**4. The use of oilseed rape**

Oilseed rape is an economically significant agricultural plant species. It is widely cultivated in many countries and is the world's second most crucial oilseed plant, which contains more than 40% of oil in its seeds. Thus, it is considered a very abundant source of oil. Oilseed rape seeds are the most widely used part of this plant. However, other parts of the oilseed rape plant are also useful [5, 15].

Oilseed rape seed oil and protein contents vary in different cultivars. The content of oilseed rape oil depends not only on the plant's genetic characteristics, but also on oil extraction conditions, e.g., solvent type, temperature, pressure, and time of processing. Many extraction methods have been tested, e.g., solvents, enzymes, gas, heat, or ultrasound. Some of these methods offer more advantages. These are safety for human consumption, less time-consuming, better oxidative stability and shelf-life, preservation or improvement of beneficial oil compounds. However, at the industrial level, the most commonly used type of extraction is the extraction by using hexane as a solvent. At the beginning of the process, seeds are heated for softening. Then they are flaked to break cell walls and cooked to promote cell disruption to release the oil. Later, residual oil is extracted using the solvent, and afterwards, the solvent is removed, and the oil is refined and processed. The negative feature of the extraction with hexane is a partial loss of beneficial antioxidants, phytosterols, and phenolic compounds [5, 19].

The types of fatty acids in the oil determine whether oil is used for edible or industrial purposes. Certain fatty acids, such as linoleic acid, are helpful for human health. They cannot be synthesised by the human body, thus must be obtained from the diet. And on the other hand, large concentrations of eicosenoic and erucic acids are harmful to human health [3, 7].

The oil obtained from the 00 cultivars is claimed to be safe both for infants and adults and is currently one of the most widely used vegetable food oils. It is valued for high nutritional value: high content of unsaturated fatty acids (which makes it more biologically valuable than animal fats), high oleic acid content, a favourable ratio of linoleic and linolenic acids, and abundance in vitamin E. It is also famous for its affordability, high cooking temperature, mild flavour and versatility as a cooking oil. It can be used at room temperature, e.g., as a salad dressing or for baking. In addition, it has been established that glucosinolate hydrolysis products can activate the human body 's protective mechanism. Glucosinolates are responsible for the pungent odour and taste, which ranges from the hot flavour in mustard seed and horseradish to the more subtle flavours of rutabaga and cauliflower. Therefore, the consumption of plants of the *Brassicaceae* family in the human diet may be associated with a lower risk of cancer [1, 3, 7, 20].

The high demand for oilseed rape oil is also related to the use of this oil for the production of biofuels. European Parliament promoted the use of biofuels by issuing Transport Biofuels Directive in 2003. It induced a dramatical increase in oilseed rape cultivation in Europe. The biodiesel produced from this renewable energy source is about 40% less polluting than diesel [1, 10, 15, 21].

Another valuable property of oilseed rape biodiesel is maintaining a fluid state even at low temperatures, and overdue of crystal formation, which makes it suitable for cold climates. Also, oilseed rape oil emits up to 90% less greenhouse gas (GHG) than fossil diesel. Thus, its use can reduce the emission of GHG from the transport sector and diminish the degradation of environmental wellness. What is more, oilseed rape biodiesel is biodegradable. It decomposes for about 30 days and accelerates the decomposition of diesel fuel when mixed. It is less toxic in water, thus reducing the impact of spills in sensitive areas. Biodiesel is often blended with fossil-fuel diesel in ratios of up to 20 per cent of biodiesel. Despite the numerous benefits, this biofuel also has disadvantages. It is vulnerable to oxidation during storage, and it can degrade some materials made of elastomer and rubber in fuel distributions. Also, due to the costs of growing, crushing, and refining oilseed rape oil, its price is higher than standard diesel fuel. Thus, biodiesel fuels are commonly made from used oil. Oilseed rape is used not only for producing edible oil, technical oil and biofuel, but also for other market needs [1, 3, 22].

A high erucic acid oilseed rape (HEAR) cultivar with erucic acid contents up to 66%, increased oil yield and increased tolerance to diseases and stress were used to make useful products, e.g. slip agent for the plastic film, emollient, food emulsifier, photographic material, ink, paper, textile, foam, plastics, etc. Moreover, oilseed rape can also be used in cosmetics and soap production. The soap is made in a cold process to save the beneficial compounds, light colour and dense. Coconut or other oils can be added to add to the aroma. Oilseed rape oil is also used as a biolubricant for biomedical applications (e.g., as a lubricant for artificial joints), as a personal lubricant or to replace 70% or more petroleum in chain saw oil. Besides, erucic, oleic and linoleic acids are helpful for maintenance of healthy hair and scalp conditions. Furthermore, a low-toxic and rapidly decomposing human and environment-safe pesticide was developed from oilseed rape oil. This insecticide is irritating and is used to fight aphids, loopers, worms, caterpillars, and mites [3, 5].

Oilseed rape meal, the residue after extraction, is widely used as a soil fertiliser, protein-rich and a functional additive for animals (cattle, pigs and birds) and human feed, as a substrate for fungi to produce enzymes (e.g., xylanase, xylosidase, cellulase, and acetyl–xylan esterase). Its incorporation in wheat, soybean, or corn-based diets affected feed efficiency, protein digestibility, energy value, and microbial community. It is also used in manufacturing capsules for bioactive drug delivery, cosmetics, and bioplastic packaging [5, 23].

Oilseed rape leaves, stems, roots, flowers, and seeds can be used for human food. Leaves and stems are a rich source of minerals, proteins, vitamins, and phenolic compounds. Their regular consumption is beneficial for human health by preventing chronic diseases. They can be used as edible vegetables or as a pot herb for seasoning. Oilseed rape flowers can be used as tea. Pollens can be consumed to strengthen the immune system and fight cancer. Seeds can be used as spices. Oilseed rape roots are also helpful due to their various diuretic, antigout, antiinflammatory, and antiscurvy characteristics [5, 9].

In animal husbandry, oilseed rape is used for green fodder and silage. Also, it is valued by beekeepers as a rich source of nectar and pollen for honeybees. It has been considered the main plant from which bees collect nectar. It has been shown that 1 hectare of oilseed rape yields 60–90 kg of honey. The period of oilseed rape flowering is about 1 month. Thus, oilseed rape provides good shelter and supplies nutrition for a long time. Oilseed rape honey has a mild medicinal, taste and aromatic properties. Its flavour is peppery, and the texture is soft-solid. It is whitish or milky yellow. It is often used as a sweetener, in confectionery and for processing [5, 24].

#### *Oilseed Rape: Biology, Use, Current Cultivation Issues and Agronomic Management DOI: http://dx.doi.org/10.5772/intechopen.109180*

Oilseed rape is a deep-rooted plant that can absorb useful substances from deeper soil layers with its long taproot. Glucosinolates, formed from glucose and amino acid and containing sulphur, perform an essential defensive function in plants of the *Brassicaceae* family, protecting crops from pests and diseases. It releases volatile mustard oils and dissolves and assimilates nutrients that are difficult for other plants to obtain. After oilseed rape harvesting, many organic residues remain in the soil. It increases the amount of humus, improves the soil fertility, structure, and porosity, improves beneficial soil bacteria and alleviates or suppresses infections, nematodes and the growth of some weeds. Additionally, crop growth and development may be enhanced with the oilseed rape hormone brassinolide [3, 11, 12].

Due to these properties, oilseed rape is also grown as a green fertiliser and is an essential crop in many arable rotations. Often, it is grown as a break crop in three to four-year rotations with cereals (e.g., wheat and barley) and break crops (e.g., peas and beans). This provides many benefits for pest and disease control by reducing the possibility of pests and diseases being carried over from one crop to another. For example, it is helpful for wheat yield due to fungus-removing properties, when wheat is sown after sowing oilseed rape. Some cultivars of oilseed rape are also used as an annual forage [11].

Oilseed rape has a long flowering period. Its flowers are widely used for ornamental purposes, e.g., to decorate indoors and outdoors and as a field to visit for leisure. Hybridisation techniques enabled colourful (white, milky white, golden yellow, orange, purple, pink, and red) flowers [5, 9].

Oilseed rape plants can also be used for phytoremediation. Their roots can absorb and accumulate heavy metals from the soil rich in heavy metal contamination, e.g., cadmium (Cd). The absorbed heavy metal stems above and is removed when the plant is fully grown. Also, it has up to a three times higher rate of radionuclides uptake compared to other grains. Thus, it was researched as a tool to decontaminate the soil after the Chernobyl catastrophe [3, 5].

Finally, agricultural waste of oilseed rape is also useful. After its seeds are harvested, straws still contain a sufficient content of proteins, which is higher than wheat and legume. Thus, oilseed rape straw is used for animal feed. The only disadvantage of using straw as animal feed is a large amount of fibre, which lowers digestibility. However, it can be removed using ammonia treatments. Moreover, pods, stalks and cake are pressed and used for biofuel, as a substrate in vermicomposting and for the production of biochars [3, 5, 11].
