Concern is being expressed by truck and bus producers in the United States about having to meet the federal government’s greenhouse gas (GHG) standards due to take effect in 2017, while still complying with EPA 2010 pollutant emission requirements. At a recent conference in Cincinnati, Ohio, there was unanimous agreement that complying with the two separate though inter-related diesel emission rules would be a formidable challenge.
Jason Krajewski, a Daimler Trucks North America fuel efficiency engineer, said today’s state-of-the-art EPA 2010 compliant Class 8 truck was “about maxed out”. He added that ‘hitting the 2017 GHG mark on time will take new technological developments’. Bill Dawson, a Volvo Trucks vice-president, concurred, pointing out that what he called “cafeteria-style spec’ing” – where buyers could choose from a wide range of horsepower and torque ratings, in combination with different transmission and axle ratios – would no longer be possible.
It is clear that increased levels of selective catalytic reduction (SCR), consuming more diesel exhaust fluid (DEF) – known as AdBlue in Europe – will be necessary to improve fuel economy, with an accompanying cut in GHG emissions. That will mean less dependence on exhaust gas recirculation (EGR) for controlling oxides of nitrogen (NOx) pollutants. It could mean abandoning EGR altogether, as Iveco has done for Euro VI compliance, albeit at the expense of controversially-higher AdBlue usage, but with the probable opportunity of avoiding the need for a diesel particulate filter.
Ken Federle from Cummins Emission Solutions told the Cincinnati conference that SCR was “still far from its mature optimal state” but he warned that cost, size (the chassis space occupied by the DEF tank, dosing unit and SCR catalyst) and performance would determine the viability of future SCR installations. Because the three factors were interdependent, pushing hard on one or two could, he said, cause the third “to buckle” unacceptably.
Among the additional technologies which hold promise for GHG (primarily CO2) reduction, without pushing up NOx levels, are turbocompounding and other more esoteric forms of waste heat recovery, which has been the subject of a US Department of Energy study programme, with Cummins as a key participant, for the best part of a decade.
In the meantime, the Environmental Protection Agency has suggested, in a perhaps rare example of lateral thinking by the agency, a quite different means of achieving real-world fuel savings, in addition to the quantified 2017 GHG/fuel-consumption limits. Vehicles and engines could, says the EPA, be “hard programmed” – implying prevention of tampering by the owner and/or driver – with European-style mandatory road speed limiters set at 65mph (105kph) or below, along with compulsory anti-idling controls which would shut down the engine after the vehicle had been stationary for perhaps five or ten minutes.
In Europe, GHG emission standards for commercial vehicles over 3.5 tonnes gvw have yet to be finalised, partly for the difficulties in determining ‘fleet averages’, as outlined in a recent Comment piece in this column, Hybrid emissions merits prompt legislative re-think. But one can be sure that EU officials are monitoring closely the discussions surrounding the North American 2017 requirements.
The opinions expressed here are those of the author and do not necessarily reflect the positions of Automotive World Ltd.
Alan Bunting has a background in engineering, and has been writing on commercial vehicle and powertrain related topics since the 1960s. He has been an Automotive World contributor since 1996.
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