In the near-term (between now and 2020), converting natural gas to hydrogen for use in a FCEV will reduce greenhouse gas pollution by approximately 51%. If that natural gas is burned in an optimized NGV, the GHGs would be reduced by only 22%; thus natural gas converted to hydrogen in a FCEV cuts GHGs approximately 2.3 times more than using that natural gas in an optimized NGV:

Near-term GHGs (g/mile) Savings (g/mile) ICV 405   NGV 316 -89 FCEV 197 -208

In the long term, FCEVs have even greater advantages, since hydrogen can be made from a variety of low- or zero-carbon sources such as biomass, solar, wind or nuclear energy, etc., while NGVs will continue to generate GHGs.  This graph shows the estimated well-to-wheels GHGs for NGVs and for FCEVs in 2050 and 2100 from our 100-year simulation program.  The red line indicates the 1990 level of GHGs from the US light duty vehicle sector, and the green line shows the goal: an 80% reduction below 1990 levels. The FCEV is the only option that could achieve that goal, reducing GHGs by 89% by 2100. The second-best option would be a natural gas plug-in hybrid electric vehicle (NG PHEV) which would cut GHGs by only 47%.  Note that optimized NGVs and even natural gas hybrid electric vehicles (NG HEVs) would increase GHGs by +41% and +29% relative to 1990 levels by the end of the century due to the assumption of increased vehicle miles traveled (VMT).

The changes in GHG levels in 2100 relative to 1990 levels are summarized in this chart: