Environmental & Conservation Balance Sheet for The California Rice Industry

Chapter 4: Air Quality in Relation to Rice Farming

The purpose of this chapter is to document the air quality issues associated with rice production in California. New information pertaining to recent initiatives, regulations, monitoring results, and other air quality issues was reviewed and is documented in this chapter.

Background

About 450,000 acres of land are devoted to rice production in California, and most of this land is in the Sacramento Valley (see Figure 4-1). Each year, approximately 3 to 4 tons of rice straw per acre remain standing after harvest. Currently, much of this residue is disposed of by burning.

Many crops benefit from burning because it is an efficient, effective, and inexpensive method to remove crop residue. It is also an effective means of controlling disease and pest problems. The benefits of rice straw burning include:

Control of the fungal diseases of rice, stem rot (Sclerotium oryzae) and aggregate sheath spot (Rhizocronia oryzae sativae)
Disposal of rice straw
Facilitation of soil tillage and seedbed preparation

Figure 4-1 Distribution of Rice Acreage in California by County	Figure 4-2 Crop Residue Burned Annually in California Prior to 1991

California crops that benefit from field burning include 10 orchard crops and 6 field crops. In 1991, four of these crops (rice, almonds, walnuts, and wheat, represented in Figure 4-2) accounted for 95 percent of the dry tonnage crop residue burned annually in the state, with rice and almonds accounting for 64 percent and 18 percent, respectively (Jenkins et al., 1991). Since that time, legislation sponsored by the California rice industry has curtailed rice straw burning by about 50 percent, and further reductions have been legislated.

Disadvantages of rice straw burning are primarily related to air quality:

Generation of air pollutants, including:
- Particulates
- Carbon monoxide (CO)
- Hydrocarbons
- Nitrogen oxides (NOx)
- Sulfur dioxide (SO2)
Production of polynuclear aromatic hydrocarbons in both gas and particulate forms, many of which are carcinogenic
Release of airborne silica fibers (small particles of straw ash with possible carcinogenic health effects)

The amount of pollutants emitted by rice straw burning depends on the moisture content of the straw, the manner in which the field is burned (heading fire, backing fire, strip-light fire), and the "emission factor" (the pollution emitted per weight unit of the fuel being burned). The farmer is responsible for monitoring the moisture content of the straw and proceeding with the burn only if the straw passes the so- called "crackle" test (indicating low moisture and emission factor) in the field. It is also up to the farmer to select the method of burning that best suits the environmental circumstances on the day that the burn is scheduled.

The California Air Resources Board (CARB) manages field burning practices in the Sacramento Valley. In response to public concern, CARB managed the Burn Days Program, under the auspices of the Sacramento Valley Agricultural Burn Plan (the Burn Plan). The Burn Plan, adopted in 1981 and renewed annually, required that certain air quality and meteorological data be collected and evaluated on a daily basis. Assembled data included presence of haze, surface and upper air winds, temperature, and rainfall. The data were evaluated for anticipated rate of smoke dispersion, and the results dictated how many acres within the Sacramento Valley were allocated for burning on a given day. Table 4-1 provides examples from CARB's daily acreage allocation equation (CARB, 1996).

Table 4-1: Acreage Allocation Under the Sacramento Valley Agricultural Burn Plan

Condition	Acres
Favorable Conditions	10,000
North Winds	8,000
Rain	3,000
Inversion + Poor Air Quality	No burn

Because the Burn Plan allowed burning only during periods of favorable meterological conditions, it significantly reduced the effects on the public living in urban centers throughout the Central Valley and complaints lodged against burning declined.

Figure 4-3

Phasedown Schedule Mandated
by Assembly Bill 1378

Nonetheless, public concern over air quality continued and the Rice Straw Burning Reduction Act (Assembly Bill [AB] 1378), sponsored by the California rice industry, was passed in 1991. This legislation mandated an effective cessation of rice straw burning by the year 2000. The scheduled phasedown is based on a percentage of acreage planted during the current year. It began in 1992 with a 10 percent reduction in the total acreage each farmer was allowed to burn. The acreage base for a given farmer is the number of acres planted with rice. The percentage of acreage restricted from burning increases incrementally each year and will continue to increase until the year 2000 when burning will be phased out entirely.

Figure 4-3 depicts the phasedown schedule mandated by AB 1378. An exception to this schedule is made for farmers who demonstrate crop loss as a result of disease. Assembly Bill 1378 allows these individuals to continue to burn up to 25 percent of their planted acreage, even beyond the year 2000. This level of burning is allowed as a control measure for the diseases stem rot and aggregate sheath spot. Both pathogens have overwintering structures that develop in the straw residue, but they can be destroyed, primarily by burning (Ducks Unlimited, 1995).

In September 1995, CARB endorsed a proposal amending AB 1378 to suspend the phaseout schedule at the 50 percent level for 3 years starting in 1997. This would give farmers a better opportunity to develop viable alternatives to burning. In December 1995, the California Rice Industry Association (CRIA) unanimously voted not to take a position on the amendment. The amendment did not succeed, and the bill supports the original commitment CRIA made to the public when it co-sponsored the 1991 law (Sacramento Bee, 1995). In early 1996, in its report to the legislature on the status of burning reduction, CARB presented a plan to allow farmers to buy credits to burn acres. This proposal could mean farmers would save money because it typically costs significantly more than $35 an acre to incorporate straw. "If a farmer wants to buy the right to burn an acre for about $35, he's actually saving." Further, "...the money collected under the program would be used to research alternative straw use which could lead to new markets for crop residue in the future" (California-Arizona Farm Press, 1996).

Assembly Bill 1378 not only mandated an immediate reduction in rice acreage burning, but also created an Advisory Committee on Alternatives to Rice Straw Burning. The advisory committee was charged with assisting in the identification and implementation of alternatives to burning and developing a list of priority goals for the development of feasible and cost-effective alternative uses for rice straw. The results of the initial efforts of the Advisory Committee were published in December 1995 (CARB, 1995).

Two central questions for the rice industry are: What are the alternatives to burning, and how will they affect the competitiveness of California rice? According to the CRIA, it costs the average rice farmer approximately $2 per acre to burn rice straw, and between $25 and $70 per acre to either plow it under or remove it (Sacramento Bee, 1996). An economically viable alternative for disposing of all or most rice straw in California is badly needed (Learn, 1993).

Non-burn alternatives discussed in this chapter include:

On-Farm Non-Burn Alternatives	Off-Farm Non-Burn Alternatives
Crop Rotation Straw Decomposition Baling	Energy Conversion Pulp Products Manufacturing Construction Products Manufacturing Straw Bale Structure Construction Composting Mushroom Production Erosion Control Livestock Feed

Table 4-2 summarizes the technological, economic, and commercial feasibility of each non-burn alternative. The pressing need for economic alternatives to burning has spurred substantial public and private investment in research into solutions, as well as implementation of pilot-scale, and even large-scale programs. The California Rice Research Board has invested over $15 million of its income from rice farmer's contributions since 1969 to fund research projects concerned with the use of rice straw. Table 4-3 identifies research projects funded by the California Rice Research Board for the periods prior to and after the passage of AB 1378.

Table 4-3:
Rice Research Board Funding of Projects Involving the Use of Rice Straw, 1969 through 1991 and 1992 through 1995

	Expenditures		Project Expenditures
	1969 to 1991	1992 to 1995	1969 to 1995	1969 to 1995
Topic	($)	($)	($)	(No. of Projects)
Plant Breeding	10,891,942	1,378,239	12,360,181	30
Burning Effects	2,277,927	250,425	2,728,352	22
Baling	274,410		274,410	24
Diseases	700,013	152,969	852,982	26
Energy Conversion	650,609		650,609	6
Livestock Feed	45,831		45,831	8
Pulp	202,154		202,154	7
Rolling	107,682	101,755	209,437	20
Utilization	103,734	112,484	216,218	18
Total	15,254,302	1,995,872	17,540,174	161

The breeding program was funded primarily to improve rice yield and farmer's profit. One principal stratagem was to create a more efficient rice plant that produces relatively more grain and less straw. The program was a success, generating these principal benefits while reducing the amount of straw that must be disposed of to produce a given amount of rice. The current cultivars produce equal proportions of grain and straw (Herkert, 1996). In addition to public investment funded by rice farmers and by agencies like the U.S. Department of Energy, individual farmers have invested heavily in the resolution of this problem. Although a precise accounting of this effort is beyond the scope of this report, many of the alternatives to burning, described in the next section, have been the subject of this investment. For example, rolling and winter flooding have been developed largely by individual farmer's initiatives, including design and fabrication of essential custom field equipment.

On-Farm Non-Burn Alternatives

Rice straw is high in silica (approximately 10 to 18 percent) and does not readily decompose, unlike the straw of wheat and other small grains. Rice farmers have developed commercial varieties that are 20 to 25 percent shorter than varieties grown previously in California. While grain yield has increased by more than 35 percent, straw yields have decreased by about 5 percent (Roberts et al., 1993). Rice now produces 3 to 4 tons of straw per acre.

The heavy clay soils that make the Sacramento Valley an ideal location for growing rice tend to remain soft and wet after harvest, particularly after fall rains. This makes it difficult to dispose of straw by any method other than burning. However, following are three on-farm alternatives to burning:

Growing rotation crops
Straw decomposition in the field
Baling and hauling straw out of the field for transformation or disposal

Crop Rotation

Rice growing is concentrated in the Sacramento Valley, primarily because of Valley soils. About 600,000 acres in the Valley contain heavy clay or hardpan soils that interfere with drainage and make it difficult to grow most crops. Because of its lack of drainage, this land can be economically flooded for long periods, making it suitable for aquatic plants such as rice. Slightly over half of this acreage is considered "rice only" soil and is poorly suited to rotation crops. On the most poorly drained part of the Valley's rice land (at least 300,000 acres), it would be difficult under any circumstances to grow another crop because these soils become waterlogged from winter rainfall and summer irrigation.

For rice acreage considered suitable for rotation crops, there are relatively few choices, the most common being wheat or safflower every third or fourth year. High-value rotation crops are not grown on this intermediate soil. In a few areas of more versatile soils, such as the Sutter Basin and District 108 in Colusa and Yolo Counties, rice is routinely rotated with various other crops, including wheat, safflower, tomatoes, cucurbits (squash, cucumbers), beans, and sugarbeets. Here, rice may be as useful for its benefit in breaking pest cycles of higher value crops as it is as a cash crop (University of California, 1992).

Where alternate crops can be grown on rice soils, one year's rotation away from rice reduces stem rot infestation; two or more years may substantially control it. The "half-life" of stem rot fungus populations is about 1.9 years. The tradeoff is economic, because the alternate crop may be less profitable and land preparation may be costly (University of California, 1992).

Straw Decomposition

Straw decomposition is a management practice developed as an alternative to burning. It is implemented by either of the following methods:

Chopping the straw and incorporating it into the soil by tillage
Rolling the standing straw into the soil using a mechanical crimping/rolling device

Chopping and Incorporating Straw into Soil

A variety of field implements can be used to chop straw. Harvester-mounted choppers shred the straw into long pieces; flail choppers pulled behind a tractor produce a range of sizes of shredded pieces; and self-propelled forage choppers leave the straw in pieces less than 2 inches long. Smaller pieces are easier to incorporate with field tillage equipment. The use of choppers on rice straw is effective, but the high silica content of the straw causes a great deal of wear on chopper blades relative to other crops.

Straw incorporation is usually accomplished by chisel or disk tillage. The number and type of field operations required to achieve a good straw/soil mixture depends on soil type. Clayey rice growing soils are difficult to till, making incorporation more difficult.

Even though micro-organisms are abundant in rice soils, certain other environmental conditions are required to accomplish the decomposition process (Ducks Unlimited, 1995). Temperature, moisture, and available oxygen are all essential factors affecting decomposition. Straw breakdown occurs between 40 and 86 F and is more rapid at the upper end of this temperature range. Soil moisture also influences the rate of straw decomposition. Straw can decay with or without air, but the pathways and byproducts produced under each condition are quite different. For straw to decompose most rapidly, an optimal mixture of air and water in soil pores is helpful. For the clay soils on which rice is grown, this moisture content is about 30 percent, with an air content of about 20 percent, both by volume. Decomposition rates decrease as soil moisture levels become extremely dry or wet.

Rolling

Rice straw rolling is a decomposition method that was developed to reduce straw incorporation costs while leaving unharvested rice grain accessible to foraging wildlife. The roller design was developed with funding from the Dow Chemical Company, Dow Elanco, and the National Fish and Wildlife Foundation (CTIC, 1995-96). Rollers take a variety of forms (e.g., rolling cages, fluted drums). Each design flattens most straw to the soil, while pressing some slightly into the soil.

A typical protocol involves draining the field and harvesting the grain, reflooding to a depth of 2 to 6 inches, then using the roller to crush straw and stubble into the soil. The stirring action creates a good mixture of soil, water, and straw, bringing the crop residue into contact with the soil micro-organisms that begin the decomposition process (Ducks Unlimited, 1995). This approach has the demonstrated advantage to waterfowl of preserving residual rice seed as a carbohydrate source and of creating winter habitat that fosters the growth and development of dietetically important invertebrate species (Brouder and Hill, 1995).

Baling and Transportation/Disposal

Baling can involve several operations, the most important of which is cutting the straw below the water line, which is the principal infection point for stem rot. Baling and removing rice straw from the field can be as effective as burning in controlling stem rot if the straw is cut below the waterline and completely removed from the field (University of California, date unknown). The usefulness of baling is restricted by the limited markets available for rice straw and rice straw products and the high cost of bale transport. Purchase, removal, and transport of straw bales from the field currently ranges from $4 to $6 per bale, depending on the transporter and destination. Alternative uses for rice straw, such as bio-energy production and building materials, are currently being evaluated for feasibility.

Off-Farm Non-Burn Alternatives

Energy Conversion

This is an attractive alternative because rice straw has a relatively high energy content (up to 8,000 Btu per pound). Bio-energy production plants often cannot afford to transport feedstocks more than 15 to 20 miles, which precludes this option for the majority of rice producers. Potential methods of energy conversion include:

Anaerobic digestion to produce methane gas
Direct combustion to produce electric power
Ethanol production

Anaerobic Digestion

This is a fermentation process in which organic waste is converted to methane and carbon dioxide gases in three stages:

Pretreatment to break down complex organic compounds into soluble components
Oxidation to produce low-molecular-weight organic acids
Fermentation to produce methane gas

The economic feasibility of agriculturally produced methane is highly dependent on the demand for methane and on the cost of competitive materials, e.g., natural gas. Taking into account high transportation costs, anaerobic digestion can only compete with natural gas in remote and isolated areas where it is feasible to generate methane on-farm (CARB, 1995).

Direct Combustion

Direct combustion alternatives include burning rice straw in biomass power plants for power generation, and the use of rice straw in logs or pellets for home heating.

At power plants, the alkalinity of rice straw (associated with the potassium and chloride content) creates costly, and seemingly insurmountable, slagging problems in furnaces.

When rice straw is burned, a large volume of ash is generated because of the high silica content of the straw. The high silica content also compromises the straw's energy conversion efficiency. Ash disposal is a significant logistical and permitting challenge. The large volumes produced, as well as the potential presence of crystalline silica, can cause its classification as a hazardous waste, potentially making ash disposal time-consuming and costly (CARB, 1995).

Ethanol Production.

The process for converting rice straw to ethanol includes the following steps:

Pulverizing the straw
Blending to produce a liquid slurry mix
Hydrolyzing cellulose molecules in the slurry mixture to produce simple sugars
Fermenting the sugar-rich liquid
Distilling fermentation products to ethanol

Two methods of hydrolysis are available, acid and enzymatic. They differ in the means by which the cellulose is broken down into fermentable sugars. Acid hydrolysis occurs in a single step in which the cellulose is exposed to a strong acid to produce the sugar liquor. Enzymatic hydrolysis is a two-step process in which the straw is pretreated to separate the cellulose and hemicellulose components. A dilute acid breaks down the hemicellulose to simple sugars, and then enzymes produced from genetically engineered fungi or bacteria break down cellulose. The two-step process is potentially more efficient because it can produce higher overall yields of ethanol from a given amount of rice straw (CARB, 1995).

The Sutter Ethanol Partners project proposes to construct a cogeneration facility north of Sacramento, California. The facility will burn natural gas to produce steam for power generation. Residual steam will be used to break down rice straw into sugar components that will then be converted to ethanol and other byproducts. The facility would convert 132,000 tons of rice straw into 10 million gallons of ethanol annually. If successful, the plant will consume up to 15 percent of the Valley's rice straw while producing clean- burning ethanol to power internal combustion engines and for other uses. The Sutter project would eliminate the need to burn rice straw on 50,000 acres near Sacramento while making cleaner-burning fuel available for automobiles (CRIA, 1991a).

The City of Gridley plans to construct an experimental plant to convert rice straw into ethanol and power. The facility would dispose of approximately 20 percent of California's rice straw, harvested annually from 80,000 acres of nearby rice fields. The facility would produce about 20 million gallons of ethanol annually, which would in turn be used to generate surplus power in an amount equal to half of Gridley's annual demand. The project is part of a feasibility study funded by Congress since 1994. It is being conducted at the University of California, Davis, and at the U. S. Department of Energy pilot plant in Golden, Colorado, that went into operation in mid-1995. The CRIA is currently preparing to deliver 85 tons of straw to the National Renewable Energy Labs in Golden, Colorado, for this study. Construction of the Gridley facility is planned to begin in 1998, pending favorable feasibility study results (Chico Enterprise-Record, 1996; CRIA, 1996).

Pulp Products

The pulping process changes raw, cellulose-rich materials (e.g., rice straw) to a form that can be used in the production of paper, fiberboard, and many molded products. Among non-wood, fibrous plant materials available for pulping, rice straw contains the highest level of silica. High-silica content makes handling difficult because it is abrasive and rigid. Also, disposal of residual high-silica black liquor sludge is difficult. These factors result in increased manufacturing costs and economic disincentives for the use of rice straw when other less demanding materials are available (CARB, 1995). According to the Earth Island Institute, a veteran environmental group, rice straw and other agricultural by-products are economical alternatives to wood, in part, because they are more economical to bleach (Our Environment Online, 1996).

Paper/Cardboard

In the early 1980s, the Rice Research Board and Louisiana Pacific joined in a study on the technological and economic feasibility of producing corrugated paper from rice straw. The study indicated that the market was inadequate to support a production facility on the West Coast. A plant producing corrugated paper from rice straw was established in California, but the plant was closed in 1989 (Moss et al, 1993). In the United States, the abundance of superior materials (i.e., wood) has all but eliminated rice straw from consideration for commercial production of paper and paper products (CARB, 1995).

Fiberboard

Manufacturing fiberboard from rice straw requires the use of chemical binders which are different from the binders used in the manufacture of fiberboard from wood chips. These binders represent a fairly new technology still under development. Difficulties encountered during experimental production of medium-density fiberboard from a 50/50 mixture of rice straw and hardwood chips are reported in the "Economic Uses for Rice Straw" from the Report to California Rice Farmers, 1969-84 (CARB, 1995).

Despite the difficulties in processing rice straw, NMC Corporation of Texas (FiberTech, Inc.) has plans to build a medium-density fiberboard manufacturing plant that uses rice straw. The proposed facility is to be located in Colusa County and would process 7,000 acres of baled rice straw annually, which is roughly the equivalent of 21,000 tons of straw. Evidently, the worldwide demand for medium-density fiber products rose 230 percent from 1985 to 1995 (CARB, 1995).

Composites

Particle Compacting Development, Ltd., owns a commercially available composite fabricating process called PACO. This proprietary process uses properties inherent in the biomass itself to complete the bonding or adhesion process. Products such as pallets, sheeting, boards, tiles, furniture, blocks, irrigation piping, etc. are produced using a wide variety of plant biomass waste. Extensive tests using rice straw have been conducted, producing excellent results (CARB, 1995).

Construction Products

Construction products for which rice straw is a raw materials candidate include wood replacement materials, bricks and cement boards, panels, and straw bale structure.

Wood Replacement Materials

Agronomic Systems is the name of a process for manufacturing a wood replacement material using 70 percent biomass and 30 percent recycled plastic. The material, marketed under the name BioComp, is waterproof, resistant to rot and insects, withstands the sun, and can be shaped and nailed. This biological composite uses a patented steam process to explosively break apart the biomass, releasing the starch, sugars, resin, and other raw materials of the fiber. The process works on any long-cell biomass, including wheat, rye, corn, rice, and barley straws. A pilot plant located in Montrose, Kansas, has made a successful pilot run using rice straw from Sutter County. A single BioComp manufacturing plant would use 3,000 to 5,000 acres of rice straw to produce up to 14,000 tons (or 14 million board feet) of product per year (CARB, 1995).

Bricks and Cement Boards

Fiber reinforced composite building materials have been used for centuries in the form of adobe bricks and other products. When straw is combined with cement, the alkalinity of cement can have adverse effects on the long-term durability of the fibers. Although alkalinity can be controlled with additives, the resulting product is heavy and difficult to handle, cut, and fasten.

When rice straw is combined with clay, the resulting product insulates well, but is not waterproof. If the straw/clay mixture is kiln fired, the composite end-product loses biomass during the firing process, resulting in a lighter weight product and further improves insulation properties (CARB, 1995).

Panel Construction

Manufacture of straw panels, or boards, was pioneered in Sweden in the 1930s and first commercialized in Germany in the 1940s. A number of areas of the world including Belgium, Australia, China, and the Philippines produce and use straw panels in construction today.

Panel construction products currently manufactured in the United States include Stramit Company's EnviroPanel, PYRAMOD International's self-supporting modular panels, and AltMatTec's Pacific Gold Board (CARB, 1995).

Stramit uses an extrusion process to manufacture rectangular building panels 4 feet by 8 feet or 4 feet by 12 feet, that weigh approximately 150 pounds. No pretreatment of the straw is required. The process currently uses wheat straw in this country, and rice straw in other areas of the world (CARB, 1995).

PYRAMOD's extruded panels are 4 to 5 inches thick and are cut into shapes that can be joined and marketed as affordable modular housing kits. The seismic stability and the thermal and sound insulation of the assembled structures are all outstanding. Annually, one extrusion machine produces paneling sufficient to build housing structures of 1 million square feet of floor area using 10,000 tons of straw. The PYRAMOD process has not been tested using rice straw (CARB, 1995).

AltMatTec's straw panel can use rice or other straws for raw material to produce a substitute for pressed board or plywood. The technology evolved in Europe and is in use at a few commercial manufacturing locations in Europe, Canada, the United States, and South America. This particular technology uses straw instead of general biomass or wood waste materials. Tests conducted using rice straw as the feedstock have been successful. AltMatTec's manufacturing system is portable and packs into two semi-trucks. One manufacturing location can process 20,000 tons (equivalent to 7,000 acres) of rice straw annually (CARB, 1995).

Straw Bale Structure Construction

Straw bale construction was first used in the midwestern U.S. in the 1800s and its use is currently being revived. A 1,600- square-foot house requires approximately 500 bales. At 80 pounds per bale, this corresponds to about 20 tons, or the rice straw from 6 acres. The bale wall structure is typically sealed with plaster or stucco and will have walls approximately 18 to 24 inches thick with an insulation R value around 50. The National Research Council of Canada demonstrated the plastered surface will withstand 1850F for 2 hours before cracking. The straw is sufficiently dense that it does not readily support combustion.

A Sacramento, California, architect is designing three rice straw structures that he expects to be built in 1996 in Dunnigan, Oroville, and Elk Grove. Owner-builders who elect to do most of their own work and minimize the incorporation of other building materials in their design will spend approximately $30 per square foot, in comparison to conventional wood-frame construction, which typically costs about $75 per square foot. In February 1996, Yolo County passed an ordinance to incorporate straw bale house construction in the County building code; Napa and Sacramento Counties are expected to follow suit shortly. In addition to houses, straw bales are used to construct sheds, lambing or animal shelters, utility buildings, and garages (CARB, 1995; Sacramento Bee, 1996).

Composting

Commercial compost companies use a mixture of several agricultural materials to produce a desired end product. Candidate materials include straw, manure, fruit and vegetable waste, leaves, grass clippings, and any other widely available biodegradable materials. The mix of ingredients is piled into long windrows (typically 5 feet high, 10 feet wide, and several hundred feet long). Compost turning equipment mixes and aerates the piles.

The carbon to nitrogen (C:N) ratio of a compost mix is critical. The goal of the composter is to acquire and mix the ingredients to a 30C:1N ratio and then compost them down to a finished product of significantly smaller mass and a C:N ratio of approximately 10:1. Commercial compost-makers use straw in their production mix because the straw has a relatively high C:N ratio, which helps keep the pile from getting too hot during the breakdown process (CARB, 1995).

Compost operations that use straw, process about 2,500 tons of straw annually. This equates to approximately 1,000 acres of rice straw (CARB, 1995).

Mushroom Production

Straw is an essential ingredient in the medium used for mushroom growing. The mushroom industry requirements include:

Cutting the straw in lengths longer than 8 inches
Harvesting with stripper headers to meet straw-quality standards
Providing straw delivery year-round

The annual use of wheat straw for production of California mushrooms is approximately 90,000 tons. Unless the quality and price of rice straw becomes substantially more attractive than wheat straw, farmers will have little incentive to switch from wheat straw (CARB, 1995).

Erosion Control

Straw is used as an erosion control material on construction areas and for rehabilitation of burned areas. It can be spread loose over a disturbed area to protect fragile soils, or it can be bundled to provide heavier defense against runoff and erosion. Rice straw has significant advantages over other types of straw in this industry. It is heavier, more durable, and less likely to harbor noxious weeds than other straws (CARB, 1995).

Residents in Oakland, California, who lost their homes in the 1991 Oakland fire, stabilized soils on their burned-out hillsides with donated rice straw from Sacramento Valley rice farmers. The straw helped protect properties from potential mud slides during heavy winter rains (CRIA, 1991b).

The market for rice straw in erosion control and fire rehabilitation is well established and because of its advantages, rice straw has little competition from other sources of straw. In addition, the demand is steady and not likely to decline in the future. Mechanisms for supplying the market (i.e., straw collection, transportation, and storage) have not been well established and appear to be the major constraint in establishing a solid niche for rice straw in erosion-control or fire-rehabilitation markets (CARB, 1995).

Livestock Feed

Rice straw is poorly digested by cattle. Cattle use 42 to 48 percent of ingested rice straw as compared to 65 to 70 percent utilization of alfalfa hay (Garret et al, 1990). Part of the reason for this may be that rice straw is high in fiber, low in protein, and does not supply enough nitrogen for the efficient metabolism and growth of rumen microbes necessary to carry out the initial breakdown of the straw. Also, silica has no nutritive value and may interfere with the digestive process. It can be used, however, by adult or pregnant animals because their requirements for energy and protein are small compared to their capacity to consume feed. Diets composed of 75 to 85 percent rice straw were adequate to support pregnant cows and result in calves with a birth weight comparable to those kept under conventional management practices on dry range or on irrigated pasture for an equivalent period of time (CARB, 1995).

Conclusions

The following sections present the justification for ratings of the rice industry's performance relative to the environmental value of air quality.

Land Preparation

As a result of legislation sponsored by the rice industry, straw disposal by burning has been reduced by about 50 percent since 1991, and is slated for further reduction by the year 2000. The rice industry, the public sector, and other private entities are investing heavily in alternatives, all of which would help alleviate current air quality impacts.

Options the industry is implementing on a pilot scale are recycling of straw to generate energy or to manufacture building and soil erosion control products. These products are used as a substitute for wood products and fossil fuels, potentially reducing demands by society on forest resources and fossil fuel reserves. It is expected that one or more of these alternatives will become more widespread by the year 2000. Rice straw disposal has been the subject of heavy investment by the rice industry and its collaborators. For example, from 1969 to 1991, the California rice industry's Rice Research Board funded 161 projects related to straw disposal, at a total cost of $17.5 million.

While tillage results in particulate (dust) suspension, it does not do so at a rate in excess of alternative land uses, such as alternative cropping. The performance of the rice industry relative to tillage is therefore considered comparable to that of alternative land uses.

Irrigation

Winter flooding, though part of the solution to the burning problem, is scored at zero. This is because the positive trends in straw management, including alternatives like winter flooding, were already considered under straw disposal.

Pest Control

Application of agricultural chemicals to any crop must be practiced in a safe and legal manner to minimize the chance of substantial spray drift. Rice farming is no exception, and rice farms and professional chemical applicators operate within these guidelines. Therefore, pest management in rice farming influences air quality values much as pest management in alternative agricultural crops does.

References

Brouder, S.M. and J.E. Hill. 1995. Winter Flooding of Ricelands Provides Waterfowl Habitat, California Agriculture, 49, 6, pp. 58-64.

California Air Resources Board (CARB), Department of Food and Agriculture, et al. 1995. Report of the Advisory Committee on Alternatives to Rice Straw Burning.

California Air Resources Board (CARB) Meteorological Division. 1996. Personal communication with Arndt Lorenzen. May.

California-Arizona Farm Press. 1996. Straw Burn Agreement Deadlines Welcome, pp. 13. March.

California Rice Industry Association Newsletter. 1991a. Rice Straw May Help Electrify North State Homes and Fuel Cars, Vol. 1, No. 1, pp. 2-3. July.

California Rice Industry Association Newsletter. 1991b. Rice Straw to the Rescue, Vol. 1, No. 3, p. 4. December.

California Rice Industry Association. Newsletter. 1996. Rice Straw Research and Development, Vol. V, No. 2, p. 3. March

Chico Enterprise-Record. 1996. Gridley Deputy Mayor Lobbies for Rice Straw Conversion Plant, p. 3A. March.

Conservation Technology Information Center. 1995-1996. Rice Straw Roller for Crops and the Environment, CTIC Partners, p. 11. December/January.

Ducks Unlimited, Inc. 1995. Rice Straw Decomposition and Development of Seasonal Waterbird Habitat on Rice Fields, Valley Habitats: A Technical Guidance Series for Private Land Managers in California's Central Valley, No. 1, pp. 1-8.

Family Water Alliance. 1995. Rice Burning: A Look Beyond the Smoke, FWA Green Ribbon Report, 8 pp. November.

Garrett, W.M., R.A. Zinn, and J.L. Hull. 1990. Utilization of Cellulosic Feedstuffs and Agricultural By-Products by Ruminants, University of California, Animal Science Dept.

Herkert, B. 1996. Conference call with Melissa Williams and John Dickey. May 1.

Jenkins, B.M, S.Q. Turn, and R.B. Williams. 1991. Survey Documents Open Burning in the San Joaquin Valley, California Agriculture, 45, 12-16.

Learn, E.W. 1993. California's Rice Crop: Market Challenges, Resource Constraints, California Agriculture, 47, 3, pp. 5-7.

Our Environment Online. 1996. http://www.maui.net, Internet.

Roberts, S.R., J.E. Hill, D.M. Bradon, B.C. Miller, S.C. Scardaci, C.M. Wick, and J.F. Williams. 1993. Biological Yield and Harvest Index in Rice: Nitrogen response of tall and semidwarf cultivars. J. Prod. Agric. 6:481.

Sacramento Bee. 1995. Rice-burning Limits Backed; Industry Wants Public Content, December 15, p. B1.

Sacramento Bee. 1996. Yolo First in Line to Allow Houses Made of Rice Straw, p. B-1. January 23.

University of California. Date unknown. Rice Straw Management Today & Tomorrow.

University of California. 1992. Maintaining the Competitive Edge in California's Rice Industry, April.

Additional Available Resources

Energy

Centre of Biomass Technology. This is a Danish biomass information network comprising four technological institutes dedicated to generating power from biomass. CBT collects and disseminates technical and economic know-how and experiences associated with the establishment and operation of straw and wood chip-fired combustion plants.

Construction

Straw Bale Construction. Straw bale construction has been used for more than 100 years in America. Recently, many new efficient homes have been built with straw bales. This page indicates some of the available information available on the Net for educational purposes.

California Code. Straw bale code requirements: Health and Safety Code, Section 18944.35.

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