HEMP PAPER
What is Tree-Free paper?
Tree-Free paper is best defined as paper made wholly from agricultural crops ans well as paper that is made without cutting new trees.
What are nonwoods?Tree-Free paper is best defined as paper made wholly from agricultural crops ans well as paper that is made without cutting new trees.
Nonwoods are pulps derived from agricultural crops. Nonwood paper is made wholly from agricultural crops or blends of nonwoods with post-consumer waste fibre. Since post-consumer fibre is nowadays mostly tree material, the term tree-free can be somewhat misleading here even though no trees were cut. Nonwood paper contains no virgin tree material.
What is post-consumer waste?
Post-consumer waste is used paper material. This can come in many forms but mostly comes in corrugated boxes, newsprint and office paper. Post-consumer waste is mostly tree fibre these days but as time goes on, (hopefully) more and more of that material will contain agricultural fibre too. Post-consumer waste fibre is generally of lower quality due to multiple processing and is also inconsistent in quality and strength. Since the reprocessing of this material is uses a lot of energy (transport, storage and repulping) it is very important to reuse first, then recycle.
What does recycled paper really mean?
It is very important to qualify what is meant by recycled because there is no regulatory body governing the use of this term. It is not uncommon to find papers that are 50% or more virgin tree labeled 'recycled.' This is misleading to say the least and most people happily accept recycled paper as environmentally friendly even though it can be mostly (or even partially) old growth!! Because recycled fibre weakens upon repulping and because the source is unknown or varied, virgin fibre is almost always added to guarantee a certain level of quality and durability.
What nonwood fibres are used in papermaking?Nonwood fibres can generally be categorized under two headings:
1) Fibre Crops
2) Agricultural Residues
Fibre crops are farmed specifically for their fibre. Literally thousands of fibre crops can be grown in Canada and make great paper! Some crops like hemp and flax are ideal papermaking fibres because of their unique strength and bonding properties.
Agricultural residues are "waste" products derived from food crops such as wheat and corn. The leftover material was until recently burned and is now mostly landfilled. Some agricultural residues are weaker fibres but still can make great paper. These agricultural residues are available in vast quantities in Canada.
What about quality?
Nonwood papers are far less of a burden to the earth and do not compromise quality like recycled paper can. Many nonwood fibres have always been used by the pulp and paper industry to create specialty grades of paper such as currency, cigarette papers, bible papers and art papers. These fibres have superior bonding quality and strength properties which is why your money didn't disintegrate in the washing machine.
Still not convinced?
Nonwood fibres contain far less lignin (natural glues) than tree fibre and therefore require far less processing chemicals for pulping and bleaching. They are naturally acid free meaning the paper will last forever without yellowing or crumbling. Since many nonwoods are stronger than tree fibre, they can be recycled more times and they add durability and integrity to recycled sheets.
Why then are we using trees for paper?
Tree fibre is cheap. Really cheap. The cost of building the forest is of course not incorporated into the cost of the fibre.
Do nonwoods cost more?
Yes and no. Nonwood paper is more expensive for regular commodity papers but the cheapest photocopy paper available is after all 100% old growth. However when looking for a quality sheet (either environmental quality or the feel of the paper) nonwoods are comparable in price. The GreenMan Nonwood Papermill carries only papers that are made without the use of any trees in an effort to reduce the demands placed on our remaining forests.
It is the goal of the GreenMan Nonwood Papermill to separate the pulp and paper industry from the forest industry. Currently they are one and the same but the pulp and paper industry should be able to draw fibre from a variety of sources integrating a bioregionalist approach and choosing the most sustainable sources of fibre for each region, product and application.
Hemp Paper
(Courtesy of Westhemp Canada)
(Courtesy of Westhemp Canada)
History of paper making The use of fibre hemp (Cannabis sativa L.) for pulp and paper dates back more than 2,000 years. The oldest surviving piece of paper in the world was discovered by archeologists in 1957 in a tomb near Sian in Shensi province, China (Temple 1986). It is about 10 cm square and can be dated precisely between the years 140 and 87 BC.This paper and similar bits of paper surviving from the next century are thick, coarse, and uneven in their texture. They are all made of pounded and disintegrated hemp fibers. Pa per historians agree that the earlier Egyptian papyrus sheets should not be referred to as paper, because the fibre strands are woven and not -wet-laid (Hunter 1957). The Chinese paper-making craftsmanship was transferred to Arabic and North-African countries, and from there to Europe. The first European paper making was reported in the first half of the 16th century (Hunter 1957).Until the early 19th century, the only raw material available for paper making was rags. Rags are worn-out clothes. Since at that time clothing was solely made of hemp and flax (sometimes cotton), almost all paper in history was thus made of hemp and flax fibers. With the industrial revolution, the need for paper began to exceed the available rag supply. Although hemp was the most traded commodity in the world up to the 1830+s (Conrad 1993), the shortage of rags threatened the monopoly for hemp and flax as paper-making fibers.This was the major incentive for inventors and industries to develop new processes to use the worlds most abundant (and cheap) source of natural fibers: our forests. Currently, only about 5% of the world's paper is made from annual plants like hemp, flax, cotton, sugarcane badges, esparto, wheat straw, reeds, sisal, abaci, banana leaf, ananas and some other more exotic species. The world hemp paper pulp production is now believed to be around 120,000 tons per year (FAO 1991), which is about 0.05 % of the worlds annual pulp production volume. Hemp pulps are generally blended with other (wood-) pulps for paper production. There is currently no significant production of 100 % true hemp paper.
Renewed interest in hemp paper
The recent renewed interest in hemp as a paper-making fibre seems to originate from a strong environmental motive. All primary forests in Europe, and most in North America have been destroyed, amongst others for paper production. Now we accuse the nations which still have primary forests of not guarding theirs.In Europe all trees harvested for paper making were intended for that purpose, so there seems to be no valid reason to switch to a non-wood or -tree-free fibre source. This of course is a little different in the Americas and in Asia and Australia, where primary forests are cleared at a huge environmental cost. In these regions hemp has a number of advantages as an alternative source of paper-making fibre. Hemp does not need pesticides or herbicides, and yields three to four times more usable fibre per hectare per annum than forests.And last but not least: paper recycling was invented to make up for the mistake of cutting down our primary forests. Technically speaking, one doesn't need to recycle hemp paper, because it is a renewable raw material. One disadvantage of using hemp or other annual plants as fibre source is that the present pulping technology has been optimized for tree-fibre pulping, so some adjustments in the pulping processes need to be made when applying this technology to hemp fibres. Before going into technical details, we will first examine the technology of pulp and paper making.
Pulping and paper making
Paper making is essentially the rearranging of elementary fibers from whatever source (a tree, a hemp stalk, an old pair of jeans or even a scoop of algae) into a flat thin sheet. Elementary fibers are the basic building blocks of trees and many plants. The average paper making fibre is about 2 mm long and about 20 micrometers (0.02 mm) thick. All fibers are assembled of chains of cellulose molecules, arranged as a rigid structure. These building blocks are glued together with other biological components (lignin's, pectin's), which give a certain flexibility and strength to the tissue, so that the tree or plant can bend at high stresses, and doesn't break in a storm, and is able to carry its seeds and fruits. The following explains what is needed to process a fibre source into paper (Smook 1982):
Pulping (from fibre source to pulp):
* Cleaning: all non-fibrous components need to be removed from the raw material, and the remaining fibers must be cleaned of dirt, rocks and other contaminants.
* Fiberizing: the elementary fibers are taken apart by either chemically removing the glue that holds them together, or mechanically tearing the fibre structure apart. From this step on, the material is referred to as "pulp".
* Cutting: especially hemp fibers are too long to give a homogeneous paper sheet, so the fibers have to be cut to the right size.
* Classification: the fibers suitable for use in paper are separated from the ones too short, too long, too wide, too thin, too crooked, too dirty and too old. Fibers can be classified by weight (centrifugal and gravitational processes) and size (various sieving processes).
* Bleaching: optionally, the suitable fibbers may be bleached to a higher "whiteness". The whiter a sheet, the better the contrast with the ink. Old-style pulp mills use chlorine compounds with hazardous side-effects. Modern pulp mills use oxygen-based b leaching (compounds like oxygen, ozone and peroxide). Hemp pulp can be bleached with relatively harmless hydrogen peroxide. For some applications bleaching is not required, for instance for packaging paper and board.
* Refining: this is a separate process step in which the fibre surfaces are "roughened". The greater surface roughness of a fibre, the better it adheres to other fibers in the paper sheet and the greater the strength of the paper. Paper making (from pulp to paper):
* Dilution: in order to lay the fibers evenly into a homogeneous sheet, the pulp is diluted with large amounts of water (sometimes up to 200 times as much water as fibre pulp).
* Formation: the fibre-water slurry is poured on a fine mesh wire. Most of the water will fall through the wire, leaving the fibers to settle into a flat sheet.
* Drying: in the next steps, the wet sheet is dried by subsequent pressing and steam heating.
* Sheeting: finally, the formed sheet is cut to the required size.
These processes are essentially the same for manual paper making and for modern paper machines, with the difference that the old paper maker put out one handmade sheet per minute, and the state-of-the-art Fourdrinier newsprint paper machine puts out 15,00 0 square meters a minute: a 10 meter wide sheet at 90 kilometers an hour! Remainders of the hemp pulp industry Although there are thousands of non-wood paper mills in the world, only a few of them use hemp as a fibre source. At present 23 paper mills use hemp fibre, at an estimated world production volume of 120,000 tons per annum. Most of the mills are located in China and India, and produce moderate quality printing and writing paper. Typically, these mills do not really have a fixed source of fibre, but they simply use whatever can be found in the region. About 10 of the mills are located in the western world ( US, UK, France, Spain, eastern Europe, Turkey), and these mills produce so-called specialty papers such as:* cigarette paper: even popular American cigarette brands have a 50% hemp cigarette paper and filter. Some countries still have legislation prescribing the use of hemp in cigarette paper, because other fibers (like spruce) generate hazardous fumes w hen incinerated (!).
* filter paper (for technical and scientific uses)
* coffee filters, tea bags
* specialty non wovens
* insulating papers (for electrical condensations)
* grease proof papers
* security papers
* various specialty art papers
These papers can generally only be produced from special fibers like hemp, flax, cotton and other non-wood fibre sources. The average hemp pulp and paper mill produces around 5000 tons per annum. This should be compared to a -normal pulp mill for wood fibre, which is never smaller than 250,000 tons per annum. The only reason the remaining mills can still produce at this extremely small size is that there is a very special use for the pulp. This partly explains the high price for a hemp pulp: about US $25 00 per ton versus about US $400 for a typical bleached wood pulp. The remaining mills in the western world are unable to cope with western environmental regulations because of their small size and archaic technology. Some mills survive by shipping their waste water to a large wood pulp mill nearby, others have to close down. There is a clear shift in capacity towards countries that do not as yet take environmental problems very seriously. One reason for the high price of hemp pulp is the inefficient pulping processes used. Another reason is that hemp is harvested once a year (during August) and needs to be stored to feed the mill the whole year through. This storage requires a lot of (mostly manual) handling of the bulky stalk bundles, which accounts for a high raw material cost.
Classical pulping technology
Most mills predominantly process the long hemp bast fibers, which arrive as bales of cleaned ribbon from preprocessing plants located near the cultivation areas. The bales are opened and fed into a spherical tank, called a digester. Water is added (5 to 1 0 times the fibre weight), together with the cooking chemicals to remove the "glue" components lignin and pectin from the fibers. Most mills use sodium hydroxide and sulphur cocktails.The fibers are cooked for several hours (sometimes up to eight hours) at elevated temperature and pressure, until all fibers are separated from each other. After cooking, the cooking chemicals and the extracted binding components are separated from the fibers by washing with excess water. This is where most of the polluting waste emerges from the process. Often wastes are discharged as such into the local surface water. The remaining clean fibers are then fed into a Hollander beater, which is best compared to an industrial size bathtub, with a large wheel revolving around a horizontal axis at one point in the tub. The wheel pumps the pulp round and round, and meanwhile cuts the fibres to the right length, and also gives the fibres the required surface roughness for better bonding capacity. This beating goes on for up to twelve hours per batch. Some mills add bleaching chemicals in this beating process, other mills pass t he pulp from the beating machines to separate tanks for bleaching. These separate bleaching treatments often use chlorine compounds, which are also discharged into the environment. The bleached pulp is then ready to be pumped to the paper machine, or can be pressed to a dryness suitable for transportation to a paper mill elsewhere. The processing time of more than twenty hours make this process very expensive, as the costly equipment and handling must be depreciated over a very low throughput.
Necessity for new technology
New applications for hemp as a paper making raw material require a new pulping technology which must be able to use hemp from wet storage. Some new technologies have been developed, albeit in laboratory or on pilot scale.
References
*Abel E.L. 1980. Marihuana, the first twelve thousand years.Plenum press, New York, 289 pp.
*Conrad C., 1993. Hemp, lifeline to the future. Creative Xpressions Publishing, Los Angeles, California.
* FAO 1991. The outlook for pulp and paper to 1995. Paper products, and industrial update. Food and Agricultural Organization of the United Nations, Rome.
* Hunter, D. 1957. Paper making, the history and technique of an ancient craft. 2nd Ed. Albert A. Knopf
* Smook G.A. 1982. Handbook for pulp & paper technologists. 2nd Ed. Angus Wilde Publications, Vancouver, B.C.
*Temple R.K.C, 1986. China, land of discovery and invention. Patrick Stevens Ltd., United Kingdom.
*Gertjan van Roekel jr. ATO-DLO Agro-technology, P.O.box 17, 6700 AA Wageningen, The Netherlands
* Van Roekel, G J, 1994. Hemp pulp and paper production. Journal of the International Hemp Association 1: 12-14.
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