i'm still hung up on this IC engine that is supposedly 100% zero emissions.
if its an internal combustion engine it has to burn something and therefore it emits something. If its not LPG, gasoline or diesel or even hydrogen cell then what is it? And the only way i can think of to reduce the trucks emissions would be to use the same concept like electric hybrid cars use, a motor to drive a generator to charge a battery pack or drive a hydrogen cell generator like the tesla cars do. The cleanest emission IC engine i know of is a natural gas powered engine and they emit emissions lower than any other engine but its not 100% zero, its close but not zero and that's provided it is perfectly tuned and stays that way.
I know of some guys that developed a small hydrogen generator in cars that use a crude generator to inject hydrogen into the fuel system but that's more for increasing gas mileage than it is for emissions purposes so i doubt this is the mystery fuel.
With todays technology on the markets its either battery, hydrogen cell, LPG or NG, gas, diesel or maybe even refined kerosene (jet fuel), nah i was kidding, not jet fuel ;oD

I'm just drawing a blank here...