Category: Vehicle Emissions – Discussion

Q. What is the difference in combustion between a diesel engine and a petrol/gasoline engine?
A. In a petrol/gasoline engine, a mix of fuel and air is injected into the chamber. This is compressed and then ignited by a spark plug.
In a diesel engine air is injected into the cylinder, and is compressed by around twice as much as in a petrol/gasoline engine. This compression generates heat, so that diesel fuel burns spontaneously when it is injected.

Q. Why are diesel cars more fuel efficient than petrol/gasoline cars?
A. Diesel fuel produces more energy for a given volume (diesel has a lower calorific value, but a higher density than petrol/gasoline). Also the higher combustion temperature in a diesel engine makes it more efficient. Heat engines can generate more useful work if they operate at higher temperatures.

Q. What does the term NOx mean?
A. It refers to nitrogen oxides. The purists would say that it refers to nitric oxide (NO) and nitrogen dioxide (NO₂) only, but most also include nitrous oxide (N₂O) in this description.

Q. Why are NOx gases produced in vehicle engines?
A. Air is a mixture of nitrogen and oxygen. When the fuel in an engine ignites, there are areas where the temperature is hot enough (above about 1500°C/ 2700°F) to oxidise some nitrogen to NOx gases.

Q. Why do diesel engines produce more NOx than petrol engines?
A. Diesel engines operate at a higher temperature and pressure than petrol engines. These conditions favour the production of NOx gases. The quantity depends on the volume and duration of the hottest part of the flame.

Q. How do you reduce NOx emissions from diesel engines?
A. By lowering the combustion temperature, typically by Exhaust Gas Recirculating (EGR). Some exhaust gas is cooled and injected back into the combustion chamber. There is less oxygen in the exhaust gas because some has been consumed by previous combustion, so there is not as much to feed the flame. The exhaust gas also has a higher heat capacity than air, so it takes longer to heat up.

Q. Are there any other consequences of using EGR?
A. Yes, there is a downside. As the combustion temperature drops, so does the power, and the fuel economy.

Q. How can you remove NOx from exhaust gases?
A. Selective Catalytic Reduction (SCR). There are various proprietary blends of ammonia and urea which can be injected into the exhaust flow. These react with NOx gases over a catalyst, which turns them into harmless nitrogen and water.

Q. Why are NOx gases harmful?

A. Internal combustion engines can produce all three nitrogen oxides.

Nitrous oxide (N₂O), also known as ‘laughing gas’.

• It is a serious greenhouse gas, and is defined as being 298 times as bad as CO₂because of its radiative effect, and the time taken to break it down.
• Used as an anaesthetic and generally considered to be non-toxic. It does react with vitamin B12, which may be a problem for those who are deficient.

Nitric oxide (NO).

• Readily oxidised in the atmosphere to nitrogen dioxide.
• Non-toxic in small quantities, infact it serves a vital role as a regulator within the human body.

Nitrogen dioxide (NO₂).

• A major pollutant and component of smog. Its brown fumes may be familiar from school chemistry experiments.
• It reacts with water to produce nitric acid, which is why it is so irritating to the eyes and respiratory tract.

Q. What are SOx emissions?
A. When fuel is burnt in an engine, any sulphur will be converted into sulphur dioxide (SO₂) gas. This readily dissolves in water to produce an acid, which accounts for the irritation to your respiratory tract if you inhale it. It also affects the ecology. Oil and gas in the ground can contain large quantities of sulphur, which have to be removed in the refinery. Some countries have lax regulations on sulphur content in fuel, with resulting high pollution levels.

Q. How are particulates formed in a diesel engine?
A. Particulates, also called Particulate Matter (PM), are solid particles formed by partial combustion of diesel fuel in the cooler parts of the cylinder. Most are removed by particulate filters, but some gets through.

Q. Why are particulates harmful?
A. Small particles can penetrate deep into the lungs and cause respiratory problems. Nano-particles can even enter the bloodstream.

Q. What is smog?
A. Fog or haze intensified by smoke or other pollutants.

• Traditional smog was caused by burning coal, particularly high-sulphur coal.
• Photochemical smog. Nitrogen dioxide, and a fellow pollutant volatile organic compounds (VOCs), combine in the presence of sunlight to produce ozone and a variety of other compounds. These have a nasty affect on the respiratory system. More detail on photochemical smog.

http://clean-carbonenergy.com/nox-emissions.html

The car industry in 2015 launched a campaign to “challenge the increasing demonisation of diesel” vehicles.

The campaign, launched by the Society of Motor Manufacturers and Traders (SMMT), promotes the credentials of the new Euro-6 standards. This Europe-wide law, which will come into force in September, limits nitrogen oxide (NOx) emissions from new diesel cars to 80mg/km in order to bring down air pollution levels that breach health regulations in many EU cities.

Diesel cars have come in for increasing criticism in the last year for their larger-than-thought emissions of NOx and small particulates. Last year London mayor Boris Johnson proposed a scheme that would pay diesel car owners up to £2,000 to scrap their vehicle and switch to a cleaner model.

It inspired British car makers to invest heavily in a manufacturing process that most countries outside Europe have ignored. In 1994 the UK car fleet was only 7.4% diesel. By 2013 there were 10.1m diesel cars in the UK, 34.5% of the total.

But studies have since shown that diesel cars’ emissions of other pollutants can have serious impacts on the health of people exposed to them.

Now the European Union is scrambling to reduce the impact of its massive diesel industry on the health of its citizens. Carmakers have had some success in cutting the particulate matter of their engines, but according to recent independent testing, NOx levels remain stubbornly high.

A Channel 4 documentary in January called the subsidisation of the diesel industry the “great car con”. In the programme the current shadow environment minister Barry Gardiner MP, who was a member of the Blair government, admitted the policy was a mistake.

“Hands up, can I say there’s absolutely no question that the decision we took was the wrong decision.”

In 2014 the European commission took the UK to court for regularly exceeding NOx limits in 16 zones from London to Glasgow.

In an attempt to restore consumer confidence the car industry has produced leaflets (available at car markers and dealerships) as well as a “myth-busting” website. The campaign shows the growth of the diesel market and claims success for car makers in reducing emissions of NOx, particulate matter and CO2.

Mike Hawes, SMMT chief executive, says: “Today’s diesel engines are the cleanest ever, and the culmination of billions of pounds of investment by manufacturers to improve air quality … The allegations against diesel cars made in recent months threaten to misguide policy making and undermine public confidence in diesel. It’s time to put the record straight.”

But the claims of the industry have been criticised by experts who say the numbers cited by car makers are based on a test that does not represent real-world conditions. For official standards, diesel cars have their emissions tested in a laboratory, but recent testing by the International Council on Clean Transportation found:

On average, real-world NOx emissions from the tested vehicles were about seven times higher than the limits set by the Euro-6 standard. If applied to the entire new vehicle fleet, this would correspond to an on-road level of about 560 mg/km of NOx (compared to the regulatory limit under Euro 6 of 80 mg/km).

The Euro-6 regulations require a real-world test to be introduced, but the timing of this is still being debated. Greg Archer from campaign group Transport & Environment says the car industry has successfully lobbied the European commission to have the likely date for an introduction moved back from 2017 to 2020.

“They’ve based it on limits and tests which are carried out in laboratories and don’t represent the amount of pollution that these vehicles actually produce on the road. And they know that.

“Carmakers are trying to greenwash dirty diesel to hide the truth that compared to a petrol car a typical new diesel car on the road emits 10 times more nitrogen oxides. While carmakers claim modern diesels are clean they are pushing to delay and weaken the introduction of new pollution tests. This is because most new diesels can’t reach the limits agreed back in 2007 without fitting new technology,” says Archer.

An SMMT spokeswoman denied the industry was pushing back on real-world testing. To the contrary, she said, they were very supportive of getting the regime in place “as soon as possible”.

“We are waiting for a finalised communication from the European commission, which will set the parameters for the real-world testing. Until we have sight of that, manufacturers cannot commence the additional engineering investment required with any degree of certainty.”

Ben Barratt, an air pollution expert from King’s College London, says the early implementation of the new test is critical for the success of the regulations.

“In the absense of a real-world test we have to question these figures because history shows us that past performance has not delivered,” says Barrett.

“The sooner the real-world test comes in the better, without doubt. Because we will not know whether to trust the Euro-6 figures until that test comes in. Cities around Europe are reliant on Euro-6 delivering the reductions it is supposed to. If Euro-6 doesn’t deliver then many parts of Europe, including London and other cities in the UK, will continue to fail to meet European Union air quality standards.”

Councils around the country are beginning to take action to discourage their residents from buying diesel cars. Islington council will introduce a £96 per year diesel vehicle parking surcharge on 1 April. It will be the highest charge of its kind in the country and one of the first such schemes introduced.

Councillor Claudia Webbe said: “Pollutants in diesel exhausts have been linked to heart and lung diseases, which are major causes of serious and long-term health issues and even death in Islington, and the surcharge will encourage a move away from diesel.”

But Hawes said the charges made “no sense from an environmental point of view” citing the results from the tests the car industry agrees are flawed. The chairman and managing director of Ford of Britain, Mark Ovenden, says the charges are an unnecessary interference in the market.

“We support customer choice and the market should determine the best technologies for meeting CO2 and air quality goals,” he says.

But the car market is far from even. The carbon emissions tax regime currently levies £180 on a new petrol-powered Ford Mondeo. The rate for the diesel version is £0. Last month the UK government rejected an environmental audit committee recommendation to remove the tax advantage enjoyed by diesel cars. Signalling it remained supportive of the diesel industry.

The SMMT document also says that the furore over diesel’s contribution to air pollution is overblown, given the relatively small contribution (14%) cars make to the nation’s overall NOx emissions. There is a large misconception over who is the real villain, says the website. More than half of those survey by YouGov incorrectly identified cars and commercial vehicles as the biggest cause of air pollution in the UK.

“It would take 42m Euro-6 diesel cars (almost four times the number on the roads) to generate the same amount of NOx as one UK coal-fired power station,”

says the Diesel Facts website.

But Archer says this is “another example of the car industry greenwashing the figures”. Where the pollution is occuring is more important than how much, he says.

“The pollution that comes out of [power stations] is highly disperesed. It’s rather different when you’re a child in a push chair being pushed along a curb breathing in the exhaust fumes which are coming out of the cars standing next to you. So in terms of exposure to pollution, vehicles are far, far more important than power stations are.”

Taken from https://www.theguardian.com/environment/2015/mar/11/have-diesel-cars-been-unfairly-demonised-for-air-pollution

Who the hell do you believe? Does the Taxi Trade get persecuted just because of the lies of the Motor Industry? Just because a few people have picked up on some spin about diesel engines? It seems that all types of engines are bad, EVEN THE HYBRID!

“In fact one petrol-hybrid was the 11th highest CO emitter we’ve found so far!” (Which?)

“Our testing has found that almost all modern diesel cars exceed official emissions limits when tested in real-world conditions. We even found some hybrids breaking the limits too. So how can we trust car emissions claims?” Read more (Which?)

“Worryingly, in our tests, two thirds of petrol cars put out more CO into the air than they’re allowed to. The worst created more than five times the amount of CO than the official limit. And it’s not just sporty or big cars that are to blame – several superminis with small capacity engines are among the top offenders. And some were so bad that they couldn’t even meet the early ‘Euro 1’ limits from 1993 – which are pretty lenient compared to modern standards.” Read more (Which?)

“To our surprise we also found some hybrid cars are also breaking emission laws. Testing revealed that some petrol-hybrid cars emit more CO than they’re allowed – in fact one petrol-hybrid was the 11th highest CO emitter we’ve found so far.” Read more (Which?)

“One recent study by scientists in EV-friendly Norway has found that in some circumstances electric cars can have a greater impact on global warming than conventional cars.” Read more (BBC)

THE REAL OFFENDER HERE IS THE CAR MANUFACTURING INDUSTRY! Until they are made to change by the Government, then nothing will change, and no age limits or specifications on types of engines will change anything at all, other than to serve to persecute the honest hard working individual, who sits out there day an night so that you can be driven home safely!

What is Nitrogen Dioxide (NO2)? – (Green Facts)