New CARB rules: Some metals 'not recommended' in fuel

Diesel Fuel News, April 15, 2002 by Jack Peckham

California Air Resources Board (CARB) aims to adopt new diesel emissions retrofit "verification" procedures at a board hearing May 16, based on the latest version of a CARB staff report (see Diesel Fuel News 2/4/02, p8) that likely will set wide precedent for establishing clean-diesel technologies.

The latest draft explains that CARB is trying to harmonize its diesel retrofit "verification" with U.S. EPA's, but differences remain (www.arb.ca.gov/regact/dieselrv/dieselrv.htm).

Biggest difference: Following technology "verifications," CARB intends to force diesel engine and vehicle operators to retrofit or retire older diesel engines in order to slash "toxic" particulate matter (PM) emissions and reduce ozone-forming nitrogen oxides (NOx). EPA's "voluntary retrofit program" on the other hand aims to allow fleets and states to earn emissions credits without mandates.

Other major differences: CARB has a three-tier qualification for PM reductions (25% minimum) and a 15% minimum for NOx reductions. EPA doesn't have any minimums or tiers.

CARB's requiring engine and chassis testing for on-road vehicles; EPA's only doing engine tests. CARB also has specific warranty minimum requirements; EPA leaves that up to manufacturers, but EPA's durability requirements match those of CARB's warranty rule.

CARB is also imposing a 20% limit on the allowable [NO.sub.2] portion of NOx tailpipe emissions created by any retrofits. This is to avoid potential excess ozone emissions (see Diesel Fuel News 2/18/02, p7).

Bottom line: CARB says it will only verify a product earlier verified under EPA's scheme "provided the following conditions are met:

1) Emissions tests by engine dynamometer;

2) Require the same warranty period as the [CARB] procedure;

3) Durability test must at least cover the durability period proposed by the [CARB] procedure;

4) Field demonstration (if all durability is [otherwise] conducted only in the laboratory);

5) Same engine testing throughout the in-use compliance test program."

Nor will Europe's "VERT" PM filter verification program qualify a system for GARB verification. However, the GARB proposal "is designed to take into account any emission and durability data for systems that have been verified under the VERT's program," GARB says.

Technologies used to cut emissions -- be they diesel PM filters (DPFs), oxidation catalysts, water-diesel emulsions, fuel-borne catalysts, whatever -- must be independently verified using a standard CARB procedure (or else EPA's environmental technology verification "ETV" procedure), then re-checked for field performance afterward.

GARB continues to struggle with how to create a verification procedure that's truly representative of a class of engines (or typical duty cycles) without requiring super-costly retesting on every single engine or every single application. The result is a novel but still-fuzzy procedure that creates "emissions control group" categories.

For instance, CARB describes one such one group as "all lower-speed vehicles with significant stop-and-go operation, fueled with standard [GARB] diesel fuel, and powered by turbo-charged, four-stroke diesel engines originally certified to the 0.25 grams/brake horsepower-hour PM standard. This emission control group would include some number of buses and refuse haulers, for instance."

Other groups could include technologies requiring ultra-low sulfur diesel (ULSD), or water-diesel emulsions, or Fischer-Tropsch fuel, or diesel fuels blended with metallic fuel-borne catalysts (FBCs) combined with diesel particle filters (DPFs).

Warning: GARB won't allow metallic FBCs to be used without DPFs unless the FBC is proven safe for health and the environment.

FBC metallics treated especially harshly in this CARB "verification" rule include copper (because of dioxin/furane emission when combined with DPF), manganese-based MMT (due to other possible health effects) and sodium (compatibility issues with DPFs).

"Past additives include those utilizing manganese, sodium and copper and are not recommended for use due to the production of deleterious emissions, such as dioxins," the GARB proposal says.

Relatively high dosages of FBC metallics (if not combined with a DPF) also can increase nano-PM emissions, GARB notes.

Hence use of such additives at high dosage rates wouldn't be approved -- unless paired with a DPF that also won't be damaged by FBCs. However, GARB proposes to require FBC/DPF testing at 10 times recommended dosage (up to 50 ppm) to ensure that DPFs won't be destroyed by accidental field over-additization.

Any company seeking GARB "verification" of such an additive "must update the environmental, toxicological, epidemiological and other health-related data pertaining to the fuel additive" every two years, under the latest CARB proposal.

"Additive strategies which involve onboard storage of the additive must include fill.. level monitors to notify the operator when refill is necessary," GARB says. Consumer hand-dosing of FBCs into fuel tanks is "discouraged as it allows for situations where the vehicle may run with an inappropriate additive dose."