“biocrude” and “biomethane” from croton bonplandianum

Resources, Conservation and Recycling, 1 (1988) 111-122 Elsevier Science Publishers B.a./Pergamon Press pie - - Printed in The Netherlands

111

"Biocrude" and "Biomethane" from Croton bonplandianum

D.K. SHARMA* and H.A. MBISE**

Centre of Energy Studies, Indian Institute of Technology, New Delhi 110016 (India)

(Received September 4,1987; accepted in revised form April 13, 1988)

ABSTRACT

Croton bonplandianum, a latex bearing plant, rich in i~t,ogen, phosphorous and potsuium (N- P-K), and which grows wild, yields good quantities (12-30~, ) of"biocrude" (defined in the text). This biocrude can be "hydrocracked" to petroleum oil T! e seeds of this plant yield 39% oil which can be a diesel oil substitute. The spent residue after extraction of biocrude can be used for the generation of methane ("biomethane") by anaerobic digestion. The spent residue has been found to give good yields (between 4.74-5.66 L/ks/day) of biogas with methane contents from 66-72%. The spent residual plant material obtained after digestion, contains enhanced N-P-K contents. This can be utilized as a fertilizer.

INTXODUCTION

Recent declines in oil prices have provided a grace period to search for future sources of oil and natural gas. World reserves of oil and natural gas are limited and these are being depleted fast. No doubt the recent price decline has en- couraged their consumption, diminishing energy conservation measures. There is a need to find a nondepletable source of oil and natural gas. Biomass is such a renewable source of ener~. L~.iciferous and resinous plants [ 1-9 ], like heavea and guaule (the rubber tloes), yield "biocrude" by tapping the plant for latex or resin or, alternatively, by solvent extraction. "Biocrude" contains a mixture of hydrocarbons, terpenes, fats, lipi&, steroids, flavonoids, waxes and polyphenols. This mixture (defined here as biocrude) can be "hydrocracked" to get petroleum oil. The main advantage of latex bearing and resinous plants is that they grow wild without much agricultural input or management, they can be grown in arid or semiarid zones, and they do not compete wil.~ food and fibre crops. Rather, in the long run, these would help in the development of these desert areas by generating employment.

Laticiferous and resinous plants can be used for the production of both oil

*Author to whom all correspondence should be addressed. **Present address: Ministry of Energy and Minerals, P.O. Box 2000, Dar-ES-Sa¼m, Tanzania.

0921-3449/88/$03.50 © 1988 Elsevier Science Publishers B.V./Perpmon Press pie

112

and substitute natural gas (methane). After extraction of biocrude from these plants, the spent residue, which is rich in cellulosic material, can be u~ed for the generation of biogas ( ~ t i t u t e natural ~ ) . In the present work, studies have been ~ out on the Croton b o ~ z h k m ~ m (Euphorbiaceae)a ~ d , latex beari~ weed having a fast growth rate. Its growth is an environmental m e ~ and problem in India and these plants have to be removed to clear land. Its utilization for the production of oil and biomethane would help elim- inate an environmental hazard. Biomethane can also be converted to methanol throuzh chemical or biochemical routes. The seeds of Croton bonpfand~anum contain about $9% oil It0]. The seeds also contain 3.5% ash which contains K20 (1.4.$%) and PROs (29.8%). This seed oil can be used as a diesel substitute and the spent r e , due obtained after extraction of oil can be compested.

EXPBRIMZNTAL

Extraction o( biocr~te

Croton b o ~ ~ (C.b.) stems and leaves were crushed and powdered to 40-60 BSS mesh size and dried in a solar drier. Dried leaves or stems (10 g ) were Soxhlet extracted with acetone. The spent residue was Soxhlet extracted with benzene.

Similarly, dried C.b. stems or leaves were extracted with methanol followed by hexans, The portion extractable was calculated from the loss in weight of the C,b. items or leaves altar each extraction.

At a larpr scale, C,b, leaves or stems (70 g) were taken in a batch extractor (i,e, S L round bottom flask fitted with a reflux condenser) under reflux conditions with methanol C/S0 mL) followed by the extraction of spent residue with hexans under similar conditions. The spent residues were taken as substrates for bioi~ production.

B/oeu product/on

Substrates (50 g) were taken each in a one litre digester bottle attached to others (Fig, I), Water (700 mL) was added to each d i p m r , leaving some space for gas formation. Digestsrs were inoculated with cowdun8 inoculum (I00 mL), All the dilpmters were incubated at constant temperature (35-37 ° C ). Gas samples were withdrawn daily and analysed for methane and carbon dioxide, usins a 8700 Nucon gas chromatograph.

RI~ULTS AND DISCUSSION

Table I shows the chemical composition of the various components, i.e., leaves, stems end roots of C.b. [ 11]. Roots contained the minimum moisture

113

o ossToe oAs COLLECTOR I

Fig. 1. Experimental set up for one set (out of six) used for the generation of bioges,

TABLE 1

Chemical composition of biomems*

Co~n~osition of Croton bonplandienum (C.b.) (%)

Leaves Stems Roots

Moisture 71 70 43 Ash 1 1 1.5 Volatil,~ matter 76 79. 65 (% on dry. basis)

Cher, fical composition of C.b. (%)

Leaves

Unextracted

Cellulose 49.0 Hemicellulose 19.8 Lignin 19.5 Extractive3 19.0

Extracted residue

50.0 9.2.0 28.0

Stems

Uneztracted

46.0 22.5 20.5 12.0

Extracted residue

52.0 25.0 23.0

Chemical composition of bagasse (%)

Moisture 8,0 Cellulose 49.5 HemicelluloN 28.5 Ligain 15.0

6.0

*Ref. [11].

114

(43%) and leaves and stems contained about 70%. The volatile matter in C.b. were 65-76% and about 1% ash. The plant components were subjected to acetone extraction, followed by benzene extraction of the spent residue, Table 2 shows the results. Acetone is expected to extract the polar components such as polyphenols, chlorophyll, etc., whereas, benzene extracts mostly the nonpolar and less polar chemical components, such as, terpenoids, steroids and hydrocarbons, There were more acetone extractives (AE) than the benzene extractivee (BE). The total AE + BE represented the biocrude yields. The yield of biocrude from the leaves was more than that from the stems. Leaves yielded 20% bioerude, whereas stems yielded only 8.1%.

In fact, leaves contain more latex than the stems and that could be the reason for higher biocrude yields. The solvent for extraction ofbiocrude from C.b. was changed tp methanol followed by the hexane for the residue. Methanol extracts the pokr components whereas, non-polar components are extracted in hexane. This solvent system provides a better fractionation between polar and nonpolar extractivee, as the difference between the polarities of methanol and hexane is more than that between acetone and benzene. In fact, the methanol extractivee (ME) were found to be more than the AE. Overall, biocrude yield through the methanol-hexane solvent system was more than that through acetone-benzene system (Table 2). Leaves yielded about 30% biocrude through methanol-hexane extraction, which was more than that (I4%) obtained through acetone-benzene extraction,

Stems yielded 9% biocrude through acetone-benzene solvent system and 12% through methanol-hexane solvent system. Table 3 shows the biocrude yield from some of the promising latex bearing plants. It can be seen that C.b. (latex bearing plant) yields 18,2% biocrude which is the maximum amongst the potential petrocrops taken for comparison. Only Pergularia e~cnsa yields biocrude equivalent to this,

The use of solar concentrators can be made for heating the extractors. The use of solar energy for heating these reactors has been demonstrated in our laboratory [ 11 ] and can reduce the processing cost by 20%.

Table I shows that C,b, leaves and stems contain 42% and 46% cellulose and

TABLE 2

Sompk Moisture contents (%)

Leav~ 71 S te~ 70 W~de plant 66

Extraction (% on dry basis ) !

Acetone Benzene Total Methanol Hexane Total qs

1~,0 2,0 14,0 20,0 10.2 30.2 8,0 1,1 9.1 8.1 3.5 11.6 9.0 1.0 i0.0 12.2 6.0 18.2

TABLE 3

Comparison of biocrude yields of C.b. and of some potential petro-crops

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Species Moisture Extraction (%) on dry basis

Acetone Benzene Total Methanol Hexane Total

Croton bonplandianum 70.0 9.0 1.0 10.0 12.2 6.0 18.2 Colotropis gigantea 78.0 7.8 0.7 8.5 5.1 2.8 7.9 Calotropis procera 53.0 7.5 0.6 8.1 5.2 1.9 7.1 Hemidesmas indicus 45.0 5.3 0.6 5.9 9.0 3.0 12,0 Pergularia eztensa 89.0 8.0 0.7 8.7 14.1 4.0 18.1 Euphorbia neriifolia 87.0 10.6 0.6 11.2 7.0 6.0 13.0 Pedilanthus tithymaloides 83.0 7.5 0.6 8.1 7.0 3.0 10.0

19.5% and 22.5% hemicellulose, respectively. The percentage of these cellulosic contents is obviously more in the spent residue obtained after biocrude extraction than these in the original C.b. Thus, these could be good substrates for biogas generation, where cellulose, hemiceUulose, fats and proteins can be converted biochemically, through methanogenic bacteria, to methane and carbon dioxide.

Common materials used for biogas generation are: animal manure, agrowastes, industrial wastes and night soil. Weeds have a comparatively favorable C/N ratio for biogasification. Thus, these are quite suitable for methane generation [12 ]. In the present work, the use of various components of Croton bonplandianum (weed) before and after extraction of biocrude has been made. The following substrates were taken: extracted leaves (EL), dried unextracted leaves (DUL), dried extracted stems (DES), unextracted stem (UES), a mixture of extracted stem and bagasse (1:1) (SB) and unextracted wet leaves (UWL). Cowdung inoculum (100 mL or 5% W/V in an IL digester) was used for the anaerobic digestion of these substrates. A group of microorganisms act on the organic substrates to convert the biopolymeric materials (cellulose, hemicellulose, fat, etc.) into soluble monomers, which become substrates for the microorganisms in the second stage, in which the soluble organic com- pounds are converted to organic acids. These organic acids are then converted to methane and carbon dioxide by the methanogenic bacteria.

Table 4 shows the cumulative volume of biogas generation per day, from 3 to 42 days of digestion (of 50 g biomass substrate). There was no significant biog~s productiozl during the first two days. Figure 2 shows the total gas production (mL) at different digestion times (days). Minimum biogas generation was from the unextracted wet leaves (UWL) (2725) mL) as these contained minimum hemicellulosic mid cellulosic contents because of high moisture contents (Table 1). Unextrncted leaves produced more biogas than the extracted leaves upto 40 days. But the biogas production after 42 days was more in the

116

T A B L E 4

C u m u b t i v e v o l u m e o f b i o ~ s ~ (mL) ( fmm3/12t86to 13/1/67)

Dilpmer containing (mL) 1 2 3 4 5 .6 7 8 9 10 U 12

C.bJ~ves - - - - U , n t m m d C . ~ - - - -

C.b.mm - - - - U n n t m m d C.b.mm - - - - UnHm~M'C~b ,mm+ba~Ne - - - - U n n t m c t ~ b ~ h C . b , b a m - - - -

1~ 14 ~ s n s .

Ext~cted C,b, l~v~ 1925

E x t ~ C . ~ m m 8800 8880 U n e x m c t e d C , b , m 4050 44?5

Umxtm~tedC.b.mm+b~lm~ 3650 4000 U n e x ~ h ~ h C . b . l u m 1500 1525

25

~ x t m ~ t e d C . b ~ m U n n t m c t ~ l C,b, b a v n -- --

~ t r a c t e d C,b,stem " "

U n e x t m c t e d C , b , # e m - - - - UnexLn~c~l C , b , ~ m + ~ - - - - U n o x ~ ~ C.hJ~vm - - - -

70 250 800 850 950 IlOO 100 300 700 '725 900 IlOO 200 400 MO 650 800 IlOO 180 87~ 650 9 ~ 1400 1850

300 400 525 600 850 IlOO 100 250 88O 480 780 1500

15 16 17 19 19 20

4175 5480 5775 6075 848O 1975

29 30 31 32 33

- - 8178 - - 8600 - - 4278 - - 5175 - - 4680 - - 1628

~7 28

6175 6475 7480 7600 6 3 ~ 8 6 ~ 8800 8600 ?800 7780 2400 ~

4100 -- --

4400 o i

5575 -- --

1725 - - - -

1175 1275 1475 1725

1200 1400 1800 2150 1600 2200 3050 3400 2350 2 8 5 0 3 3 6 0 3 8 0 0 1600 2060 2700 33OO 1150 1250 1400 1450

21 22 23 24

48?6 4678 - - 5175 6100 - - 6300

6125 6475 ' 69?5 68?8 7278 - - 7680 6150 6450 - - 7000 2125 3335 - - 2725

6675 6975 71 - - - - ?800 8000 ~OO - - - - 8878 9 1 ~ 9225 * * 8 8 0 0 9 0 0 0 9200 - - - -

?900 8050 8250 - - - -

marinated C.~iRvm UnexU~ctMI C.b.luvH ~ tm~tK I C.~ttem UnRtqwt~l C.b.mm U n R ~ t ~ / C . b . ~ t m + b ~ m e U~xtm~ted bmh C, I~ IRm

' R R d l n p not takem

34 35 36 ~ i 38 39 40 41 42

???S 79?5 §175 83?8 - - - - - - 9125 9475 8600 8684) 8/00 8800 - - - - - - 9150 9150

100115 10175 10575 10578 ' ' * 11075 11325 9950 10150 10184) 10300 - - - - - - 10850 11150 8600 8750 8900 9080 - - - - - - 9880 9880

case of extracted loaves (9475 mL) than that from unoxtracted leaves (9150 mL). This showed that the biops generation from leaves is reduced after extraction of biocrude.

Fatty components are removed from the leaves during biocrude extraction, which result in the initial dropping of biogas yields up to 40 days, but after 40 days, the biogas generation was more in the extracted leaves. This is thought due to the digestion of cellulose becoming predominant through solubiUsation and microbial degradation in the prolonged process of biogas generation. Therefore, after 40 days the gas yield from extracted leaves containing comparatively more cellulosic contents (Table I) is enhanced.

Stems showed more b i o ~ production tha~i leaves, which could be due to the fact that stems contain more cellulosic and hemicellulosic contents than

14

. . I

~w

w iO

5 ~ a

W i -

j 6

Q, J

x 10 3

. . . . O 1: Extracted CB leaves

. . . . . . . . . . . . O 2: Unextrocted CB leaves D 3: Extracted CO stem

. . . . . . . . . D ¢ : Unextracted CB stem O S: Unextracted CB stem • bagasse D 6: Unextracted fresh CB leaves

Average fermentation temp: 35-37 'C Total solids: 7%

Cow clung inoculum: S %

0 ~ - - ~ I i I i I i I , I 0 6 16 2~ )2 &0

REI'ENTIOH Tilde (days)

117

Fig. 2. Cumulative volume of biogas production at different retention times.

leaves (Table 1). Biogas generation from extracted stems (11335 mL) was more than that from unextracted stems (11150 mL).

Statistical analyses of the data obtained on the biogas generation from different substrates was done and the conclusions drawn from the data were con- firmed [11]. This showed that biocrude extraction was a beneficial pretreatment for biogas generation. There could be two reasons for this. One could be that extraction breaks the plant cells by extracting the cytoplasmic fluid, i.e. latex extractives. Action of solvents (hexane and methanol) under reflux conditions breaks the cells to extract the biocrude from cytoplasm. In fact, latex is accumulated mostly in specialized cells or vessels known as lac- tifere [18]. In stems, latex is stored in the rings of lactifers in the bark. Ex- traction of latex (biocrude) from the stem (bark) exposes the hemicellulose, cellulose and lignin. As cytoplasmic fluid (latex) is removed by solvents from plant tissues, cells collapse, and cell wall components, such as, cellulose, lignin, hemicelhlose and proteins, are disrupted and their association is disinte- grated. Moreover, extraction increases the surface area and porosity of the biomass, alJowing the better accessibility for bacteria and methanogenic bac- terial enzymes. Another reason could be that biocrude extraction increases the percentage of cellulosic contents (Table 1 ) in the spent residue. Further work on finding these reasons is currently underway.

Table 5 shows the overall average of biogas production rate, expressed as

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TABLE 5

Ovendl averqe of biops production rate in a one litre disester

D i s e s t e r c ~ w i t h : Dif~tion Totaivolume mL/h mL/d~ time (days) (mL) (Based

onS0g subltrate)

L/ks/d~v (Bmedon lkS sub#rate

DI: F, xtracted C.b. leavn 40 9475 9.87 236.90 4.74 D~: Unextracted C.b. l~veJ 40 91S0 9.53 228.70 4.57 D~: ~tmcted C.b. item 40 11825 I!.79 282,96 5.66 D4: Unextlm~C.b,e~m 40 11150 11.61 278.64 5.57 D~: Unez~ct, dC.b. 40 10880 11.33 271.96 5.44

i t e m + ~ D6: Unextt~cted fresh 35 2725 3,55 85.20 1.70

C.t~ IMvu

mLlh, mL/day (based on 50 g of biomass) and L/kg/day. Average hourly, daily or by weight daily rates were maximum in the extra©ted stems of C.b.: 11.79 mL/h, 282.96 mL/day, 5.66 L/kg/day, respectively. This was followed by the rate for unextra©ted stem of C.b. The biogas production rate for the mixture of bagasse and extracted C.b. was less than that for the unextra©ted stem,

Rutes of biogas generation from leaves were less than those from stems. Minimum rates could be seen from wet leaves (3.55 mL/h, 85.20 mL/day and 1.70 L/kg/day) and the biosas generation rate for extracted leaves was more than that for the unextracted leaves. This follows from the same reasoning as given earlier for blobs generation.

These studies showed that extraction of biocruds renders the spent residue more susceptible to anaerobic digestion.

The mixture of bagasse and extracted C.b. stems showed less biogas yields (10880 mL) than the extracted (11325 mL) or unextracted C.b. (11150 mL). Table 1 shows the composition of bagasse. Bagasse was added on the premise that this would be digested smoothly and thus, would help in the digestion of Croton bonp/endianum, but this did not happen. It seems C.b. is better substrate for biops generation than bagasse. In fact, extracted C.b. stem contains more holocellulose than bagasse, though bagasse contained more of these than the unextracted C.b. stem. Moreover, C/N ratio in weed is 26:1, which is op- timum ratio for biopsification by anaerobic digestion (using methanogenic bacteria) [ 12 ]. This could be the reason for the better oiu~tLicatlon results from C.b. stems. A mixture of latex bearing plant, such as Euphorbia tiruealli Linn. with cowdung (1/1 W/W), has been reported [ 14 ] to give higher output of total gas by anaerobic digestion than that from cowdung alone. Even more methanogenic activity was observed in the digestion where a mixture of Eu-

119

phorbia tirucaUi and cowdung was used as compared to that from cowdung alone.

The yields of biogas from extracted and unextracted C.b. stem was found to be more than that from agrowastes and was comparable to that from cowdung [ 11]. Further work on the studies of biogas generation using mixtures of Cro- ton bonplandianum, water hyacinth and bagasse is being extended.

Figure 3 shows the methane contents in the biogas per week. Methane contents from all the substrates studied were found to increase with increase in the digestion time. Maximum methane contents (72%) were found in the extracted stem of C.b., followed by 70% from extracted leaves of C,b. Unextracted stem of C.b. showed the minimum methane contents of 62%, which were less than those from the mixture of extracted stem of C.b. and bagasse (66%). Wet leaves showed a greater methane content (68%) than those in the weekly biogas from unextracted leaves. Statistical analyses of the data obtained were done [ 11 ] and supported the above results. The mixture of extracted C.b. stem

20 r

\

. . . . O I : Extracted CB kczves

. . . . . 02: Unextracted C8 leaves O3 : Extracted CB stem

- - - - . . - - - - Or, • Unextracted CB stem . . . . . . . . . . . . . OS : Unextractecl CB stem. bagasse - - - - - - - - - - O6 : Unextracted fresh CB leaves

1

i

g~

I i/ I /

#

\ , \ \

I I I I ! 2 3 4 S 6

WEEK NUMBER

120

70

60

SO

~0 . |

f }0 I

|0

x O! Etl~Jcted CO leaves

o O~ Ue, ettmc~ted CBINveJ 0 0]1 Eelmcted CO s l ~ I O~ tNxlm¢led CB Item • OS U~tnc l~ l CB shm.l~gaue • D6 Ue~tmct~ fre~ CB leaves

I I I I I I

DAYS

Fig, 3, (a), Weekly biogas production: (b), Methane contents in blobs.

and bas~se showed hiilher methane contents in the biogas than those in the biolla8 from extracted or unextracted C.b. stem in the first 4 weeks. This showed some advantap of usin8 basasse along with C.b. stem, i.e. the use of bagasse enhances methane yields in the first 4 weeks. These studies are being extended further. Althoush the b i o ~ yield from leaves was less than those from the stem of C.b., still the methane contents in biops were more from the leaves, especially in the first four weeks. This could be due to the fact that the cellulose in the lignocellulosic biomu8 of leaves has loose lignin-~ellulose chemical bonds and is easily solub'dized and the action of methanopnic bacteria is faster in leaves which are softer than stems. Above studies had shown that extracted C.b. stem 8ive8 the maximum biosas yields. Table 6 shows the methane contents in biops pnerated every week from the extracted C.b. stem. The methane contents increased from 2'7% in the first week to 72% in the sixth week. The methane percentap did not show maxima or minima. Rather it showed all increase with an increase in dipstion time. This is due to the fact that as the dipmtion time incumses, the reaction of methanogenic bacteria also increases, to convert more and more of the acids to methane. Also, more COs is

121

TABLE 6

Relationship between wee, kilt c u ~ ~, ,~ ;ota! volume of biogas and methane content (%) from extracted C.b. stem

Week no. Total volume (Litres) Methane (%)

1 0.800 27 2 3.050 46 3 2.625 54.8 4 2.400 58.4 5 11.275 69.3 6 0.225 72.0

converted to CH, over an extended incubation period, thus reducing the CO~ concentration and increasing the CH4.

The spent residue of C.b. obtained after the biogesification was found to be enriched in potash, nitrogen and phosphorus, because of three reasons: (1) extraction of biocrude raises the N-P-K contents in the spent residue; (2) conversion of cellulose through biogasification also raises the N-P-K contents in the spent residue; and (3) the original C.b. is rich in N-P-K which makes it suitable for composting. Thus, the spent residue of C.b. obtained after biogasification can be utilized as fertiliser/soil conditioner, with or without chemical fertilizers.

CONCLUSION

The studies reported here show that about 12-30% yields of biocruds can be obtained from the leaves and stems of Croton bonp~m~mnum, along with the extraction of 39% of diesel fuel substitute from its seeds. Therefore, Croton bonp~m~i~num appear~ to be a potential candidate for "petrofarming". The biocrude obtained can be hydrocracked to get oil. The spent residue obtained from the extraction of biocrude from C.b. can be utilized for the generation of biogas. The methane content in the biogas is between 66-72% and can be used as a substitute natural gas. Methane obtained can be converted to methanol under high temperature ( 400-600 ° C ) and high pressure (5-10 MPa ) with cop- per or nickel catalysts [ 15 ]. Methane can also be converted to methanol through biochemical routes under milder conditions by inhibiting the methanol dehy- drogenase enzyme by using iodoacetic acid in the anaerobic digestion process [ 16,17 ]. Therefore, petrocrops could form an alternate and renewable source of oil, natural gas and methanol.

Since the extracted stems produced more bioges than the unextracted stems, this indicates that extracted ~tems are better substrates for biogas generation. Further work is being undertaken to study anaerobic digestion of latex alone.

122

In some countries latex bearing plants are being commercially used for biogas generation [ 11 ]. It would be worthwhile to recover biocrude before charging these to digesters for biogas generation.

ACKNOWLEDGEMENTS

This work was carried out as project work of Mr. H.A. Mbise, under the United Nations University Programme in Renewable Energy Systems at the Centre of Energy Studies, Indian Institute of Technology, New Delhi, 110 016, India.

REFERENCES

I Calvin, M., 1977. Energy Res., 1: 290. 2 Hillen, L.W., Wake, L.V. and Warren, D.R., 1980. Fuel, 59: 446. 3 Hall, D.O., 1982. Experientia, 38: 3. 4 Bhatia, V.K., Srivastava, G.S., Garg, V.K., Gupta, V.K., Rawat, S.S. and Singh, J., 1983.

Fuel, 62: 953. 5 Erdman, M.D. and Erdman, B.A., 1981. Economic Botany, 35: 467. 6 Sharma, D.K. and Babu, C.R., 1984. Fuel Sci. & Technol., 3: 49. 7 Sharma, D.K. and Prasad, R., 1986. BiomMs, 11: 75. 8 Srivastava, G.S., 1986. Proc. Nat. Workshop on Petrocrops, New Delhi. 9 Bhatia, V.K., 1986. Proc. Nat. Workshop on Petrocrops, New Delhi.

10 The Wealth of India, 1950. Paw Materials, Vol. 11, Published by C.S.I.R., New Delhi. ! ! Mbise, H.A., 1987. Petroleum Extraction U~ing Solar Energy and Production of Biogas or

Alcohol t~m Petrocrops. Project Report of United Nations University Programme on Re- newable Sources of Energy, Submitted in liT, Delhi, February.

12 Guide Book on Btogas Development, 1980. Energy Resources Development Series No. 21 United Nations, New York.

13 Introduction to Plant Biochemistry, 1983. T.W. Goodwin and E.I. Mercer (Eds.), Second end,, Pergmon Preu, UK,

14 P~Mekaran, P., Swaminathan, K.R. and Krishanavani, S., 1986. Pro¢. Nat. Solar Energy Convention, Madurai, India, Sept. 12-15.

15 Hunter, N.R., Geuer, H.D., Morton, L.A. and Prakaah, C.B., 1984. Pro¢. 4th int. Syrup. on A|cohoi Fuels, Ottawa.

16 Sharma, D.K., Personal Communication. 17 Sharma, D,K,, Unpublished Results.

“biocrude” and “biomethane” from croton bonplandianum

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