7 - 15 - 2010 Strawman for SCR Workshop Discussion As we approach the Selective Cataly tic Reduction (SCR) public workshop on July 20, 2010 ( see 75 Fed. Reg. 39251, July 8, 2010 ), EPA would like to present some initial thought s regarding possible outcomes concerning th e operation of heavy
- duty highway engines equipped with SCR. This document is intended to be a strawman to be used as a starting
- off point for the workshop discussion only . The ideas presented here are based on our experience with SCR to date and do not represent final agency decisions. In order to maximize the productiveness of the workshop, presentations from the public should directly respond to the topics and ideas outlined. In addition to comments received at the workshop , the agency

will accept written comments through August 20, 2010 (see 75 Fed. Reg. 39251, July

8, 2010 for submission instructions). All input received will be considered in evaluating future policies regarding SCR technology
. As alway s in implementing EPA ’s NOx (and all other) s tandards, certificat ion will require engines to comply

with applicable regulations. In particular, 40 CFR § 86.004
- 25 and 40 CFR § 86.094 - 25, pertinent to allowable maintenance, 40 CFR § 86.094
- 22, pertinent to adjustable parameters, and 40 CFR § 86.004
- 2 , 40 CFR § 86.0 82 - 2 and 40 CFR § 86.004
- 16, which address Auxiliary Emission Control Devices (AECDs), are provisions that are particularl y relevant to engines using SCR technology
. Applicability  All complete heav y- duty highway engine certification applications submitted after January 1, 2011 (based on normal certification practices ) Reductant Level Monitoring  Need some indication of reductant level for the operator Inducement for Low Level Reductant  A final inducement should be initiated so the engine/v ehicle is limited to 5 mph, no power, or idle onl y when the SCR system is no longer able to dose  Final inducement (5 mph limit , no power or idle only) to be determined b y manufacturer should account for safety concerns and allow for diagnostics and restart after refill  Initiate operator warning prior to any inducement ( for example at 2.5% or higher reductant level)  If inducement is phased in, initiate another operator warning prior to final inducement Reductant Quality  Need quality sensor or NOx sensor sy stem with comparable capabilities by January 1, 2012  Be able to detect poor reduc tant quality that causes non
- compliance with applicable regulations  Should be able to detect non
- compliance with applicable regulations within 1 hour o f engine restart or chan ge in level of reductant tank7 - 15 - 2010

Inducement for Poor Quality Reductant  Notify

operator when non
- compliance with applicable regulations (or tampering fault

– see below) is detected  A final inducement should be initiated so the engine/vehicle is limited to 5 mph, no power, or idle onl y within 4 hours of detecting non
- compliance with applicable regulations  Final inducement (5 mph limit, no power or idle only) to be determined by manufacturer should account for safety concerns and allow for diagnostics and restart  Initiate operator warning prior to any inducement  If inducement is phased in, initiate another operator warning prior to final inducement  If poor quality reductant (or same fault for tampering

– see below) is detected a gain within 4 0 hours: o Immediately notify

owner o Ramp to 5 mph limit, no power or idle onl y within 30 minutes Indicators of Tampering  S ys tems should be designed to be tamper resistant to reduce the likelihood that the SCR sy stem will be circumvented  Manufacturers should be careful to revi ew any element of design that could be tampered with and prevent the proper operation of the SCR sy stem  The following actions should be considered at a minimum: o Disconnected reductant level sensor o Blocked reductant line or dosing valve o Disconnected re ductant dosing valve o Disconnected reductant pump o Disconnected SCR wiring harness o Disconnected NOx sensor (that is incorporated with the SCR system) o Disconnected reductant quality sensor o Disconnected exhaust temperature sensor o Disconnected reductant temperature sensor Inducement for Tampering  Same as inducement for poor quality reductant Maintenance Intervals  Petitions for new maintenance and maintenance intervals shorter than that required b y regulations ( adjustment, cleaning, repair or replacement of the reduc tant or filter) may be supplied by

each manufacturer or b y a group explicitl y representing the manufacturer  Each petition must address the technological necessity of the proposed maintenance intervals Freeze Protection  Freeze protection s ys tems will be ev aluated as Auxiliary Emission Control Devices (AECDs)  The following test procedure has been offered as an example of a test procedure that could be used for ensuring that the AECD is used appropriatel y7 - 15 - 2010

 SCR systems that are capable of full y functional dosing at the conclusion of the test procedure might be considered acceptable 1. Prior to Procedure :  Temperature: Reductant at 20° F (maximum) 2. Soak Conditions :  Temperature: 0° F (maximum)  Time: 72 hours or solid reductant (whichever occurs first) 3. Test Duty

C ycle :  Temperature: 0° F (maximum)  Time: 70 minutes (or 40 minutes) (maximum) a. Start engine and idle with no engine load for 20 minutes b. Operate engine at no more than 40% load at rated speed for up to 50 minutes (or 20 minutes)  Ensure, b y J anuary

1, 2012, that reductant does not refreeze during operation  Ensure, b y J anuary

1 , 2012, that dosing occurs with in 40 minutes instead of 70 minutes outlined in the original test procedure Unregulated Pollutants  No emission control device or s ys tem shall be used that cause s or contributes to an unreasonable risk to public health, welfare or safety  NH3 Slip - Emissions below 10 PPM average over the applicable test cycle s would be considered acceptable and not require further review ( Need to show durability

for entire useful life )  Dioxins - Copper zeolite test program at NVFEL o Not final o B ased on results to date, there is no indicatio n that the Cu - z eolite catalysts tested cause unreason able risk o Certification applications with Cu - zeolite cataly st configurations represented by NVFEL test results can be approved Infrastructure  S how that reducing agent will be widely available and readil y accessible  At a minimum , manufacturers should have reducing agent available at dealerships and provide a back up plan (such as a toll free numb er) that operators can use if the are unable to obtain it elsewhere  Manufacturers should also work with 3 rd parties to ensure that reductant is widely available at appropriate locations , in addition to dealerships