Air Quality



The emissions of regional air pollutants from rice were significantly reduced from 1980 to 2010. These included emissions from open burning of rice straw as well as from fuel combustion in equipment used to grow, transport, and process the rice. The emissions from uncontrolled burning dominated these other sources of emissions through about 2000. Figures 1-3 show the overall reduction levels for criteria pollutants including NOx (oxides of nitrogen, ozone and particulate precursor), VOC (volatile organic compounds, ozone precursor), and PM (particulate matter, direct pollutant) per unit of rice production. These pollutants have all been reduced by 80-90 percent.

Specific Program Areas Managed by CRC

The major programs managed by CRC include (1) rice straw burning activities, (2) climate change programs, and (3) policies affecting emission from diesel trucks and farm equipment.

Rice Straw Burning

Traditionally, rice fields were burned after harvest to dispose of the left over straw and to control disease and pest problems that can carry over between crops. Unfortunately, the burning impacted the air quality of the Sacramento Valley region during burn season. The rice industry worked with the State Legislature on a program to significantly reduce rice straw burning between 1990 and 2000 to improve air quality. This agreement has reduced annual acreages burned to about 10 percent. This has left rice growers three primary ways of managing the remaining acreages of rice straw: (1) incorporation of the straw into the soil coupled with active winter flooding, (2) straw incorporation without active winter flooding, or (3) harvesting the rice straw for use in other industries. Figure 4 shows the percentage reduction in burned acres and increase in the use of other practices that occurred between 1990 and 2000.

The rice industry also partners with state and local air officials to manage the very limited amount of disease-control rice straw burning (10 percent, year over year). A major component, called the Sacramento Valley Smoke Management Program, is a network of approximately 14 weather-monitoring stations owned and operated by the California rice industry. The data from these stations is shared with regional air officials and is critically important in determining how all Sacramento Valley agricultural burning is regulated to minimize smoke impacts.

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Climate Change Programs

Rice farming requires producing a crop under flooded conditions. In fact, much of our acreage is now flooded in the winter months also as a primary non-burning alternative method to decompose rice straw. Incidentally, this winter flooding has now become very critical habitat for millions of waterbirds using the Pacific Flyway. These flooded habitats also emit methane, which is a potent greenhouse gas (GHG). How much do we emit? Rice cultivation in California emits about 3 tons GHG per acre (CO2 equivalent). This is less than one percent of the emissions of greenhouse gases emitted each year in California. Even so, CRC is working with the California Air Resources Board (ARB) and the Environmental Defense Fund to adopt a voluntary rice protocol to encourage practices that reduce methane emissions from rice production. Adoption by ARB is now expected in early-2015. Once adopted, CRC efforts will shift toward promotion of opportunities to generate and market the greenhouse gas reduction credits.

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Diesel Truck Regulations

To address emissions from diesel trucks hauling rice up to our mills, the ARB has done a great job at coming up with a special program that allows limited use of these vehicles up until 2022, at which time they will all have to be converted to fleets that are compliant with ARB’s Statewide Truck Rule (model years 2010 or newer). The CRC very much appreciates the ARB’s willingness to consider a reasonable solution to these trucks that operate such few hours each year to serve agricultural industries including rice.

Recent Clarifications by ARB

Recently, questions were raised regarding the ability of trucks enrolled in the Air Resources Board’s (ARB) special agricultural truck program to make certain hauls related to rice industry operations. Specifically, the ability of rice trucks to haul paddy rice from storage/drying facilities and how those trucking operations had to be managed were brought into question. The ARB took swift and effective action to draft special clarifying guidance. To best clarify the issue, the ARB posted the following two questions and answers on its website:

Question 1: Can I transport rice from a dryer to a mill if I am using the agricultural vehicle extension?

Answer: Yes, a truck that transports rice between the dryer and the mill remains eligible for the agricultural vehicle extension as long as the rice is in paddy form whether the truck is farmer owned or is for hire. If the rice has been processed (or milled) and is no longer in paddy form, it cannot be transported by a truck that is using the agricultural vehicle extension.

Question 2: Can a farmer-owned truck be hired if the truck uses the agricultural vehicle extension?

Answer: Yes, a farmer can use the agricultural vehicle extension for trucks that are used for work on the farm, to get supplies for the farm, and to take harvested crops to the first point of processing. A farmer-owned truck could also be hired by others to take harvested crops from the farm to the first point of processing just like other non-farming businesses can when using the agricultural vehicle extension. The truck does not qualify for the agricultural vehicle extension if it is used for non-agricultural uses, or if it transports other goods like canned goods, finished lumber or other products on a for hire basis.

Annual Reporting Required

Growers please remember, as an owner of a vehicle enrolled in the agricultural vehicle extension program you have one main responsibility. All such fleet owners must submit annual reports on these vehicles by January 31 of each year. This is very important for you to maintain compliance and receive your annual compliance certification. You may also be requested by rice mills contracting for your hauling services as proof of compliance with the regulation.

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NOx Emissions from California Rice Production
Figure 1. NOx Emissions from California Rice Production. 1980-2010


VOC Emissions from California Rice Production
Figure 2. VOC Emissions from California Rice Production. 1980-2010


PM Emissions from California Rice Production
Figure 3. PM Emissions from California Rice Production. 1980-2010



Straw Management Practices in California Rice
Figure 4. Straw Management Practices in California Rice. 1980-2010


Reference: Nearly all the data reported in this section can be referenced in a May 2012 CRC Publication titled Environmental Sustainability Report