Diesel facts: pass it on to nonbelievers.
Got this off a TDI website, good stuff to know so you got some ammo against the diesel-ignorant and the eco-terrorists out there:
Forget about all those smoky old buses and trucks, the truth is that the modern diesel car is as clean, and probably cleaner than an equivalent petrol car. Don't believe me? Read on.
The five main emissions for petrol and diesel cars are:
Carbon Dioxide (CO2)
Carbon Monoxide (CO)
Nitrogen Oxides (NOx)
Of these five, a diesel car is better than a petrol car with three of them, about the same with one, and worse with one. Only one of these classes of emissions is visible (particulates, or soot), and rather unfortunately for diesel cars, that is the one which is worse for them. The three emissions for which petrol cars are worse are invisible, so you won't realise that they are there; however they still cause harm to health and the environment.
What problems do these emissions cause, and how does diesel stack up:
Carbon dioxide is the main cause for concern at the moment, and is the subject of international agreements to try to reduce its output. Carbon dioxide is causing global warming; this is a known fact. Carbon dioxide is produced by any burning of fossil fuels, and is caused by production of electricity by most current powerstations; this means that electric cars cause carbon dioxide emissions too. Carbon dioxide does not cause any health issues.
Carbon dioxide emissions are directly proportional to fuel consumption, and as diesel cars use 30 to 40% less fuel, they emit 30 to 40% less carbon dioxide than petrol cars. Natural gas and LPG cars are actually quite fuel inefficient, if otherwise cleaner burning, and so produce more CO2 than a diesel.
Although CO2 emissions are not directly harmful to us, they are changing our climate. The legacy these emissions will leave will be felt by every generation after us.
Carbon monoxide is a poison. It has no smell, but can kill you without you realising what is happening. Carbon monoxide is the reason why you should not run you car engine (petrol) in a confined space. Diesel engines produce virtually no carbon monoxide, a petrol engine produces enough to kill you. The main remedy to carbon monoxide emissions of petrol engines has been the introduction of catalytic converters, however there are problems with cats:
They don't work until they are hot, maybe 10 or 15 minutes of driving. As most car journeys only last 10 or 15 minutes, the cat is not terribly effective.
They increase fuel consumption.
They are easily poisoned and stop working.
They are easily mechanically damaged.
Nitrogen is the main constituent of the air that we breathe. When it is exposed to high pressures and temperatures it combines with oxygen in the air to form nitrous oxides. The nitrous oxides then combine with low level ozone to form smog. Because of the way a diesel engine works, with an excess of air inside the engine (rather than "just enough" as in a petrol engine, which is what causes CO emissions), nitrous oxides are more likely to be formed. However tests of actual cars reveal that whilst emissions of NOx are higher in a new diesel than a new petrol car, that by 50,000 miles or so they are the same, and after that the petrol engine produces more than the diesel. Therefore over the life cycle of the car, petrol and diesel engine emissions of nitrous oxides are similar. Emissions of nitrous oxides can be effectively reduced in both petrol and diesel cars by use of exhaust gas recirculation (EGR). EGR reduces the combustion temperature to below the point where nitrogen effectively burns.
Hydrocarbons include chemicals such as benzene. Benzene is an extremely carcinogen chemical, and has been declared unsafe by the World Health Organisation in any concentration. Hydrocarbon emissions are contained in petrol engine emissions much more than in diesel engine emissions. Benzene is also present in the fumes which can be smelt when filling up with petrol at a service station, this is not a problem with diesel.
Particulates or smoke are really the only problem for diesels (compared with petrol engines). Most of the controversies and newspaper scare stories center around particulates. Various groups have been trying for years to prove a link between diesel smoke and cancer, and so far have failed to actually prove anything. Friends of the Earth may come up with statements such as "Small particles are believed to lead to 8,100 premature urban deaths every year (1.9% of all deaths in urban areas)" and then apply them to diesel emissions, but this is flawed because:
The studies were carried out in American cities where the penetration of diesel in the market is lower. Any increase in deaths due to particulates, if it exists, may be caused be particulates from some other source; the particulates in question have not been indisputably linked with diesel emissions.
Even in Europe, particulates from diesel cars are a very small percentage of the particulate emissions which we breathe; most are from industry.
Diesel engines emit more PM10 particles, that is particles which have a diameter up to 10 microns, but petrol cars actually emit more PM1 particles than diesel ones. These particles are smaller than 1 micron and are invisible. They are also more likely to penetrate deeply into human lungs (as they are smaller) and look less like a natural dust particle, which human lungs have evolved to cope with.
Even if particulates are a factor in the deaths of 8,100 people every year in the UK, then these are the most seriously unwell people in the country. The fact is that we are talking about 8,100 people who are about to die, with or without particulates around.
The original research which led to the link between deaths and particulates is being questioned. See Merlise Clyde's paper, Model Uncertainty and Health Effect Studies for Particulate Matter, which can be downloaded from THE NATIONAL RESEARCH CENTER FOR STATISTICS AND THE ENVIRONMENT in Washington.
Diesel cars are better than petrol cars with reference to carbon dioxide, the global warming gas.
Diesel cars are better than petrol cars with reference to carbon monoxide, a poison.
Diesel cars are better than petrol cars with reference to hydrocarbons which cause cancer.
Diesel cars are similar to petrol cars with reference to nitrous oxides, which cause smog.
Diesel cars are worse than petrol cars with reference to particulates, which have unproved health impacts.
Cool stuff. Good to know.
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