A) Extraction with alcohol (also called one-step extraction)

Advantages:

· relatively simple technology
· lower investment required
· makes use of all products, therefore no waste
· possible use of the extraction plant for other products

Disadvantages:

· quality of the final product is greatly dependent on the quality of the raw material
· often low stability/short shelf-life of the products

The neem seeds are crushed into crude powder and extracted with ethanol or methanol by maceration or percolation. The alcohol should have only a low water content, and its quality (purity) is also important.

The alcoholic extracts contain the active ingredients. Using the moving-bed contacting method, the kernels will be stirred for 3-4 hours by an overhead stirrer in a mixing-settling tank. After decantation of the crude cake, the neem solution is drained out, filtered and passed to the next procedure. The dilute neem solution will be further evaporated until a specific volume - called the "concentrated extract" (CE) has been achieved, and the solvents are recycled.

Neem kernels contain a large percentage of oil (up to 48%, average 40%), which is of considerable value on its own. The oil disturbs the extraction of the active ingredients. Therefore it would be best to remove the oil with solvents such as hexane or by cold pressing with an oil expeller. It is also possible to remove the oil content from the extract by cooling or freezing to separate the oil. The de-oiled neem cake could be further extracted with methanol to gain the azadirachtin. The oil component of neem is currently used in formulating a pet shampoo, e.g. in Thailand, or as an acaricide.

The sticky CE is dressed with carriers which will form an eventually an emulsified extract (EC) formulation

Finally the solution obtained can be bottled and supplied to the consumer.

This sort of technology is used in the smaller neem-processing plants (100 - 500 t of kernels annually) such as those in Myanmar, Thailand and Kenya. The products contain between 0.3 and 1% azadirachtin A as well as many teranortriterpenoides and other substances (residual fat, sugar etc.).

Furthermore, some of the products are formulated for a specific purpose. However, the information about formulation technology of neem pesticides is a commercial secret and often patented.

Figure 1 is a schematic diagram of a production line using a single-step extraction method for producing commercial neem-based formulations. This technology is used in Thailand, Myanmar and Kenya:

Figure 1: Example of batch extraction (from Thailand)

Machinery required for one-step neem extraction:

· Dryer for the seeds (solar dryer), thresher, oil press or hexane extraction plant, hammer mill, percolators and solvent tanks, pumps

· Evaporator, cooling tower, boiler (steamer)

· Dryer for recycling the solvents from the extracted cake, desolventiser, filling and packing equipment, cooling room, laboratory for quality control

The costs of such extraction plants (of 2000 t capacity) are approx. US$ 500 000 - 750 000 $ (CIF), without a laboratory for quality control.

The processing of neem involves many operations, as shown in Figure 2 and requires a certain mount of equipment. Figure 2 shows the equipment for commercial neem processing in Thailand.

Figure 2: Equipment required for commercial neem processing