NO₂ limit for Class 2 RECs

The Class II REC requirements allow a limited increase in NO2 from fitment of a REC (30 percentage points above baseline in the 00 version). There has been on-going discussion as to whether this could be reduced to 20 percentage points.

The EIC (O’Sullivan) gave a presentation (REC-16-04) identifying that NO2 is considered to be the most reliable system for regeneration, recognising the concerns of Member States but pointing out that Diesel PM is considered to be a greater public health issue than NO2 and that all NO is converted to NO2 in a matter of tens of seconds. The EIC considered that meeting a 20 percentage points maximum NO2 increase would result in higher failure rates/reduced reliability. Modelling data was presented to show that regeneration would be less effective and soot loading would not reduce sufficiently with a system designed to meet the 20% figure. Although the 20% figure is already a US requirement, the REC Regulation is very much a worst case as the NO2 test uses the largest catalyst with highest Pt loading, fitted closest to the engine and with limited de-greening. Also the engine-out NOx:PM ratio is often better for US engines over a transient cycle. The alternatives to NO2 for regeneration were described: fuel-borne catalysts (FBC), electrical systems and burners or fuel injection. The drawbacks of such systems were identified. EIC concluded that REC certification already places a major cost of compliance for the retrofit industry for a limited number of sales and smaller retrofit companies would not be able to support the development costs.

In discussion it was noted the issue is political rather than technical, with some EU Member States unable to accept (for the 01 step) the 30 percentage points NO2 increase that had been agreed for the 00 step of the Regulation. Participants were reminded that Contracting Parties could agree to incentivise only Class I RECs (no NO2 increase permitted) or combined PM and NOx (Class IV) devices and could prohibit use of Class II systems in LEZs, but had to allow use of Type Approved Class II devices in their country.

It was also commented that the retrofit market in Europe is declining, but the 20% limit would inhibit the use of the cost-efficient systems in the growth area of developing markets with air quality problems, to the detriment of the European industry. It was also suggested that the 20% figure would be very difficult to achieve for NRMM.

It was suggested that a solution could be to have a 90% efficiency + 30% NO2 requirement for the 01 step and a 90% efficiency + 20% NO2 requirement as a near-simultaneous eventual 3rd step. In discussion, this appeared to be a viable solution provided it could be ensured, before agreeing the 01 step, that the third (02) step with a 20% increase could be introduced.

The chairman agreed to consult with the GRPE chairman and the UN secretariat on the viability of this option. If the simultaneous adoption of the 2 stages would not be possible, he would examine with them a further possible option of submitting a 01 standard to the March 2014 meeting of WP.29 and a 02 standard to the June 2014 meeting. If neither of these solutions is possible, then he will examine a further option of having a 30% limit as a 02 amendment, even though this could be confusing as it would normally be expected to be more, not less, stringent than the preceding stage. If none of these options are possible the chairman would submit the 01 proposal to the January 2014 session of GRPE only with the 20% NO2 figure.