The renewable fuel standard (RFS) mandates that a portion of the fuel supply be composed of an alternative fuel, in this case advanced biofuels (similar to the RFS included in the US Energy Independence and Security Act of 2007, which gradually phases in biofuels over 15 years).
It acts like a giant spark plug, busting apart a tiny portion of the diesel fuel with an electric charge so that the molecules rearrange themselves into carbon monoxide and hydrogen.
This is possible because with the lasers, the location of the ignition can be in the center of the air-fuel mixture, rather than just the portion closest to it.