Improving air quality in urban areas

Air quality in cities: Vehicle emissions and Low Emission Zones 

It is not only buildings that are being required to improve their environmental credentials with many councils across the UK having introduced low emission zones (LEZ) for all but the latest combustion engine vehicles.

In London an Ultra zone Emission Zone has been introduced and from April 2019 tighter emission standards will be introduced that affect petrol and diesel vehicles and from 2020 higher standards will apply. There are different target rates and a toxicity charge or "T" charge is in operation with a Ultra Low Emission Zone to be introduced from April 2019. The daily "T" charge is currently £10 on top of the congestion charge of £11.50 and a T-charge daily rate will apply if the vehicle is being driven. The daily charge for the ULEZ will be £12.50 and a fine of £130 will apply for non-payment prior to entering a zone.   

In Scotland the main cities Aberdeen, Edinburgh, Glasgow and Perth are all to introduce LEZ's.  Scotland's first  LEZ introduced covers Glasgow city centre and surprisingly is already in place. The Glasgow LEZ applied to buses from December 2018 in Glasgow City and by the end of 2022 it will apply to diesel  built before 2014 and petrol cars built before 2005. 

It seems like only yesterday we were being told of the virtues of diesel. 

"Green has never felt so right," said the Audi Green Police A3 TDI ad that premiered at the US Super Bowl XLIV 2010. That was the year in which Audi A3 was heralded as the "Green Car of the Year." Diesel was seen as the environmentally friendly fuel with lower greenhouse gas emissions. Since then much has happened. The so-called Diesel-gate scandal, in which VW hid the true emissions of its diesel vehicles by installing "defeat devices" that reduced (NOx) emissions under test conditions, did much to sully diesel's reputation, and we now know far more about the potential harm of emissions from diesel vehicles.
Vehicle Emissions

Emissions from fossil fuels
CO2 emissions from diesel cars are on average 120g CO₂/km, significantly lower than the 200g CO₂/km produced by petrol cars. However, it is a different story with nitrogen oxides (NOx) of which there are three main ones: nitrogen dioxide (NO₂) which is toxic; nitrous oxide (N₂O), another greenhouse gas, and nitric oxide (NO) which subsequently forms nitrogen dioxide (NO₂).
In a petrol car, a three-way catalytic convertor converts these gasses to nitrogen and oxygen, considerably reducing NOx emissions. In a diesel vehicle, this isn't possible; only two-way catalytic convertors can be used. On average petrol cars emit 30% less NOx than diesel.
While NOx is associated with respiratory problems, another problem with diesel cars is particulate matter, or PM. These are fine particles of soot that can penetrate deep into the lungs and cause cancer and other health problems. PM filters remove a large proportion of PM, but only if they are adequately maintained. When you see a diesel vehicle emitting dark coloured smoke, it is a toxic cloud of PM that can severely Damage your health.

Does diesel and petrol have a future in automotive use?
Driven by the requirement to reduce levels of pollution, the UK government has increased road tax on new diesel cars to encourage people to switch to greener alternatives. Drivers of older diesel cars are also facing additional charges for driving in the London Congestion Zone. The Ultra-Low Emissions Zone (ULEZ) charge will be introduced in 2019 and effectively will apply to petrol vehicles over 11 years old and to diesel vehicles over two years old in 2017. Other cities are expected to follow suit. 

But car manufacturers have invested heavily in creating the latest generation of diesel engines to comply with the most recent Euro 6 emission standards and will be resistant to let that go to waste. The problem is that while modern diesels are far less polluting, the new engines are highly complex making them expensive to manufacture and repair. Indeed diesel cars are losing their popularity. In the year 2018 sales of diesel vehicles fell by nearly 30% compared to the previous year.

Dieselgate?
Earlier this year Theresa May said, "I'm very conscious of the fact that past governments have encouraged people to buy diesel cars and we need to take that into account when we look at what we do in the future". Sadiq Khan has called for a "national vehicle scrappage fund" for diesel vehicles. Certainly, VW and other motor manufacturers tried to lull both governments the public into a false security regarding the environmental credentials of diesel cars. One employee is already serving a prison sentence in the US and many others are under investigation.

But the fact is: diesel and also petrol cars are doing harm. Pollution in our cities has risen to unacceptable levels, and we are in breach of European limits. Air pollution in London, mainly due to NOx and PM, is responsible for 9,500 premature deaths a year. Reducing these levels must be a priority, even at the price of penalising diesel owners. It is just unfortunate that we weren't made aware of these problems seven years ago. 

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