Cows just aren’t used for their milk anymore. The first passenger train fueled by beef-based biodiesel traveled from Oklahoma City to Fort Worth, Texas yesterday. This is a yearlong test in hopes to see if beef-based biodiesel is capable of running the Amtrak Heartland Flyer passenger train. The test is also to see if the new biodiesel can cut fuel costs, reduce emissions and make sure that the ride if just as comfortable for passengers. The fuel is a mixture of 80% diesel and 20% biofuel called B20. The yearlong trial has been funded by the Federal Railroad Administration and has a $274,000 grant…