Fifty years of evolving legislation have helped reduce the damage vehicle emissions inflict on the world’s atmosphere. Today, as we stand on the threshold of a new era of multiple fuel and powertrain choices, the challenge of establishing an all-encompassing set of rules is even greater.

It was back in 1966 that the state of California introduced the world’s first legislation to curb tailpipe emissions. Ever since then, the debate over the extension of these exhaust standards has been intense and often bitter, confronting the global auto industry with some of the biggest conundrums in its long history.

So today, more than 50 years later, one of the most crucial questions facing the industry is what comes after Euro 6. Ricardo is a key player and part of a consortium set up to work with the EU Commission to come up with the answer. Other members include OEMs, oil companies and Tier 1 suppliers.

Avoiding Catch 22

The growing enthusiasm for electrification in the public and political arenas is often driven by emotion rather than science. The European Commission agrees that electrification is not the single solution and that it may not necessarily be the panacea for the world’s emissions woes that people think it is.

It certainly won’t be the pathway for heavy duty vehicles, and there’s huge potential for light duty vehicles as well in terms of combustion-based technology. There will have to be other solutions, too, and there is a great deal of effort being focused in the industry on parallel paths that will accompany electrification. The likelihood is that more pollutants and greenhouse gases will be addressed in the next stage of regulations, but it will be vital to ensure that new regulations don’t inadvertently make matters worse.

“the growing enthusiasm for electrification in the public and political arenas is often driven by emotion rather than science”

Dealing with the emission of one particular substance inevitably leads to a Catch 22 situation, where the steps taken to neutralise the effect of one pollutant can cause knock-on impacts on another. A prime example is the way the introduction of diesel particulate filters contributed to the urban NO2 problem. In the same way, though electrification is without doubt a powerful environmental tool, its wider consequences beyond the EU could be profound if not carefully controlled, thanks to upstream factors such as the impact of mining on local air and water quality.

Creating the bigger picture

For that reason, I’m keen to emphasise the importance of the bigger picture. That means considering continental problems as well as local ones, or what I call ‘problems in the neighbourhood’.

In addition to tailpipe emissions, local problems can include non-exhaust emissions which also degrade air quality. So let’s not drive policies focussed solely on exhaust emissions: that could damage the rest of the world just to solve local issues. On a continental level, we need to factor in trans-boundary pollution from countries getting their energy predominantly from coal, and also to include secondary aerosols (produced by the reaction of particles in the atmosphere) as well as the contribution of the familiar well-to-wheel emissions. Then, expanding the scope still further, there is a universal level where the whole world is contributing to emissions. These can derive from irresponsible raw material sourcing, and emissions of greenhouse gases that contribute to global warming, as well as other noxious pollutants. If you take this holistic view, the generally accepted idea of what is environmentally sound, and what isn’t, suddenly becomes less convincing. If EVs are charged with electricity from grid networks that use predominantly coal-fired power stations (and there are many globally), then well-intentioned policies may later turn out to have unintended consequences.

In contrast, the latest super-clean diesels burning low carbon fuels could easily outperform an EV running on non-renewable grid energy. This underlines the importance of life cycle (or at least, well-to-wheels) analysis. In these two cases, which one would be the angel and which the devil?

The next stage will be the last

One thing the European Commission and the stakeholders all agree on unequivocally is that the next stage will be the last stage of emissions regulation. It may be called Euro Ultimate or Euro Omega, or it may be called something other than “Euro” because we want buy-in from a much larger geographic region.

Looking ahead, there are several factors to take into account, factors which go well beyond the current suite of emissions already legislated for. One is the possibility of a new fuels directive to enable the introduction of low-carbon fuels, something that would help to perpetuate internal combustion engines and put them on a fair footing with electric vehicles.

A ‘zero emission’ electric vehicle is not zero emission if you take into account its entire life cycle. I believe there will be a new fuels directive, but at this stage no one can say how big its scope will be. The complexity is that the specification for any new fuels has to be agreed between the fuel suppliers and OEMs, and it has to be rigorously understood so that vehicle warranties will stand with the new fuels. The liquid and gaseous road fuels of today have evolved slowly over a long period of time, so having a paradigm shift in fuel chemistry will be very demanding – yet the timeframe for the next legislative stage is relatively short.

Extending the scope

A second factor is the extension of the range of pollutants the legislation will cover. It is expected that a number of new species of pollutants will be included in the regulations, and I suspect these might even be applied in further steps of Euro 6 preceding this next major ‘ultimate’ step of a holistic standard.

The inclusion of these new pollutants is likely to go hand in hand with a strengthening of the durability criteria for new cars. At the moment, full useful life in Europe is assumed to be 160,000 km; in the US it is 240,000 km and I wouldn’t be surprised to see it go even further, to, say, 300,000km. In essence, that vehicle will have to produce lower emissions even if you keep it for 15 years and drive it for 300,000 km.

Complex questions surrounding durability include things like who looks after the vehicle and who warranties an aftertreatment system for 15 years. In-service compliance (ISC) will be a further consideration. This involves some means of monitoring the emissions control efficiency of vehicles in the real world. Measures may include the use of remote sensing, portable emissions measurement systems (PEMS) both for certification and for in-service compliance testing. I think we will see the PEMS boundary conditions tighten. For example, the scope will encompass higher altitudes and both higher and lower temperatures than currently legislated for, as well as more aggressive transients and the urban component becoming shorter. Whereas Real Driving Emissions (RDE) assessments currently represent 95 percent of normal driving, they could go much higher, to 99 percent, for example. Some non-governmental organisations (NGOs) are pushing for testing to include every possibility, something which is hardly realistic, but the scope of RDE testing will certainly be increased.

A fourth consideration will be in-use performance monitoring (IUPM), which is linked to new on-board sensors. Modern vehicles already include NOx sensors, and the Lambda sensors that enable three-way catalytic converter systems have been around for a long time. The proliferation of all types of new sensors for various uses makes it a fairly straightforward proposition to constantly monitor the health of the vehicle and send the data up to the cloud. If the vehicle’s emissions systems go awry, the vehicle will be called in for an emissions test. This is already happening to some extent, and Fiat Chrysler Automobiles already monitors the fuel consumption of its vehicles in this way. The data has revealed a wide range of CO2 emissions depending on driver styles and region – useful incremental information as RDE testing does not yet include CO2 (fuel consumption) measurement.

Intelligent travel

Intelligent transport systems and connectivity (ITS) will also be included. It should be possible to make a car behave differently when it is in a city, and you can use geofencing to do that.

Geofencing monitors the position of a vehicle using GPS and triggers an alert should it cross a virtual ‘fence’ defined in software by map co-ordinates. Vehicle tracker systems are an example of geofencing already in widespread use today. “When the vehicle crosses the boundary it could be switched into a different mode, or the system could be used to prevent vehicles from leaving a certain area because they won’t function outside. Those possibilities are a little more remote but they are certainly being discussed.

Technological neutrality is under consideration too, where all technologies are subject to the same level of regulation. Whereas today, for example, gasoline and diesel vehicles are subject to different pollutant limits, in the future they would have to co-exist on an equal footing. China is already heading in that direction following the US.

“I’d like to see LCA applied to pollutant emissions as well as just greenhouse gas, because that would produce a genuinely level playing field”

Technical neutrality for tailpipe emissions will help preserve the focus on local air quality – for instance, on what causes a nitrogen dioxide (NO2) or carbon monoxide (CO) problem in a particular area. The legislation will address low carbon pathways for internal combustion engines, as touched on earlier. Pathways should be compared on a well-to-wheel or life cycle analysis (LCA) basis to avoid unintentionally incentivising those coal-powered EV scenarios. We don’t want to get in the situation where we rule out the internal combustion engine and then find we haven’t got all the materials to make the EVs that we need, so we have to have the parallel paths. Ideally, I’d like to see LCA applied to pollutant emissions as well as just greenhouse gas because that would produce a genuinely level playing field, and truly realise the environmental benefit.

The importance of good science

Measurement of emissions and limits will need to be based on ‘good science.’ There is not enough time between now and the likely introduction of the final-stage legislation by the end of the next decade to conduct health studies that are comprehensive enough to reliably link those measures directly to obvious health effects. Instead, there will need to be a link to benefits and air quality targets.

The timeline for the final stage of the emissions regulation is aggressive, with Euro stages typically spaced from five to seven years apart. Under normal circumstances that would point to around 2025 for the new rules to come into effect but, as there is so much to implement, that timeframe may be stretched to 2028 or 2030.

The likelihood, however, is that to ease the burden of the transition some new measures will be introduced earlier as part of the Euro 6 emissions series. By happy coincidence, the expected timeframe for the transition to lower carbon fuels is possible in the 2025-2030 timeframe, making
a convenient fit with the future regulations.

Nanoparticles: a health warning

One thing the European Commission is especially keen to see implemented as soon as possible is a way of dealing with nanoparticles – the tiny particles that are not just produced by diesels.

The existing 23 nanometre (nm) lower particle size limit was established to force the use of soot-trapping DPFs, but below that size range (and independent of the soot) there are metal oxide particles and other sources of particles, at quite high levels. Diesel DPFs already deal with these smaller nanoparticles, but mandating the use of particle filters on gasoline and even gaseous fuel engines would be the next step. Because filters have a near 100 percent clean-up rate, the problem of the smaller particles would be solved without lowering the emissions limit, instead simply extending the size range of particles for certification.

“one thing the European Commission is especially keen to see implemented as soon as possible is a way of dealing with nanoparticles”

The future scope of regulation to include new pollutants extends to the ‘nitrogenous’ species. As well as NO2 and nitric oxide (NO), the regulation will include the greenhouse gas nitrous oxide (N2O – commonly known as ‘laughing gas’). Ammonia, a pollutant which also transforms to PM2.5 in the atmosphere, will also be accounted for. This will be important because particulates pose a more serious health hazard than NO2, despite the media focus on the latter.

Isocyanic acid (HNCO) is also of interest to the European Commission. It’s not something we’ve looked at yet, but it is an intermediate in the process where the urea used in selective catalyst reduction (SCR) aftertreatment systems decomposes to ammonia; it can also be produced under rich-lean transitions by catalysts that have a reductive capability, such as three-way catalysts and lean NOx traps.

The carbon species of CO2 and CO are already accounted for, yet in the forthcoming regulations sulphur dioxide (SO2) and hydrogen sulphide (H2S) will not be regulated at all. This is because we have been so successful in pushing down the sulphur content in lubricants and fuels that there’s not enough of either to be of concern in general operation.

The hydrocarbon methane should be classified as a greenhouse gas rather than a pollutant, and the expectation is that in the future methane and nitrous oxide will be grouped together as CO2 equivalents (CO2e). What you don’t want to do is have a separate limit value for these: instead, you just add them to the CO2 targets. Nitrous oxide is generated by nearly all types of aftertreatment system and if you set too stringent a limit for it the aftertreatment challenge increases without delivering a pollution benefit. Dealing with the nitrous oxide by classing it as CO2 is the most effective way.

New suites of gases under the microscope

Other forms of hydrocarbon under consideration are the non-methane hydrocarbons (NMHC), non-methane organic gases (NMOG), aldehydes and acetaldehydes. An interesting question (and one which highlights the fact that it is easy for measurements to mislead if they are misunderstood) is the classification of NO together with NO2 for emissions purposes, the two simply being referred to as ‘NOx’. This is done because, over time, NO oxidizes to NO2 in the atmosphere anyway – yet in terms of local pollution it is only NO2 which is a major health hazard and NO is much less harmful. Were they to be treated individually to reflect only the amount of the harmful gas NO2 present in the air, another problem would arise. NO is lighter than NO2, but in classifying them together, its weight is assumed as equal to NO2. Were they separated, anyone adding the two individual quantities together would see an apparent reduction in the original NOx level. Such is the complexity of representing emissions in a meaningful way, especially as NO2 is widely and regularly discussed in the media. We’re not even close to having the discussion as to how to deal with that yet, but when we do, it will be an interesting one.

Finding the best way forward

The intention is that this new wave of post Euro 6 regulations will be the last ‘ultimate’ stage of European emissions regulation. It will need to encompass a massively wider spectrum of new fuels and power sources, and to take a whole-life approach to all the elements involved.

Whatever shape the finished framework takes, it will be huge and multi-faceted. Its complexity means it will take longer than usual to complete, possibly until 2030. Before then, there may be more stages to go through to bridge the gap between now and the final stage.

New pollutants will come under scrutiny, something which may create new challenges in aftertreatment development. The first of these new pollutants to be considered could be sub-23nm PN (number of particles measured smaller than 23 nanometres). Limit values of various pollutants need to be carefully considered to avoid the setting of arbitrary limits which may, as we have seen, have an unfavourable impact elsewhere in the emissions suite; additionally, the way in which greenhouse gases and CO2 equivalents are dealt with in the future will also need careful consideration.

Internal combustion and EV pathways will need to be developed in such a way that both the local and the global issues surrounding them are considered for the long term. Yet, and perhaps the most important of all, it is vital to take a holistic life cycle view of the impact of both greenhouse gases and pollutants to establish truly sustainable mobility for the future.

Emission perception

Perception plays an important part in understanding the impact of emissions. NO2 is the focus of attention regarding local air quality in cities based on quoted NOx figures. But broken down, the facts paint a different picture. NOx is a blanket term for three gases: nitric oxide, nitrogen dioxide and nitrogen dioxide. All three are grouped together for the purpose of setting emissions limits and it is the last of these which is the cause for concern in terms of local air quality because of its harmful effects on health. But of NOx emitted from the latest diesel, only around 10 percent or less is nitrogen dioxide. Yet most air quality models assume that 30-50 percent of NOx is NO2, a huge departure from reality. Removing the old diesels from urban environments could solve the local nitrogen dioxide problem in cities, where pushing the introduction of EVs in place of new EU6 diesels can never do so.