Is natural gas not a good fuel source for vehicles in some cases? The University of British Columbia (UBC) has just published a study which details some surprising news. It turns out that using compressed natural gas (CNG), generally considered a clean fuel, is actually having a negative environmental impact when used in two-stroke engines.
In 2003, New Dehli, India converted 90,000 buses, taxis and auto-rickshaws to run on CNG. The intention, of course, was to reduce emissions and negative climate impact, but the UBC study found that the use of CNG in New Dehli’s over 5,000 auto-rickshaws with two-stroke engines had actually worsened the vehicle emissions. Extensive laboratory testing of the auto-rickshaws revealed that up to 1/3 of the CNG wasn’t being burned properly by the two-stroke motors. As a result, the auto-rickshaws produced significantly higher levels of methane gas and plenty of noxious blue smoke, due to unburned lubricants.
According to the research team, New Dehli would have been better off upgrading the two-stoke auto-rickshaw fleet to four-stroke engines. That approach would have reduced both emissions and fuel consumption and saved a bunch of money as well. As it stands, the auto-rickshaws are putting out as much particulate per unit of fuel as a diesel bus.
“Our study demonstrates the importance of engine type when adopting clean fuels,” said lead author and UBC post-doctoral fellow Conor Reynolds. He added, ““If policymakers have information about emissions and their potential impacts, they can make better decisions to serve both the public and the environment”