CARB close to finalizing clean-diesel retrofit rule

CARB close to finalizing clean-diesel retrofit rule – California Air Resources Board

Jack Peckham

California Air Resources Board (CARB) closes public comment on its clean-diesel retrofit rule on February 13, following some two years of public debate, discussion and draft regulations.

The final CARB draft (see continues to put tight controls on fuel-borne catalysts (FBC) or other additive technologies, requiring that they pass California requirements for no-harm to public health or environment, plus meet U.S. EPA fuel/additives registration requirements (see Diesel Fuel News 2/4/02, p8).

Fuel additives also must be used in combination with “level 3” (over 85% efficiency) diesel particulate filters (DPFs) unless proven safe otherwise. On-board dosing schemes must include a low-level operator alarm and shut-off additive supply if a DPF problem is detected.

What’s more, such additives must be tested (for no-harm) at 10 times normal dosage, unless such levels would cause “catastrophic engine damage.”

The rule also puts a 20% limit on any increase in engine-out nitrogen dioxides (NO2) caused by CARB-verified catalyzed DPFs, starting Jan. 1, 2004. This is to prevent any ozone demerits from particulate matter (PM) benefits.

CARB’s rule also would impose a 25 parts/million limit on ammonia slip from ureaor ammonia-based selective catalytic reduction (SCR) systems for nitrogen oxides (NOx) control, per the strict National Institute for Occupational Safety & Health (NIOSH) standards.

“Conditional” CARB verification of “alternative” diesel fuels (such as Fischer-Tropsch diesel, biodiesel blend, water-diesel emulsions) can be granted under “some form of permission from U.S. EPA,” but “full” CARB verification is “contingent on completion of the U.S. EPA registration process within one year after receiving conditional verification,” the proposed rule says.

Such “alternative” fuels also must reveal fuel viscosity, volatility, ignition quality, operating temperature, engine-wear tendencies, corrosion, lubricity and flash-point. Any “toxic” compounds or potential to form such compounds also must be revealed.

CARB verification is only somewhat similar to the U.S. EPA-supervised “Environmental Technology Verification” (ETV) scheme. On-highway engines will be tested via one cold-start and three hot-starts on the standard FTP heavy-duty transient cycle, or three hot-starts on the UDDS cycle for chassis testing. Off-road engines must follow CARB steady-state test cycle (three hot starts) and stationary engines also must follow a CARB-mandated steady-state test cycle.

Verifying NOx reductions likely will require multiple tests — and the smaller the claimed benefit, the larger the test runs required, as in the ETV test scheme.

Unlike EPA’s “ETV” process, CARB will require “minimum durability” tests of emissions control devices for 50,000 miles or 1,000 hours for on-road engines; 1,000 hours for non-road, and 500 hours for stationary emergency generators.


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