The Cropwatch Files

The agarwood Files

 

Distillation of Agarwood.

 

 

 

Copyright Tony Burfield 2005

 

 

 

Accounts of agarwood distillation vary from source to source as we will see. Baruah et al. (1982) distinguished four grades of infected fragrant wood: the poorest grade being buff-coloured (Dhum) and being exclusively used for distillation, better grades being used to make incense agar-battis. Chaudhari (1993) named these as:

 

Grade 1 Black/True Agar: mainly exported to Arabia as incense

Grade 2 Bantang: mainly exported to Arabia as incense
Grade 3 Bhuta or Phuta: sometimes extracted for a superior oil
Grade 4 Dhum: used for oil

Chaudhari also estimated the amount of wood available in India as 31 metric tons, which would yield 77.5Kg agarwood oil on a 0.25% yield basis, naming the stills in the Naga Hills as being at Manipar Road (3 stills), Barapathar (27 stills) and Dhansari (now shut down).

 Distillation of dhum yields 0.75% to 2.5% agarwood oil according to Mahindru (1992), but Sadgopal (1980) had earlier maintain that dhum yielded a smaller amount of oil (0.1%) compared with infected brown wood (0.4%), with infected dark brown wood giving 0.9% and the best grade of black wood giving 1.2% plus. Chakrabarty et al. (1994) give the yield of agarwood oil from black agar as 0.09-2.5%.

An 80 year-old tree can yield 6-9 Kg of agarwood oil (Sadgopal 1960), although Mahindru (1992) puts the figure at 2.7 to 3.6 Kg/tree for 50-year-old trees in India, and Gianno (1986) puts it even lower at 1kg per tree with a girth of above 20cm dbh. 

The fragrant oils that result from the individual field still distillations are classified as follows: ­ primary grade oil, usually a darker colour originating from the more heavily stained­ wood sections, which incidentally are often associated with the ­pathogenic fungus Philophora parasita. Secondary grade oil is ­usually lighter in colour, often originating from pale to ­gray-stained fungal infected sections. The spent wood after distillation is dried and often used for making agar-battis, although processes are reported for extracting oil from the spent wood.

The Chakrabarty K et al. (1994) describe the distillation of Agarwood oil in great detail in the towns of Hojai, Nilbagan and Islamnagar in the Naogaon district of Assam as a result of the Traffic investigations of 1993, speculating that 500-1000 tolas a month of oil (1 tola = 46.48g) are produced in Hojai, legally obtained wood being supplemented by that illegally obtained from India and Bhutan. The report also mentions distillation in Manipur in Thambu Bazar, and pinpoint Bombay as the production centre for agarwood attars. Finally the authors identify Myanmar and Tuensang in Nagaland as a major smuggling points.

Wood from felled trees is cut into pieces and thrown into water –  those pieces containing more than 25%  oleoresin, will sink. Infected areas of wood are carefully scraped out with a special tool (called a batali). After sorting pieces into grades, the selected pieces are  ground and soaked in water (often in a drum container) for 48 hours, although other reports say 1-5 days. The wood is the powdered manually with a dhenki. Distillation is carried out for 5-6 hours with cohabation of the distillation waters, although 24-48 hours is reported elsewhere. Chakrabarty et al. (1994) suggest 8-12 Kg of wood in 80 litres of water are distilled for 3 days, describing a cohabation arrangement, although it also describes an improved process developed at the Regional Research Laboratory, Jorhat in Assam which uses a stainless steel still and yields a clear oil free from metallic impurities.