Sweet sorghum R&D at
the Nimbkar Agricultural
Research Institute (NARI)
A. K. Rajvanshi and N. Nimbkar
Nimbkar Agricultural Research Institute
(NARI),
Phaltan, Maharashtra, India.
ABSTRACT
The research work on sweet sorghum carried out at the
Nimbkar Agricultural Research Institute (NARI) during last twenty-five years
has been summarized. American lines were
crossed with a local Indian fodder/grain variety to produce varieties with a
juicy stalk and good quality grain.
Further breeding was carried out to produce varieties and hybrids giving
high yield of good quality grain while retaining the characteristic of juicy
stalks high in sugar. Complete
development of indigenous technology for fermentation of sweet sorghum juice,
solar distillation of ethanol and finally its use as a cooking and lighting
fuel in new and improved stoves and lanterns was carried out. The technology of producing jaggery
(unrefined sugar) and syrup from sweet sorghum was also developed. Consumer response to these products was
assessed by marketing them in limited quantities. A completely automated multifuel gasification
system capable of producing thermal output between 120-500 kW was developed for
direct heat applications such as those in jaggery and syrup making units. Sweet sorghum bagasse was also tested in an
existing paper mill to assess its suitability for paper manufacture. Areas of possible research for better
exploitation of sweet sorghum have been suggested.
INTRODUCTION
Sweet
sorghum [Sorghum bicolor (L.) Moench] is the only crop that provides grain and stem
that can be used for sugar, alcohol, syrup, jaggery, fodder, fuel, bedding,
roofing, fencing, paper and chewing. It has been used for nearly 150 years to
produce concentrated syrup with a distinctive flavour [7]. Sweet sorghums have also been widely used for the production of forage and silage for animal
feed. The oil crisis of 1973 and 1976
renewed interest in the commercial production of sweet sorghum for biological
transformation into ethyl alcohol for use as fuel or fuel additive [1].
Nimbkar Agricultural Research Institute
(NARI), a non-profit, private organization started work on sweet sorghum
R&D in the early 1970s. This
institute is situated in western Indian State of
Breeding
high yielding varieties and hybrids for grain and sugar production
Cultivars
developed by the U.S. Sugar Crops Field Station at Meridian, Mississippi, Texas
Agricultural Experiment Station, Weslaco and Georgia Agricultural Experiment Station, Griffin were brought to the Nimbkar Agricultural
Research Institute during the early 1970’s.
Their major drawbacks were felt to be: (1) Greater susceptibility to
pests and diseases than the normally cultivated grain/fodder sorghums in
Since sorghum
grain is the staple food grain in our part of
A total of
22 sweet sorghum accessions were tested for three years to identify the most
promising ones for ethanol production. S
21-3-1 and S 23-1-1 were found to be the most promising in terms of stalk and
grain yields, juice quality and total energy production per unit land area
[12].
Hybridization
was carried out with both non-sweet, dwarf and sweet, tall female lines
successfully. Hybrids were generally
found to possess greater uniformity and were felt to be more desirable than
varieties from commercialization point of view.
Thus as can be seen from Figure 1, sweet sorghum planted in 1 ha
area has been found to yield different products viz. grain, leaves, bagasse,
jaggery, syrup or alcohol in given quantities.
Attempts are underway to achieve further increase in the total
quantities of these products obtained as well as qualitative improvement, so
that it becomes more remunerative for the farmers to plant this crop. Our
hybrid "Madhura" is now one of the major crop
in
Development of ethanol production technology including fermentation,
distillation using solar energy and development of stoves and lanterns running
on ethanol
Sweet
sorghum has been noted for its potential as an energy crop. Unlike sugarcane, which is a tropical plant,
sweet sorghum can be cultivated in nearly all temperate and tropical climatic
areas. At NARI, technology of alcohol
production from sweet sorghum and its use as a cooking and lighting fuel for
rural
The
fermentation studies conducted at the Institute have shown that out of the 16
strains tested, the strain NCIM 3319 of yeast, Saccharomyces cerevisiae
gave good results in batchwise fermentation of unsterilized juice to produce
ethanol. Fermented juice containing
10-11% (w/w) total fermentable sugars yielded about 6% (v/v) ethanol after 48
to 72 hours. The batch size was 200 l and no nutrient supplementation of juice was carried out
[2].
A pilot solar distillation
plant consisting of 38 m2 of flat plate solar collectors coupled
to a hot water storage tank of 2150-l capacity was set up at NARI campus ( Fig.
2) in early 1990s. Distillation column
of this completely instrumented facility was of packed bed type and was specifically
designed to run at distillation temperatures of 50-700C. These temperatures are easily obtainable from
solar collectors.
This plant logged about 4000 hours of
operation proudcing 30-40 l.day-1 of 95% (v/v) ethanol [4]. About 70% of total yearly distillation heat
load came from solar energy, while the rest had to be provided by electric
heaters or a biomass-powered producer gas unit.
Technoeconomic analysis for setting up a 10,000 lpd distillery was
carried out. Calculations showed that
for 95% (v/v) ethanol,
the cost will be Rs. 14.5/l ($ 0.40/l) for sweet sorghum stripped stalk cost of Rs. 300/ton ($
8.60/ton).
Fig 2. Solar powered Ethanol distillation plant
An
improved, multifuel lantern called
“Noorie” was developed. It is a pressurised mantle lantern producing light
output of 1250-1300 lumens (equivalent to that from a 100 W light bulb). Compared to existing pressurised kerosene
lanterns, this lantern consumes only 60% of the kerosene and operates at
one-third the pressure. It can run on
kerosene, ethanol or diesel. Ethanol concentrations of a minimum of 80% (v/v) are
required [5]. A pressurised alcohol
stove has also been developed. It
requires a minimum ethanol concentration of 50% (w/w) and above to run. Its heating capacity is 2.5 kW (thermal) for
50% (w/w) ethanol concentration and its thermal efficiency is between 40-55%.
Fig 3. Shows the stove.
Fig 3. Low concentration Ethanol Stove
Development
of protocols for jaggery and syrup production
Industry
for producing jaggery (traditional unrefined sugar) and khandsari (partially
refined sugar) from sugarcane is a Rs. 30,000 million ($ 860 million) rural
industry in
Jaggery of
excellent quality was prepared whenever the brix of sweet sorghum juice was at
least 15 degrees and when the ratio of sucrose to reducing sugars was at least
nine. In contrast to the normally
manufactured sugarcane jaggery, no chemical additives were utilized in the
production of either of these products.
Stalk yield and juice quality data for hybrid “Madhura” have been
collected from year-round plantings carried out every month. It was possible to produce good quality
jaggery from crops planted either during April-May or mid-November to
mid-January.
Excellent quality syrup could
be made when the brix of raw juice was at least 14 degrees, which was more or less throughout the
year. The prepared syrup generally has a
final brix of 70-75 degrees (corresponding to syrup temperatures of
approximately 1060C) and a minimum shelf-life of 6 to 9 months. Lower brix was encountered only in the winter
season plantings (October-November), as these planting dates gave high
grain yields. Most farmers in this area
plant grain sorghum in winter, so this is the only time when grain
becomes available. All other seasons
show a heavy bird predation. It was
possible to increase the brix of juice in winter season by harvesting the
stalks 10-15 days after grain maturity.
Till
todate, about 400-kg jaggery and 1500 kg syrup has been test
marketed. The consumer response has been encouraging. The syrup was found to be especially rich in
calcium, vitamin C, proteins, riboflavin and nicotinic
acid and was free of sulphur or any pesticide residues. The syrup in addition to being a table syrup
to be eaten with bread or pancakes, can be used in salad dressing, as a
sweetener in baked goods or as ice-cream topping [11]. It could also provide a syrupy base for
pharmaceutical formulations. Recently it has been shown to have excellent
antioxidant properties thereby increasing its medicinal value. The Table below
shows the constituents of Madhura syrup and its comparison with honey.
Constituents of Madhura Syrup and
its comparison with Honey
(Analysis
of a sample of Madhura
by CFTRI, Mysore and ITALAB Pvt.
Ltd., Mumbai)
|
|
Madhura |
Honey (Average) |
|
Calorific
value, Cal/g |
2.60 |
3.26 |
|
Total
solution solids, % wt |
77.00 |
81.00 |
|
Total
reducing sugars, % wt |
70.30 |
70.40 |
|
Proteins
(N x 6.25), % wt |
1.65 |
- |
|
Ash, % wt |
3.69 |
0.59 |
mg/100g
|
Calcium |
160.00 |
5.00 |
|
Phosphorus |
11.00 |
4.10 |
|
Riboflavin
(Vitamin B2), |
10.00 |
0.06 |
|
Vitamin C |
11.50 |
5.00 |
|
Nicotinic
Acid |
153.00 |
32.00 |
|
Iron |
0.86 |
0.59 |
|
Sodium |
86.00 |
4.70 |
|
Potassium |
1810.00 |
90.00 |
|
|
Not
detected |
8.00 |
|
Benzoic
acid |
Not
detected |
|
|
Added
coloring matter |
None |
|
|
Pesticide
residues |
Not
detected |
|
* Date for Honey is from Literature
Development of an efficient biomass gasifier which can run on sweet
sorghum bagasse and can be used as a source of heat in the furnace for jaggery and
syrup manufacture
One of the
major improvements in jaggery or syrup making can be affected by improving the
furnace efficiency. Existing furnaces
normally have only 10-15% overall efficiency.
A completely automated multifuel gasification system capable
of producing thermal output between 120-500 kW was developed. In addition to sugarcane leaves and bagasse
from sweet sorghum, or
sugarcane, it can also use other
low-density biomass like wheat and safflower residues and grasses like Cenchrus
and hybrid Napier (Table 1).
The modern
jaggery and syrup-making unit set up at NARI includes this gasifier, an efficient gas combustion unit and a
furnace. The system is controlled by a
programmable logic controller (PLC)-based unit and includes automatic biomass
feeding and diagnostic controls for the gas system [9]. Unlike conventional units, there is no smoke
pollution from this unit. The cold gas
efficiency of the gasifier for direct heat applications is about 45% resulting
in great savings of biomass.
The
gasifier is an open top,
throatless (cylindrical) type and requires the biomass residues
to be chopped into 1-10 cm long
particles, which is carried out using a
2.3 kW electric chaff cutter. The gas
produced (mainly comprising of 15-25% carbon monoxide, 10-20% hydrogen and 1-5%
methane), is combusted in a special
burner designed at NARI. It is basically
a venturi-type burner with a plate for flame stabilization. It produces a bluish-white flame with
temperatures exceeding 12500C. Figure 3 shows the gasifier with the
flame.
Fig 3. Biomass Gasifier and
furnace
The
gasifier also produces char [20% w/w) of input biomass feed] as a by-product. It can be mixed with a suitable binder like
cowdung (15% w/w) to form briquettes using a hand-operated briquetting machine
[9]. These briquettes are smokeless and
make an excellent fuel for chulhas (traditional cooking stoves). Experiments were carried out to study the
potential of this char as a soil conditioner.
Various crops were grown on soils treated with different doses of char,
without any adverse effects.
For direct
heat applications, in
addition to jaggery and syrup making units,
potential beneficiaries of this technology can be rural agro-based
industries like fruit and food processing plants, bakeries, foundries, brick kilns etc. Gasifiers can also be used for drying of
agricultural produce and proudcts, and in crematoriums where substantial
wood saving can result. In addition to direct heat applications, this gasification system can also be
used for electricity generation by powering a diesel genset [14].
Assessment of possible use of fiber from sweet
sorghum bagasse for paper manufacturing
It has been
reported that pulps of sweet sorghum lines can be used for the manufacture of
fine quality writing and printing paper as well as corrugated and solid
particleboard [6].
The most
critical issue facing the Indian industry is the availability of cost-effective
fibrous raw materials. There has been a
chronic shortage of forest-based raw materials, viz. bamboo and pulpwood. The shortage is likely to escalate with
dwindling forest cover. The collection
and recovery of waste paper in
In the
light of this situation it was felt that sweet sorghum
may be an ideal crop to form the raw material of an alcohol-paper complex. Some samples of bagasse from our sweet
sorghum hybrid “Madhura” were given to M/s Shirke Paper Mills Pvt. Ltd., Shirwal for testing. They are one of the few bagasse-based paper
manufacturing units in
The
experience of working with sweet sorghum crop for more than two decades has
shown that better exploitation of
this promising crop will be possible with the development of the
following :
a)
a mechanical whole-stalk harvester;
b)
a leaf stripping unit which can be used before or
after stalk harvest;
c)
improved fermentation methodology and extraction technology;
d)
improved cultivars, which are photoinsensitive, disease and insect resistant,
stress-tolerant, high-yielding and new male-sterile lines, which are sweet and
tall.
Thus the
total utilization of the sorghum plant in a balanced production of food, feed and selected industrial products will
become increasingly important in the developing countries. A total utilization of all components in the
sorghum plant for use in the manufacturing and food industries would increase
cash flow to the farmer and thereby constitute an incentive for him to increase
his production.
ACKNOWLEDGEMENTS
Funding for
the above R&D has been received from MNES, ICAR,
CAPART (all Government of India agencies), USDA and Rockefeller Foundation (
REFERENCES
1.
Schaffert, R. E.
and Gourley, L. M.
1982. Sorghum as an energy
source. Pages 605-623 in Sorghum
in the eighties :
Proceedings of the International Symposium on Sorghum, 2-7 Nov. 1981,
2.
Ethanol production from sweet sorghum. 1988.
A final project report submitted to the Department of Non-conventional Energy Sources,
3.
Breeding sweet sorghum for the
production of sugar. 1988. A final project report submitted to the
United States Department of Agriculture, by the Nimbkar Agricultural Research
Institute, Phaltan. 44 pp.
4.
Rajvanshi, A. K., Jorapur,
R. M., and Nimbkar, N.
1989. Ethanol from sweet sorghum. Publication No. NARI-ALC-1, published by Nimbkar Agricultural Research
Institute (NARI),
5.
Rajvanshi, A. K., and Sudhir Kumar. 1989. Development of improved lanterns for rural
areas. Publication No. NARI-LAN-1, published by Nimbkar Agricultural Research Institute
(NARI),
6.
Hallgren, L.,
Rexen, F., Peterson,
P. B., and Munck, L.
1992. Industrial utilization of
whole crop sorghum for food and industry.
Pages 121-130 in Utilization of sorghum and millets : proceedings of the international workshop on
policy, practice, and potential relating
to uses of sorghum and millets, 8-12 Feb. 1988,
7.
Schaffert, R. E.
1992. Sweet sorghum substrate for
industrial alcohol. Pages 131-137 in
Utilization of sorghum and millets : proceedings of
the International workshop on policy, practice, and potential relating to uses
of sorghum and millets, 8-12 Feb.
1988,
8.
Breeding sorghum for grain and sugar. 1992.
A final project report submitted to the Indian Council of Agricultural Research,
9.
Rajvanshi, A. K., and Jorapur, R. M.
1993. Development of leafy
biomass gasification systems.
Publication No. NARI-GS-1, published by Nimbkar Agricultural
Research Institute (NARI),
10.
Rajvanshi, A. K., De, T.
K., Jorapur, R. M.,
and Nimbkar, N. 1993. Jaggery
and syrup from sweet sorghum.
Publication No. NARI-GUR,
published by Nimbkar Agricultural Research Institute (NARI),
11.
Rajvanshi, A. K., Jorapur, R. M., and Nimbkar,
N. 1994. Sweet sorghum R & D
for food and fuel. Pages 29-34 in To
explore the possibilities of cultivation and processing of supplementary sugar
crops : proceedings of VII Joint Convention of the Deccan Sugar Technologists’
Association (DSTA) and the Sugar Technologists Association of India,
DSTA, Pune 411 005,
India.
12.
Development of sweet sorghum [Sorghum bicolor (L.)
Moench] lines giving high stalk yield and good quality juice for production of
industrial ethyl alcohol. 1995. A final project report submitted to the
Ministry of Non-conventional
Energy Sources,
13.
Shinde, J.
1995. Editorial. Bharatiya Sugar. 22 (1) : 5-53.
14.
Jorapur, R. M., and Rajvanshi, A. K. 1995.
Development of a Sugarcane Leaf Gasifier for Electricity
Generation. Biomass and Bioenergy. 8 (2) : pp 91-98.
Table 1: Characteristics of Biomass Residues Used in
NARI Gasifier
|
Sr. No. |
Biomass Residue
|
Yield T/ha- yr (oven dry) |
Bulk density of chopped material
(kg/m3 ) |
Ash content (%) (w/w,
dry) |
Suitability for gasification |
|
1. |
Sugarcane
leaves |
4-6 |
26-40 |
7-8 |
Excellent |
|
2. |
Sweet sorghum stalks |
20-30 |
70-120 |
4-5 |
Excellent |
|
3. |
Sweet sorghum bagasse |
10-14 |
70-90 |
4-5 |
Very good |
|
4. |
Safflower
residues |
3-8 |
70-80 |
2-3 |
Good;
increased tar products |
|
5. |
Hybrid
napier grass |
24-40 |
42-48 |
8-12 |
Fair;
problems with bridging of fuel & rapid combustion |
|
6. |
Cenchrus
grass |
5.5-7.0 |
26-30 |
11-15 |
-do- |
|
7. |
Wheat
husk |
4-10 |
49-53 |
4.3-11 |
Good |
|
8. |
Sugarcane
bagasse |
17-20 |
150-160 |
1.3-1.5 |
Very good |
September
2001
©NARI 2001
Recently (2015) a high yielding sweet sorghum variety
Madhura-2 has been released by NARI. This can be grown both in Rabi (post
monsoon) and Karif (monsoon) seasons.
A recent paper on our work on sweet sorghum syrup has been
published in Current Science. 25 December 2020