This article is about the cultivation and uses of industrial hemp, not its psychoactive variant, Cannabis (drug). For the biology of the plant, see Cannabis. For other uses of the word hemp, see Hemp (disambiguation).

Hemp (from Old English hænep, see cannabis (etymology)) is the common name for plants of the entire genus Cannabis, although the term is often used to refer only to Cannabis strains cultivated for industrial (non-drug) use.

Industrial hemp has been tried for many uses, including paper, textiles, biodegradable plastics, construction, health food, and fuel^[1], with modest commercial success.^[2] In the past three years, commercial success of hemp food products has grown considerably. ^[3][4]

Hemp is one of the fastest growing biomasses known,^[5] producing upto 25 tonnes of dry matter per hectare per year,^[6] and one of the earliest domesticated plants known.^[7] For a crop, hemp is relatively environmentally friendly as it requires few pesticides^[8] and no herbicides.^[9]

Cannabis sativa L. subsp. sativa var. sativa is the variety grown for industrial use in Europe, Canada, and elsewhere, while C. sativa subsp. indica generally has poor fiber quality and is primarily used for production of recreational and medicinal drugs. The major difference between the two types of plants is the appearance and the amount of Δ⁹-tetrahydrocannabinol (THC) secreted in a resinous mixture by epidermal hairs called glandular trichomes. Strains of Cannabis approved for industrial hemp production produce only minute amounts of this psychoactive drug, not enough for any physical or psychological effects. Typically, Hemp contains below 0.3% THC, while Cannabis grown for marijuana can contain anywhere from 6 or 7 % to 20% or even more.

Industrial hemp is produced in many countries around the world ^[10]. Major producers include Canada, France, and China. While more hemp is exported to the United States than to any other country, the United States Government does not consistently distinguish between marijuana and the non-psychoactive Cannabis used for industrial and commercial purposes.

Uses

Hemp is used for a wide variety of purposes, including the manufacture of cordage of varying tensile strength, clothing, and nutritional products. The bast fibers can be used in 100% hemp products, but are commonly blended with other organic fibers such as flax, cotton or silk, for apparel and furnishings, most commonly at a 55%/45% hemp/cotton blend. The inner two fibers of hemp are more woody, and are more often used in non-woven items and other industrial applications, such as mulch, animal bedding and litter. The oil from the fruits ("seeds") dries on exposure to air (similar to linseed oil) and is sometimes used in the manufacture of oil-based paints, in creams as a moisturizing agent, for cooking, and in plastics. Hemp seeds have been used in bird seed mix.^[11]. Hempseed is also widely used as a fishing bait.

Food

Hemp seeds contain all the essential amino acids and essential fatty acids necessary to maintain healthy human life^[12]. The seeds can be eaten raw, ground into a meal, sprouted, made into hemp milk (akin to soy milk), prepared as tea, and used in baking. The fresh leaves can also be eaten in salads. Products range from cereals to frozen waffles, hemp tofu to nut butters. A few companies produce value added hemp seed items that include the seed oils, whole hemp grain (which is sterilized as per international law), hulled hemp seed (the whole seed without the mineral rich outer shell), hemp flour, hemp cake (a by-product of pressing the seed for oil) and hemp protein powder. Hemp is also used in some organic cereals, for non-dairy milk^[13] somewhat similar to soy and nut milks, and for non-dairy hemp "ice cream."^[14]

Within the UK, the Department for Environment, Food and Rural Affairs (Defra) has treated hemp as purely a non-food crop. Seed appears on the UK market as a legal food product, and cultivation licenses are available for this purpose. In North America, hemp seed food products are sold in large volumes, particularly from Canada to the USA, and typically in health food stores or through mail order.^[15]

Nutrition

About 30–35% of the weight of hempseed is hemp oil, an edible oil that contains about 80% essential fatty acids (EFAs); i.e., linoleic acid, omega-6 (LA, 55%), alpha-linolenic acid, omega-3 (ALA, 22%), in addition to gamma-linolenic acid, omega-6 (GLA, 1–4%) and stearidonic acid, omega-3 (SDA, 0–2%). Hempseed also contains about 20% of a highly-digestible protein, where 1/3 is edestin and 2/3 are albumins. Its amino acid profile is close to "complete" when compared to more common sources of proteins such as meat, milk, eggs and soy.^[16] The proportions of linoleic acid and alpha-linolenic acid in one tablespoon (15 ml) per day of hempseed oil easily provides human daily requirements for EFAs. Unlike flaxseed oil, hempseed oil can be used continuously without developing a deficiency or other imbalance of EFAs.^[17] This has been demonstrated in a clinical study, where the daily ingestion of flaxseed oil decreased the endogenous production of GLA.^[18]

Hempseed is an adequate source of calcium and iron. Whole, toasted hempseeds are also a good source of phosphorus, magnesium, zinc, copper and manganese.

Hempseed contains no gluten and therefore would not trigger symptoms of celiac disease.

Storage

Hempseed oil is a highly unsaturated oil. It can spontaneously oxidize and turn rancid within a short period of time if not stored properly. Hempseed oil is best stored in a dark glass bottle, in a refrigerator or freezer (its freezing point is -20C) Preservatives (antioxidants) are not necessary for high quality oils that are stored properly. Highly unsaturated oils are unsuitable for frying

Dietary supplement

Hempseed oil has been shown to relieve the symptoms of eczema (atopic dermatitis).^[19]

Medicine

Hemp seed oil has anti-inflammatory properties.^[20]

Fiber

The fiber is one of the most valuable parts of the hemp plant. It is commonly called bast, which refers to the fibers that grow on the outside of the woody interior of the plant's stalk, and under the outer most part (the bark). Bast fibers give the plants strength. Hemp fibers can be 0.91 m (3 ft) to 4.6 m (15 ft) long, running the length of the plant. Depending on the processing used to remove the fiber from the stem, the hemp may naturally be creamy white, brown, gray, black or green.^{[citation needed]}

The use of hemp for fiber production has declined sharply over the last two centuries, but before the industrial revolution, hemp was a popular fiber because it is strong and grows quickly; it produces 250% more fiber than cotton and 600% more fiber than flax when grown on the same land.^{[citation needed]} Hemp has been used to make paper. It was used to make canvas, and the word canvas derives from cannabis.^[21][22] Hemp was very popular as it had many uses. Abaca or Manila replaced its use for rope. Burlap, made from jute, took over the sacking market. The paper industry began using wood pulp. The carpet industry switched over to wool, sisal, and jute, then nylon. Netting and webbing applications were taken over by cotton and synthetics.

Building material

In Europe and China, hemp fibers have been used in prototype quantities to strengthen concrete, and in other composite materials for many construction and manufacturing applications^[23]. See Hempcrete.

Composite materials

A mixture of fiberglass, hemp fiber, kenaf, and flax has been used since 2002 to make composite panels for automobiles. ^[24][25] The choice of which bast fiber to use is primarily based on cost and availability.

Paper

There is a niche market for hemp paper. World hemp paper pulp production was believed to be around 120,000 tons per year in 1991 which was about 0.05% of the world's annual pulp production volume.^[2] The cost of hemp pulp is approximately six times that of wood pulp,^[2] mostly due to the small size and outdated equipment of the few hemp processing plants in the Western world. Hemp pulp is bleached with hydrogen peroxide, which can also be used for wood pulp. Kenaf is another fast-growing plant which can be used as a replacement for wood pulp. Kenaf paper has been produced in commercial quantities.^[26]

In 1916, US Department of Agriculture chief scientists Lyster H. Dewe, and Jason L. Merrill created paper made from hemp pulp, which they concluded was "favorable in comparison with those used with pulp wood."^[27] [5] Jack Herer later summarized the findings of the bulletin in his book The Emperor Wears No Clothes.^[28] Herer wrote:

In 1916, USDA Bulletin No. 404, reported that one acre of cannabis hemp, in annual rotation over a 20-year period, would produce as much pulp for paper as 4.1 acres (17,000 m²) of trees being cut down over the same 20-year period. This process would use only 1/4 to 1/7 as much polluting sulfur-based acid chemicals to break down the glue-like lignin that binds the fibers of the pulp, or none at all using soda ash. The problem of dioxin contamination of rivers is avoided in the hemp paper making process, which does not need to use chlorine bleach (as the wood pulp paper making process requires) but instead safely substitutes hydrogen peroxide in the bleaching process...If the new (1916) hemp pulp paper process were legal today, it would soon replace about 70% of all wood pulp paper, including computer printout paper, corrugated boxes and paper bags.

^{[citation needed]}

New technology has allowed for more environmentally-friendly paper production from wood pulp, though the production of wood pulp paper still claims the one of the highest CO₂ emissions by industry (second only to concrete production)^{[citation needed]}. The recovery boiler was invented in the early 1930s. The first recovery boilers were commissioned to wood-pulp mills during the mid-1930s,^[29] ECF (Elemental Chlorine Free),^[30] or TCF (Total chlorine Free) bleaching, better fiber filters etc. has created less of a demand for alternative raw materials. Hemp is currently of little significance as raw material for paper; however, it is scarcely grown in the developed world. The long-term price for pulpwood has been low compared with any alternative except recycled paper. ^[31]

More about wood pulp technology in bleaching of wood pulp.

The decision of the United States Congress to pass the 1937 Marihuana Tax Act was based in part on testimony derived from articles in newspapers owned by William Randolph Hearst, who, some authors stress, had significant financial interests in the forest industry, which manufactured his newsprint.

The background material also included that from 1880 to 1933 the hemp grown in the United States had declined from 15,000 to 1,200 acres (4.9 km²), and that the price of line hemp had dropped from $12.50 per pound in 1914 to $9.00 per pound in 1933.^[32][33] In 1935, however, hemp would also make a significant rebound.^[33] Hearst began a campaign against hemp, and published stories in his newspapers associating hemp with marijuana^[34] and attacking marijuana usage.^[35] As a result of the act, the production and use of hemp was discontinued.

Fabric

A modest hemp fabric industry exists. Recent developments in processing have made it possible to soften coarse fibers to a wearable level. Characteristics of hemp fiber are its superior strength and durability, resistance to ultraviolet light and mold, comfort and good absorbency (8%).^{[citation needed]} The original Levi Strauss jeans were made from lightweight hemp canvas.

Cordage

Hemp rope is notorious for breaking due to rot as the capillary effect of the rope-woven fibers tended to hold liquid at the interior, while seeming dry from the outside.^[36] Hemp rope used in the age of sailing-ships was protected by tarring, a labor-intensive process (and source of the Jack Tar nickname for sailors). Hemp rope was phased out when Manila, which does not require tarring, became available. Manila is sometimes referred to as Manila hemp, but is not related to hemp; it is Abacá, a species of banana.

Animal bedding

Hemp shives are the core of the stem. In EU, they are used for bedding (horse bedding for instance), or for horticultural mulch.^[37] Industrial hemp is much more profitable if both fibers and shives (or even seeds) can be used.

Water and soil purification

Hemp can be used as a "mop crop" to clear impurities out of wastewater, such as sewage effluent, excessive phosphorus from chicken litter, or other unwanted substances or chemicals. Eco-technologist Dr. Keith Bolton from Southern Cross University in Lismore, New South Wales, Australia, is a leading researcher in this area. Hemp is being used to clean contaminants at Chernobyl nuclear disaster site.^[38]

Weed control

Hemp, because of its height, dense foliage and its high planting density as a crop, is a very effective and long used method of killing tough weeds in farming (by minimizing the pool of weed seeds of the soil).^[39] Using hemp this way can help farmers avoid the use of herbicides, to help gain organic certification and to gain the benefits of crop rotation per se.

Fuel

Biofuels such as biodiesel and alcohol fuel can be made from the oils in hemp seeds and stalks, and the fermentation of the plant as a whole, respectively.

Henry Ford grew industrial hemp on his estate after 1937,^[40] possibly to prove the cheapness of methanol production at Iron Mountain. He made plastic cars with wheat straw, hemp and sisal. (Popular Mechanics, Dec. 1941, "Pinch Hitters for Defense.") Filtered hemp oil can be used directly to power diesels. In 1892, Rudolph Diesel invented the diesel engine, which he intended to fuel "by a variety of fuels, especially vegetable and seed oils."^{[41][42][43][44]}

Cultivation

Millennia of selective breeding have resulted in varieties that look quite different. Also, breeding since circa 1930 has focused quite specifically on producing strains which would perform very poorly as sources of drug material. Hemp grown for fibre is planted closely, resulting in tall, slender plants with long fibers. Ideally, according to Britain's Department for Environment, Food and Rural Affairs, the herb should be harvested before it flowers. This early cropping is done because fibre quality declines if flowering is allowed and, incidentally, this cropping also pre-empts the herb's maturity as a potential source of drug material. However, in these strains of industrial hemp the tetrahydrocannabinol (THC) content would have been very low regardless.

The name Cannabis is the genus and was the name favored by the 19th century medical practitioners who helped to introduce the herb's drug potential to modern English-speaking consciousness. Cannabis for non-drug purposes (especially ropes and textiles) was then already well known as hemp.

The name "marijuana" is Spanish in origin and associated almost exclusively with the herb's drug potential.

Historical cultivation

Hemp has been grown for millennia in Asia and the Middle East for its fibre. Commercial production of hemp in the West took off in the eighteenth century, but was grown in the sixteenth century in eastern England.^[45] Due to colonial and naval expansion of the era, economies needed large quantities of hemp for rope and oakum. The endless European Wars, and ever expanding naval fleets, all used the material. To this end, the young United States of America became a large hemp producer. The Gulf and Carolina states had very large hemp industries. In fact the market was second only to cotton fibre. Machinery was invented in the United States for producing hemp fiber. An unpleasant task performed by prison labor was the manufacture of rope and boat caulking. Before the age of nylon rope, hemp rope had a short lifetime and was ever in need of replacement. In the 19th century it was cultivated by binders.

Harvesting

Smallholder plots are usually harvested by hand. The plants are cut at 2 to 3 cm above the soil and left on the ground to dry. Mechanical harvesting is now common, using specially adapted cutter-binders or simpler cutters.

The cut hemp is laid in swathes to dry for up to four days. This was traditionally followed by retting, either water retting (the bundled hemp floats in water) or dew retting (the hemp remains on the ground and is affected by the moisture in dew moisture, and by molds and bacterial action). Modern processes use steam and machinery to separate the fiber, a process known as thermo-mechanical pulping.

Varieties

There are broadly three groups of Cannabis varieties being cultivated today:

• Varieties primarily cultivated for their fiber, characterized by long stems and little branching, extreme red, yellow, blue or purple coloration, or thickness of stem and solid core, such as hemp cannabis oglalas, and more generally called industrial hemp.
• Varieties grown for seed from which hemp oil is extracted or which can be dehulled.
• Varieties grown for medicinal, spiritual development or recreational purposes.

A nominal if not legal distinction is often made between hemp, with concentrations of the psychoactive chemical THC far too low to be useful as a drug, and Cannabis used for medical, recreational, or spiritual purposes.

Diseases

Hemp plants can be vulnerable to various pathogens including bacteria, fungi, nematodes, viruses and other miscellaneous pathogens. Such diseases often lead to problems such as reduced fiber quality, stunted growth, and (eventually) death of the plant. Diseases rarely significantly affect the yield of the field, which is why hemp does not need the use of pesticides.

History

Hemp use dates back to the Stone Age, with hemp fibre imprints found in pottery shards in China and Taiwan^[46] over 10,000 years old. These ancient Asians also used the same fibers to make clothes, shoes, ropes, and an early form of paper.^[46] Contrary to the traditional view that Cai Lun invented paper in around 105 AD, specimens of hemp paper were found in the Great Wall of China dating back 200 years earlier.^{[citation needed]}

Hemp cloth was more common than linen until the mid 14th century.^{[citation needed]} The use of hemp as a cloth was centered largely in the countryside, with higher quality textiles being available in the towns. Virtually every small town had access to a hemp field.^{[citation needed]}

In late medieval Germany and Italy, hemp was employed in cooked dishes, as filing in pies and tortes, or boiled in a soup.^[47]

The traditional European hemp was by tradition and due to its low narcotic effect not used as a drug in Europe. It was cultivated for its fibers and for example used by Christopher Columbus for ropes on his ships.

The Spaniards first brought hemp to the Western Hemisphere and cultivated it in Chile starting about 1545.^[48]However, in May 1607, "hempe" (sic) was among the crops Gabriel Archer observed being cultivated by the natives at the main Powhatan village, where Richmond, Virginia is now situated^[49]; and in 1613, Samuell Argall reported wild hemp "better than that in England" growing along the shores of the upper Potomac. As early as 1619, the first Virginia House of Burgesses passed an Act requiring all planters in Virginia to sow "both English and Indian" hemp on their plantations^[50]. The Puritans are first known to have cultivated hemp in New England in 1645.^[48]

George Washington and Thomas Jefferson both cultivated hemp on their farms. Benjamin Franklin started the first American paper mill, which made paper exclusively from hemp, and the Declaration of Independence was drafted on paper made from hemp fibers.^[51]

In the Napoleonic era, many military uniforms were made of hemp.^{[citation needed]} While hemp linens were coarser than those made of flax, the added strength and durability of hemp, as well as the lower cost, meant that hemp uniforms were preferred.

Hemp was used extensively by the United States during WWII. Uniforms, canvas, and rope were among the main textiles created from the hemp plant at this time. Much of the hemp used was planted in the Midwest and Kentucky. Historically, hemp production made up a significant portion of Kentucky's economy and many slave plantations located there focused on producing hemp.^[52]

By the early twentieth century, the advent of the steam engine and the diesel engine ended the reign of the sailing ship. The advent of iron and steel for cable and ships' hulls further eliminated natural fibers in marine use, although hemp had long since fallen out of favor in the sailing industry in preference to Manila hemp. The invention of artificial fibers in the late thirties by DuPont further put strain on the market.

Countries that produce hemp

Over 30 countries produce industrial hemp including Australia, Austria, Canada, China, Great Britain, France, Russia and Spain.^[53]

From the 1950s to the 1980s the Soviet Union was the world's largest producer (3,000 km² in 1970). The main production areas were in Ukraine,^[54] the Kursk and Orel regions of Russia, and near the Polish border. Since its inception in 1931, the Hemp Breeding Department at the Institute of Bast Crops (Russian: Научно-исследовательский институт лубяных культур) in Hlukhiv (Glukhov), Ukraine, has been one of the world's largest centers for developing new hemp varieties, focusing on improving fiber quality, per-hectare yields, and low THC content.^[55][56]

Other important producing countries were China, North Korea, Hungary, the former Yugoslavia, Romania, Poland, France and Italy.

In Japan, hemp was historically used as paper and a fiber crop; it was restricted as a narcotic drug in 1948. The ban on marijuana imposed by the US authorities was alien to Japanese culture, as the drug had never been widely used in Japan before. There is archaeological evidence that cannabis was used for clothing and the seeds were eaten in Japan right back to the Jōmon period (10,000 to 300 BCE). Many Kimono designs portray hemp, or "Asa" (Japanese: 麻), as a beautiful plant.

France is Europe's biggest producer, with 8,000 hectares cultivated. Canada (9,725 ha in 2004),^[57] the United Kingdom, and Germany all resumed commercial production in the 1990s. British production is mostly used as bedding for horses; other uses are under development. The largest outlet for German fibre is composite automotive panels. Companies in Canada, UK, US and Germany among many others process hemp seed into a growing range of food products and cosmetics; many traditional growing countries still continue to produce textile grade fibre.

Hemp is illegal to grow in the U.S. under federal law due to its relation to marijuana. Some states have defied federal law and made the cultivation of industrial hemp legal. These states — North Dakota, Hawaii, Kentucky, Maine, Maryland, Montana, West Virginia, Vermont, and Oregon — have not yet begun to grow hemp due to resistance from the federal Drug Enforcement Administration.^[58]

Industrial growth under license

Licenses for hemp cultivation are issued in the European Union, Canada, in three states of Australia, and two states in the United States.^{[citation needed]}

In the United Kingdom, these licenses are issued by the Home Office under the Misuse of Drugs Act 1971. When grown for non-drug purposes hemp is referred to as industrial hemp, and a common product is fiber for use in a wide variety of products, as well as the seed for nutritional aspects as well as for the oil. Feral hemp or ditch weed is usually a naturalized fiber or oilseed strain of Cannabis that has escaped from cultivation and is self-seeding.

In Australia the states of Victoria, Queensland and most recently New South Wales issue licenses to grow hemp for industrial use. Victoria was an early adopter in 1998, and has reissued the regulation in 2008^[59]. Queensland has allowed industrial production under license since 2002^[60] where the issuance is controlled under the Drugs Misuse Act 1986^[61]. Most recently New South Wales now issues licenses^[62] under a law that came into effect as at the 6th of November 2008, the Hemp Industry Regulations Act 2008 (No 58)^[63].

Vermont and North Dakota have passed laws enabling hemp licensure. Both states are waiting for permission to grow hemp from the Drug Enforcement Agency (DEA). Currently, North Dakota representatives are pursuing legal measures to force DEA approval.^[64]

See also

• Cannabrick construction
• Hemp for Victory
• Hemp Industries Association
• Hempcrete
• Natural fibre
• Plant textiles

References