Available online at www.sciencedirect.com

Biomass and Bioenergy 25 (2003) 113–117

Bio-oil from pyrolysis of cashew nut shell—a near fuelPiyali Das, Anuradda Ganesh∗

Energy Systems Engineering, Indian Institute of Technology, Mumbai 400076, India

Received 6 March 2002; received in revised form 21 August 2002; accepted 28 October 2002

Abstract

Cashew nut shell (CNS) has been studied for the product distribution in a packed bed vacuum pyrolysis unit. The e3ectof pyrolysis temperatures on the product yields is also studied. The oil-to-liquid ratio in the pyrolysis products was found toremain almost constant in the range between 400◦C and 550◦C. The properties of CNS oil has been found to be amazinglynear to that of petroleum fuels with calori7c value as high as 40 MJ kg−1, the oil has a low ash content (0.01%) and watercontent is limited to 3–3:5 wt% of oil.? 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Cashew nut shell; Vacuum pyrolysis; Bio-oil

1. Introduction

India is the largest producer, processor and exporterof cashews, Anacardium occidentale Linn., in theworld. It was brought to India during the 1400 by Por-tuguese missionaries. Cashew came, conquered andtook deep root in the entire coastal region of India.While the tree is native to central and South Americait is now widely distributed throughout the tropics,particularly in many parts of Africa and Asia. InIndia Cashew cultivation now covers a total area of0.70 million hectares of land, producing over 0.40million metric tons of raw cashew nuts [1]. Presently,cashew nut shell liquid (CNSL) is obtained as aby-product of cashew industry.The Cashew nut has a shell of about 1/8 inch

thickness, with a soft honeycomb structure inside,containing a dark brown viscous liquid. It is called

∗ Corresponding author. Tel: +91-22-2576-7886; fax: +91-22-2576-7890.

E-mail address: aganesh@me.iitb.ac.in (A. Ganesh).

CNSL, which is pericarp Guid of the cashew nut [2].Commercially, CNSL is extracted by various methods[3,4] like roasting nuts and collecting expelled liq-uids, extraction with hot CNSL without charring thekernels, superheated steam treatment method and sol-vent extraction method, etc. The CNSL is reported tobe 15–20% by weight of the unshelled nut in Africa,25–30% by weight in India and 25% overall [4].CNSL and its derivatives have been reported tobe useful in innumerable applications [5–8] inpolymer-based industries like friction linings, paints,primers, and varnishes, cashew cements, adhesives,binder resins, polyurethane-based polymers, etc.CNSL forms the basic raw materials for vast num-ber of chemicals and intermediates [9,10] includingbactericides, germicides, insecticides, disinfectants,emulsifying and surface active agents.The present paper reports the studies on pyrolysis

of CNS for production of oil and its potential use as afuel. Pyrolysis is one of the thermochemical conver-sions in the absence or limited supply of air or oxy-gen. Today, pyrolysis is generally used to describe

0961-9534/03/$ - see front matter ? 2002 Elsevier Science Ltd. All rights reserved.PII: S0961 -9534(02)00182 -4

114 P. Das, A. Ganesh / Biomass and Bioenergy 25 (2003) 113–117

processes in which preferred products are liquid oilsespecially those with desirable chemical compositionand physical attributes for liquid fuels, fuel supple-ments and chemical feedstock [11]. The liquid pyrol-ysis fuels apart from being energy rich, are easier tohandle, store and transport in combustion applicationand can be upgraded to obtain light hydrocarbons fortransport fuel.

2. Experimental procedure

Cashew nut shell (CNS) obtained from Pondicherry,an union territory in southern part of India, has beenused for the present study. The sample belongs to thevariety Vengurla, one of the most common varietiesgrown in India. Immediately after harvest the cashewnuts were sun dried for few days to have moisturecontent between 8% and 10% after which they wereshelled. It is to be noted that during the measurementof moisture content using ASTM method, dark brownoil oozes out along with the moisture removal. Themoisture content has been calculated as the di/er-ence of the weight of the original biomass and theweight of the ‘oil plus the de-oiled biomass’ at thecorresponding temperature.Weighed amount of CNS is taken for drying in two

di3erent petridishes and placed in the oven at 105◦Cfor 3 h. The temperature of the oven is then raised ata step increase of 25◦C to a maximum temperature of200◦C keeping for 2 h at each temperature level. Forone of petridishes the oil oozed out at every temper-ature was removed, weighed and kept separately andonly the de-oiled cashew was kept in the oven backfor next step increase of temperature. In the case ofsecond petridish, at each stage, the petridish was re-moved, weighed and put back into the oven for thenext step increase of temperature.The CNS after removal of oil up to 150◦C is

weighed and pyrolysed for the study of product dis-tribution in a packed bed vacuum pyrolysis unit. Theproximate and ultimate analysis of both, CNS andde-oiled (up to 150◦C) CNS, have been given inTables 1 and 2, respectively. However, in case ofthe de-oiled CNS, proximate and ultimate analysisresults were calculated on the basis of original CNS,i.e., the mass loss during de-oiling process been takeninto account. The reactor is made of stainless-steel

Table 1Proximate analysis of the CNS and de-oiled (upto 150◦C) CNS

CNS De-oiled CNS(wt% on as (wt% on as receivedreceived basis) CNS basis)

Moisture 10.43 —Volatile matter 69.31 58.00Fixed carbon 19.26 19.20Ash 1.00 0.9

Table 2Ultimate analysis of the CNS and de-oiled (upto 150◦C) CNS

CNS De-oiled CNS(wt% on as (wt% on as receivedreceived basis) CNS basis)

C 48.7 34.63H 6.96 4.95N 0.36 0.36O (by di3erence) 42.96 34.22

304 pipe of scheduled 10. The length of the reactoris 600 mm. The reaction conditions are maintainedat, initial reactor vacuum pressure of 5 kPa and atvarious maximum temperatures between 400–600◦C,with an increment of 50◦C for each experiment. Theproduct distribution at each of these temperatures hasbeen analysed. The volatiles removed on pyrolysisare gradually condensed in a preweighed condensingtrain, from atmospheric condensation to condensa-tion in an ice bath (5–7◦C). The total condensablecollected in the condensing train is termed as totalliquid. Among the total liquid, 2rst three fractions,which are directly combustible without any furthertreatment, are termed as bio-oil CO2. The otherfractions, which are noncombustible, contain waterand light organics.

3. Results and discussion

3.1. Experiments at low temperatures (100–200◦C)

Fig. 1 represents the cumulative oil yield at vari-ous temperatures from 100◦C to 200◦C. In case of thecumulative oil yields calculated based on the oil re-moved at every temperature level, it can be seen that

P. Das, A. Ganesh / Biomass and Bioenergy 25 (2003) 113–117 115

0

2

4

6

8

10

12

14

16

18

cum

mul

ativ

e oi

l yie

ld (

%)

105 125 150 175 200

temperature

percentage oil yield of CNS (without removing oil at every stage)

percentage oil yield of CNS (with removing oil at every stage)

Fig. 1. Percentage oil yield of CNS with heating temperature.

after 150◦C, the increase in the oil yields is marginal.On the other hand, the cumulative oil yields calcu-lated without removing the oil separately at each stage,implies that, at each temperature level the oil includesthe amount oozed out at that temperature and also ac-counts for any oil loss through vaporisation. In thiscase, it is interesting to note that after 150◦C there isa decrease in the cumulative oil yields, indicating thedecrease of the oil yield by evaporation being morethan the marginal addition in the oil percentage bythe oil oozed out at higher temperatures. Therefore, atemperature of 150◦C has been selected to be an opti-mum temperature for removal of low temperature oilalong with the moisture. The CNS used for pyroly-sis is therefore, the one, which has been subjected to150◦C and the oil collected separately. This oil calledas oil CO1 for any further references in this paper.

3.2. Experiments at high temperatures (vacuumpyrolysis)

The product distribution (wt% of total liquid, charand gas) on pyrolysis of CNS at di3erent tempera-tures are represented in Fig. 2. The total liquid per-centage varies from 37% (400◦C) to a maximum of42% (500–550◦C) and dropping to 36% (at 600◦C).

0

5

10

15

20

25

30

35

40

45

400 450 500 550 600

Temperature(°C)

Wt.

% o

f pro

duct

yie

ld o

n dr

y C

NS

bas

is

Total Liquid Char Gas

Fig. 2. Pyrolysis product distribution of CNS with temperature.

The typical char yields are about 19–23% in the rangeof 400–600◦C being maximum at 400◦C and 14–20% gas yields (measured by di3erence) in that range,with a maximum at 600◦C. Fig. 3 shows the varia-tion of bio-oil yield (within the total liquid) with py-rolysis temperature. The maximum bio-oil yield wasachieved at 500◦C. It is interesting to note that thebio-oil-to-total liquid ratio remains almost constantin the entire range between 400–550◦C as shown in

116 P. Das, A. Ganesh / Biomass and Bioenergy 25 (2003) 113–117

18

19

20

21

22

23

24

25

400 450 500 550 600

Temperature(°C)

Wt.%

of o

il on

dry

CN

S b

asis

Oil

Fig. 3. Percentage weight variation of CNS pyrolysis oil withtemperature.

Table 3Variation of oil-to-liquid ratio with temperature of CNS pyrolysis

Packed bed temperature (◦C) Oil-to-liquid ratio

400 0.549450 0.557500 0.566550 0.554600 0.590

Table 3. At 600◦C however, it is seen that there is adecrease in the total liquid content, which is attributedto thermal cracking at this temperature. This is in ac-cordance to the resulting higher gas content at thistemperature as seen in Fig. 2. All the further studieshave been conducted at 500◦C, i.e. at the condition ofmaximum oil yield. The oil obtained at 500◦C will bereferred as oil CO2 in the later sections of this paper.

4. Physical properties of CNS oil

The physical properties of the oil CO1 and CO2have been studied using standard test procedures andare reported in Table 4. It is interesting to observe thatthese oils have a much higher calori7c value in com-parison to the values obtained for bio-oils from otherbiomass. The calori7c value of the bio-oil from thepyrolysis of CNS is as high as that of conventionalpetroleum fuels. This is in accordance with the loweroxygen percentage found in the elemental composi-tion of the oil. The Gash point also being high indicatesthat the oil is suitable for storage at room tempera-

Table 4Physical properties of oil CO1 and CO2

Properties Oil CO1 Oil CO2

Ash 0.01 0.01(ASTM D482)Moisture 3.5 3(ASTMD1744)Density at 28◦C (kg m−3) 0.993 0.987ASTM D4052-86 And IP 365/84Absolute Viscosity (cSt) at30◦C 159 16660◦C 33 3980◦C 17 16(ASTM D445-88 and IP 71/87)Flash point (◦C) 180 164(ASTM D93 and IP 34/88)Pour point (◦C) −5 −5(ASTM D97-87 and IP 15/67)Elemental composition(wt% on dry basis)C 76.4 79.9H 10.5 11.8N ¡ 0:2 ¡ 0:2O (by di3erence) 12.9 8.1Calori7c value (MJ kg−1) 33 40(ASTM D240)Solid content (%) Nil Nil(as methanol insoluble material)Miscibility (%)Hexane 100 73Methanol 100 100Acetone 100 100Diesel (HSD) 100 100

tures. The high miscibility with diesel and methanolis an useful factor for considerations as a fuel. Theviscosity, though on the higher side at 30◦C, reducedrastically at higher temperatures.

5. Conclusions

The CNS oil (both obtained by heating between100◦C and 150◦C and on vacuum pyrolysis) has fuellike properties worth a detail study. The maximumoil yields of about 40% (∼ 15–16% obtained up to150◦C plus 24% obtained on pyrolysis) have beenachieved. A temperature of 500◦C for pyrolysis is op-timum yielding the maximum percentage of oil. How-ever, the liquid-to-oil ratios are independent of themaximum temperature of pyrolysis in the temperature

P. Das, A. Ganesh / Biomass and Bioenergy 25 (2003) 113–117 117

range between 400◦C and 550◦C. The calori7c valueof the oil from CNS is unusually high like petroleumfuels and therefore can be considered to be a promis-ing bio-oil with a potential as a fuel.

References

[1] http://www.cashewindia.org.[2] http://www.bolacashew.com/cnsl.htm.[3] Maharnawar AP. Characterisation and processing of CNSL.

Master of Science (Technology) thesis, Department ofChemical Technology, University of Bombay, 1994.

[4] http://www.hudsonintco.com/cnsl.htm.[5] Harvey MT. (Harven corpn), US Patent 2, 165, 140, 1939.[6] Mihara K, Kobiyame K, Yoshiwa Y. (to Cashew Corpn. Ltd),

Ger. O3en, 1, 813, 794, 969.[7] Mannary VM, Raval BA. Paintindia 1990;40(8):59–60.[8] Dhamaney CP. Paintindia 1976;26:20.[9] Novothy EE, Vogelsank GK. US Patent 2, 251, 547 (1941),

Vide CA: 35:7076-5, 1941.[10] Kudwa KG, Kamath NR. Indian Patent 31, 509 (1948), Vide

CA.: 42:7557, 1948.[11] Soltes J. Of biomass, pyrolysis, and liquids thereofrom. In:

Slots J, Milan TA, editors. Pyrolysis oils from biomass.Producing, analysing and upgrading. Washington, DC:American Chemical Society, 1988.