From CO2 to NOx
A rapid change in environmental focus, from carbon dioxide to nitrogen oxide emissions, poses a major challenge for corporate fleets looking to operate the ‘cleanest’ vehicles possible.
The goalposts have moved. Environmentally-focused fleet operators, who once concentrated on the carbon dioxide emissions of their vehicles, are now tasked with reducing emissions of nitrogen oxides (NOx).
Global warming remains an urgent issue for the planet, but national and local governments appear more concerned with local air pollution than greenhouse gases. Unfortunately, the technology that combats C02 actually increases NOx emissions and vice-versa.
CO2 versus NOx“A car engine running at high temperature tends to emit less CO2 but more NOx,” explains the ACEA, the European Automobile Manufacturers’ Association. “A lower engine temperature will result in more CO2 but less NOx.”
The change in emphasis from CO2 to NOX presents a problem to corporate fleets accustomed to a world where selecting vehicles with low CO2 emissions delivered multiple advantages. The close correlation between CO2 emissions and fuel consumption meant that low emitting vehicles also had cheaper fuel bills. Tax incentives added extra motivation for both fleets and company car drivers to choose cars with the lowest CO2 emissions; at least 20 EU countries base some or all of their car taxation on CO2 emissions.
The combination of these factors explain why diesel has increased its market share over petrol, especially in the fleet market. In the UK, only 33% of company cars were powered by diesel in 2002-03; today that figure is above 82%.
The Asthma issue
But diesel exhaust is in the crosshairs of health professionals, who blame the fuel for dangerous levels of air pollution. The International Agency for Research on Cancer, part of the World Health Organisation, has classified diesel exhaust as carcinogenic, while exposure to NOx is blamed for triggering respiratory diseases including asthma.
Dr Samantha Walker, director of research and policy at Asthma UK, said: “Two thirds of people with asthma tell us that air pollution makes their symptoms worse, putting them at an increased risk of a potentially life-threatening asthma attack. It’s vital that action is taken to address this.”
Action is being taken. Legal cases across Europe are forcing local authorities and national governments to respond. In Paris, the new Crit'Air scheme has introduced six different emissions standards for cars, which will make it easier for the authorities to block the city’s streets to the most polluting cars and give priority access to the cleanest. Across the Channel in London, a T-charge (toxic) of £10 (€9) per day will come into force in October for vehicles that do not meet Euro 4 standards.
The challenge for fleets that want to be environmentally friendly, operationally efficient and cost effective is to identify vehicles that will satisfy future emissions standards.
Few experts doubt that the long-term solution lies with zero emission vehicles, either battery powered or hydrogen. But in the short-term, identifying the cleanest internal combustion engines is difficult. That’s because new vehicle testing procedures are turning official emission figures on their head.
WLTP
The new Worldwide harmonized Light vehicles Test Procedures (WLTP) should provide more realistic CO2 results than its predecessor, the New European Driving Cycle (NEDC), but a far bigger disruption will occur when the Real Driving Emission (RDE) test procedures begin this September.
The RDE is focused on NOx, and actually takes cars out of the laboratory and onto the road to measure their performance – a truly ‘real world’ test. Tests commissioned by the Dutch Ministry of Infrastructure and the Environment, and carried out by TNO, found that NOx emission levels were five to six times higher under RDE conditions than laboratory testing.
“Although vehicles perform well during a type approval test, their real-world NOx emissions generally and almost with no exception deviate substantially from the type approval limits,” said TNO.
When RDE starts, its threshold for diesel NOx emissions will be 168mg/km, more than twice the 80mg/km limit set by Euro 6. The PSA Group has committed to publish RDE type-approval NOx figures for its vehicles this year, alongside lab-tested figures, information that will give fleets a more accurate picture of NOx emissions.
To control and limit pollutants from diesel engines involves significant investment from vehicle manufacturers in air management, fuel injection control, and after treatment systems, such as lean-NOx traps and catalytic reduction systems that work with ammonia-based additives such as AdBlue. Impressively, Mercedes-Benz new family of diesel engines already meets the 80mg/km threshold, even when tested under RDE conditions.
The issue facing fleet operators, however, is whether this type of clean diesel will be treated favourably by authorities, in terms of both tax and access to polluted city centres; or will authorities use a blunter tool, increasing the tax on diesel as a fuel and diesel vehicles, and treating all diesel vehicles as part of the problem not solution?