The humble two-stroke gasoline engine has done yeoman work for well over a century. The noisy beasts, invented by Sir Dougald Clerk in 1876, are reliable, easy to maintain, and powerful for their size. But they have a dirty secret.
Traditionally they belch out a cocktail of hazardous emissions in a haze of blue smoke, powering chain saws, weed whackers, snowmobiles, scooters, outboard motors, and the like.
Earlier this month, the US Environmental Protection Agency (EPA) announced long-awaited tough new emissions rules on small engines (25 horsepower or less), many of which still use two-stroke engines, as opposed to cleaner four-stroke ones.
When fully implemented in the next few years, the new standards will reduce hydrocarbon and nitrogen oxide emissions by 35 percent, the EPA says. The agency estimates that by 2030 these reductions will result in significant health benefits, reducing hundreds of premature deaths and hundreds of thousands of workdays and schooldays lost because of pollution-related illnesses. That would translate into a cost savings of between $1.6 billion and $4.4 billion, the EPA says.
But even as the US takes action, a bigger battle against dirty two-stroke engines awaits in Asia, where the engines power most scooters and motorcycles, many of which are used as unlicensed taxis.
“One of these dirty three-wheel taxis in India or the Philippines produces the pollution of about 50 modern automobiles,” says Bryan Willson, a professor of mechanical engineering at Colorado State University in Fort Collins. “And you’ve got 50 to 100 million of these in Asia, so you’re looking at over 2.5 billion car-equivalents of pollution. So that’s a huge environmental impact.”
Asian governments are looking at a number of measures to cut pollution from two-stroke engines, including replacing them with four-stroke power plants similar to those found under the hood of nearly every automobile. But because these small vehicles provide vital transportation and jobs for millions of people in Asia, simply mandating that they be taken off the streets isn’t an option.
A five-year-old nonprofit company called Envirofit International (envirofit.org) is promoting a solution that combines one part technology and one part entrepreneurship. Envirofit wants owners of these smoky vehicles, sometimes called rickshaws or tuk-tuks, to retrofit them with a kit that converts them to direct in-cylinder fuel injection. That reduces carbon monoxide emissions 90 percent and nitrogen oxides 70 percent, says Ron Bills, chairman and CEO of Envirofit in Fort Collins, Colo.
The conversion kits cost about $200, a huge investment for taxi owners who may make only a few dollars per day. That’s why Envirofit is working with micro-lending groups to help drivers afford the conversion. It’s also helping to train local mechanics to install the converters, creating more income for local people.
The incentive to taxi drivers comes in the form of a big boost in gas mileage once the engines are converted, about 35 percent better. That’s because unburned oil and gasoline no longer escape through the engine’s exhaust as smoke, a longtime drawback of two-stroke engines. Drivers can save about $2.80 a day on fuel (currently about $3.75 a gallon in Manila), meaning the conversion pays for itself quickly, says Mr. Bills, whose résumé includes a time as president and CEO of Segway, the maker of the innovative standup electric scooters. The money that drivers don’t spend on gasoline “goes directly into the local economy instead of out the tailpipe of a motorcycle,” he says.
Envirofit is operating in the Philippines now, which has about 1.3 million dirty two-stroke taxis, often consisting of a sidecar bolted onto a motorcycle, Bills says. The nonprofit has also run a demonstration project in India and plans to extend into Sri Lanka next.
It also is selling a second product, a line of simple wood-burning cooking stoves. Some 3 billion people use wood, animal dung, crop waste, or other biomass to cook food, Bills says, creating high levels of indoor pollution and subsequent health problems. The stoves, costing from $10 to $70, burn fuel more completely, cutting toxic emissions up to 80 percent while using only half as much fuel.
Meanwhile, direct-injection technology may change the image of two-stroke engines from that of a big-time polluter to a modern power source, says Dr. Willson, founder of the Engines & Energy Conversion Laboratory at Colorado State that developed the two-stroke conversion kit. “These simple two-strokes are some of the dirtiest and least efficient we have. But they also can be the cleanest and most efficient engines we have,” once they have been converted, he says.
The trick with direct injection, he says, is that only air, not fuel, is brought in through the intake port. Because the intake and exhaust ports open at the same time in two-stroke engines, up to 35 percent of the fuel can escape through the exhaust. “We [add] fuel directly to the cylinder late in the cycle when it isn’t lost through the exhaust ports,” he says.
In fact, two-stroke engines aren’t necessarily going to become extinct even in the United States, says Kris Kiser, a spokesman for the Outdoor Power Equipment Institute in Alexandria, Va. Some companies intend to develop clean two-stroke engines that will meet the new standards, he says.
The industry has been supportive of the changes and has worked closely with the EPA on setting them, Mr. Kiser says.
“Once [the regulations are] fully implemented by 2015, EPA will have reduced our emissions by 95 percent” compared with 1997, he says – “a very dramatic emissions reduction.”
Though prices for chipper-shredders, chain saws, leaf blowers, and the like may rise, manufacturers may absorb the cost to try to preserve market share. “Our industry is very price-sensitive,” Kiser says. But even if prices do rise, he says, owners will save money on fuel in the long run.
The EPA predicts that some small engines may need to employ catalytic converters, similar to those found on cars.
“EPA’s new small engine standards will allow Americans to cut air pollution as well as grass,” said EPA administrator Stephen Johnson in announcing the standards.
The regulations, which cover small watercraft as well, are expected to trim annual emissions of hydrocarbons by 600,000 tons, nitrogen oxide by 130,000 tons, particulate matter by 5,500 tons, and carbon monoxide by 1.5 million tons – as well as save about 190 million gallons of gasoline each year, the EPA estimates.
95% Amount new EPA regulations will cut pollution from small gasoline engines by 2015 (from 1997 levels)
5.4 million Projected number of walk-behind mowers to be sold in America in 2009
2.5 million Projected chain-saw sales in 2009
51.5 million Tons of carbon monoxide expected to be cut yearly by new EPA regulations
190 million Gallons of gasoline saved each year by the new regulations
Source: Outdoor Power Equipment Institute
[Editor's note: In the original version, the photo of the man on the scooter was incorrectly credited.]