VANCOUVER, British Columbia, March 1 (UPI) -- Canadian researchers say a program by one of the world's largest cities to switch its vehicles to clean fuel has not significantly improved emission levels.
Researchers at the University of British Columbia say their study of the impact New Delhi's 2003 conversion of 90,000 buses, taxis and auto-rickshaws to the "clean fuel" of compressed natural gas has had can provide guidance for other cities considering such projects, a university release said Tuesday.
Crucially, in New Delhi's 5,000 auto-rickshaws with two-stroke engines -- a widely used form of transportation in both Asia and Africa -- the conversion to natural gas produced only minor reductions in emissions that cause air pollution. The switch actually resulted in an increase in other emissions that negatively impact climate change.
The New Delhi program could have achieved greater emission reductions at a cheaper price by simply upgrading two-stroke models to cleaner, more fuel-efficient, four-stroke engines, the researchers said.
"Our study demonstrates the importance of engine type when adopting clean fuels," lead author and UBC post-doctoral fellow Conor Reynolds said. "Despite switching to CNG, two-stroke engine auto-rickshaws in Delhi still produce similar levels of particulate matter per kilogram of fuel to a diesel bus -- and their climate impacts are worse than before."
As much as one-third of natural gas is not properly burned in two-stroke engines, producing high emissions of methane, a major greenhouse gas that contributes to climate change, the study said.
Several Asian cities have even more two-stroke auto-rickshaws than New Delhi, researchers said, including rapidly industrializing cities in India, Pakistan, Bangladesh, Philippines, Thailand, and Indonesia.