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Lorries are greener than scooters

By raccars Published

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Two-wheeled transport seems to have escaped most of the environmental attention directed at the motoring industry. Perhaps because they have small engines and don’t take up as much road room, they have always seemed to be more environmentally acceptable. New research, however, has highlighted some rather surprising facets of the humble scooter, which may shock those concerned with the emissions of our vehicles. A study, conducted by the Centre for Atmospheric Science at Cambridge University, has found that a scooter can give out far higher levels of organic aerosols than an HGV. Indeed, proportionally, although there are fewer scooters on the roads than cars and trucks, they give out much more pollution in our cities. The scientists added that the scooters also emitted worrying levels of benzene, a known carcinogenic, in addition to other toxic chemicals, collectively known as `reactive oxygen species.' They went on to conclude that even being behind a scooter while it waits at a junction could be 'highly deleterious to health'.

One of the team behind the Cambridge study, Markus Kalberer, confirmed the surprising findings: "We showed that, in contrast to the general belief, scooters can be a dominant source of air pollution, including soot and organic particles, in urban areas. We showed that the particles transformed the atmosphere from these scooter emissions which are especially toxic."

One of the reasons behind the increased emissions level is the two-stroke engine that is typically used by scooters. This type of engine offers less efficient combustion than the engines found in cars and lorries. The scooter’s exhausts are also less able to remove pollutants than the more efficient catalytic converters found on most cars. Unburnt, harmful chemicals from the scooter’s fuel therefore end up coming out of the exhaust.

The study measured emissions from a variety of different vehicles and discovered that the two-stroke scooters emitted a significantly greater level of volatile organic compounds and organic aerosols, caused by the incomplete combustion of fuel. A further issue arises when these chemicals react with the air and soot to create secondary organic aerosols, compounds known to cause lung and heart disease.

The problems caused by scooters are not unknown in other countries. Scooters have been banned in a number of Chinese cities and authorities have reported significant improvements in air quality. A paper published in Nature Communications, a scientific journal, suggested that scooters may account for as much as 60% of roadside pollution in some cities. They concluded: "Restrictions on two stroke scooters, already implemented in China, could improve air quality in many cities around the globe."

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