Natural gas is cleaner burning and produces a lower carbon footprint than diesel. However, it’s not a zero-emissions choice. It may be a good interim step, but it won't qualify for ZEV mandates under the ACT and ACF mandates.
NACFE: SuperTruck Innovations Pave the Way for Zero-Emission Trucks
The Department of Energy’s SuperTruck program is resulting in technologies that will not only improve the efficiency of diesel engines, but also will help in developing longer-range zero-emission trucks.