Checking in on Tier 5 timing

Oct. 27, 2023
Here's where CARB is in its process.

As if managers don’t have enough to worry about, Tier 5 is coming. Eventually.

Public workshops are happening right now in California, where the California Air Resources Board (CARB) is looking at potential amendments to “Diesel Engine Off-Road Emission Standards: Tier 5 Criteria Pollutants and CO2 Standards.”

CARB calls it Tier 5 rulemaking. And what happens in California doesn’t always stay there, as the EPA is constantly watching.

Current EPA Tier 4-F standards reduce harmful emissions by about 85% to 90%, but EPA Tier 5 would be focused on reducing such emissions to zero with a major emphasis on eliminating ultra-fine sub-micron particles of soot in diesel exhaust.

Tier 5 rulemaking eyes a goal of reducing NOxx and particulate matter (PM) emissions from new, off‑road compression-ignition (CI) engines compared to what is allowed by current Tier 4-F standards.

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It will likely include more stringent exhaust standards for all power categories, including those that do not currently utilize exhaust aftertreatment such as diesel particulate filters (DPFs) and selective catalytic reduction (SCR).

This means a lot of that newer iron deliberately manufactured to come in under 74 horsepower along with more traditional compact equipment—and that is a very long list.

As of model year 2020, CARB reports that more than half of all new off-road CI engine families continue to be certified in California to the Tier 4-F emission standards without DPFs.

CARB staff is considering possible elements to achieve NOx standards up to 90% more stringent, and PM standards up to 75% more stringent than today’s standards under Tier 4. First-time carbon dioxide (CO2) emission standards for off-road engines may also be proposed.

Other possible elements, according to CARB, include enhancing in-use compliance, proposing more representative useful life periods, and developing a low load test cycle. Staff is also investigating first-time, off-road, on-board diagnostics requirements and encouraging the development of zero-emission off-road equipment. Staff plans to bring a proposal to the Board in 2025, with implementation of the Tier 5 standards expected to begin in 2028.

As these dates creep closer in the collective consciousness, fleet managers are taking notice. One has made his on-road moves first.

“We’re reading about Tier 5 interim getting ready,” says Matt Case, CEM, head of Manatee County, Florida’s government fleet. “I don’t want to call it the death of the diesel, but we’re there; it’s on life support. I don’t know how much cleaner they can make them run. But it is quite amazing at what and how strict they [emissions regulations] are going to be.

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“We’re interested to see the cost [of compliance],” Case says. “I have personally moved the fleet into gasoline in a lot of applications. We run diesel in Freightliner ambulances, for example. They are heavy-duty, you can get parts, they’re dependable. The aftertreatment…is not. It requires constant service, constant maintenance.

“We’ve actually transitioned over to gas F-550 chassis,” Case says. “They’re literally servicing, getting gas, and going back on the road. They have no issues.

“So, we’re looking at what type of fossil fuel we could use,” he says. “We’ve done some research on renewable diesel. Here’s my feeling on it: Renewable diesel doesn’t void a warranty, but the damage it causes, and can cause, will void warranties.”

More moves—and countermoves—by wary fleets look to be just around the corner.

About the Author

Frank Raczon

Raczon’s writing career spans nearly 25 years, including magazine publishing and public relations work with some of the industry’s major equipment manufacturers. He has won numerous awards in his career, including nods from the Construction Writers Association, the Association of Equipment Manufacturers, and BtoB magazine. He is responsible for the magazine's Buying Files.