Flax Straw and Fibre
Past and Present Uses
Growing flax can present “the straw problem.” Oilseed flax has a significant
percentage of long tough stem fibres that decay slowly over time. This makes it
difficult to incorporate flax straw into the soil after harvest since the fibres wrap
themselves around and/or plug disks, wheels and shovels. In the past, the only way to cope with flax straw was to drop it in windrows after the combine and then burn
it directly or harrow or rake it into piles and then burn it. More recently, straw choppers on the largest new combines have been used to effectively chop and spread flax straw, if the straw was relatively short. The straw has also been used as animal bedding, duck
nesting sites, lining for drainage ditches,
horticultural mulch or as a fuel source in “bale burners.”
Traditionally, the major commercial users and buyers of prairie flax straw have been two flax straw processing companies based in Winkler, Manitoba, which extract flax fibre for use in the production of specialty papers (i.e., paper for cigarettes, currency, bibles, prayer books, artwork, stock and bond
certificates, etc.). In recent years, a flax
straw processing plant was also set up
in Canora, Saskatchewan. In addition to extracting flax fibre for use in specialty
paper production, this plant produces fibres to replace the fibreglass presently used to make automotive parts like dashboards
Processors look for tall, weed-free,
contamination-free (i.e., no litter or items made with plastic) flax crops situated within 100 km of a processing plant or a processor’s bale stack yard. Processors normally pay
$5 to $10 per tonne for the straw,
depending on the year and whether or not the straw can be baled in the spring.
In addition, the processing plant usually arranges and pays for the baling, transport and storage of the straw.
Depending on the acreage planted and the rainfall, the potential salvageable oilseed flax straw on the Prairies is 500,000 to 1,000,000 tonnes annually. With fibre
content ranging from 8 to 40%, this means that the potential pure fibre production from the flax presently grown on the Prairies would be between 100,000 and 250,000 tonnes annually. The three commercial processors mentioned above process from 150,000 to 250,000 tonnes of straw
annually. The vast majority of the extracted flax straw is exported and the total value of such flax fibre exports would range from
$20 to $30 million annually (i.e., 10 to 15% of the total value of flax seed exports).
Potential Future Developments
Alternative and new uses
Several developments are changing flax straw from being seen as a “problem” into a new “opportunity.” It is even feasible that,
in the future, some growers will grow fibre flax (i.e., linen flax) instead of oilseed flax and receive the majority of their income from the straw and not from the seed. However, management and technical
requirements, and planting and processing costs will also increase if higher net incomes from flax straw are to be realized and if rural communities want more value-added
processing of flax straw.
Whole flax straw
Bio-fuel – Several companies and individuals are developing large scale burners for flax straw that have
automated feeding systems for flax bales. With these systems flax straw becomes physically easier to use as a fuel source for large commercial users of heat like greenhouses, alfalfa
dehydration plants, hog barns, potash mines and hospitals.
Flax straw has a per tonne heating value similar to soft coal and thus has a heating value greater than other crop residues. Flax straw is not only cheaper than conventional fuels; it is also a
carbon neutral fuel. This means that the flax plant takes carbon from the air during the growing season to
produce the straw. When this straw is burnt, carbon, in the form of carbon dioxide, is released into the air, where it can, once again, be used the
following year in the production of straw. When conventional fuels are burnt, they release carbon into the air that has been stored for millions of years and hence increase the carbon dioxide content of the present day atmosphere.
Pulp Sweetners – When paper is recycled, it must be re-pulped before it can be made into paper. Each time paper is recycled, it loses some of its strength. In many applications, paper strength is important and often 20% or more of strong virgin wood fibre must be added to recycled paper pulp to give it the necessary strength.
The addition of extra strong fibre
into a pulp mix is referred to as a “pulp sweetener.” Since flax fibres are
considerably stronger and longer
than virgin wood fibres, a smaller amount of flax fibre can be used to replace the virgin wood fibre used to strengthen recycled paper pulp. This means that the percentage of recycled paper in the pulp can be increased.
As recycled paper and tree-free paper become more popular, the use of flax fibre as a pulp sweetener is expected
Geotextiles – Increasingly, road, railroad and building sites require a mesh of fibres to reduce the levels of dust and erosion that are produced during construction. Such geotextiles are especially needed where bare earth is placed into a highly sloped position (e.g., road construction in the
mountains, highway overpasses).
In addition, geotextiles are finding increasing use in horticultural
applications as mulch and/or a weed barrier. At the present time, it is
common to use synthetic fibres
(e.g., nylon) and/or coconut fibres
for such geotextiles. There is growing pressure to find alternative fibres for use in geotextiles in inland areas
where the freight costs for nylon and coconut fibre products are relatively high. Thus, the use of flax fibres for eotextiles can be expected to increase in the future, especially in areas where the end user is situated relatively close to flax-growing regions.
Insulation – When flax fibres are only processed to a limited extent, they remain quite stiff and coarse. When they are more aggressively processed, they can be turned into quite soft, fine fibres. A combination of coarse and fine flax fibres can be blended and processed to produce insulation batts with similar insulating properties to the fibreglass batts now commonly used to insulate walls
and ceilings. Cost-effective,
environmentally friendly chemical treatments are used to give flax
insulation resistance to burning and
to rodent and insect infestations. In Western Europe there are more than four companies producing flax-based insulation to compete with fibreglass insulation. These factories are
relatively small scale operations and hence have higher production costs than large scale fibreglass insulation factories. In spite of this higher cost, the demand for flax fibre-based
insulation is growing by more than 40% annually in Europe. The driving force behind this growing demand is the awareness that flax fibre insulation can be easily decomposed when its useful life is over, whereas fibreglass will end up in a landfill, a situation that many European consumers no longer tolerate.
Plastic Composites – Many
everyday plastic products contain fibreglass to give strength, reduce weight and/or reduce cost. When
plastic resin is combined with another material, the resultant product is called a plastic composite. Tractor fenders, car dashboards, decking,
fencing materials, sewer pipes and
septic tanks are but a few examples of products that are being made from plastic composites. Researchers have found that, in many plastic composite applications, flax fibres can be used in place of fibreglass. Flax fibres are
generally cheaper, lighter in weight and impart more springiness than fibreglass. In addition, flax fibres take less energy to manufacture and are
easier to decompose or burn than fibreglass.
The demand for flax fibres in
plastic composites is growing by more than 50% annually in Europe and
this trend has now started in North America. By far the largest users are automotive parts manufacturers who are being pressured to make cheaper and lighter weight vehicles with lower gas consumption and use more
environmentally friendly materials in their construction. Fibreglass comes in many grades and prices. At the present time, flax fibre is able to substitute only for lower grade, lower priced fibreglass. This is mainly because the flax straw processors buy is quite inconsistent. It will take time for processors and growers to learn the management techniques needed and make the necessary capital investments to produce more consistent, higher-grade types of flax fibre. As quality improvements take place, an increase in demand, and a corresponding increase in the average price of both the fibre and the straw can
Cottonized Flax – The demand for cotton worldwide in 2000 was roughly 20 million tonnes and is growing by about 200,000 tonnes annually. Physically, the fibres in the stems of flax are actually bundles of tiny fibres called “ultimate fibres” (see Fig. 5, 6
& 7). These ultimate fibres are
roughly the diameter and length of cotton fibres. Flax fibres absorb about 50% more moisture than cotton fibres. Hence, garments made from flax fibres will feel cooler and drier than cotton garments, especially on hot, humid days. Over 90% of the world’s spinning and weaving
equipment is designed to use fibres with the approximate length and diameter of cotton fibres and most synthetic fibres are extruded so they can be easily used in the cotton system of textile manufacturing.
Over the years, the above factors have led to the development of mechanical processes which attempt to break down flax fibre bundles into ultimate fibres to produce a flax based fibre that could be spun on the cotton equipment. Such flax is generally referred to as cottonized flax. In the past, the mechanical systems used to produce cottonized flax created large amounts of dust and waste fibres and could only use relatively expensive flax fibres that were properly retted. This led to a final cost of cottonized flax that was considerably higher than
cotton. Hence it had only very limited demand in several small markets. However, researchers are looking at alternative ways to produce cottonized flax that minimizes the waste and
produces a more consistent, lower cost fibre. These methods include the
use of enzymes, flash hydrolysis
(steam explosion) and ultra-sound. Breakthroughs have been made in all of these methods and costs are rapidly falling to the point where cottonized flax could compete with cotton fibre. Hence, there is growing potential to build processing plants that can
produce cottonized flax. The demand for flax fibre for this end use is large since the cotton market is so huge and cottonized flax garments are more comfortable to wear than pure cotton garments.
Long line flax for pure linen
Flax fibres have been used for over 5,000 years to produce yarn that can be woven into cloth and turned into garments. The yarn and fabric made from flax fibres are called linen (only in the last century has linen also come to mean fabric-based items used on tables and beds). In modern times, the fibres used to produce linen yarns are 50 to 100 cm (19.7 to 39.4 in.) in length and are easy to divide into finer fibres, yet are strong enough to be spun and woven without breakage. Such fibres must also be clean of all non-fibre components. These
requirements cannot normally be met unless the flax straw is retted.
Retting refers to any of several
methods that allow flax straw to be rotted to the point where the fibre can be easily separated from the straw but not to the point where the fibre becomes weak.
At the present time in North America, all the commercially grown flax is based on oilseed varieties which have been bred to be short and
produce high yields of seed. Under good growing conditions, taller
varieties of oilseed flax could be retted and used to make linen. However,
private companies and researchers in several areas of North America (including the Canadian Prairies) are now trying to grow and ret fibre
flax varieties. These varieties are taller,
have a higher fibre content and a lower seed yield than oilseed flax
varieties. Traditional linen spinners in several overseas countries have assessed the quality of the fibre produced from these trials and have found the fibre produced to be acceptable for
traditional linen spinning.
Traditionally, pure linen yarn was uneven and could only be woven.
This produced a fabric that was very comfortable and long lasting but one that wrinkled very easily. However, in the last decade, spinners have finally found ways to make linen yarn even enough so that it can be knitted. This, in turn, has allowed the production of linen garments that do not wrinkle easily. In addition, researchers have developed several chemicals that can be used to treat linen fabrics so they are wrinkle-resistant.
These developments have increased the demand for flax straw that could be used for the production of pure linen yarn. It will take investment funds, further agronomic research and trained management to develop this market. The net revenues that can be generated by the grower and straw processor by growing fibre flax
varieties are much higher than the returns that can be expected when oilseed flax is grown. However, the management and capital requirements are also much higher.
When flax fibres are extracted from flax straw, the non-fibre parts of the stem, not including the seed, are normally referred to as shives. In oilseed flax, shives make up from
70 to 85% of the total straw weight and in fibre flax varieties the shives make up from 50 to 75% of the total straw weight. Thus shive is a major by-product of flax straw processing plants. Unfortunately, to date, flax shives have not found many high value end uses. In Europe and Asia, flax shives are often used to make
particleboard but wood particles are generally so cheap in North America that this is not a viable commercial use at this time. Flax shives are often burnt as fuel or used as horticultural mulch. They are also increasingly being used as horse, livestock and pet bedding. They can also be ground and used as a filler to reduce the weight and cost of certain plastic items.
On the Prairies many of the flax
shives are simply spread back on the farmland from which the flax straw was collected.
It is expected that, in the next decade, there will be a significant expansion in the size and number of firms processing flax straw on the Prairies. In the future, it is
likely that at least some processors will pay significantly more for flax straw than what they are paying now. Those that pay high prices for straw will only pay a premium for the straw that meets a variety of quality requirements. Such quality standards for straw will be put in place so processors can start selling flax fibres into the higher value fibre markets. In such markets, flax fibres must compete with glass, cotton and
synthetic fibres which have measurable and generally quite consistent proper ties. If flax fibres are to effectively compete in such
markets, growers and processors must be able to produce consistent straw and fibre with easily measured properties.
STRAW AND FIBRE QUALITY
Research has begun on examining how specific varieties, agronomic practices and harvest methods affect the quantity and quality of both oilseed and fibre flax straw and fibre grown under prairie conditions.
In addition, American and Canadian fibre specialists and industry labs are working
with the American Society for Testing and Materials (ASTM) to develop industry accepted methods that will be used
throughout North America to test and
qualify the characteristics of flax fibre, shives and straw that are important to processors and end users. These methods include rapid measurement systems using near-infrared machines similar to that presently used to test protein in wheat. Characteristics include the cleanliness, length, fineness, strength and consistency of the fibres; the cleanliness, dust content, and particle size and consistency of the shives; and the cleanliness, height, fibre content, degree of retting, average diameter and consistency of the straw. Ultimately, both growers and processors must be able to quickly identify which straw, fibre and shive samples are superior; must know how to influence various characteristics; and must receive sufficient financial incentives to
produce the characteristics for which end users will pay.