Tanzania Sisal Industry: Auditing and Characterization of Sisal Post ...

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), pp. 84-94
International Journal of Pure and Applied Sciences and Technology
ISSN 2229 - 6107
Available online at www.ijopaasat.in
Research Paper
Tanzania Sisal Industry: Auditing and Characterization
of Sisal Post-Harvest Wastes as a Bio-Resource for Bio-
Refining
Anthony Manoni Mshandete 1, *, Oscar Kibazohi 2 and Amelia Kajumulo Kivaisi 1
1 Department of Molecular Biology and Biotechnology, College of Natural and Applied Sciences,
Uvumbuzi Road, Mwl. J.K. Nyerere Mlimani Campus, University of Dar es Salaam, P.O. Box 35179,
Dar es Salaam, Tanzania
2 Department of Chemical and Mining Engineering, College of Engineering and Technology,
University of Dar es Salaam, P.O. Box 35131, Dar es Salaam, Tanzania
* Corresponding author, e-mail: (Anthony.mshandete@yahoo.com; mshandete@amu.udsm.ac.tz)
(Received: 11-12-12; Accepted: 5-2-13)
Abstract: A waste audit case study was conducted for sisal post-harvest waste
(SPHW) generated at Fatemi sisal estates in Tanzania to evaluate its potential for
use as substrate for mushroom cultivation and biogas production by integrating
quantitative with qualitative methods and laboratory analysis. Annual generation
of fresh sisal boles waste (SBW) and remnant leaf stubs (RLS) per hectare was
estimated at 22 and 44.5 tons, respectively. The chemical compositions of SBW
and RLS as well as the leachate extracted from the fractions were established.
Regardless of the fraction analyzed, contents of volatile solids, total carbon, total
organic matter were in the ranges of 93-98%, 49-55% and 91-98% on dry weight
basis, respectively. Total sugar contents of the solid and liquid fractions ranged
between 8-27% and 30-35 mg/l, respectively. The chemical oxygen demand
(COD) content of the SBW and RLS fractions were between 20 and 26 gO 2 /l,
respectively. The high values of organics contained in the SPHW fractions is
indicative of its potential as feedstock for a biorefinery that produces food
(mushroom), feed, biofuels (biogas, bioethanol), biochemicals and other
bioproducts. On the basis of the established characteristics, an innovative
approach for the utilization of the waste is proposed.
Keywords: Sisal waste, biorefinery, utilization, management.

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 85
1. Introduction
Sisal is a semiarid and marginal land crop of the tropics whose leaves are used for extraction into
natural hard fibers by either wet or dry decortications (Kimaro et al., 1994). Tanzania is the forth
world's largest sisal producer currently at 24,600 tons of sisal products per annum earning the country
foreign exchange through exports. However, sisal fibre production is a high waste process currently
using only 2% of the plant and the remaining 98% biomass being various fractions of wastes. Sisal
processing wastes include; sisal leaf decortications wastes (SLDW), short fibres (flume tow),
wastewater and sisal dust. The industry also produces post harvest waste (SPHW) that comprises of
sisal stems (comprising of boles and leaf remnant stubs) and poles (Muthangya et al., 2009). SLDW
is commonly disposed off raw into the environment and SPHW is disposed off before replanting and
mostly by burning.
Although currently a menace to the environment, the 98% could be regarded as a bioresource not a
waste (TSA, 1995;Bisanda and Enock, 2003). Sisal waste is now known to be more valuable than the
2% of fibre if fully exploited to produce high value commodities such as edible mushrooms, biofuels,
biofertilizer, foam liquid (cement foaming substance which enlarge sand and cement mixture),
organic acids (lactic acid, citric acid, acetone, butanol), composite, low calorie dietary fibers,
functional foods, sweeteners, thickeners in ice creams, sandwich spreads, chocolate products, breads
and pastries etc, fine and green chemicals (Kimaro et al., 1994; TSA, 1995;Bisanda and Enock,
2003; Muruke et al., 2006; Mshandete and Cuff, 2008; Elisante and Msemwa, 2010;Mshandete,
2011). Adding value to waste will make the industry more competitive through diversification of its
markets. Despite this big potential, it is only one factory in Tanzania that is utilizing SLDW at
industrial scale for biogas to electricity generation of 150-300 KWh/day from a 1700 m 3 biogas plant
since 2007. As for the rest, sisal waste remains grossly underutilized.
In order to be able to utilize sisal waste for commercial production, information on their availability,
quantity and composition is crucial. Whereas elaborate information on generation rates and
characteristics of sisal wastewater and decortications waste is provided in the literature (Mshandete et
al., 2004; Mshandete et al., 2006; Muthangya et al., 2009) while that on SPHW is scanty (Mshandete,
2011). The aim of this study was to establish the quantity and quality of SPHW available for
cultivation of oyster mushrooms and using the spent SPHW for biogas production.
2. Materials and Methods
2.1 Waste Quantification
Quantification of SPHW involved a field survey to Fatemi sisal estate, which is owned by
Mohammed Enterprises Tanzania Ltd (MeTL) and is located in Morogoro, Tanzania for site
reconnaissance. Information was gathered on acreage of the estate, sisal density of sisal plants per
hectare, rates of generation of the waste and its current management methods through guided
interviews of the estate management staff.
Twelve samples of sisal boles with the attached leaf stubs were collected randomly from one-hectare
farm area and transported to the laboratory. They were each weighed before the leaf stubs were
removed from the core-sisal boles by using a machete and categorized by weight to small, medium,
large and extra-large. The fresh weights of the core-boles and leaf stubs fractions were recorded. Both
fractions were then chopped into 3-5 cm pieces and dried in the sun and their weights recorded once
more. Fresh and dry samples of the two fractions were taken for physico-chemical analysis according
to Gumisiriza et al. (2009).

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 86
2.2 SPHW Leachate (juice) Extraction
The chopped pieces of the core-bole and leaf stubs were crushed and minced using a laboratory
mincer. One hundred grams of the processed core-bole and leaf stubs were weighed using an
Adventurer TM balance (Ohaus Corp, Pine Brook, NJ, USA) each separately into 1000 ml of tap
water. Extraction of leachate (juice) from core-bole and leaf stubs was done by hot water extraction
method according to Gaafar et al. (2010). The mixtures of core-bole and leaf stubs and tap water were
brought to a boil at 100°C in two separate pans using a laboratory table hot plate (E.G.O. (Elektro-
Gerätebau GmbH), Germany) and boiling was continued for 20 minutes. The boiled slurry was left to
cool to room temperature. To extract the leachate (juice) the slurry was squeezed manually through
two layers of cheesecloth. The filtrate obtained was subsequently filtered manually by squeezing
through a 2 mm mesh size plastic sieve. The extracted liquid was referred to as leachate (juice). The
solid left after leachate (juice) extraction was sun dried for five days and was referred to as biomass
residue after leachate (juice) extraction.
2.2 Analytical Methods
Determination of total solids (TS), volatile solids (VS), total nitrogen (TN), ash content, chemical
oxygen demand (COD), biological oxygen demand (BOD 5 ) was done according to standard methods
(APHA, 1995). On the other hand, total carbon was estimated according to Allen (1989) and Nelson
and Sommer (1996). The organic matter content was determined by the dry combustion method
described by Jiménez and García (1992) and Lyimo et al. (2002). Total fibers were determined by the
permanganate method as Neutral detergent fiber (NDF) and Acid detergent fiber (ADF) according to
Goering and Van Soest (1970). Total sugars of SPHW fractions were determined by phenol-sulphuric
acid method according to Dubois et al. (1956). Total dissolved solids (TDS), conductivity and pH
were measured using a portable pH microprocessor probe and meter (HANNA-Italy). Minerals
content were determined as described by AOAC (1984) and Allen (1989). Crude fiber was
determined using Near Infrared Spectrophotometer (NIRSystems, Inc, USA). Volatile fatty acids and
alkalinity were determined by titration method described by Buchauer (1998) and Lahav and Morgan
(2004).
3. Results
3.1 SPHW Production and Disposal at Fatemi Sisal Estate
The sisal plant currently grown at Fatemi sisal estate is Agave hybrid 11648. The estate’s area under
cultivation is 2,000 hectares each with a population of 5,000 plants grown in double rows. The sisal
post harvest wastes comprises of sisal poles, core-sisal boles and stubs of leaves that remain on the
boles after every cutting. The sisal bole is the intermediate part between roots and stem covered with
a hard lignified cortical layer or bark of 2-3 mm thick, onto which leaves are attached. SPHW
fractions account for 50% of the sisal plant and are produced at the end of the plants’ productive life
(6-12 years). The average weights of the various sizes of sisal boles with the attached leaf stubs are
shown in Table 1. The weights of the core-boles and leaf stubs ranged between 19 and 129 kg. The
largest and smallest core-sisal boles without leaf stubs weighed between 44 and 4 kg and their sisal
leaf stubs weighed between 85 and 15 kg, respectively. Generally, the weight of the leaf stubs
contributed much more to the total weight of the waste than the core-boles (Figure 1).
Poling of sisal plants is not uniform and differs even on the same plot due to many factors including
type of soil and available soil nutrients, dry and rainy season, temperature, humidity and other microclimate
factors. Experience revealed that after 3-4 years of economic life, about 40-50% of the plants
are uprooted and 80-90 % are uprooted within 5-12 years in order to replant the farm. Therefore it is
assumed that each year 10 % of sisal plants are uprooted before replanting new ones. Based on X-

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 87
large category (44 kg sisal bole and 85 kg sisal leaves remains), about 22 tons and 42.5 tons of sisal
boles and leaf stubs, respectively can be projected per hectare annually from Fatemi sisal estate.
When sisal boles and sisal leaves remains were chopped and sun dried for seven days, they became
35% and 38%, respectively of their original fresh biomass. These translate into an annual production
of about 15,000 tons of dry sisal boles and 32,000 tons of sisal leaf stubs. Currently, the boles are
crushed and left to rot on the farm and the poles are sold/and or given for free to be used by the local
community around the factory.
3.2 Characterization of SPHW
The chemical compositions of the various fractions of the core-sisal boles and the leaf stubs are
shown in (Tables 2 and 3). Generally, the solid fractions were rich in biodegradable substances in
terms of volatile solids (VS) in the range of 93-98% and total sugars ranging between 8 and 27 mg/l.
The fresh SBW fraction had the highest VS content and its dried fraction had the least. On the part of
total sugar content, the fresh RLS fraction had the highest content whereas the biomass residue after
leachate extraction from the same had the least content. Furthermore, the solid fractions were
characterized by high crude fiber content in the range of 25-81% and high C:N ratios ranging between
24 and 285. The biomass residue after leachate extraction from SBW fraction had the highest crude
fiber and C:N ratio values. Similar to the solid fractions, the leachate extracts were found to be rich in
biodegradable substances in terms of VS at about 93 and 97% and in total sugars at about 30 and 35
mg/l whereby the leachate from the RLS fraction had the highest content of VS and total sugars.
4. Discussion
4.1 Quantification of Sisal Post-Harvest Waste
Availability of a substrate in abundance and at low or not cost is the basis for choosing to utilize it for
industrial production and in this context SPHW qualifies. In this case study, the annual generation of
SBW and RLS fractions was estimated at 15,000 and 32,000 tons of dry weight, respectively for the
2000 ha Fatemi sisal estate (Table 1 and Figure 1). Applying this generation estimation rate to a total
of 52,000 hectares under cultivation in Tanzania (Semotony, 2012), total SPHW generation by the
sisal industry amounts to 1,222,000 tons annually. To our knowledge, this study is for the first time
reporting elaborate information on generation of SPHW in Tanzania, and the region. Brief
information on relative weights of sisal boles, which tallies with the findings of this study was
reported by Kimaro et al. (1994).
4.2 Composition of Sisal Post-Harvest Waste Fractions
Suitability of any biomass as feedstock for processing to bioproducts very much depends on its
chemical characteristics (Table 2 and 3). The various solid fractions of SBW and RLS were
characterized by high organic matter contents of up to 97% in terms of VS and about 55% in terms of
total organic carbon. These values are similar to those obtained previously for sisal leaf
decortications pulp by Mshandete et al. (2004) and Muthangya et al. (2009). Apart from high organic
carbon content, the fractions had high total sugar contents in the range of 8-27%. These results are in
agreement with the high (16.3%) inulin sugar content reported by Elisante and Msemwa (2010) for
sisal boles. Furthermore, all the fractions showed low hence safe levels of light metals including Na,
Mg and Ca, which are required for microbial growth but cause inhibitory effects when found in high
proportions as previously documented (Chen et al., 2008). Judging from their solid and organic
matter content, the total sugars in particular, the waste fractions generally contain easily
biodegradable substances hence potential feedstocks for bioconversion to a wide range of value
added products such as organic acids, alcohols, pharmaceutical chemicals and biogas through
applying a biorefinery approach (Francesco, 2010).

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 88
Despite the high organic matter profile, the fractions had high crude fiber content ranging between 25
and 81%. This characteristic makes the fractions to be categorized as heavily biodegradable
(hydrolysable) materials requiring pre-treatment for subsequent bioprocessing including when
anaerobic digestion is an option. Besides, their high C:N ratio in the range of 24-201 necessitates codigestion
with nitrogen rich materials for an improved anaerobic digestion process (Mata-Alvarez et
al., 2012). This effect was previously demonstrated by Mshandete et al. (2004) by co-digesting sisal
decortications pulp with fish processing waste.
This study further characterized the extracts (leachates) of the waste fractions to explore the
possibility of utilizing them instead of the solid materials. The chemical profiles of the leachates from
the fresh SBW and RLS were to a greater extent found to be similar to those of their original fractions
(Tables 2 and 3). Use of the leachate instead of the solid fractions may be an innovative approach for
easy handling and pumping in bioreactor systems. The leachate extraction cost may be off-set by the
benefits considering the sample percolation methods available (Gaafar et al., 2010). If the option is
anaerobic digestion for biogas production, biomass percolation has been shown to increase methane
production and ensure waste stabilization (Busch et al., 2009). The biomass residues after leachate
extraction was characterized by very high crude fiber values in the range of 63-81% and their total
sugar content was about 50% of that obtained for the original fractions and the leachates.
Nevertheless, the rest of the parameters were similar to the rest of the fractions, which still makes
them potentially suitable substrates for bioconversion to a number of products including mushrooms
4.3 Proposed Integrated Utilization of Sisal Post-Harvest Waste
As mentioned previously, sisal fiber production is conventionally a high waste industry with low
profitability at high capitalization hence unable to be sustainable and compete in the global market
(UNIDO, 2002). In order to ensure ecologically sustainable industrial development, reversal of the
current situation from utilizing only 2% of the sisal plant to 98% was proposed under the Cleaner
Production Programme (UNIDO, 2005). This would be achieved through diversifying processing and
products. From the sisal leaf decortications waste, production of wax, alcohols and other chemicals or
biogas and biofertilizer was proposed. For the post-harvest waste (boles and roots), they proposed
production of alcohol, inulin and pharmaceutical chemicals. On the basis of the results of this study,
we propose an innovative two-in-one approach within the UNIDO framework (Figure 2). In the first
option, the entire sisal bole is used for cultivation of mushrooms and the mushroom spent substrate is
co-digested with cow-dung manure anaerobically for biogas production. The effluent of the process
known as biogas manure is valuable biofertilizer. In the second option, the two fractions may be
utilized together or separately depending on the desired products. Here, the chopped and crushed
fractions are used for leachate extraction and the leachate may be used in a biorefinery for production
of a wide range of products such as inulin, organic acids, ethanol and biogas. The biomass residue
after leachate extraction may be utilized for mushroom cultivation as well as for animal feed
production using white rot fungi. Again the mushroom spent substrate may be a feedstock for
anaerobic digestion process. Unlike the UNIDO proposal for the post-harvest waste, this approach
has more options for more products giving the industry more flexibility in choices, which is an
additional competitive advantage.
5. Conclusions
Although highly fibrous and poor in nitrogen, sisal post-harvest waste produced by cultivation of
Agave hybrid 11648 has high contents of organic matter and rich in total sugars. These characteristics
make it potentially suitable for production of a wide range of high value commodities. The waste
generated by Fatemi sisal estate is currently available for free and in abundance awaiting exploitation.

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 89
Tables and Figures:
Table1: Weights of different size categories of sisal boles and leaf stubs.
Size
Core-Sisal bole
(kg)
(Mean±SD, n=3)
Sisal leaf
stubs
(kg)
Small 4±2.0 15±2 19
Medium 16±1.5 38±1 54
Large 34 ±1.0 84±2 118
X-Large 44 ±2.0 85±3 129
Total weight
(kg)
Table 2: Chemical characteristics of SBW fractions (Mean±SD, n=3)
Parameter Fresh Dry fraction Biomass residue after Leachate
fraction
leachate extraction
Total solids (TS 30.91±0.95 80.88±7.18 36.05±0.75 9.72±0.01
%)
VS (% TS) 98.17±0.52 93.27±1.43 94.19±0.60 93.51±1.50
Total carbon 54.4±0.55 52.69±0.16 54.81±0.32 54.24±0.27
(%TS)
Total Nitrogen 1.13±0.13 1.46±0.02 0.22±0.02 1.24±0.13
(%TS)
C:N ratio 48:1 36:1 285:1 44:1
Total organic 97.99±1 94.83±0.28 98.66±0.58 97.63±0.49
matter (%TS)
Total sugars 15.32±3.91 13.27±0.91 8.45±0.50 30.24±2.26
Crude fibers 51.43±1.06 40.35±1.06 81.17±2.34 1.1±0.13
(%TS)
NDF (%) ND 22.7±0.36 ND ND
ADF (%) ND 20.18±0.07 ND ND
Hemicellulose 20.14±1.89 10.14±0.89 8.14±0.22 6.41±0.26
(%TS)
Ash content 1.83±0.52 6.73±1.43 5.80±0.60 6.48±1.50
(%TS)
Calcium (%TS) 4.13±0.13 5.32±0.16 4.96±0.28 8.14±0.10
Magnesium (%TS) 0.20±0.02 0.62±0.12 0.12±0.01 2.10±0.11
Potassium (%TS) 1.18±0.09 1.34±0.23 0.79±0.31 1.24±0.16
Phosphorus (%TS) 0.11±0.01 0.25±0.05 0.10±0.01 1.42±0.21
Sulphate (%TS) 0.03±0.01 0.04±0.01 0.01±0.001 3.52±0.98
pH ND ND ND 5.77±0.07
Conductivity ND ND ND 3,970±2
(µS/cm)
TDS (ppm) ND ND ND 1,983±3
COD (g/l) ND ND ND 20.07±0.13

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 90
BOD 5 (g/l) ND ND ND 16±0.16
VFA (mg/l) ND ND ND 2,862±6.8
Alkalinity (mg/l) ND ND ND 121±1
ND=Not Determined
Table 3: Chemical characteristics of RLS fractions. (Mean±SD, n=3)
Parameter Fresh Dried fraction Biomass residue after Leachate
fraction
leachate extraction
Total solids 33.55±0.56 87.80±0.51 37.01±1.41 10.07±0.25
(%fresh)
Volatile 96.8±0.24 94.3±3.3 96.84±0.34 95.78±0.35
solids(%TS)
Total carbon 54.6±0.32 50.92±1.70 54.37±0.33 48.74±0.45
(%TS)
Total Nitrogen 1.62±0.11 2.16±0.01 0.27±0.04 2.14±0.76
(%TS)
C:N ration 34:1 24:1 201:1 23:1
Total organic 98.32±0.58 91.66±3.06 97.87±0.21 87.53±1.10
matter (%TS)
Total sugars 27.41±2.28 26.20±1.28 14.27±4.16 35.24±2.50
Crude fibers 56.91±2.71 72.16±2.78 63.25±1.26 1.26±0.66
(%TS)
NDF (%) ND 35.91±0.11 ND ND
ADF (%) ND 32.76±0.29 ND ND
Hemicellulose 31.19±1.12 12.16±1.50 11.26±1.24 11.26±1.24
(%TS)
Ash content 3.1±0.24 5.69±3.29 3.15±0.34 4.04±0.22
(%TS)
Calcium (%TS) 3.30±0.30 5.62±0.38 5.62±0.38 10.12±0.50
Magnesium (%TS) 0.16±0.01 0.52±0.11 0.10±0.02 2.16±0.12
Potassium (%TS) 3.60±0.53 5.26±1.53 0.55±0.04 1.37±0.31
Phosphorus (%TS) 0.31±0.01 0.22±0.02 0.05±0.01 3.50±0.60
Sulphate (%TS) 0.05±0.01 0.05±0.01 0.01±0.001 6.70±1.54
pH ND ND ND 5.36±0.04
Conductivity ND ND ND 2,785±5
(µS/cm)
TDS (ppm) ND ND ND 1,390±2
COD (g/l) ND ND ND 26.24±0.21
BOD 5 (g/l) ND ND ND 20.8±0.27
VFA (mg/l) ND ND ND 140.85±3.7
Alkalinity (mg/l) ND ND ND 102±1.5
ND=Not Determined

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 91
Figure 1: Contribution of Core-boles and leaf stubs to total bole weight

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 92
Poles
Sisal Post-harvest waste
Sisal boles including leaf
stubs
Construction
materials
Chopping, crushing, leachate
extraction
Chopping, drying, grinding
Biomass
residue
Leachate
Mushroom cultivation
Mushrooms: To
markets
Chemical/fermentation processing
Spent mushroom substrate
Inulin, organic acids,
ethanol, biogas, etc.
Co-digestion with animal
manures for biogas
Biogas
Biofertilizer to sisal plantations
Figure 2: Proposed integrated utilization of sisal post-harvest waste.

Int. J. Pure Appl. Sci. Technol., 14(2) (2013), 84-94 93
Acknowledgements
We wish to acknowledge the Swedish International Development Cooperation Agency (Sida) for the
financial support. We thank the BIO-INNOVATE programme for including environmental
biotechnology as one of the research themes in the programme. The participation of Fatemi Sisal
Estate Management under the leadership of Mohammed Enterprise Tanzania Limited (MeTL) is
highly appreciated.
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