Crop description. Linum usitatissimum L.—commonly known as lin­seed, flaxseed, lint bells, or winterlien—belongs to the family Linaceae (see Fig. 4.8). This annual herb can grow up to 60 cm in height in most temperate and tropical regions. This plant is native to West Asia and the Mediterranean [96]. The seeds contain 30-40% oil, including palmitic

acid (4.5%), stearic acid (4.4%), oleic acid (17.0%), linoleic acid (15.5%), and linolenic acid (58.6%).

Main uses. Medicinal properties of the seeds have been known since ancient Greece. It is used in pharmacology (antitussive, gentle bulk lax­ative, relaxing expectorant, antiseptic, antiinflammatory, etc.) [97]. As the source of linen fiber, it was used by the Egyptians to make cloth in which to wrap their mummies. However, today it is mainly grown for its oil [98, 99], which is used in the manufacture of paints, varnishes, and linoleum. Linseed oil is used as a purgative for sheep and horses. It is also used in cooking. There is a market for flaxseed meal as both animal feeding and human nutrition [96].

Lang et al. transesterified linseed oil by using different alcohols (methanol, ethanol, 2-propanol, and butanol) and catalysts (KOH and sodium alkoxides). Butyl esters showed reduced cloud points and pour points [100]. Some authors have found that biodiesel from linseed oil presents a lower cold filter plugging point (CFPP) than biodiesel from rapeseed oil, due to large amounts of linolenic acid methyl ester and their iodine value [101]. Long-term endurance tests have been carried out with methyl esters of linseed oil, showing low emission characteristics. Wear assessment has shown lower wear for a biodiesel-operated engine [102]. Experimental investigations on the effect of 20% biodiesel blended with diesel fuel on lubricating oil have shown a lubricating oil life longer while operating the engine on biodiesel [103]. Oxidation stability have shown better results compared with methyl esters of animal origin [104]. Lebedevas et al. have suggested the use of three-component mixtures (rapeseed-oil methyl esters, animal methyl esters, and linseed oil methyl esters) to fuel the engine. These three-component mixtures reduced exhaust emissions significantly, with the exception of NOx that increased them up to 13% [105].