California Department of Resources Recycling and Recovery (CalRecycle)

Agricultural and Forest Waste Feasibility Study

Agricultural Residues: Compressed Rice Straw Products (Part 5)

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 Rice Straw Caskets

Rice Straw Casket

Rice Straw Casket BioFab LLC, located in Redding, California, is fabricating coffins made of compressed rice straw.  The $375 coffin will have simulated wood grain contact paper on the outside and is put together with wooden pegs.  Once the $72 worth of hardware is removed at the grave-site, it will be completely biodegradable.  BioFab LLC hopes to utilize approximately 11,000 to 12,000 tons of straw a year.  This company also markets rice straw office partitions, ceiling tiles, decorative partitions, and wallboard. 

 

Rice Straw Bales 

Straw Bale HouseK&R Farming in Willows, California is bailing rice straw and trying to develop new markets for the former waste material.  K&R Farming estimates it costs approximately $70 per acre to bale the material, compared to $3 per acre to burn the straw in the field.  Each acre of rice generates approximately 60 bales of rice straw, and each bale can be sold for about $2.  If a stable market for the baled rice straw could be developed, this new commodity could be managed in a cost-effective way.

K&R Farming had a unique opportunity to market the baled rice straw in 1996 after a huge fire in the Mendocino National Forest.  Once the fires had been extinguished, the task of reseeding the forest and stabilizing the fire-ravaged hillsides began.  K&R Farming sold 5,000 bales of rice straw to the U.S. Forest Service to be used as mulch for reseeding and erosion control. 

K&R Farming has also sold approximately 70 tons of rice straw to a company that used the material in the construction of new homes in the Central Sacramento Valley.  The bales of rice straw were used as infill material in the walls of the structures, where it provides excellent insulation and acoustical qualities.  There is another 70 ton order pending to be shipped to another developer in the Los Angeles Basin.  In addition, another 35 tons of baled rice straw was sold to a landscape contractor for use as mulch.

Another rice farmer and owner of a construction and developing firm in California has created a business that bales rice straw for construction and erosion control projects.  His business is increasing fourfold every year.  About 60 percent of his bales are for home construction and 40 percent for erosion control, mainly for the U.S. Forest Service.  Last year he baled 500 to 550 acres of rice straw, which is a tiny proportion of the 450,000 acres grown in California every year.

Straw bale construction is very energy efficient (R-55 walls), durable (many are still in use after more than 70 years), fire resistant (ideally suited for brush and wildland areas), and recyclable (cows eagerly ate the grasses in the walls of straw bale buildings when they were torn down in Nebraska many decades after building).

The use of straw bales in building is increasing rapidly across the country and in California, including at a winery and architects office in San Luis Obispo, in the walls of a retail center in Hopland, at a mine storage building in San Bernardino County, and for homes in Mendocino, San Luis Obispo, and Inyo Counties. 

Slowly, county by county, building inspectors are signing off on the idea of straw bale building construction.  Straw bale houses, barns, community centers, and even commercial buildings are beginning to show up in California. 

Assembly Bill 1314, encouraging straw bale construction, passed in 1995 and was signed by Governor Pete Wilson.  The bill encourages local building departments to adopt straw bale building codes.  Several counties are already in the process of adopting building codes allowing straw bale construction.

Yolo and Napa counties are among the first to pass ordinances regulating the use of straw bales in construction.  Yolo County has one house under construction, and Napa County has two rice straw barns under construction.  These projects use rice straw bales as infill between the wood frames.  Napa County is

reviewing a project to build a load-bearing rice straw structure where the straw bales themselves support the roof. 

Sacramento County has no special ordinance covering rice straw bale houses, but it will allow them and will require a special inspection for moisture content.  There are currently no projects in the works in Sacramento.

Some counties are not only supporting rice straw construction, but requiring it.  In Colusa County, a cellular phone company wanted to erect a cellular tower and a 500 square foot building outside Arbuckle.  The project was approved by the Colusa County building department only if the building was made from rice straw.  The project was successfully completed in the summer of 1996.

Rice Straw Sound Walls

In a first effort from a public agency to finance a prototype rice straw sound wall, Caltrans has partnered with the IWMB to conduct a pilot project, which is likely to be located in Colusa County outside a migrant camp along Interstate 5.  Caltrans has allocated a total of $30,000 through an interagency agreement to the IWMB for the pilot project.

If the pilot test is successful, it could mean that future sound walls along California's highways could be constructed using stacked bales of straw covered with chicken wire and stucco. 

A Colorado architectural firm, The Roybal Corporation, was awarded the design and engineering subcontract by the IWMB.  Roybals lead designer theorized that, whereas concrete walls ricochet noise into the highway, a straw bale absorbs noise and is expected to match a concrete barrier in terms of noise insulation outside the highway.  The use of straw bales is inexpensive, sustainable, nontoxic, and environmentally friendly.  Also, the construction using straw bales is more cost effective than traditional materials.  The test wall is anticipated to be at least 12 feet high and about 150 feet long.

This project is awaiting Caltrans approval of the design phase before proceeding to the construction phase.  Caltrans hopes to have construction underway in 1999.  The IWMB will monitor the wall for two years to understand, for instance, how weatherproof it is, how easy it is to build, and how well it works to block out noise.

Rice Straw Paper

The California Air Resources Board facilitated a project in 1996 that used rice straw to make paper.  Approximately 28 tons of rice straw were delivered to Vulcan, Alberta, Canada and were processed into pulp by Arbokem, Inc. of Vancouver, Canada.  The pulp was then delivered to Smurfit Newsprint Corporation in Oregon City, Oregon and made into paper.  Some California newspapers tested the product on their front pages to determine its suitability to replace present newsprint stock.

Arbokem is planning in the next year or two to site and construct a pulp and paper making plant in the Sacramento Valley to take rice and wheat straw and make various paper products (i.e., newsprint, copier paper, bond paper, etc.) from them.

Straw is a competitive, alternative source of fiber for paper making to reduce the pressures on harvesting of old growth forests in Northern California and the Pacific Northwest.

Gasification of Rice Straw

In recent years, the California rice crop has been grown on about 514,720 acres producing about 1.5 million tons of straw.  The energy content of a pound of dry rice straw is about 6,500 Btu.  Thus, the annual energy stored in the straw by the growing crop is 1.95 x 1013 Btu. 

If the straw was gasified and used to replace natural gas for heating, the annual renewable energy generated from the rice straw would be equivalent to 1.56 x 108 therms of natural gas (1 therm = 100,000 Btu), assuming that 20 percent of the straw energy content was used in the total system for collecting and converting the rice straw to low-Btu gas.  Assuming a value of $0.50 per therm for natural gas, the annual rice straw residue would have a value of $78 million. 

Gasified rice straw can also be used to operate gasoline, diesel, and natural gas engines.  Each engine type requires some modification to operate with low-Btu gas, although retrofits can be extensive and expensive.  Assuming a value of $1.50 per gallon of gasoline and using about 30 percent of the rice straw energy for the overall energy conversion system, the annual rice straw production could replace 11,375,000 gallons of gasoline having a value of $17,062,000.  Similarly, to replace No. 2 diesel fuel valued at $1.25 per gallon, gasification of the annual rice straw crop would produce 9,750,000 gallons of diesel worth $12,187,000.

The gasification of rice straw is most promising for the replacement of natural gas, gasoline, and diesel fuel when used for stationary engine applications.  Drying rice and pumping irrigation water from wells in the Sacramento River, Delta, and San Joaquin water basins would require the gasification of about 730,000 tons of rice straw.  Thus, supplying these annual energy requirements by gasification of rice straw would use about half of the rice straw residue.

Other Uses for Rice Straw

Composting

Composting is the decomposition of rice straw to enable recovery of portions of its nutrients and organic components.  It can be done in open windrows or in an enclosed controlled environment.  Best results are obtained when feedstock materials have a high nitrogen content to obtain a better carbon to nitrogen ratio.  Factors affecting composting are oxygen availability, moisture content, pH, temperature, and the carbon/nitrogen ratio.  Rice straw is slow to decompose and usually will take up to a year with moisture content of the pile remaining high.

Worm Farming

Ground rice straw can be used as a worm growing media.  The most effective material is in the range of 1 to 3 millimeter (mm) particles produced by grinding through 3 mm screens.

Hydroseeding

Defiberized rice straw can be used in hydroseeding (a process of planting in liquid solution along steep banks (i.e., roadsides, etc.) for erosion control.

Potting Media

Either ground or defiberized straw is suitable for potting media for commercial uses.  The use would be similar to and in competition with peat moss.

Animal Bedding

Rice straw has been used as bedding for livestock for many centuries, primarily to soak up the urine and provide a carrier for the dung.  Used material may be composted and sold as fertilizer.

Poultry Litter

Chopped straw litter can be used for poultry kept on a built-up litter system.  The used litter has a useful fertilizer value or can be utilized as cattle feed.

Growing Substrate

Rice straw bales can be used for production of many crops such as cucumbers, tomatoes, and flower crops.  The bales are soaked in water and impregnated with nitrogen in powder or other forms or with fertilizers.

Erosion Control and Soil Stabilization

Rice straw is an effective material both in commercial erosion control practices and in rice field erosion control.  Bales of rice straw can be shredded on site and blown into roadside cuts and fills to provide soil 

stabilization.  Manual placing of the rice straw can also be practiced if the proper placement can be obtained.  Rice straw used in hydroseeding activities also assists in erosion control and soil stabilization.

Frost Control

Layers of rice straw can be used for frost control in areas with low temperatures.  These uses are usually closely allied with mulching and composting and it is difficult to determine which one of the practices is dominant.

Sewage Sludge Mixing

Rice straw would be a suitable bulking agent for sewage sludge composting and disposal.  It would appear that chopped or fiberized straw would increase both absorbency and acceleration of decomposition.

Building Materials

Rice straw has been used to bind clay in built-up wall construction and in the manufacturing of fired brick.  The resultant burn-out product provides lightweight material with good insulating properties.  Shredded or fiberized straw may also be used in layered products such as roofing paper, insulating paper, and overlay products.

Padding for Tile Drains and Pipelines

A widespread use for baled straw is in the construction of drains and pipelines.  Rice straw is eminently suited to this use because of its strength and resistance to decay.

Plastic Moulding Powders and
Plywood Glue Filler

Rice straw can be ground and screened through an 80 mesh sieve to produce commercial plastic moulding powder.  The properties equal and sometimes surpass other materials.  This finely ground straw flour may also be used as a filler in resin glues, particularly for plywood.

Firelog Use


Firelog Made of Rice Straw

Firelog Made of Rice Straw
Extruded firelogs can be made from rice straw, but the high silica content of the rice straw dampens the burning rate and seals off the surface of the burning log, requiring agitation of the fuel bed.  Lower heat content and the pungent odor of the rice straw log when burning reduces the attractiveness for this use.

 

 

Packing Materials

The compaction resistance and resiliency of rice straw makes it a very good packing material.  However, in many countries there has been a decrease in the use of natural products such as rice straw and an increase in the use of synthetic and manufactured materials.  Increased cost of petroleum-based products is likely to reverse this trend.

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Last updated: January 18, 2001
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