CASHEW NUT SHELL LIQUID – A POTENTIAL RENEWABLE ENERGY SOURCE

Cashew nut shell liquid – a potential renewable energy source

1.  Biofuel and renewable energy in the world

Energy is vital for the economic development and every sector of the economy such as agriculture, industry, transport, commercial and domestic sectors require energy. Fossil fuel-based fuel sources such as petroleum, coal and natural gas have been the predominant sources of energy all over the world for a long time. The majority of the world energy needs, about 81.1% is supplied through petrochemical sources such as coal, oil and natural gas. Nuclear, hydro, biofuel and other renewable energy  (wind power, solar energy) account only 18.9%. of every country. With cashew nut shell oil we have the raw material for potential renewable energy. 

Biofuel and renewable energy

Biofuel and renewable energy

The world is confronted with a twin crisis of limited supply and the increasing cost of fossil fuels. In particular, cashew nut shell liquid (CNSL) is a potential fuel source that Vietnam dominates because it is a strong exporter of cashew kernels to many markets around the world. In the 15 years from 2006-2020, Vietnam is the world’s leading raw cashew exporter according to information from the Vietnam Cashew Association (VINACAS). In 2020, the export of raw cashew nuts reached more than 3.1 billion USD (about 80% of the total world production of cashew kernels).

2.Application of cashew nut shell liquid (CNSL) as fuel

Cashew nut shell liquid is a product extracted from the by-product of cashew nut shell, used as a fuel to replace burning oil. Cashew nut shell liquid when burned gives off high heat equivalent to FO oil (> 9,000 kcal / kg) and is completely compatible with the combustion system of FO oil while the cost is about 60-70% compared to FO oil. . This is an advantage for businesses to switch to using cashew shell oil instead of FO oil with a lower cost per device. Practical application of cashew nut shell liquid as an industrial fuel in factories producing sillicat, cramite bricks, aluminum smelting, industrial boilers, clinker. With cashew nut shell oil we have the raw material for potential renewable energy.

Cashew Nut Shell Liquid (CNSL)

Cashew Nut Shell Liquid (CNSL)

3.Cashew nut shell liquid (CNSL) manufacture method

The Cashew nut shell liquid has a shell of about 1/8 inch thickness, with a soft honeycomb structure inside, containing a dark brown viscous liquid which called cashew nut shell liquid (CNSL). CNSL is extraction from cashew nut shell (CNS) by using of different methods. CNSL is classified into Technical CNSL and natural CNSL depending upon the type of Extraction. Technical CNSL is rich in Cardanol (also known as Decarboxylated CNSL) where as Natural CNSL is rich in Anacardic acid. There are three main methods generally used in extracting cashew nut shell liquid from cashew nuts namely thermal, mechanical and solvent extraction.

  1. Thermal extraction: there are three methods such as Roasting method, hot oil bath method or by using solar cooker. In order to extract the retained CNSL, the nuts are roasted in baths at a temperature of 180–185ºC. Vents in the equipment dispel the unpleasant fumes. This method recovers 85–90% of the liquid. In hot oil bath method cashew nut shells were collected in the cylinder, where steam heating was applied at temperatures around 200-250°C for 2-3 minutes. CNSL was then released from the shells and the process was repeated. This method yields CNSL of around 7-12% by weight. Where as in Solar cooker method Cashew nut shell oil was extracted using concentrating solar cooker of 1.4 kW capacity and a diameter of 1.4m. The focal point diameter of the cooker was 30m and was used to collect the reflected heat from reflector and achieved a temperature of 225-300°C [17].
  2. Mechanical extraction: The raw cashew nut shells are put in the hydraulic press on screw pressing and then exert high pressure in order to release CNSL from shells. By using screw speed of 7-13 rpm and feeding rate of 54-95 kg/h, the percentage of CNSL extracted was 20.65-21.04 percent, the percentage of CNSL purity was 85.53-87.8 wt % and the rate of extraction was 11.93-14.90 kg/h 40 [17]
  3. Solvent extraction: This method gives off most of CNSL compared to other methods. The oil remains in the residue was less than 1% by weight. Extraction solvents fall into two groups; those which are less dense than water and those which are denser. Commonly used extraction solvents which fall into the first group include diethyl ether (the most common extraction solvent of all), ethyl acetate and hydrocarbons, such as light petroleum, hexane or toluene. The second group comprises chlorinated solvents, such as dichloromethane and chloroform, with dichloromethane being the preferred solvent because of its lower toxicity. Solvent-extracted CNSL contains anacardic acid (60–65%), cardol (15–20%), cardanol (10%) and traces of methyl cardol. Technical CNSL is obtained by roasting shells and contains mainly cardanol (60–65%), cardol (15–20%), polymeric material (10%), and traces of methyl cardol.

We, Vinh Thanh Dat (VTDIMEXCO) specialize in supplying oils and fats domestically and for export with the ability to supply to the market up to 5.000 – 10.000 tons per month. Product quality, prestige, stable and long-term supply are the criteria that Vinh Thanh Dat (VTDIMEXCO) consider as priority.

Our specification of Cashew Nut Shell Oil (CNSL) as below:

Commodity name: Cashew Nut Shell Oil (CNSL)
Net Calorie (Kcal/kg)9,300 – 9,500
Density (25oC,  kg/l)0.9536
Viscosity (25oC, Cps)148
Moisture (%)0.29
Impurities (%)1.6
Ash content (%)1.07
PH7 – 9

Reference:

  1. International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Impact Factor (2012): 3.358
  2. https://www.nature.com/articles/s41598-019-55403-4

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