This press release showed up in my news feed today: Natural gas versus diesel: Examining the climate impacts of natural gas trucks (http://www.eurekalert.org/pub_releases/2015-05/acs-ngv052015.php). We have worked with fleets considering conversion to compressed natural gas (CNG) and have also ventured into lifecycle analysis, so I had to take a look.
The paper itself had not been published yet, but the authors found that switching big fleets of diesel vehicles to CNG may not have quite the greenhouse gas benefits that we usually hear about. Why? Because of energy consumption and methane (natural gas) releases during the extraction and production of natural gas. As methane is a much more potent greenhouse gas than carbon dioxide, even small releases of methane have a large impact on the relative greenhouse gas intensity of fueling a vehicle with CNG.
Without reading the paper itself, I can’t say whether the authors’ assumptions and scenarios make sense, but the finding is very plausible, so we will be keeping an eye on this discussion. If you have any questions about greenhouse gas reduction or CNG as a transportation fuel, please don’t hesitate to contact us.