Hemp is the common name for a non-psychoactive variety of Cannabis sativa that is usually grown for industrial use. Cultivation licenses may be issued in the European Union and Canada. In the United Kingdom licences are issued by the Home Office under the Misuse of Drugs Act 1971. When grown for industrial purposes hemp is often called industrial hemp (or industrial cannabis), and a common product is fiber for use in a wide variety of products. Feral hemp, or ditchweed, is wild growing fiber or oilseed varieties of Cannabis that have escaped from cultivation, have naturalized, and are now self-seeding annuals.
Cannabis sativa subsp. sativa is the major hemp crop, while C. sativa subsp. indica has poor fiber quality, and is used for production of recreational and medicinal drugs. The chief difference lies in the amount of delta-9 tetrahydrocannabinol, or THC, secreted in resins from epidermal glands— the strains of Cannabis sativa used for industrial hemp production contain almost none of this resin while other varieties secrete significant amounts. Some botanists dispute these labels and more genetic analysis will be needed to gain consensus.
Hemp is used to make cordage of greatly varying tensile strength, clothing, food, and the oils from the seeds can be made into paint or used for cooking. In Europe and China hemp fibers are increasingly used in plasters and composites answering to many construction and manufacturing needs. Mercedes-Benz uses a "biocomposite" principally of hemp in the interior panels of some of its automobiles. Hemp use in the United States is severely depressed by laws supported by governmental drug enforcement bodies, which fear that high T.H.C. plants will be grown amidst the ultra-low T.H.C. plants used for hemp production. Efforts are underway to change these laws, allowing American farmers to compete in the growing markets for this crop. As of 2006, China controls roughly 40% of the world's hemp fiber. Hemp seeds are also found in wild bird seed mix.
70% of the Cannabis plant's total weight is made up of the 'hurd' or woody inner core. This part of the plant does not contain tetrahydrocannabinol (THC) and can be used in housing construction. The silica leached from soil by the plant combined with unslaked lime (calcium oxide) forms a chemical bond similar to cement which is both fire and waterproof.
Hemp (the seed) may be grown also for food. The seeds are comparable to sunflower seeds, and can be used for baking, like sesame seeds. Products range from cereals to frozen waffles. A few companies produce value added hemp seed items that include the oils of the seed, 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. Within the UK, the Department for Environment, Food and Rural Affairs (Defra) treats hemp as purely a non-food crop. Seed can and does appear on the UK market as a legal food product although cultivation licences are not available for this purpose. In North America, hemp seed food products are sold in small volume, typically in health food stores or by mail order.
30–35% of the weight of hempseed is oil containing 80% of the unsaturated essential fatty acids (EFAs), linoleic acid (LA, 55%) and Alpha-linolenic acid (ALA, 21–25%). These are not manufactured by the body and must be supplied by food. The proportions of linoleic acid and Alpha-linolenic acid in hempseed oil are perfectly balanced to meet human requirements for EFAs, including gamma-linoleic acid (GLA). Unlike flax oil and others, hempseed oil can be used continuously without developing a deficiency or other imbalance of EFAs. Hemp also contains 31% complete and highly-digestible protein, 1/3 as edestin protein and 2/3 as albumin protein. Its high quality Amino Acid composition is closer to "complete" sources of proteins (meat, milk, eggs) than all other oil seeds except soy.
The ALA contained in plant seed oils by itself is sufficient for nutrition, as the body is capable of converting it into other fatty acids. However, this conversion process is inefficient, and the broader spectrum of omega-3 fatty acids obtained from oily fish is easier for the body to immediately utilize (see fish and plants as a source of Omega-3).
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 was used to make the first pieces of fabric ever found and was therefore also used as the first material for paper (paper used to be made of rags). It was used to make canvas, and the word canvas itself is derived from cannabis. Hemp was very popular, and it had many uses. However, as other coarse-fibre plants were more widely grown, hemp fibre was replaced in most roles. Manila yielded better 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.
Hemp rope is notorious for breaking due to rot. Hemp rope rots from the inside out, and thus the rope looks good until it breaks. Hemp rope used in the age of sail was protected by tarring, a labor-intensive process and the reason for the Jack Tar nickname for sailors. Hemp rope was phased out when Manila, which does not require tarring, became available.
There is a niche market for hemp paper, but the cost of hemp pulp is approximately six times that of wood pulp, mostly due to the small size and outdated equipment of the few hemp processing plants in the Western world. Hemp pulp is processed with hydrogen peroxide, avoiding the sulphuric acid waste problem associated with wood pulping. Kenaf is another fast-growing plant which can be used as a replacement for wood pulp. Kenaf paper has been produced in commercial quantities since 1992.
A modest hemp clothing industry exists. Recent developments in processing have made it possible to soften up coarse fibres to a wearable level.
Hemp is very beneficial to the environment. It helps eliminate deforestation because it produces four times as much paper as trees and grows much faster (up to 16 feet in only 110 days). According to the American Hemp Historic Association, when hemp is nourished with milk, or any high calcium fluid, it grows stronger and faster. Hemp paper also can be bleached with little or no chemicals. Hemp also helps reduce the use of pesticides. Hemp is an ecologically friendly substitute for cotton and while cotton uses 25% of the Earth's pesticides, hemp does not need any. Cotton also requires heavy irrigation while hemp flourishes with very little watering.
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 fibre, a process known as thermo-mechanical pulping.
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.
In the Twenties, the early oil barons such as Rockefeller of Standard Oil, Rothschild of Shell, etc., became paranoically aware of the possibilities of Henry Ford's vision of cheap methanol fuel,* and they kept oil prices incredibly low - between one dollar and four dollars per barrel (there are 42 gallons in an oil barrel) until 1970 - almost 50 years! Prices were so low, in fact, that no other energy source could compete with it. Then, once they were finally sure of the lack of competition, the price of oil jumped to almost $40 per barrel over the next 10 years.
* Henry Ford grew marijuana on his estate after 1937, 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.") In 1892, Rudolph Diesel invented the diesel engine, which he intended to fuel "by a variety of fuels, especially vegetable and seed oils."
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 fibres. Ideally, according to Defra in 2004 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, even though the tetrahydrocannabinol (THC) content would still be very low with these strains of hemp.
The name Cannabis is the genus and was the name favoured 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. That marijuana is now well known in English as a name for drug material is due largely to the efforts of US drug prohibitionists during the 1920s and 1930s.
There are broadly three groups of Cannabis varieties being cultivated today:
* Varieties primarily cultivated for their fibre, characterized by long stems and little branching, called industrial hemp
* Varieties grown for seed from which hemp oil is extracted
* Varieties grown for medicinal 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.
While the fibre has been grown for millenia in Asia and the Middle East, commercial production of hemp in the West took off in the eighteenth century. 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 Republic 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 fibre. An unpleasant task performed by prison labour 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.
'"From the 1881 Household Cyclopedia':
The soils most suited to the culture of this plant are those of the deep, black, putrid vegetable kind, that are low, and rather inclined to moisture, and those of the deep mellow, loamy, or sandy descriptions. The quantity of produce is generally much greater on the former than on the latter; but it is said to be greatly inferior in quality. It may, however, be grown with success on lands of a less rich and fertile kind by proper care and attention in their culture and preparation.
In order to render the grounds proper for the reception of the crop, they should be reduced into a fine mellow state of mould, and be perfectly cleared from weeds, by repeated ploughings. When it succeeds grain crops, the work is mostly accomplished by three ploughings, and as many harrowings: the first being given immediately after the preceding crop is removed, the second early in the spring, and the last, or seed earth, just before the seed is to be put in. In the last ploughing, well rotted manure, in the proportion of fifteen or twenty, or good compost, in the quantity of twenty-five or thirty-three horse-cart loads, should be turned into the land; as without this it is seldom that good crops can be produced. The surface of the ground being left perfectly flat, and as free from furrows as possible; as by these means the moisture is more effectually retained, and the growth of the plants more fully promoted.
It is of much importance in the cultivation of hemp crops that the seed be new, and of a good quality, which may in some measure be known by its feeling heavy in the hand, and being of a bright shining color.
The proportion of seed that is most commonly employed, is from two to three bushels [per acre], according to the quality of the land; but, as the crops are greatly injured by the plants standing too closely together, two bushels, or two bushels and a half may be a more advantageous quantity.
As the hemp plant is extremely tender in its early growth, care should be taken not to put the seed into the ground at so early a period, as that it may be liable to be injured by the effects of frost; nor to protract the sowing to so late a season as that the quality of the produce may be effected. The best season, on the drier sorts of land in the southern districts, is as soon as possible after the frosts are over in April; and, on the same descriptions of soil, in the more northern ones, towards the close of the same month or early in the ensuing one.
The most general method of putting crops of this sort into the soil is the broadcast, the seed being dispersed over the surface of the land in as even a manner as possible, and afterwards covered in by means of a very light harrowing. In many cases, however, especially when the crops are to stand for seed, the drill method in rows, at small distances, might be had recourse to with advantage; as, in this way, the early growth of the plants would be more effectually promoted, and the land be kept in a more clean and perfect state of mould, which are circumstances of importance in such crops. In whatever method the seed is put in, care must constantly be taken to keep the birds from it for some time afterwards.
This sort of crop is frequently cultivated on the same piece of ground for a great number of years, without any other kind intervening; but, in such cases, manure must be applied with almost every crop, in pretty large proportions, to prevent the exhaustion that must otherwise take place. It may be sown after most sorts of grain crops, especially where the land possesses sufficient fertility, and is in a proper state of tillage.
As hemp, from its tall growth and thick foliage, soon covers the surface of the land, and prevents the rising of weeds, little attention is necessary after the seed has been put into the ground, especially where the broadcast method of sowing is practised; but, when put in by the drill machine, a hoeing or two may be had recourse to with advantage in the early growth of the crop.
In the culture of this plant, it is particularly necessary that the same piece of land grows both male and female, or what is sometimes denominated simple hemp. The latter kind contains the seed.
When the grain is ripe (which is known by its becoming of a whitish-yellow color, and a few of the leaves beginning to drop from the stems); this happens commonly about thirteen or fourteen weeks from the period of its being sown, according as the season may be dry or wet (the first sort being mostly ripe some weeks before the latter), the next operation is that of taking it from the ground; which is effected by pulling it up by the roots, in small parcels at a time, by the hand, taking care to shake off the mould well from them before the handsful are laid down. In some districts, the whole crop is pulled together, without any distinction being made between the different kinds of hemp; while, in others, it is the practice to separate and pull them at different times, according to their ripeness. The latter is obviously the better practice; as by pulling a large proportion of the crop before it is in a proper state of maturity, the quantity of produce must not only be considerably lessened, but its quality greatly injured by being rendered less durable.
After being thus pulled, it is tied up in small parcels, or what are sometimes termed baits.
Where crops of this kind are intended for seeding, they should be suffered to stand till the seed becomes in a perfect state of maturity, which is easily known by the appearance of it on inspection. The stems are then pulled and bound up, as in the other case, the bundles being set up in the same manner as grain, until the seed becomes so dry and firm as to shed freely. It is then either immediately threshed out upon large cloths for the purpose in the field, or taken home to have the operation afterwards performed.
The hemp, as soon as pulled, is tied up in small bundles, frequently at both ends.
It is then conveyed to pits, or ponds of stagnant water, about six or eight feet in depth, such as have a clayey soil being in general preferred, and deposited in beds, according to their size, and depth, the small bundles being laid both in a straight direction and crosswise of each other, so as to bind perfectly together; the whole, being loaded with timber, or other materials, so as to keep the beds of hemp just below the surface of the water.
It is not usual to water more than four or five times in the same pit, till it has been filled with water. Where the ponds are not sufficiently large to contain the whole of the produce at once, it is the practice to pull the hemp only as it can be admitted into them, it being thought disadvantageous to leave the hemp upon the ground after being pulled. It is left in these pits four, five, or six days, or even more, according to the warmth of the season and the judgment of the operator, on his examining whether the hempy material readily separates from the reed or stem; and then taken up and conveyed to a pasture field which is clean and even, the bundles being loosened and spread out thinly, stem by stem, turning it every second or third day, especially in damp weather, to prevent its being injured by worms or other insects. It should remain in this situation for two, three, four, or more weeks, according to circumstances, and be then collected together when in a perfectly dry state, tied up into large bundles, and placed in some secure building until an opportunity is afforded for breaking it, in order to separate the hemp. By this means the process of grassing is not only shortened, but the more expensive ones of breaking, scutching, and bleaching the yarn, rendered less violent and troublesome.
After the hemp has been removed from the field it is in a state to be broken and swingled, operations that are mostly performed by common laborers, by means of machinery for the purpose, the produce being tied up in stones. The refuse collected in the latter process is denominated sheaves, and is in some districts employed for the purposes of fuel. After having undergone these different operations, it is ready for the purposes of the manufacturer.
Hemp use dates back to the Stone Age, with hemp fibre imprints found in pottery shards in China and Taiwan over 10,000 years old. These ancient Asians also used the same fibres to make clothes, shoes, ropes, and an early form of paper.
Hemp cloth was more common than linen until the mid 14th century. 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.
In late medieval Germany and Italy hemp was employed in cooked dishes, as filing in pies and tortes, or boiled in a soup.
Thomas Jefferson drafted the United States Declaration of Independence on hemp paper.
In the Napoleonic era, many military uniforms were made of hemp. 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.
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 ship's hulls further eliminated natural fibers in marine use. The invention of artificial fibers in the late thirties by DuPont further put strain on the market. It is documented that DuPont lobbied the government to make Cannabis a Class 1 drug, a narcotic, in order to vilify by association hemp, and effect the transfer to polyester ropes.
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, the Kursk and Orel regions of Russia, and near the Polish border.
Other important producing countries were China, North Korea, Hungary, the former Yugoslavia, Romania, Poland, France and Italy.
Canada, 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, USA and Germany among many others are processing hemp seed into a growing range of food products and cosmetics; many traditional growing countries still continue with textile grade fibre production. However, hemp is illegal to freely grow in the US because the plant is related to Marijuana. The US is the only industrialized country where hemp is illegal to grow.
In the last decade hemp has been widely promoted as a crop for the future. This is stimulated by new technologies which make hemp suitable for industrial paper manufacturing, use as a renewable energy source (biofuel), and the use of hemp derivatives as replacement for petrochemical products.
Hemp Plastic is a new technology based on 20-100% hemp fibre based plastics that can be moulded or injection moulded. The use of fibre reinforced composites and other natural plastics are expected to become more popular as oil prices rise and the world becomes more environmentally aware.
The increased demand for health food has stimulated the trade in shelled hemp seed, hemp protein powder and hemp oil as well as finished and ready-to-eat food products using these derivatives as ingredients. Hemp oil is increasingly being used in the manufacturing of bodycare products.
Hemp contains delta-9-tetrahydrocannabinol (THC), which is the psychoactive ingredient found in hashish and marijuana. The THC levels in hemp are minute and have very little intoxicating effects. THC is present in all Cannabis plant varieties to some extent. In varieties grown for use as a drug, where males are removed in order to prevent fertilization, THC levels can reach as high as 20-30% in the unfertilized females which are given ample room to flower.
In hemp varieties grown for seed or fibre use, the plants are grown very closely together and a very dense biomass product is obtained, rich in oil from the seeds and fibre from the stalks and low in THC content. EU and Canadian regulations limit THC content to 0.3% in industrial hemp.
On October 9, 2001, the US Drug Enforcement Administration (DEA) ruled that even traces of THC in products intended for food use would be illegal as of February 6, 2002. This Interpretive Rule would have ruled out the production or use of hempseed or hempseed oil in food use in the USA, but after the Hemp Industries Association (HIA) filed suit the rule was stayed by the United States Court of Appeals for the Ninth Circuit on March 7, 2002. On March 21, 2003, the DEA issued a nearly identical Final Rule which was also stayed by the Ninth Circuit Court of Appeals on April 16, 2003. On February 6, 2004 the Ninth Circuit Court of Appeals issued a unanimous decision in favor of the HIA in which Judge Betty Fletcher wrote, "They (DEA) cannot regulate naturally-occurring THC not contained within or derived from marijuana-i.e. non-psychoactive hemp is not included in Schedule I. The DEA has no authority to regulate drugs that are not scheduled, and it has not followed procedures required to schedule a substance. The DEA's definition of "THC" contravenes the unambiguously expressed intent of Congress in the Controlled Substances Act (CSA) and cannot be upheld". On September 28, 2004 the HIA claimed victory after DEA declined to appeal to the Supreme Court of the United States the ruling from the Ninth Circuit Court of Appeals protecting the sale of hemp-containing foods. Industrial hemp remains legal for import and sale in the U.S., but U.S. farmers still are not permitted to grow it.
Strong opposition to such trace amounts of THC, a chemical shown by almost all scientific research to be less addictive or harmful than legal nicotine or alcohol, leads some of its critics, like Jack Herer in The Emperor Wears No Clothes, to charge ulterior motives such as protection of the synthetic-fibre, wood pulp, petrochemical, and pharmochemical industries. The US government's position has not been completely constant, as shown by the wide-spread cultivation of industrial hemp in Kentucky and Wisconsin during World War II. Critics of the HIA, however, argue that the necessities of the war and the unavailability of adequate synthetic substitutes outweighed the social, health, and public safety risks of producing hemp.
The presence of (some) THC in hemp varieties and the fear that THC could be extracted from industrial hemp for illegal purposes has hampered the development of hemp in many countries. Since the early 1990s, however, many countries, including Canada, Australia, the UK, The Netherlands and Germany, allow hemp plantings and commercial scale production. Plant breeders are working on the development of new varieties which are low in THC.