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

More documents

Recommendations

Info

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-
Page 1: Int. J. Pure Appl. Sci. Technol., 1
Page 5 and 6: Int. J. Pure Appl. Sci. Technol., 1
Page 11: Int. J. Pure Appl. Sci. Technol., 1

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

Create successful ePaper yourself

Delete template?

Save as template?