As January 2010 draws near, fleet managers and owner/operators will have to decide between two competing technologies to meet EPA2010 emissions standards. By now, most will know that Navistar is going to ramp up exhaust gas recirculation (EGR) levels in order to become EPA2010-compliant, while all other manufacturers are employing the exhaust aftertreatment system known as Selective Catalytic Reduction(SCR).
Each solution has its advantages and each also presents some concerns.
This is Part 3 in a series of blogs that will address some concerns and/or myths about EPA2010 emissions standards and both of the solutions that will be presented to the market. These blogs will be comprised of information obtained through many interviews I’ve conducted on the subject and plenty of additional research.
If you’re a stakeholder in this debate, and wish to comment on any of the points below, feel free to post a comment. Some spirited comments were posted in response to Part 1 and hopefully those contributors will stick around and answer any questions you may have on the subject of 2010 emissions solutions. I should also note that, while it’s a bit like talking to myself, I added a comment to Part 2. Rather than end the post with a question, I felt it behooved me to ask that very question and I have posted the response. It may be worth taking a look.
In Part 3 of the series, we’ll explore how SCR and Navistar’s EGR approach measure up when it comes to fuel consumption.
EPA2010 FACT: SCR will deliver better fuel economy than EGR
I’m wading into murky waters with this post. I’ve labeled the claim that (Selective Catalytic Reduction) SCR will deliver better fuel mileage than a non-SCR approach as FACT – and it is. It’s one of the strongest value propositions behind SCR. But while even the Navistar camp concedes SCR will consume less diesel, it counters that a like amount of diesel exhaust fluid (DEF) will be required by trucks using SCR, essentially nullifying the cost savings.
Proponents of SCR say their EPA2010 solution delivers anywhere from 2-5% better fuel economy than a non-SCR alternative. A 2-5% fuel savings is no small thing. By Cummins’ estimation, if averaging 6 mpg, at 120,000 miles per year and $4/gallon diesel (it will surely return to that level eventually), every 1% of fuel savings is worth $800 per truck per year. So a 5% fuel savings can add about $4,000 per truck to the bottom line each year. That’s a figure that’s hard to ignore, especially when extrapolated over a fleet.
The fuel savings is mainly due to the fact SCR users can reduce EGR flow rates, recovering some of the fuel economy they lost when they first introduced EGR in 2002 and then boosted EGR rates in 2007. Reducing EGR levels will allow engine manufacturers using SCR to tune their engines for optimum fuel mileage, since they can produce as much NOx as they want in-cylinder, and eliminate it downstream in the SCR catalyst.
With (advanced/massive/mature – call it what you will) EGR, on the other hand, NOx is being reduced in-cylinder so Navistar does not have the luxury of dialing back EGR flow rates – in fact it will increase the amount of gas being recirculated back into the cylinder by about 10%.
SCR backers also point out that NOx plays an important role in the efficient regeneration of the diesel particulate filter (DPF). They say they will nearly eliminate active DPF re-gens (which of course, consume fuel) and have questioned whether an in-cylinder solution will allow for the passive regeneration of the particulate filter.
Navistar officials I’ve spoken with concede that SCR will deliver better fuel mileage than its own solution, if by ‘fuel’ you mean ‘diesel.’ This is where the issue gets a little cloudy. Navistar says that its engine and an SCR engine will consume about the same amount of ‘fluid’ as they travel down the road, when you take into account that diesel exhaust fluid (DEF) will be consumed at about a 2-3% ratio (vs. diesel).
So, while engines with SCR will use less diesel fuel, it’s possible that the consumption of DEF will offset any cost savings. When measuring operational costs, one must consider the cost of DEF. If it will cost less than diesel, it stands to reason that SCR will, in fact, deliver the lower cost of operation. On the other hand, if DEF costs considerably more than diesel, then the fuel economy benefits touted by the SCR camp may be for naught.
In the next installment, we’ll look at the anticipated cost of DEF and its impact on overall cost of operation.
Have your say
We won't publish or share your data