Now that the California Air Resources Board (ARB) has passed new rules designed to reduce air quality emissions for on-road heavy-duty diesel trucks, it is turning its attention to farm equipment vehicles, including tractors, harvesters and other machinery.

The new truck rules, passed in December, are designed to reduce air quality emissions from on-road heavy-duty diesel trucks to help bring California in line with Clean Air Act requirements for air pollutants including diesel particulate matter and NOx. The rule, in a nutshell, requires all trucks and buses operated within California with a gross vehicle weight ratio of more than 14,000 pounds to comply with 2010 engine standards for PM10 and NOx emissions within the next 14 years.

The on-road diesel truck rules require that, beginning in 2011, pre-1994 engine model year trucks must be retrofitted with a Verified Diesel Emission Control System or soot filter. Rules will be phased in annually according to engine year models until all trucks have been retrofitted or contain a soot filter by Jan. 1, 2014. Concurrently, beginning in 2013, older motors will need to be replaced with cleaner burning engines that meet emissions levels for NOx of a 2010 or newer engine. These rules will also be phased in over 10 years until all trucks have cleaner burning engines by the year 2023.

Thanks in part to input from ag commodity groups, the regulation does contain some exemptions for low-use, low mileage, limited mileage, and/or specialty agricultural vehicles.

Low-use vehicles, defined as trucks that operate less than 100 hours and 1,000 miles per year, are exempt from the new rules, but owners, as of January 2009, must report their mileage, owner and vehicle information annually to ARB.

Low-mileage agricultural vehicles — those that operate less than 10,000 miles per year — as well as clearly defined specialty agricultural vehicles, are exempt from the rules until Jan. 1, 2023. Specialty ag vehicles include nurse rigs used for fueling or loading aerial sprayers, cotton module movers, water trucks and feed trucks.

Ag provisions also provide an extension on compliance until Jan. 1, 2017, for limited mileage agricultural vehicles. The definition of limited mileage is gradated based on the age of the engine: Diesel engines in model year 2006 or newer can drive less than 25,000 annually; model year engines from 1996 to 2005 can operate less than 20,000 miles annually; and trucks with pre-1996 model year engines can drive less than 15,000 miles annually.

Note that for any ag trucks to function under the exemption, they need to have been owned for ag use prior to Jan. 1, 2009, and will require special labeling to allow easy enforcement.

With rules now passed for on-road and off-road vehicles, Air Board staff is beginning the process of drafting similar rules for agricultural vehicles. ARB plans to schedule hearings on a draft tractor rule this year and adopt regulations by the end of 2009, with implementation beginning in 2014.

There are many questions about exactly what shape those new rules are going to take. One thing is certain, however: input from growers, PCAs, custom farming operators and others who will be affected by the new rules will be critical over the next year to help ensure that reasonable and realistic regulations are put to the ARB for a vote.

Data from agriculture was critical in getting key exemptions for lower-use agricultural on-road trucks in the recently passed rules, and that information will be even more important as the ARB drafts a new set of rules related to farm vehicles.

It is likely that new farm equipment rules will have similar filter and/or engine replacement requirements by 2014. This could create significant issues for specialty crops, such as almonds, that rely on specialized farm equipment such as sweepers, shakers and harvesters, often for only two to three months out of the year. These specialized pieces of equipment are frequently designed around an engine compartment that may not accommodate retrofits or replacements, and cleaner burning Tier 4 engines are not currently on the market for many of these pieces of equipment.

Agricultural groups, including the Almond Board of California, will work with ARB over the next year, providing data as it drafts these regulations to be sure these types of issues are represented in their discussions. It is likely you, as a grower or equipment operator, might be asked to provide information about your use of diesel-powered farm equipment as we begin this process. Please take a few minutes to answer and return any surveys from your representative agricultural group related to farm equipment use in your operation.