The hemp plants, lat. Cannabis sativa ssp. indica and Cannabis sative ssp. sativa, belong to the family of Cannabaceae - hemp plants. It is one of the oldest useful plants on earth. The robust plant reaches different heights of growth. Under favorable environmental conditions, it can grow up to 7 meters high. Ideal locations are moist but not waterlogged soils with good nutrient supply. The robust hemp plant binds a lot of CO2 during the growth phase and does not tend to leach the soil.
The palmate leaves have a serrated edge. The number of leaflets varies. The first pairs of leaves usually have only one leaflet, others can have up to 13 leaflets, depending on the genetic condition and site conditions. Towards the terminal flower the number of leaflets decreases again. In the lower part of the plant, the leaves are mainly opposite, in the upper part, however, alternate. Most hemp species are dioecious, i.e. there are female and male plants. Monoecious plant specimens are also described, but are rarer.
The female flowers are arranged in racemes, the male loosely in panicles. In monoecious specimens, the different flower types either form in separate inflorescences, or develop simultaneously in one inflorescence. Pollination is by wind. The fruits are 3-5 mm in size with greenish-gray surface and green seeds. Various products can be made from the components of the plant such as the fibers, seeds, leaves and flowers, such as ropes from the stem fibers, edible oil from the seeds and essential oil from distilled flowers and leaves.
In order to achieve the highest possible yield (>1200kg/ha), hybrid varieties or monoecious varieties (male and female flowers) are preferably grown for oil production. Pure seed and fiber plants contain a low THC content of less than 0.2%, so that a medical application is excluded.
Hemp is considered the first plant cultivated by humans. It already played a decisive role as a supplier of raw materials in the early advanced civilizations. As early as 12,000 years ago, hemp was cultivated as a foodstuff in Persia and China. Hemp-cultivating farming societies developed in China, in the Mesopotamia of the Euphrates and Tigris rivers and in the Nile delta.
The seeds of hemp were traditionally used for food, the fibers for clothing. In China, paper was produced from the plant stalks at an early stage. From the first millennium B.C. until well into the 19th century, hemp was the most widely cultivated crop worldwide. In the 13th century, the coveted raw material for paper made its way to Europe. As an indispensable fiber for sailcloth and ship ropes, it spread throughout the world by seafaring.
The harvest time depends on the ripeness of the fruit and the degree of defoliation of the plant. Hemp oil is obtained from the seeds of the plant. Hemp harvesting is done with special harvesters that only cut off the top parts of the plant to extract the seeds. The lower parts of the plant often remain in the field to initiate the so-called field retting: Components of the stems are decomposed by bacteria and fungi, which finally facilitates the extraction of the fiber. These are then further processed into ropes or other composite materials.
These harvested seeds are 3-4 mm in size and enclosed in a firm pericarp. They are shelled after harvest or directly cold pressed (40-60 degrees Celsius). With an oil content of 30-35%, about 30 liters of oil can be obtained from 100 kg of seeds (160-350l/ha). The pressed residues (so-called press cake) still contain small amounts of oil and are used, among other things, as animal feed or for biogas development.
The world's largest cultivation areas for commercial hemp today are in China and France.
The oil of the seeds was used as cooking oil and as lamp oil, and medicine was also obtained from the flowers and seeds. Thus, the hemp plant was also sought after for its healing power. People covered the wounds of the injured with the leaves and used hemp oil, for example, against gout.
Typical for hemp oil are the nutty taste and the green color (pressing with shell), which results from the extremely high content of chlorophyll. Warm pressed oil, on the other hand, has a dark green color. Extraction processes can result in an intense yellowish color.
Due to its composition, hemp seed oil is considered one of the healthiest edible oils available. It contains up to 80 percent of essential unsaturated fatty acids. The ratio of vital omega-3 fatty acids to omega-6 fatty acids is perfect for our organism. The rare gamma-linolenic acid is also included at 2-4%. In addition, the minerals magnesium and calcium, potassium and iron, phosphorus and zinc, copper and manganese, and sodium are found in the oil of hemp seeds. Hemp oil is rich in phytochemicals and especially in certain vitamins of the B group, namely B1 and B2, also beta-carotene and vitamin E. In hemp seed oil there are no psychoactive substances such as THC or similar.
The oil has a low smoke point at <165 degrees Celsius, which is associated with the destruction of the valuable active ingredients. It can therefore not be used for frying or deep-frying (steaming is theoretically possible).
Hemp seed oil can be used for many diseases, both internally and externally. The gamma-linolenic acid has an anti-inflammatory effect, so hemp oil can be used for diseases such as rheumatism or arthritis. The spectrum of symptoms for which hemp oil can help is wide. Vascular diseases, hormonal problems and cardiovascular diseases can be alleviated. Hemp oil is always used cold, so that the valuable ingredients are preserved.
In the cosmetics industry, the oil is used as an additive in massage oils, ointments, shampoos and creams due to its good lubricating and emollient properties. The linoleic acid it contains is suitable for rough and inflamed skin. For certain conditions, such as skin diseases, a combination of the two can be particularly successful. It is often used in skin creams because of its soothing effect.
Chemical processes such as sulfation or saponification can be used to obtain raw materials for the cleaning industry. Due to its natural origin, the desired biodegradability is often given. Use as biofuel is possible, but is not practiced due to the low yield relative to other oil plants.
Hemp oil belongs to the drying oils and tends to oxidize/"go rancid" quickly. It should therefore be stored in a cool, dry and dark place. Shelf life can be extended up to 9 months after pressing, depending on the variety and production, if stored properly.
Contrary to some misinformation, the oil from hemp seeds does not contain psychoactive ingredients, because it is not an essential oil or an extract from the resin of the plant. Hemp is also known as cannabis and thus as a drug. However, it is mainly used industrially. In most countries, THC (tetrahydrocannabiol) <1% is considered a non-medicinal form of cannabis. Cannabis grown under artificial light and specifically cultivated for high THC content, on the other hand, can have an active ingredient content of 10 to 20%. In Germany and throughout the EU, hemp cultivation is strictly regulated. Hemp is still considered a drug, and home cultivation is also prohibited. However, in the context of medicinal use, it is permitted to grow selected plants in Germany with the appropriate permission.
Important to the sustainability debate is that hemp does not require pesticides or herbicides to grow successfully. Inorganic fertilization can also be dispensed with. The plant is not demanding. It requires little help for healthy growth. It does not leach the soil and is characterized by high CO2 fixation. High yields can be achieved without artificial fertilizers and sprays. Hemp thrives from the Arctic Circle to the equator and is a plant that accompanies cultures, it has always accompanied mankind on its way to all regions. In addition to its use as a fiber, medicinal and oil plant, hemp is an important renewable raw material that is also used in the construction industry, for example.