical" cetane: 45), and US Soy 50 Field Diesel ("extra high cetane number": 50). The overall quality depends on the petro-diesel used to begin with: their Gold Diesel is 45 cetane while their Gold 50 Diesel is 50. Therefore the BD blends should be great stuff for your TDI!!! At least with respect to the cetane number and lubricity of the fuel. Lubricity indeed is the forte of biodiesel.
In our neck of the woods (literally!), the available petro-diesel is only 40-42 cetane, and the use of biodiesel as an additive has an immediate effect on engine sound and smoke if there is any. We use 1/2 gal per 10 gals because we like the stuff so much (it even smells good) and because the fuel in our area is not acceptable to us as it is.
Go ahead and try the stuff and report back to see how it went! I'm sure many here would be interested in a comparison between Amoco Premier and US Soy 50 Field Diesel!!!