4 February 2002

The California Air Resources Board (ARB) has introduced a number of revisions to its draft diesel control strategy verification procedure. A public workshop to discuss the changes will be held in El Monte, California on 20 February 2002.

Some major proposed changes in the revised procedure include the following:

  • Verification levels have been changed as follows: Level 1 ≥ 25 < 50% PM reduction; Level 2 ≥ 50 but < 85%; Level 3 ≥ 85%, or 0.01 g/bhp-hr. Previous levels were 30 to 60%, 60 to 85%, and 85% or more. This modification, requested by emission control manufacturers, will make it easier to obtain ARB verification for a number of technologies that have been certified to provide a 25% PM emission reductions under the UBRR program. These technologies are mostly diesel oxidation catalysts. The ARB is allowing devices of PM emission reduction as low as 25% to allow the use of diesel oxidation catalysts in applications which are not suitable for retrofitting with ARB-verified diesel particulate filters, such as older, 2-stroke urban bus engines.
  • Verification of oxides of nitrogen (NOx) reductions - ARB will recognize NOx reductions as low as 15%, as well as at the 25% level.
  • Durability demonstration requirements, as requested by equipment manufacturers, have been reduced for on-road applications to 50,000 miles or 1,000 hours (from the original 150,000 miles). The durability periods for off-road and stationary applications are reduced to 1,000 hours and stationary emergency generator to 500 hours.
  • Minimum warranty period has been increased to equal that of the original durability periods, for example 150,000 miles or five years for heavy heavy-duty vehicles (up from the original 100,000 miles).
  • In view of the durability period reductions, the conditional verification would be eliminated for on-road applications, but retained for stationary and off-road applications because of the smaller populations and the necessity to encourage speedy implementation.
  • The scope of the diesel emission control strategy verification procedure would be extended to include the verification of alternative diesel fuels.
  • In addition to alternative diesel fuels, the procedure will also address fuel additives. ARB proposed that fuel additives be allowed only when used in conjunction with a particulate filter.

The ARB has also expressed a concern over the increased emissions of nitrogen dioxide, NO2, which are possible from catalytic emission control devices. The ARB requested comments on an NO2 limit in the verification procedure.

The verification procedure is being developed for use in diesel retrofit programs to be implemented under the diesel risk reduction plan adopted by the ARB in September 2000. According to the plan, a number of existing diesel engines in California are to be retrofitted with particulate filters and/or other control strategies. All control devices to be used in the retrofit programs will have to be verified by the ARB to determine if a given diesel emission control strategy’s emission reductions are real and durable, to establish the emission reduction level, to verify that the diesel emission control strategy has had successful field experience, and to investigate any secondary emissions of concern.

ARB workshop announcement
Draft verification procedure

Source: California ARB