Way back in 2003, New Delhi, India converted 90,000 buses, taxis and auto-rickshaws to compressed natural gas (CNG). It was an ambitious program for its day, and perhaps too ambitious for its own good. A recently released study by the University of British Columbia found that the 5,000 auto-rickshaws using 2-stroke engines that were converted to CNG exhibited only minor reductions in emissions. Even worse, the types of emissions that affect climate change actually increased after the conversion.

The problem here is not the fuel type, it's the engine. The study found that there were high emissions of methane coming from the 2-strokes because as much as a third of the CNG is sometimes improperly burned. Methane is a greenhouse gas and has a global warming potential significantly higher than CO2. In addition, unburned lubricating oil in these engines produces substantial high particulate matter emissions.

The study also tested 4-stroke engines, and these had significantly lowered emissions across the board. In fact, according to the researchers, it would have been better for the environment – and cheaper overall – to simply upgrade the 2-stroke engined rickshaws to the cleaner gas-burning four-stroke models. Well, now we know.

[Source: Science Daily | Image: Carol Mitchell – C.C. License 2.0]

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