Two-stroke Engine Pollution Solution

Cities across the South choke on the pollution made by the small two-stroke engines (http://www.howstuffworks.com/two-stroke.htm) powering motor scooters, motorcycles, auto rickshaws, tuk-tuks and other vehicles. People choose these vehicles to get around because they are cheap, powerful and easy to fix. But the environment – and human health – suffers as a result. And as cities balloon and populations grow, the number of journeys and two-stroke engines grows with it.

In large cities across Asia, 1 million three-wheeled auto-rickshaws form an important means of daily transportation, and a source of income for their drivers. And the Asian Development Bank estimates there are over 100 million vehicles using two-stroke engines in Southeast Asia. But these vehicles cause serious air pollution and emissions of carbon dioxide (CO2), which contributes to global warming.

Because two-stroke engines burn an oil-gasoline mixture, they also emit more smoke, carbon monoxide, hydrocarbons and particulate matter than the gas-only, four-stroke engines found in newer vehicles.

In the Philippines, auto rickshaw drivers are pioneering specially adapted two-stroke engines that reduce particulate emissions by 70 percent and carbon dioxide emissions by 76 percent.

Tim Bauer, the 31-year-old American mechanical engineer who developed the technology, said auto rickshaws “play an essential role in the social and economic fabric. But their impact on public health is disastrous.”

Motorized tricycles produce an astonishing amount of pollution: each one is equivalent to 50 cars. In Bangkok, Thailand, two-stroke engines contribute 47 percent of pollution particulates in the air.

The World Health Organization (www.who.org) ranks urban outdoor air pollution as the 13th greatest contributor to disease burden and death worldwide. It has been estimated that the air pollution leads to the deaths of more than half a million people a year. About two-thirds of the residents of Delhi and Calcutta suffer from respiratory symptoms such as common cold and dry and wet cough, much of this caused by two-stroke engine emissions.

Two-stroke engines are highly inefficient users of fuel: up to 40 percent of the fuel and oil goes out of the exhaust pipe unburned. This exhaust is packed with oxides of carbon, nitrogen, sulphur, hydrocarbons and fine dust – all toxic contributors to air pollution.

But the attraction of these engines remains strong. “They are powerful, simple, reliable and robust,” said Bauer, “and spare parts are easy to find. They also have a long lifetime.”

Bauer faced some strict constraints in developing the technology.

“It had to substantially reduce emissions without impairing the engine’s performance. It had to be installed without machining the engine crankcase, and with only a basic tool set. Of course, it also had to be affordable for Filipino drivers.”

Using off-the-shelf components, Bauer developed a kit that turns two-stroke engines into fuel-injection machines. This adjustment reduced particulate emissions by 70 percent and carbon dioxide emissions by 76 percent. He now sells the kits through Envirofit, a non-profit organization (http://www.envirofit.org/). It has been pilot tested at two Filipino holiday resorts, Vigan and Puerto Princesa.

Auto-rickshaw drivers tend to be poor and earn on average US $3 to US $4 a day. The cost of fitting vehicles with Bauer’s new technology is met by microcredit.

“Drivers earn money daily, so it’s easy for them to pay back their loan, and 90 percent of them do it in less than a year,” he said. Over 260 taxi drivers have already installed the new kit.

“These drivers are at the base of the economic pyramid and these tricycles are a testament to their ingenuity and work ethic. At the end of the day, we can improve their lives with a cylinder head, a few brackets and, of course, hard work.”

Bauer pioneered his solution while working on fuel injection in snowmobiles at the Engines and Energy Conservation Lab at Colorado State University. He started to market the solution in Asia in 2004. Bauer has won a Rolex Award for Enterprise to pay for the distribution of the kits throughout Asia.

There is, of course, another solution: an outright ban or measures to push the vehicles off the road. In the Philippines’ San Fernando City, economic incentives were what drove the transition from two-stroke to four-stroke (less polluting) tricycles. In 2001, three-quarters of the city’s 1,600 registered tricycles ran on two-stroke engines. But after a city council mandate to totally phase out the vehicles by 2004, and offers of interest-free loans for down-payments on four-stroke models, more than 400 four-stroke tricycles had replaced the older two-stroke models.

When Bangkok toughened up vehicle inspections and emissions standards in 2000, two-wheelers made up over 96 percent of the city’s traffic. But by March 2004, they made up only 40 percent, according to Supat Wangwongwatana, deputy director general of Thailand’s Pollution Control Department.

By David South, Development Challenges, South-South Solutions

Published: December 2008

Read more about the impact of air pollution on human health in Beth Gardiner's Choked: The Age of Air Pollution and the Fight for a Cleaner Future (Granta, 2019). 

Beth Gardiner shows off the first galley proof of Choked on Twitter.

Development Challenges, South-South Solutions was launched as an e-newsletter in 2006 by UNDP's South-South Cooperation Unit (now the United Nations Office for South-South Cooperation) based in New York, USA. It led on profiling the rise of the global South as an economic powerhouse and was one of the first regular publications to champion the global South's innovators, entrepreneurs, and pioneers. It tracked the key trends that are now so profoundly reshaping how development is seen and done. This includes the rapid take-up of mobile phones and information technology in the global South (as profiled in the first issue of magazine Southern Innovator), the move to becoming a majority urban world, a growing global innovator culture, and the plethora of solutions being developed in the global South to tackle its problems and improve living conditions and boost human development. The success of the e-newsletter led to the launch of the magazine Southern Innovator.  

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