Basics of Industrial Hemp
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Basics of Industrial Hemp An Open Textbook
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Table of Contents Chapter 1: What is Industrial Hemp?......................................................................1 Legal Definition.............................................................................................................1 Hemp Versus Recreational Cannabis...........................................................................2 Hemp Versus “Medical” Cannabis................................................................................2 Chapter 2: History of Industrial Hemp...................................................................3 Chapter 3: Industrial Hemp Uses.............................................................................5 Live Plants......................................................................................................................5 Fiber................................................................................................................................5 Hurds..............................................................................................................................6 Seed.................................................................................................................................6 Leaves, Flowers, and Roots...........................................................................................7 Chapter 4: Economics of Industrial Hemp.............................................................9 Global Market................................................................................................................9 Market Volatility............................................................................................................9 Profitability..................................................................................................................10
Cultivation.................................................................................................................... 11 Processing..................................................................................................................... 11 Services......................................................................................................................... 12
Chapter 5: Cultivation of Industrial Hemp.........................................................13 Preparing the Soil........................................................................................................13 Selection of Seed Stock................................................................................................14 Planting and Seed Density..........................................................................................14 Water Requirements....................................................................................................15 Harvesting....................................................................................................................15 Chapter 6: Processing Industrial Hemp...............................................................17 Decortication................................................................................................................17 Fiber..............................................................................................................................17 Degumming.................................................................................................................. 17 Spinning........................................................................................................................ 18 Weaving........................................................................................................................ 18 Felting........................................................................................................................... 19 Specialty Materials...................................................................................................... 19
Hurds............................................................................................................................19 Shredding...................................................................................................................... 19 Pelletizing..................................................................................................................... 19 Bailing........................................................................................................................... 20 Forming......................................................................................................................... 20 Pulping.......................................................................................................................... 20 Seed...............................................................................................................................21 Viable Seed Stock......................................................................................................... 21 Hemp Grain.................................................................................................................. 21 Hearts........................................................................................................................... 22 Hemp Seed Oil.............................................................................................................. 22 Meal and Cake.............................................................................................................. 22 Extracts........................................................................................................................22
Figure 1: A drawing of Cannabis sativa originally published in Franz Eugen Köhler's MedizinalPflantzen, Gera Untermhaus, FE Köhler, 1887 (public domain). Key: (A) flowering male and (B) seedbearing female plant; (1) male flower, enlarged detail; (2) and (3) pollen sac of same from various angles; (4) pollen grain of same; (5) female flower with cover petal; (6) female flower, cover petal removed; (7) female fruit cluster, longitudinal section; (8) fruit with cover petal; (9) same without cover petal; (10) same; (11) same in crosssection; (12) same in longitudinal section; (13) seed without hull.
Chapter 1: What is Industrial Hemp? Industrial hemp is any cannabis plant (species Cannabis sativa) which is grown for industrial or commercial purposes other than those grown for recreational, health supplementation, or ornamental use. Cannabis, including industrial hemp, is a leafy annual which reaches one to five meters (3 to 19 feet) in height. The basic raw materials which can be obtained from hemp stalks are hemp seeds, long bast fiber from the skin of the plant, and chunky cellulose from the core of the plant called hurds. From the seeds one can produce hemp seed oil. The seeds, which are high in essential fatty acids, are also eaten as a food in many countries. Soaps and cosmetics frequently use hemp seed oil in their formulations because of its demonstrated benefits to the skin. Hemp seed oil is also used to make biofuels and plastics, however high demand for hemp seed oil for food and cosmetics makes this use economically unfeasible at this time. The long bast fiber from the outer skin of the hemp plant is washed with steam and chemicals, or it is retted Figure 2: Magnified to remove the nonfibrous gluelike materials such as hemp seed grain. lignin and pectin. The resulting fibers have many industrial uses from rope and twine to soft bed linens. Hemp fibers are commonly used to increase the strength of materials such as plastics and concrete. Specialty uses include woven mats which replace fiberglass and carbon fiber in composite construction and conductors in supercapacitors Figure 3: Processed which may make electric vehicles and power storage more economical. hemp bast fiber. The inner core of the hemp plant, called hurds, is used without processing as animal bedding, or the hurds can be burned as a source of fuel. The short cellulose fibers in the hurds make them ideal as a source for paper pulp. Other uses being researched include using the hurds as a feedstock for biofuel. Figure 4: Hurds are pieces of In addition to the traditional industrial raw the core which remain after materials, modern uses are being developed for bast fiber is removed from the leaves, flowers and roots. These materials hemp stalks. are commonly left behind in industrial hemp farming, however this may not be the case in the near future. Research has shown that these materials provide opportunities for the extraction of precursors for plastics, natural scents and flavors, solvents, and medicines. Industrial hemp refers to the industrial use of the hemp plant from the trade of viable hemp seed, its intermediate raw and processed materials, through to Figure 5: Roots of a the consumer goods made from those products. Industrial hemp refers to the industry as a whole as well as the materials and goods produced by that hemp plant. industry.
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Basics of Industrial Hemp Legal Definition Industrial hemp is legally defined in nearly all cases as being a plant of the species Cannabis sativa which has a very limited amount of the psychoactive, or euphoria producing substance THC (tetrahydrocannabinol). Various legal jurisdictions define the maximum allowable levels of THC in industrial hemp differently from one another, however the current consensus seems to be forming at three tenths of one percent (0.3%) of the dry weight of the flowering portion of the plant.
Hemp Versus Recreational Cannabis The primary difference between industrial hemp and recreational cannabis varieties is that industrial hemp will not produce euphoria when consumed. This means that smoking, eating, or applying hemp preparations to your skin will not produce the “high” commonly associated with other varieties of cannabis consumed for recreational purposes. Industrial hemp generally contains much higher levels of CBD (cannabidiol) than THC. CBD has been demonstrated to counter the psychoactive effects of THC. Smoking or eating hemp to achieve a high would likely result in the opposite effect if any psychological effect would be noticed.
Hemp Versus “Medical” Cannabis The only difference between industrial hemp varieties of the cannabis plant and those used personally as a health supplement or at the recommendation of a doctor is the THC level. Excluding THC as the only exception, industrial hemp varieties can be developed to produce any other cannibinoids present in varieties currently being used for their supplemental health benefits. Many of these cannabinoids are of potential medical importance. One such substance which has gained the attention in the scientific research community as well as the media is CBD. Without producing a euphoric effect, this substance has been shown in preliminary studies to have beneficial effects on a number of other symptoms and conditions. Research has demonstrated potential for CBD to reduce muscle spasms related to Parkinson's disease, and to restore proper brain and muscle function in those suffering from epilepsy and related conditions. Studies are currently being conducted on the effects of CBD on patients with psychological conditions such as Post Traumatic Stress Disorder (PTSD). In addition to CBD there are over 60 other cannibinoids which have been isolated from the cannabis plant. Only a few of these cannabinoids have been studied individually, however evidence suggests that cannabinoids may be more effective in combination. Industrial hemp is medically relevant, with the primary difference being that preparations made from hemp are not able to produce the euphoric “high” commonly associated with traditional “medical” cannabis use. Hemp is also medical cannabis, even if the term “medical” is commonly used to refer to cannabis containing high levels of THC and sold from medical cannabis dispensaries. This confusion of terms makes it difficult to discuss cannabis in a general manner. The THC content alone is what makes one variety of cannabis industrial hemp and another a highly regulated substance only sold from specific licensed shops in those areas where a regulated medical cannabis market has been established.
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Chapter 2: History of Industrial Hemp
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Cultivation of cannabis for industrial purposes predates written history. Industrial hemp use also predates medical and recreational use of the cannabis plant. The oldest records discovered are from China (around 500 A.D.) which describe use of the fiber having originated nearly 5000 years ago (2800 B.C.). Other texts also describe the Figure 6: "Ma" seeds being used as food and the stalks being burned as fuel, however no early texts is the Chinese directly indicate that cannabis was used as a medicine at that point in history. symbol for the Evidence indicates that Europe was introduced to hemp plant. the cannabis plant around 1500 B.C., however the ancient Greeks and Romans do not mention hemp until around 0 A.D. By the sixteenth century (i.e. 15011600 A.D.) industrial hemp was common throughout Europe as both a source of fiber and a food grain. The plant was named Cannabis sativa by physician and botanist Dioscorides in 1537, describing both its utility as a source of industrial fiber as well as its medicinal benefits. The cannabis plant was first brought to South America by Spanish explorers around 1545, but did not make its way to the U.S. colonies for another one hundred years. Both jute and abaca were being inexpensively imported and therefore competed with hemp fiber. This contributed to the slow adoption of industrial hemp in the United States, particularly because of the amount of manual labor required to harvest and process industrial hemp prior to the development of mechanized hemp decortication. Cotton became a much more popular crop once mechanized processing was invented, and its increased popularity meant competition for hemp. The cotton gin was invented in 1793, nearly one hundred years before the first mechanical break was invented for industrial hemp.
Figure 7: Cannabis sativa plant as depicted in the Vienna Dioscurides manuscript of De Materia Medica by Pedanius Dioscorides circa A.D. 515.
In 1890 an Italian named Bernagozzi invented what is believed to be the first hemp decorticator. Prior to this time all hemp was manually broken by a variety of methods and the fiber was commonly separated from clinging hurds simply by flailing the hemp stalks. It was not until the early 1900s that the U.S. began to make common use of mechanical processing of industrial hemp. While many states grew hemp in varying amounts, nearly all industrial hemp produced in the U.S. was grown in Kentucky between the 1860s and the early 1900s. The first World War created a need for industrial hemp fiber and cultivation increased in many U.S. states in order to supply the demand.
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Basics of Industrial Hemp Interest in industrial hemp increased slowly until the Marihuana Tax Act of 1937 was passed which heavily regulated the cultivation of industrial hemp in the United States. Under the guise of restricting access to what they characterized as a dangerous narcotic drug, the U.S. government imposed unlawful tax stamp requirements which effectively prevented any and all cultivation of industrial hemp in the country. However, the U.S. government began Figure 8: An example of a tax stamp issued by the U.S. issuing tax stamps once it became government for industrial hemp cultivation circa 1945. necessary due to increased demand for industrial fiber at the beginning of the second World War. The issuance of the tax stamps dwindled again once the war ended, with an extremely limited number of industrial hemp producers remaining. The last industrial hemp farm in America harvested its final crop in 1958 in Wisconsin. The onerous requirements of the Marihuana Tax Act of 1937 were eventually determined in Timothy Leary V. United States to be unconstitutional because the act required self incrimination, a violation of the fifth amendment to the U.S. Constitution. Leary's conviction for possession of cannabis was overturned and the prohibition of all cannabis, including industrial hemp was rendered unenforceable for a brief period of time (19 May 1969 until 27 October 1970). U.S. Congress then passed the Comprehensive Drug Abuse Prevention and Control Act of 1970. This legislation defines viable seed and many other parts and extractable components of the cannabis plant to be Controlled Substances and requires registration for producers and distributors of the plant. This legislation exempts nonviable seeds and the stalks and other portions of the plant from registration, however the live plant, regardless of THC content, and its viable seed are considered by this legislation to be a dangerous substance worthy of rigorous controls. The U.S. government also worked to pass international treaties and to encourage prohibition of cannabis cultivation in many other countries around the world. This effort met with varied results, with some nations adopting similar legislation prohibiting industrial hemp as well as varieties containing THC, while other nations outlawed use of cannabis as a drug but maintained their ability to grow hemp as an industrial crop. Today many states in the U.S. have begun to relax regulations regarding cannabis and to specifically authorize industrial hemp cultivation. This decriminalization and regulation in multiple states has lead to changes in U.S. federal law which now allow for state departments of agriculture and institutions of higher education to cultivate industrial hemp for research purposes. In the U.S. confusion remains regarding the ability of even those specifically authorized by federal law to import viable industrial hemp seed. The U.S. Department of Justice continues to assert regulatory authority over industrial hemp imports despite the 2014 U.S. federal farm bill clearly stating that the ability to cultivate industrial hemp is granted to state departments of agriculture and institutions of higher education, regardless of the Controlled Substance Act or any other federal law.
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Chapter 3: Industrial Hemp Uses The variety of materials and products which are able to be made from industrial hemp are far too numerous to list here exhaustively. Based only on raw materials traditionally obtained from the hemp plant, many thousands of items can be manufactured from industrial hemp. With modern innovation in materials sciences and increasing medical research the number of potential uses for the hemp plant have become too numerous to predict. New uses are being discovered for components extracted from the leaves, flowers and even the roots, as well as novel uses for traditional hemp raw materials.
Live Plants One use of industrial hemp that has gained increased interest relatively recently is soil remediation using hemp plants. Various industrial toxins are difficult to remove from the soil, however industrial hemp has demonstrated the ability to absorb the toxins from the soil and sequester them in the plant material. In this case the raw materials would be used for nonfood purposes, such as concrete aggregate and fuel. Industrial hemp is very effective at choking out weeds because of how densely and rapidly it grows. Studies have shown that even the most tenacious weeds, such as bindweed and napweed, are significantly reduced after as little as one season. The industrial hemp crop not only crowds out the other plants, reducing their access to light, but it also competes for nutrients, growing deep and broad root systems. It is rare, however live hemp plants are grown for ornamental purposes. When grown individually with plenty of space to branch, the plants grow quickly and form shrubs which some consider aesthetically pleasing.
Fiber The fibrous skin of the hemp plant, called the bast, is considered to be one of the highest quality fibers available for many applications. In fiber varieties of industrial hemp, the long fibers extracted from the stalks may be more than two meters (6 feet) in length. Compare this to cotton fibers which range from 0.3 to 6.4 cm (1/8th to 2.5 inches). For ropes, twine and woven fabrics this exceptional fiber length generally increases strength and durability of the final product. This fiber can be used without much processing to make rope and twine, or can be washed in a process called degumming to produce very soft and light colored fibers suitable for fine bed linens, terry cloth, fleece and other high quality and durable fabrics. Specialty fabrics, such as woven mats which replace fiberglass in resin composite construction, can be made with similar strength to and less weight than both fiberglass and carbon fiber.
Figure 9: Comparison of three types of hemp fabrics: fleece, canvas, burlap (bottom).
Hemp fibers will likely also find their way into the electric cars of the future as energy storage moves from expensive chemicalbased batteries to much more efficient supercapacitors. Highly specialized uses for hemp fiber are being discovered such as the research project at the University of Alberta which has found a way to produce
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Basics of Industrial Hemp a material similar to graphene for use in supercapacitors. Graphene is expensive to produce and is not yet available in large quantities, while the hemp fiber based nano material costs an insignificant fraction to produce. Shorter fibers called tow are removed during the processing of the long fiber. This hemp tow is used for many purposes, including spinning into fine textile thread similar to that of cotton, pulping for paper, and many other uses.
Hurds Processing industrial hemp by decortication results in the separation of the outer bast fiber from the inner portion of the hemp stalk. This is generally done by breaking the inner core into pieces and mechanically or manually removing those chunks from the long bast fibers which resist breaking under the crushing process. This means that in most cases the inner core of the stalk is broken into various sized pieces called hurds. Unlike the length of the bast fibers, the cellulose fibers found in the hurds are generally very short, averaging 12mm (0.04 to 0.08 inches). They are also tightly glued together with lignin and pectin, which limits their usefulness without further processing. Being of very low density makes them unsuitable for long distance transport in their unprocessed form. Without any processing, the hurds are used to generate heat for steam boilers, power generation, and a number of other industrial uses able to process solid flammable fuel. The unprocessed hurds are also able to be used as a feedstock for generating biofuels such as ethanol and woodgas, a methane based biofuel similar to natural gas. The hurds can be minimally processed to produce animal bedding and for use as an aggregate in cement and limebased building materials. Using hemp hurds significantly reduces the weight of the resulting slab or wall and may one day allow for significant innovations in construction standards.
Figure 10: Hurds are pieces of the core which remain after bast fiber is removed from hemp stalks.
In many countries hemp hurds are currently being made into building materials including a type of wood sheeting called particle board or press board. This material is made by coating the wood chips or hemp hurds in adhesive and then compressing them with heavy rollers into sheets of the desired thickness. Particle board made from hemp hurds is suitable for many applications, including shipping crates where its light weight reduces shipping costs. Paper pulp can easily be made from the hurds which produces high quality papers. Hemp fibers, as long as they are processed properly, are archival safe and naturally resist many types of mold and fungus which cause degradation and staining of archived documents and books.
Figure 11: Particle board made from hemp hurds.
Industrial hemp hurds may someday be used as a renewable and carbon neutral source for disposable paper products such as paper towels and toilet paper. Adding industrial hemp fiber to paper also increases its ability to be recycled multiple times. Less virgin cellulose fiber must be added to the pulp, meaning the same quality of paper is made using a higher percentage of recycled content.
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Chapter 3: Industrial Hemp Uses Transparent bioplastic is also able to be produced from the cellulose in the hurds which makes it possible to produce product packaging, biodegradable or compostable greenhouse covers, plastic windows for envelopes, and many other products.
Seed The primary use of hemp seed is as viable planting stock for hemp cultivation. In areas where hemp cultivation has only recently been reauthorized by the government, most producers of hemp seed will likely find an eager market for their viable hemp seed without requiring any processing beyond traditional seed cleaning.
Figure 12: Hemp seed grain. Industrial hemp seeds can also be expeller pressed to produce hemp seed oil, and seed cake. The seed cake is generally used directly, or as a component of animal feeds, for its high levels of protein, essential fatty acids, fiber, vitamins and trace minerals.
Hemp seed oil has many uses. It can be used similarly to olive oil for recipes like salad dressings and sauces, and to replace cooking oil in low temperature baking. When a surplus exists, causing a reduction in the market value, it can also be made into biodiesel and even plastics. Hemp seed oil has been shown to have significant benefits to the skin and its use in cosmetics is increasing. Hemp seed oil is also frequently used in soaps for the saponified fats as well as a superfat which is added after saponification as a beneficial element to the skin.
Leaves, Flowers, and Roots Modern materials science research, combined with expanded authority and funding for cannabis related medical research, has demonstrated uses for the leaves, flowers and even the roots of the cannabis plant. Industrial hemp cultivation has traditionally left these materials in the field during harvest, considering them of very low value. Today cannabinoids and other substances are able to be extracted for use in many different industries. One common mode of research is testing the medical efficacy of these substances against common ailments and diseases. While CBD (cannabidiol) has received the most attention from researchers and the media, there are more than 60 identified cannibinoids which may have separate or combined benefits with other cannibinoids and traditional treatments. Potential uses of the extracted oils from the flowers, called terpenes, include manufacturing a wide range of possible natural flavors and scents. The cannabis plant has been shown to produce an amazing number of aromatic terpenes, from pine to citrus and nearly everything in between. The roots also contain cannabinoids in different proportions than the remainder of the plant. This allows for the roots to be used in the isolation and purification of different substances than would be easily extracted from the leaves or flowers. Some researchers studying the medical benefits of industrial hemp have been focused on the roots as a source of CBD and other cannabinoids. Figure 13: Roots of a hemp plant.
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Chapter 4: Economics of Industrial Hemp While the global economy of industrial hemp may change relatively slowly, the effect of authorizing its cultivation in a large region results in significant and often sudden economic shifts in that region. For this reason we must look at the economic aspects of industrial hemp from a few perspectives and at various scales to obtain a complete picture.
Global Market The global market for industrial hemp has changed drastically over time with fluctuations in demand being driven by taxation, war, prohibition and especially competition by other industrial fibers. Recently there has been a dramatic increase in demand for hemp seed oil as as source of food and for cosmetics while international demand for hemp fiber has not seen much increase. Textile producing countries such as China have been exporting more and more consumer goods produced with blended fibers containing some portion of hemp. This leads to the reasonable conclusion that the fiber is being used within the region as little incentive exists to transport the relatively low density fiber long distances. International trade of industrial hemp seed and oil is unrestricted for the most part. This combined with its high energy and nutrition density makes it valuable on the global market. Finished goods made from the fiber and hurds are more valuable than those raw materials themselves, as many alternative raw materials are available to regions not producing industrial hemp. The global market effectively sets a ceiling on the value of industrial hemp raw materials. This provides a natural incentive to manufacture near the area producing the raw materials. The value of regional production is increased which provides an economic benefit to the local community even while trading on a national or international scale. By manufacturing higher value materials and goods from the inexpensive local raw materials the farming community nets an economic gain compared to exporting only the raw materials.
Market Volatility We can look to regions such as Canada, which have recently reauthorized industrial hemp cultivation, and conclude that similar market effects will follow in other regions now relaxing regulations and prohibitions. It can be observed that the market price for raw materials made from industrial hemp saw a steep decline in the Canadian market as production levels peaked shortly after the law was changed to allow its cultivation. Other factors, such as water availability and weather conditions also affect the regional price of industrial hemp raw materials. Drought can cause industrial hemp plants to mature early and reduce overall hemp production of raw materials. Ideal conditions will increase production and cause a surplus in the market, which may reduce the market price in the region for raw materials. None of these factors will generally have as great an effect on the market price as would the initial condition of rapid expansion of hemp cultivation in the absence of a corresponding expansion of industries and technologies incorporating the use of the now abundantly available raw materials.
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Basics of Industrial Hemp Market demand is a critical factor in the value of industrial hemp raw materials. When the focus is shifted from producing raw materials for sale to one of producing the raw materials at cost for manufacturing this creates demand for the raw materials in conjunction with their production. Instead of relying on existing manufacturing techniques to retool for a new raw material, or new companies to enter the market, the demand for wholesale and retail products is converted into demand for industrial hemp cultivation. In economic terms this method of combining the supply side with that of the production is referred to as Vertical Integration. While the concept generally relates to large enterprises the concept scales down to an individual farm or a local association of farmers quite well. By considering the industrial hemp crop as an atcost source of raw materials for the production of a manufactured good, the immediate value of the raw materials becomes less relevant to the value of the resulting product. This reinforces the need to focus on vertical integration from the bottom up. For example, the market value of fabric or particle board moves slowly in comparison to their raw materials. Further these finished products are able to be transported more cost effectively. Clearly the way to reduce the effects of market volatility for industrial hemp raw materials is to integrate processing and manufacturing as well as professional services into one's business model. In times of high valued raw materials the vertically integrated business pays the actual cost of producing the raw materials required for production. When the market value is depressed they have access to inexpensive raw materials and may be able to increase production or reduce wholesale pricing of their goods to take advantage of market conditions.
Profitability For the vast majority of those who choose to cultivate hemp their primary focus will be on monetizing and sustaining their operation. This means that the value of the crop must exceed the costs associated with growing it. Traditional attempts to calculate the value of growing industrial hemp have focused on one or more of the basic raw materials as the final product to be sold. This approach has lead to varied conclusions often substantially tied to the regional or national demand for the raw materials. The conclusions of these attempts range from being competitive with wheat $250 USD per hectare ($100 per acre) to a similar value to that of tobacco at $3000 per hectare ($1200 per acre). Clearly the extent to which the conclusions vary demonstrate the uncertain and unpredictable nature of the industrial hemp market for its raw materials. Modern attempts to determine the profitability of industrial hemp cultivation must consider the rapid expansion of the medical cannabinoid field of research. New uses for extracts of the cannabis plant have created another revenue stream for industrial hemp. When the focus is shifted from the value of the raw materials to products and industrial materials which can be made from hemp the projected return on investment becomes much more stable. As production rapidly increases in a region the value of the raw materials will likewise drop suddenly. To the industrial hemp farmer this may be catastrophic, while to the producer of hemp fabric this is simply a reduction in the cost of producing fabric, while the wholesale value of hemp fabric remains tied to global demand and pricing. As a global trend, agricultural resources are being centralized in such a way that the farms themselves are an asset of the company or group which also owns the production and distribution
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Chapter 4: Economics of Industrial Hemp systems for the commodity. This model converts the risk associated with market volatility into a benefit of reduced cost to the production side regardless of the local market for the raw materials. From the perspective of a manufacturer, the highest value for industrial hemp raw materials is set by the global market, while lower prices caused by regional increases in production reduce the cost of their manufactured goods. As an observable trend in the agricultural industry the absence of vertical integration at the local and regional level results in the local farms filing for bankruptcy and their land being purchased by larger corporate interests seeking to increase their ownership of the supply side of their various industries. Vertical integration has demonstrated itself to be the dominant strategy for commercial efficiency. Any individual looking to enter the agricultural market should likely be doing so with the objective of producing a wholesale or retail commodity and not relying on the market value of the raw materials to turn a profit.
Cultivation The economics of industrial hemp cultivation is heavily influenced by a number of factors. Most notably the cultivation of cannabis is heavily regulated in some regions meaning that a change in laws may create highly volatile markets for the raw materials in that region. The profitability for the local farmer is also influenced by international production levels and demand. As large commercial agricultural groups begin cultivating industrial hemp the market value of the raw materials will tend towards the actual cost of production. This makes reliance on the raw materials as a source of profit infeasible as a long term goal. The value of the industrial hemp crop is in what can be made from its raw materials. By considering the cultivation expense the cost of raw materials in a larger business model from the outset, the potential negative impact of market volatility in emerging markets and the eventual trend in industrial hemp value towards that of the international market value are both effectively reduced. There are many niche markets where cultivation of specific cannabinoidrich varieties or those producing fiber of a specific quality are economically viable crops. However, even in these cases the producer would realize a much greater return if they were to process the hemp into its final commodity form. For example the value of one tonne of high quality hemp fiber in one market may be around $400 USD, while if it were woven into fiberglassreplacement mats the value of the same fiber could exceed $1200 per tonne.
Processing Industrial hemp requires expensive and often specialized equipment to harvest and process. Many industrial hemp farmers may not have the resources to purchase equipment for their sole use, and those able to purchase it may not be interested in cultivation. This provides an opportunity for dedicated processing facilities which are either independent operations or cooperatively owned by a group of farmers. Industrial hemp is cost prohibitive to ship in its unprocessed form. Regions with any significant amount of industrial hemp production will require a processing facility within the region in order to remain competitive with international market prices. Some business models may be able to work around this, such as industrial hemp grown for seed oil, with the stalks being shredded and used for concrete aggregate or solid fuel.
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Basics of Industrial Hemp In general, the hemp stalks themselves will be processed at or near the farm that produced them and the raw materials prepared for transportation to the processing facility, whether or not it is local. This means that the processing company should be prepared to either require delivery of the industrial hemp stalks to their facility by the farmer, or should have processing equipment which can be transported to the farm to be used in conjunction with harvesting equipment at the point of harvest.
Services Industrial hemp cultivation, processing and manufacturing all require significantly specialized professional services to maintain their operation. Many of these will simply be opportunities for expansion for existing businesses, such as equipment maintenance or industrial suppliers. However, many opportunities are unique to industrial hemp cultivation. These include consulting regarding industrial hemp agriculture and manufacturing, cannabinoid testing, as well as many other industrial hemp specific services. Especially in regions where industrial hemp has recently been reauthorized, those with specific knowledge will find themselves in high demand. The same goes for those with specialized equipment, such as that used for testing cannabinoid content. Many professional services required by industrial hemp production overlap with those of traditional agriculture, while many are yet to be discovered. There exists an immense opportunity for innovation in the industrial hemp market because we are at a point in history where the medical benefits of the cannabis plant are being confirmed while the laws restricting its cultivation are being relaxed at a rapid pace. Many industrial hemp farmers may wish to seek opportunities to provide professional services to other hemp farmers in order to increase the return on investing in the equipment or specialized training for their own operation. For example one farmer with a seed drill could seed the fields of many farmers. Likewise, a single farmer with a decorticator could process the stalks of other nearby industrial hemp farms.
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Chapter 5: Cultivation of Industrial Hemp Industrial hemp varieties are numerous and vary greatly in their traits. Not all varieties are grown for seed, especially those grown to produce long bast fibers. Many varieties of industrial hemp are imported from regions with different environmental characteristics, such as length of day, and therefore do not produce seeds in that region even if they would in their native region. Varieties grown primarily for seed are generally shorter because they must mature quickly and in various light and temperature conditions. Bast fiber and hurds are still produced by harvesting the seed varieties, however the yield of these components will be lower. In many markets the demand for seed far outweighs that for fiber and hurds and therefore this compromise is acceptable. If one wishes to maximize the amount of hemp seed as well as fiber and hurds produced on their farm it is necessary to select a variety that grows tall but also matures to seed in their environmental conditions. This may require a few growing seasons in which multiple varieties are grown and the best performing varieties are selected. The farmer may also choose to cross pollinate the varieties which produce desirable traits in order to develop their own variety, however doing so on a large scale will create numerous new varieties with unpredictable traits. This method may or may not result in a crop with the desired characteristics in subsequent growing seasons. Genetic research resulting in new and predictable varieties is generally done in very controlled conditions and the desired traits verified over many generations of planting. Most hemp farmers growing hemp for a specific purpose will likely purchase viable hemp seed from a known source which produces certified seeds. This is of course if they are able to import viable hemp seed into their country or region. In many cases where local hemp cultivation is authorized, the availability of local hemp seeds will be a determining factor as to what variety is grown, or if industrial hemp is able to be grown at all.
Preparing the Soil Industrial hemp requires well draining, sandy loam. This means that the clay and peat content are not too high and will not reduce oxygen flow to the roots through excessive retention of water. However, soil should not be too sandy and arid or the plants may not germinate well and may begin maturing too early in the season. In many cases the soil must be amended to include the proper proportions of nitrogen, phosphorous and potassium. This ratio is commonly referred to as the NPK content, with each letter representing one of the components respectively (N for nitrogen, P for phosphorous, and K for potassium). If the soil contains too high a ratio of nitrogen, to the exclusion of phosphorous and potassium, then the resulting hemp plants will become leggy, or tall and weak, and will easily break in the wind. If the nitrogen content is too low the plants will grow slowly and will appear to be sickly and yellow. It is important to have the soil tested before planting to ensure that sufficient nutrients are present and exist in the proper proportions. It may be best to discuss the soil test results with the provider of the seed stock to determine appropriate fertilization rates.
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Basics of Industrial Hemp Typical fertilization rates vary widely based on the starting soil composition and the region in which the industrial hemp is to be grown. For nitrogen amendment, typically suggested rates vary from 40 kilograms per hectare (36 U.S. pounds per acre) to a nominal maximum of around 120 kg/ha (100 pounds/acre). Maximum suggested nitrogen amendment can exceed 200 kg/ha (180 pounds/acre) in extreme cases where soil contains little to no nitrogen, however care should be taken not to over fertilize with nitrogen or negative growth characteristics will result. Phosphorous amendment is typically recommended at levels as low as 30 kg/ha (27 pounds/acre) and top out around 100 kg/ha (90 pounds/acre). Potassium amendment is generally recommended at a rate of 40 kg/ha (36 pounds/acre) to a nominal maximum of about 100 kg/ha (90 pounds/acre). However, it should be noted that some regions have found much higher rates produce better results. For example, in France, Poland and the Netherlands suggested rates fall within the range of 150 kg/ha (135 pounds/acre) to 200 kg/ha (180 pounds/acre). Excessive potassium has been found by some to reduce the yield and quality of the produced hemp fiber.
Selection of Seed Stock The best variety to grow in any specific scenario depends on the desired raw materials which are to be produced. For example, varieties of industrial hemp grown for fiber may not produce seed, and oil seed varieties are likely to mature early and produce less fiber and hurds. Fiber varieties are often densely planted, causing tall but thin stalks which contain fewer and smaller hurds. Various factors, such as ultraviolet (UV) exposure and available nutrients, affect the amount of THC produced by the hemp plant. In regions with strict legal limits on THC levels this means that a variety should be selected that is known to produce little THC in a similar environment to that being selected for growth. Latitude is a factor when it comes to THC production, with UV exposure increasing as one approaches the equator. A variety that produces just under 0.3% THC in France may exceed the legal limits when grown in a southern U.S. state. Traditionally the choice has been between a seed or fiber variety. However, with research into using cannabinoids found in hemp for their medicinal benefits some hemp growers have begun selecting for high levels of CBD, CBN (cannabinol) and other cannabinoids with the expectation of selling the leaves, flowers and roots of their industrial hemp crop. In some areas hemp growers have chosen to forgo processing of the hemp fibers and hurds entirely, finding a much greater demand for the seeds and CBDrich plant matter. This decision may be forced based on the lack of available industrial hemp processing equipment. Industrial hemp varieties which produce seed tend to reseed heavily during harvest. If the crop is being grown for viable hemp seed, care should be taken to minimize cross pollenization of a new variety grown in the same field as previous industrial hemp crops. In cases where seed oil or feed grain is being produced the genetic makeup of the resulting seed is irrelevant.
Planting and Seed Density While very small crops of industrial hemp may be able to be seeded by hand most commercial crops are seeded with a seed drill. Seeds should optimally be planted at a depth of two to three centimeters (3/4 to 1 1/4 in). Seed spacing varies based on the desired raw materials to be produced.
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Chapter 5: Cultivation of Industrial Hemp For fiber varieties the row spacing is generally tighter, around 8 cm (3 in). This will increase the amount of bast fiber and reduce the amount of hurds and leaf matter produced. The stalks will also be smaller in diameter and easier to cut down during harvest. Row spacings of up to 18 cm (7 in) are also common. Row spacings broader than this will increase the amount of weeds competing with the hemp plants and may significantly reduce yield and consistency of plant size, including the proportion of bast fiber to hurds. Recommended seeding rates in regions with established industrial hemp production are generally in the range of 35 to 70 kg/ha (30 to 60 lbs/acre). For traditional industrial hemp crops high density planting is preferable when possible. Planting an oilseed variety extremely sparsely does not generally result in higher seed production unless the crop is heavily weeded manually to reduce competition.
Figure 14: Sparsely planted hemp competing with weeds
However, in instances where the Industrial hemp is being grown for medical research purposes (e.g. a CBD rich variety) it is becoming more common to grow in containers or in very widely spaced rows to maximize branching and thereby the number of inflorescences, the flower clusters at the end of each branch which have the highest concentration of cannabinoids of any part of the industrial hemp plant.
Water Requirements Hemp requires supplemental irrigation in most regions unless rainfall is extremely consistent. To ensure uniform germination and early development it is essential that the soil be kept moist throughout the first six weeks of growth. Once a strong root system has been developed the plants are able to withstand short durations of dry soil, however extended periods of drought will trigger early maturation and result in shorter plants and reduced yield. The amount of supplemental irrigation necessary depends on the soil quality, average temperatures, and of course the amount of natural rainfall which occurs in the region. Studies of water use in Europe have found that 50 to 70 cm (2028 inches) of irrigation, including rainfall, is required for hemp to produce optimum yield. They also found that 25 to 30 cm (1014 inches) of that amount should be made available during the vegetative stage of growth (i.e. prior to the start of flowering). It is important that irrigation is uniform or inconsistent results will occur. This is often a factor of the soil quality. The ability of the soil to retain water is beneficial as long as excess pooled water drains relatively quickly. Extremely sandy soil may not support flood irrigation as it may drain too quickly to evenly moisten the field. Industrial hemp cultivation has historically focused on areas with high annual rainfall levels and therefore research is necessary to develop broadly applicable irrigation recommendations.
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Basics of Industrial Hemp Harvesting In areas with established industrial hemp cultivation farmers will find ready access to harvesting equipment and processing facilities. Many times the harvesting will be done by contract with an organization established to harvest and market the resulting raw materials. In areas where industrial hemp cultivation has only recently been reintroduced, access to necessary processing equipment may be an impediment to effective and profitable cultivation of the crop. In this case it may be desirable to initially grow short seed varieties which are able to be harvested with a grain combine. In such a market, the seeds will be highly sought after and low value hemp stalk material is minimized. In fact, the stalks may simply be shredded and used for concrete aggregate without removing the bast fiber. The included fiber increases the strength and durability of the concrete. Industrial hemp is processed in many different ways depending on the intended use of the raw materials. In many cases it is simply winrowed, or cut and piled into rows in the field. The stalks are then left to field ret, a process which utilizes natural bacteria and fungus to consume the gluelike substances surrounding the fiber. Once retted, the stalks are collected, usually by bailing, and transported to the processing facility for separation of the fiber from the hurds, a process called decortication. Other methods of removing the lignin and pectin gluing the fibers to the stalks include water retting, where the stalks are submersed in water for an extended period of time, or they are processed after harvest using chemicals and/or steam to rapidly separate the fibers. Most retted hemp obtains a brown, ruddy, or bluish tint left behind by the biological processes which consumed the lignin and pectin in the industrial hemp stalks. Modern techniques, including specialized harvesting equipment, have demonstrated that it is possible to decorticate in the field at the point of harvest. This process removes the bast fiber while the plants are still wet. If the moisture is squeezed from the fiber with rollers prior to bailing then biological activity is minimized and the color of the fibers remains extremely white in comparison to retted industrial hemp fibers. Seed collection is generally done at the point of harvest. Short seed varieties are able to use a grain combine to separate the hemp seed from the stalks. Tall varieties which produce seed require equipment designed to remove and process the tops of the stalks prior to cutting the base. Corn harvesting equipment has been modified by some for use with tall industrial hemp varieties that produce seeds.
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Chapter 6: Processing Industrial Hemp Once harvested, the various raw materials are processed into both industrial and retail products. Each of the raw materials must be looked at independently since they all serve very different purposes.
Decortication Industrial hemp is often decorticated prior to processing, however in some regions where processing equipment is not common there will be local trade in unprocessed hemp stalks. These will need to be decorticated and the raw materials sold to buyers or returned to the producer of the hemp. This is the first stage of processing even if performed at the point of harvest. The decorticator consists of a machine designed to crush the hemp stalk which breaks up the inner brittle core while leaving the outer bast fiber mostly intact. This allows the chunks of hurds to be rapidly separated from the fiber.
Fiber The long bast fiber of industrial hemp is used for textiles, cordage, insulation, and various specialty materials. Depending on the use, the fiber may need to be washed to remove the nonfiber content. Then the fiber is spun into thread and woven into textiles, or it can be made into mats by felting. These are each described below, along with other fiber processing methods.
Degumming Most industrial hemp fiber is washed in a process called degumming which removes the lignin and pectin, as well as remaining chlorophyl and other water soluble substances which remain attached to the fiber. This separates the fibers from one another and gives the material a softer and fluffier feel. Without degumming the fiber will be Figure 15: (A) Unprocessed, like the hemp twine that is commonly and (B) opened hemp fiber available. The color is brownish and the ready for spinning. texture is very coarse. The method of retting also tends to affect the color and texture of the final product. Industrial hemp which is harvested and processed green will have the lightest color, with field and water retting each imparting a ruddy or bluish hue to the fibers, depending on the types of biological processes Figure 16: (A) Unprocessed and organisms which consume the nonfiber portions of the stalks and fiber made into hemp twine, leave behind residues which stain the fiber. (B) degummed fiber machine Degumming generally uses hot water or steam combined with various spun into textile yarn. chemicals, such as washing soda, to clean and separate the fibers. The fibers may also be put under pressure to decrease the required processing time. In addition to degumming, the fiber is often bleached. While industrial hemp is frequently bleached with chlorine, the natural fiber responds well to nonchlorine bleaching methods including the use of
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Basics of Industrial Hemp hydrogen peroxide and ultraviolet light. Reducing the use of chlorine in the processing of textiles is beneficial to the environment.
Spinning Industrial hemp thread and yarn is made by spinning the long bast fibers together. Yarn can be made from degummed bast fiber through the process of machine or hand spinning, however finer threads are generally made by machine spinning. The spinning process imparts twist into the fibers and in effect tangles the fibers against each other. This makes a string that is longer than any of the individual fibers by overlapping multiple fibers. Multiple strands of this singleply string are bound around each other by imparting twist into each strand and then allowing the strands to twist themselves around each other. This increases the overall strength and decreases the tendency of the cord to come unraveled. These multipleply strands can then be made into even larger cords through the same process of plying. The spinning process starts by taking the washed and degummed hemp fiber and combs it in a machine called an opener. This machine has many drums covered with fine metal pins, called the clothing. These drums spin and the pins separate and align the fibers in the same direction, preparing them to be spun into yarn or thread. The opener also removes clumps of fibers and pieces of plant matter still clinging to the fibers. The result of opening is called sliver (pronounced slyver, like “diver”), which is a loose bundle of fiber all aligned in the same direction. This sliver is then stretched and very slightly twisted into an extremely coarse yarn called roving. This fluffy singleply roving is then stretched and spun even further to decrease its diameter and increase its strength. These drawnout strands are then spun together to make yarn and thread which can be woven into fabrics, used for other industrial purposes, or sold for domestic crafts such as sewing, hand knitting, and crochet. Hand spinning can be accomplished using either the sliver or the roving produced through traditional mechanized processing. The retted and washed hemp fibers are also able to be cleaned and carded by hand to produce a completely handmade yarn. In some regions this is the primary method of processing hemp fibers for yarn production, however in industrialized regions even hand spinners generally choose to start with commercially available sliver or roving.
Figure 17: Comparison of hemp fiber: unprocessed, degummed & opened sliver, and roving (bottom).
Weaving The textile yarn produced by spinning can then be woven on hand looms, or more commonly in industrialized regions, with mechanical looms. The types and varieties of fabric which are made from industrial hemp are numerous and range from coarse sackcloth to extremely fine linens and soft, absorbent materials.
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Chapter 6: Processing Industrial Hemp Industrialquality materials, such as sackcloth, are generally made from fairly low grades of industrial hemp. The brown color and rough texture are not a factor in these use cases. Durable, consumer grade fabrics can be made from fibers of average quality. These include fabrics rated for outdoor or automotive use, dust covers, draperies and many other applications. These fabrics are often dyed or plastic coated and could frequently use unbleached, natural colored fiber. The finest processed fibers can be made into soft and durable fabrics including terry, fleece, and jersey knit cloth. These are used to make luxurious bath towels and robes, sweaters, sleep ware, and fine bed linens. This demonstrates the versatility of industrial hemp fiber.
Figure 18: Three types of hemp fabrics: fleece, canvas, burlap (bottom).
Felting Hemp fiber is made into mats using many different methods. Felting refers to the process of making nonwoven web, or a continuous sheet of material, without weaving, knitting, or stitching the fibers together. The traditional method of felting used Figure 19: Felt mat made for both animal and vegetable fibers involves the use of water, heat, and friction from unprocessed hemp fiber. to bind and tangle the fibers together into a mat. Modern methods include steam and friction, but also include the use of chemical adhesives or the addition of synthetic fiber which allows heat bonding of the fiber blend. Felted hemp material may remain flexible, as in the case of upholstery Figure 20: Magnified view of felted hemp shows shiny batting , or may be very rigid, as in interior automotive panels and trim components. synthetic binder fibers.
Specialty Materials Research at the University of Alberta has demonstrated the ability of hemp fiber to be processed with heat and pressure to produce a substance similar to graphene, which is a highly specialized and costly substance with unique chemical and electrical characteristics. Researchers have recently demonstrated how a hempbased carbon nanomaterial has similar properties to much more costly graphene. Industrial hemp fiber, when grown and processed properly, is similar in strength to carbon fiber and has been demonstrated as a replacement for carbon fiber mats in composite construction methods. It is also lighter than both carbon fiber and fiberglass, making the lightweight materials even lighter.
Hurds Although industrial hemp hurds can be used without any processing for many applications, such as animal bedding, even in these cases it is often preferable that the particle size is fairly uniform. In other cases it is essential that the particles are of similar size and shape, such as in
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Figure 21: Hemp hurds.
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Basics of Industrial Hemp paper pulping where various sized particles require different amounts of time to achieve the desired consistency. Once shredded with a hammermill to produce a uniform particle size, the hemp hurds are processed in a variety of different ways. They may be pelletized into small, dense pellets or pulped to make industrial paper pulp which is sold to paper producers. The unprocessed hemp hurds are able to be bailed or compressed into bricks for transportation.
Shredding The first step in processing industrial hemp hurds is to use a hammermill designed to recirculate the hurds through a chopping blade until they fit through a specific sized screen. This ensures a maximum particle size, however it often produces dust and other smaller particles which may not be suitable for the desired purpose. In this case the shredded hurds are screened to remove this dust.
Pelletizing Industrial hemp hurds are of very low density. This makes them expensive to transport over significant distances. Compressing the hurds into small pellets makes them much more dense and increases the cost effectiveness of transportation. Hemp hurds are compressed in a pellet mill. This machine is loaded with shredded hemp hurds and a heavy roller presses them through a thick metal plate with the desired diameter holes drilled through it, called the die. The particles adhere to each other from the force of being compressed in the die and cylindrical pellets are formed. The size of pellets depends on the desired use. Pellets of about 67mm (1/4 inch) make superior animal bedding to that made from unpelletized hemp hurds, especially because they expand to absorb urine. A small pellet size is also easier to reconstitute for the purpose of pulping or molding in forms. A larger pellet size may be desirable for an industrial fuel. A smaller pellet will burn faster, and may be suitable for home heating and small scale industrial uses. As hurds are a plentiful byproduct of industrial hemp cultivation their use as a fuel for heat and energy production will increase.
Bailing Unprocessed industrial hemp hurds are able to be bailed into compressed bails or bricks which are more cost effective to transport. These bails often shed hurds during transport making it necessary to wrap them in hemp sackcloth. Depending on the intended use of the bailed hurds it is feasible to use plastic or paper material to wrap the bail or brick and prevent shedding, for example when packaging for retail distribution. Bails of hurds may eventually be used by the concrete industry as an aggregate in regions without much industrial hemp cultivation. Industries such as those producing building materials or using hemp hurds as feedstock for biofuel production may prefer bailed hemp to pellets depending on their needs.
Forming Hurds are able to be formed into nearly any shape by coating the hurds in adhesive and pressing them into a form. The adhesive is often a thermoset resin, or a glue that becomes solid from the
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Chapter 6: Processing Industrial Hemp application of heat. This allows removal of the item from the form almost immediately and significantly decreases the cycle time when compared to solvent based resin curing times. The most common item formed from hemp hurds is hempbased particle board. The resulting product has been found to be as strong as conventional particle board while being much lighter. While hemp particle board is common in regions with established industrial hemp markets, multiple attempts in the U.S. to produce hempbased particle board have so far been unsuccessful due to the high cost of importing hurds. As industrial hemp cultivation increases in the U.S. and hemp hurds become more economical, many of the existing particle board manufacturers in the region will likely begin producing hemp based Figure 22: Particle board composite products. Standards and building codes must also be updated made from hemp hurds. to include hemp based materials before widespread adoption, and therefore demand for a product is realized. The extremely low cost of the material will likely be a driving factor, and may encourage new manufacturers to enter the market.
Pulping Industrial hemp hurds are pulped in a paper beater using mechanical force to open and hydrate the fibers, or are pulped chemically with caustic soda to form cellulose pulp. While it is difficult to overbeat using a mechanical beater, it is very easy to over treat chemical pulp. It is also important to start with hemp hurds of uniform size when using chemicals to make paper pulp to ensure that all particles are processed evenly. The pulp may be made directly into paper or it may be made into dried paper pulp which is sold to paper producers. This type of pulp is preferred by paper makers because it reconstitutes with little effort and is generally of a known and consistent quality.
Figure 23: Recycled paper pulp containing 10% hemp.
Seed Hemp seed is generally removed from the stalk at the time of harvest and cleaned to remove debris and plant material. Once the seeds are cleaned they may be sold as viable seed, if the local laws allow, or may be further processed to produce various industrial, agricultural and retail products.
Viable Seed Stock Seeds, whether viable or sold as grain, must be cleaned before they are ready for sale. The seed itself does not contain any significant cannabinoids internally, however the flowering portion of the plant has the highest concentration of cannabinoids. Without cleaning, the seeds will be coated in a film rich in cannabinoids.
Figure 24: Dried hemp seedheads ready for cleaning.
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Basics of Industrial Hemp Seed cleaning machines vary in design, however their primary purpose is to separate the remaining plant matter and immature seeds from the heavier mature seeds. A seed cleaning device suitable for cleaning hemp seeds must agitate the seeds sufficiently enough to remove the waxy coating. In some regions where local cultivation and transfer of viable hemp seed is authorized, yet national laws restrict importing certified hemp seed, uncertified local seed stock may be the only source available to industrial hemp growers. While it would be unwise to rely on import restrictions for long term profitability, this legal imbalance may temporarily boost the local value of uncertified seeds. When certified seed stock is used and the crop is grown according to the guidelines of the seed supplier, the resulting seeds may potentially be able to be sold as the same variety. Seed certification and other registrations may be necessary in order to transport seeds outside of the local jurisdiction, such as the state or country. To avoid the complexities of seed certification, many farmers may wish to keep only as much hemp seed as necessary to replant their own crops and convert the remainder into hemp grain, hearts, seed oil, or other nonviable hemp seed products which are traded with fewer restrictions.
Hemp Grain While viable industrial hemp seed can be used as grain, hemp seed sold for grain is generally heat sterilized to prevent its germination. This makes the grain suitable for import into countries that have strict limits on importing viable industrial hemp seed. There are multiple methods of sterilizing hemp seeds, however the heat treatment method has become the most common. The seeds are subjected to a brief but intense burst of heat which causes cracks to form in their hulls. Seeds processed in a manner that removes the hull or causes the seed to be crushed do not require heat sterilization because the seeds are no longer viable after this process. However, many producers sterilize all hemp seed sold as grain regardless of whether it is to be exported. For this reason it is impossible to know whether hemp seed products have been subjected to heat treatment unless the producer is also the grower and specifically states low temperature production methods were used.
Figure 25: Hemp seed grain.
Hearts The shells of the hemp seeds are removed leaving behind the soft interior called the heart. This is done with a huller, or seed decorticator. This device has the same name as the fiber decorticator used to separate the bast fiber from the hurds. This is because it removes the fibrous hull from the soft interior, performing the same function on the seeds as the fiber decorticator does to the stalks. These hemp hearts are sold as a food and as a nutritional supplement for their high protein content and their healthy balance of omega3 to omega6 essential fatty acids which happens to be the optimal ratio recommended for human nutrition.
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Figure 26: Hulled hemp seeds, also called hearts.
Chapter 6: Processing Industrial Hemp
Hemp Seed Oil Industrial hemp seeds are pressed in an oil expeller or are crushed and the hemp oil extracted with solvents. Due to the high demand for food grade hemp oil, the expeller method is most common. Hemp seed oil begins to break down at 50°C (121°F). To maintain optimal health benefits the oil should be extracted below this temperature. Hemp seed oil is used in many industries and can be used similarly to other vegetable oils. This makes chemical extraction feasible when performed in a closed loop system which utilizes solvent recycling. Many different solvents are able to be used and range from various alcohols and hexanes, to supercritical solvents such as liquid carbon dioxide or butane. When carefully purged of solvent using a vacuum chamber these oils are of high purity, however they are generally not used for food grade applications without further refinement, with the exception of liquid carbon dioxide which is a food grade solvent. Hydrogenated hemp seed oil can be used as a biofuel similar to diesel. The raw hemp seed oil is generally refined and filtered. It is then processed with hydrogen gas to convert less combustible materials in the oil into hydrocarbons which produce much less residue and fouling in the engine.
Meal and Cake The hulls produced in the production of hemp hearts and the solid matter remaining after pressing, called seed cake, are high in dietary fiber, protein and other vitamins and minerals. These byproducts are sold to animal feed producers without further processing as a nutritional ingredient in their feeds. The seed cake is also ideal for adding to wood fuel pellets or for compression into manufactured fire starter logs due to its remaining oil content.
Extracts The essential oils which are extracted from the flowers and other parts of the plant including the roots are extracted using physical or solvent based methods. Both dry and wet screening is effective at separating the cannabinoids secreted by glands on the plant surface, as they are generally within a specific range of particle sizes. The substances within the membranes of the plant generally require some type of solvent extraction. Nonpolar (oil dissolving) solvents are also effective at extracting the oils while leaving behind the undesirable water soluble and insoluble substances. This however comes with a price, as most solvents do not cleanly evaporate, leaving some amount of solvent remaining in the extract. This makes solvents which are a gas at room temperature preferable in many cases to using liquid solvents. The industrial hemp plant matter from which the extraction will be made is generally dried, although this is not a strict requirement of all extraction methods. Fully drying, or curing, the plant material changes the makeup and composition of the cannabinoids within it. Depending on the type of substance being extracted this may make either fresh or fully cured industrial hemp preferable for that specific purpose. The industrial hemp plant matter is generally ground into uniform sized pieces and placed within an extraction vessel or column. In crude setups this may be as simple as a beaker or canning jar, while in scientific or industrial settings it is generally a glass or stainless steel column of sufficient size to hold the material necessary for one extraction batch.
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Basics of Industrial Hemp Solvent is generally added to the top of the column and the plant material is saturated thoroughly. In most cases all of the resulting extract is combined, however in some instances it is possible to use the mobility, or the speed at which the substance travels through the column, to fraction the resulting fluid into separate parts. Each part would then have differing dominant cannabinoids and other solutes, allowing for the selection or removal of specific substances from the final extract. Other methods, such as supercritical carbon dioxide extraction, or closed loop systems which recycle the solvent, resemble the previously described liquid solvent extraction method, however the system is designed to operate under pressure. This causes the solvent to remain liquid at higher temperatures. Or in closed loop systems, to cycle through low and high pressure phases causing the solvent to evaporate off into a gas and then recondense into a liquid for repeated extraction with a small amount of solvent. While solvent extraction is today the most popular method of extracting oils from plant material, one of the oldest and still practiced methods of collecting the cannabinoidrich terpenes from cannabis is through screening the plant material to isolate a specific particle size. Industrial hemp plants are covered on most surfaces with glands called trichomes which secrete cannabinoid rich spheres at their tips. These trichomes and the waxy spheres they produce fall within a specific particle size and can be collected by sieving or screening. The plant material is often Figure 27: Hemp seed pod showing blended into a slurry with extremely cold water to aid in the screening process, however dry screening is also common. trichomes. The concentrated extracts resulting from some methods are of a higher purity than others. Some may require refining into more and more specific substances as necessary. Specialized lab processes allow for the isolation of substances such as CBD to above 99% purity.
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