Neem oil is a plant oil pressed from the fruits and seeds of the neem (Azadirachta Indica), an evergreen tree which is endemic to the Indian sub-continent and has been introduced to many other areas in the tropics. It is yellow to brown, has a bitter taste, and a garlic/sulfur smell. It has been used for hundreds of years to control pests and diseases. Components of neem oil can be found in many products today. These include bio-pesticides, toothpaste, cosmetics, soaps, and pet shampoos. Neem oil is a mixture of components. Azadirachtin is the most active component for repelling and killing pests and can be extracted from neem oil. The portion left over is called clarified hydrophobic neem oil.
Uses and Benefits
Neem oil is made of many components. Azadirachtin is the most active. It reduces insect feeding and acts as a repellent. It also interferes with insect hormone systems, making it harder for insects to grow and lay eggs. Azadirachtin can also repel and reduce the feeding of nematodes. Other components of neem oil kill insects by hindering their ability to feed.
Safety and Environment
Azadirachtin, a major component of neem oil, is rapidly broken down. Microbes and light break down the pesticide in soil, water and on plants. The half-life of Azadirachtin in soil ranges from 3 - 44 days. In water, the half-life ranges from 48 minutes to 4 days. It also rapidly breaks down on plant leaves; the half-life of 1 - 2.5 days. The remaining components of neem oil are broken down by microbes in most soil and water environments.
Neem oil is practically non-toxic to birds, mammals, bees and plants. Neem oil is slightly toxic to fish and other aquatic organisms. Azadirachtin, a component of neem oil, is moderately toxic to fish and other aquatic animals. It is important to remember that insects must eat the treated plant to be killed. Therefore, bees and other pollinators are not likely to be harmed.
Neem oil extraction usually has three different ways: pressing, steam distillation, and solvent extraction, which is mostly used for soap manufacturing. The method of extracting neem oil influences the quality and composition of the neem oil obtained.
For pressing, neem seeds need grinding according to the amount of oil content in the seeds and sizes as well, after which they are woven dried and feed into the neem oil pressing machine. As the screw moves forward, neem oil is pressed out under high pressure and strong forces.
As for steam distillation, the dried neem seeds are put into the steam boiler. Then they get swollen by steaming, thus neem oil in squeezing becomes easy. This steaming process is accompanied by increasing pressure in the boiler which drives the neem oil out of neem seeds.
In solvent extraction, the solvent, usually hexane, is mixed with neem seeds after woven drying. Or the added neem seeds can be pressed if needed. Solvent extraction is working on the principle of counter current and moving bed, permitting excellent penetration and percolation of solvent for absolute neem oil extraction. Extracted neem oil is collected by vaporizing solvent out for later recovery.