Natural Gas vehicles Methane Emissions raises their CO2e emissions to >2x diesels - PennState

[Bill USA]

http://www.research.psu.edu/events/expired-events/naturalgas/documents/trans-fuels-position-paper.pdf


CNG and LNG offer the promise of both displacing petroleum, thereby increasing energy security and improving the national balance of trade, and lowering emissions, due to the clean burning characteristics of natural gas relative to gasoline and diesel fuel and the enhanced hydrogen content (H/C ratio) of natural gas compared to petroleum, which lowers CO2 emissions.

[font size="3"].... Unfortunately, it is evident that despite the supposed greenhouse gas benefits of natural gas utilization, CNG vehicle fleet tests are showing that CNG provides little improvement in CO2 equivalent emissions and may emit higher net greenhouse gases per mile of operation. Table 2 presents some data from research sponsored by the Gas Research Institute and Natural Fuels Corporation at the Colorado School of Mines.2 These results clearly show that the inferior thermal efficiency of the CNG vehicle negates the CO2 emissions benefits one would expect by burning a high H/C fuel (H/C=4 for CNG and H/C~2 for Diesel).

.... Similarly, the[font color="red"] CH4 emissions are nearly 100 times higher for CNG, and methane has 10 times higher global warming effect than CO2[/font]. The CH4 emissions from the CNG vehicle lead to CO2 equivalent emissions of 1890 g/mi, compared to the 1785 g/mi of CO2 emitted by the diesel vehicle. If one uses the current EPA estimate for the GWP for methane of 20,3 then the CO2 equivalent emissions for the CNG vehicle are [font color="red"]3780 g/mi[/font].



Nationwide interest in the application of natural gas in transportation has grown dramatically, representing a long‐term, low‐cost, domestic and secure alternative to petroleum‐based fuels. Compressed natural gas (CNG) and liquefied natural gas (LNG) vehicles represent a significant potential to directly displace petroleum.

However, the cost of conversion, the tailpipe emissions of unburned methane, and the limited refueling infrastructure represent barriers to deployment of natural gas throughout the transportation system. [font size="3"]Other pathways to the use of natural gas in transportation, instead of direct use CNG or LNG, may be worth considering, such as application of gas‐to‐liquids processes to convert natural gas to liquid synthetic fuels[font color="blue"](one of which would be Methanol_Bill USA)[/font][/font] or the combustion of natural gas in power plants to provide the electricity needed for powering range‐extended hybrid vehicles, such as the new Chevy Volt or the all‐electric Nissan Leaf.