Zimbabwe Journal of Technological Sciences

Towards utilization of water hyacinth for industrial products: A Review paper

N Sibanda, C Murungweni, C Zvidzai, AB Mashingaidze, E Ngadze — Thu, 17 Mar 2016 00:00:00 +0000

Water hyacinth is a useful weed in the cleaning of water bodies loaded with industrial effluent but can become an environmental problem if its growth is not controlled. Water hyacinth is a potential raw material of several industrial applications. However chemical structure of the lignocellulosic hyacinth biomass has to be broken down first in order to obtain fermentable sugars. Wood rotting fungi has been known to delignify plant biomass. Wood rotting fungi secrete extracellular enzymes including lignin peroxidase, manganese peroxidase and laccase that are important industrial enzymes with numerous biotechnological applications in bio-fuel, food, brewery and wine, animal feed, textile and laundry, pulp and paper and agricultural industries. This paper reviews the potential use of white rot fungi's (Pleurotus sajor caju, Pleurotus ostreatus and Lentinus edodes) extracellular enzymes to biodegrade water hyacinth biomass.

Keywords: water hyacinth, lignocelluloses, wood rotting fungi, extracellular enzymes

Activated carbon from baobab fruit shells through domestic processes

JJ Kodzwa, C Danha, L Mangori, A Chemura — Thu, 17 Mar 2016 00:00:00 +0000

Surface and groundwater pollution is rampant due to poor waste management and runoff. Dry regions of the country also writhe from water scarcity which leaves communities to resort to unsafe water supplies for domestic use. It is estimated that about 90% rural households in Zimbabwe consume untreated water (Hoko, 2005) and that more than 75% of Zimbabwe's population lives under water stressed conditions in most rural areas (Manyanhaire et al., 2009). Commercially produced activated carbon is expensive. The aim of the research was to investigate the production of activated carbon from baobab fruit shells (a cheap raw material) using a method that can be employed at rural homesteads in removing organic pollutants. Two methods of producing activated carbon were also compared i.e. activating before carbonization and activating after carbonization. Activating with salt after carbonization proved to be the efficient (adsorption% 93.2). A contact time of 60 minutes was determined as the maximum time required for adsorption and a pollutant concentration equivalent to 0.3M oxalic acid gave the highest adsorption of 98.9%. The activated carbon from baobab fruit shells follows a Langmuir isotherm which explains the existence of a monolayer and the saturation of adsorption sites on the activated carbon. It was concluded that activated carbon from baobab fruit shells have the potential of removing organic pollutants from water.

Keywords: activated carbon, percentage adsorption, carbonization, adsorption, organic pollutants and fruit shells

Physical and chemical characterization of acid tar waste from crude benzol refining

CH Chihobo, S Kumar, PK Kuipa, DJ Simbi — Thu, 17 Mar 2016 00:00:00 +0000

The physical and chemical composition of acid tar waste is important in assessing and developing technological processing options for their subsequent utilization. In the present investigation gas chromatography/mass spectrometry (GC/MS), fourier transform infrared (FTIR), inductively coupled plasma/atomic emission spectrometry (ICP/AES), scanning electron microscopy with energy dispersive Xray (SEM/EDX) were mainly used to characterize the acid tar waste from crude benzol refining. The acid tar waste had a moisture content within the range 7-11%, pH values < 2.5 at a Liquid Solid (L/S) ratio of 20. Chemical analysis indicated the presence calcium, phosphorus and iron at 56.3, 15.7 and 11.3 ppm respectively with trace concentrations of lead, zinc, manganese and chromium. Organic analysis of the aromatic fraction of the acid tar waste by GC-MS revealed a wide range of compounds, including polycyclic aromatic hydrocarbons, furans, phenols, thiophenes and biphenyls. FTIR analysis was used to complement GC-MS. These results may be useful in the design and development of technological processes that can utilize acid tar waste.

Keywords: Acid tars; Analytical techniques; Hazardous waste; Hydrocarbons

Characterization of acid tar waste from benzol purification

C Danha, DJ Simbi, PK Kuipa — Thu, 17 Mar 2016 00:00:00 +0000

The use of concentrated sulphuric acid to purify benzene, toluene and xylene produces acidic waste known as acid tar. The characterization of the acid tar to determine the composition and physical properties to device a way to use the waste was done. There were three acid tars two from benzene (B acid tar), toluene and xylene (TX acid tar) purification streams and one which was from the storage tank (HT acid tar). The viscosity and density varied greatly amoung the three acid tars with B acid tar having the lowest viscosity (28.3mPa.s) and HT acid tar having the highest viscosity (63.592Pa.s). For density HT had the lowest (1.43g/ml) and TX had the highest (1.549g/ml). The sulphuric acid % concentration was 15.4% for HT, 23.7% for TX and 24.2% for B acid tar. The solubility test also showed a difference in the three acid tars, B acid tar was more soluble in water than in methanol while the other two were more soluble in methanol than in water. GC MS and FT-IR results showed that TX and HT acid tars had weak organic acid such carboxylic acid, alcohols and aldehydes. The B acid tar had few organics as compared to TX and HT. The results show that the sulphuric acid is being lost in the holding tank and the physical and chemical properties of B and TX acid tar are different thus the need to treat differently if they are to be treated separately. The HT acid tar has properties that make it easier to work with; an example is the high viscosity and the high organic content.

Keywords: Acid tar, benzol processing, sulphuric acid, organic acids, characterization and viscosity

Objective selection criteria and mating strategy of indigenous Nguni cattle under low-input in-situ conservation programs

O Tada, Muchenje Vand, K Dzama — Thu, 17 Mar 2016 00:00:00 +0000

Participatory Rural Appraisal techniques were employed to determine the breeding objectives of Nguni cattle under community-based management of indigenous livestock genetic resources. Six groups each composed of nine representative farmers from communal and small-scale conservation enterprises participated in deriving the objective selection criteria of breeding animals using data on economic weights of preferential traits. The shuffled focus groups brainstormed on the mating strategy and management of breeding animals within low-input conservation enterprises. An economic-weight dependent culling method (EWCM) and two-tier open nucleus breeding scheme were conceptualized. The Nguni breeding animals ideally need to maintain optimum body condition score (4 - 6) and low tick counts across seasons under low-input production system. The indigenous breeding bulls need to have high reproductive efficiency while breeding cows must have calved before reaching 27 month age. The farmers set a two-and-half-year service period of breeding bulls in the in-situ conservation enterprise before culling. Farmers are recommended to objectively assess breeding animals and maintain an updated performance data and information recording system.

Keywords: economic weight-dependent culling, focus group discussion, preferred traits, two-tier open nucleus breeding

Conservation Agriculture challenges in developing countries and possible suggestions - the case of Gokwe South District, Zimbabwe

G Mashango — Thu, 17 Mar 2016 00:00:00 +0000

Globally, food insecurity is a huge challenge, especially among developing nations. The severity of the problem varies from one continent to the other. Development practitioners, researchers, government leaders and scientists are struggling to come up with a sustainable solution in addressing food insecurity. Conservation agriculture (CA), which is a concept for resource-saving agriculture crop farming system that strives to achieve acceptable profits together with high and sustained production level while concurrently conserving the environment is one of the potential remedy to food shortage. CA is characterized by three major principles minimum soil tillage, soil cover (mulch) and crop rotation. CA is widely perceived as one way of sustainably addressing food insecurity not only in Africa but also in other developing countries globally. Research has shown that CA when properly practised can lead to increased yield, improved soil structure and increased utilization of agricultural resources. Despite CA's numerous benefits, some farmers in developing nations are reluctant to adopt the farming system. The reasons behind this are immense and diverse and this study aimed to achieve the following objectives: (i) to assess why there is low uptake of CA, (ii). to assess contribution of CA to food security (iii). to recommend strategies and appropriate approaches in resolving food insecurity. A total of four wards of Gokwe South District were purposively sampled and 403 households were interviewed. Evidence from survey results indicated that although CA contributes significantly to household food security for smallholders 'as a best practice' itis not a 'best fit' practice since results fluctuate from one agro-ecological zone to the other. It was found out that low uptake of CA is emanating from high labour requirements, multi-usage of crop residue in mixed farming systems, lack of knowledge and poor markets. CA should not be promoted as a full package but as farming options for the farmers to choose what is appropriate to them. Introduction of conservation agriculture in Zimbabwe was input driven supported mostly by non-governmental organisations hence sustainability of the concept is highly questionable. CA should be promoted using developmental approaches which are more sustainable than humanitarian.

Keywords: Sustainability, Conservation Agriculture, Food Security, Smallholder farmers, Household

"A Roadmap for Flue-curing Tobacco Barns: Towards Developing Improved Energy Efficient Barns for Small holder Farmers in Zimbabwe".

W Munanga, C Kufazvineyi, FT Mugabe — Thu, 17 Mar 2016 00:00:00 +0000

Tobacco crop currently provides the best economic return per hectare amongst all the major annual crops grown in Zimbabwe. Tobacco production currently contributes 30 % of the total exports and nearly 10 % of the GDP. According to the Tobacco Industry and Marketing Board, of the 106 127 number of registered tobacco growers, about 84 % belong to the smallholder category. The small holder section contributes more than 50 % of the total tobacco output. This article details the curing process and phases as well as the necessity of curing efficiency. An overview of the relationship between tobacco production and deforestation in Africa, and especially in Zimbabwe, is highlighted. A justification of the need for improved energy efficient flue-curing tobacco barns is presented. The article also reviews the different types of curing barns in Zimbabwe with particular attention to their development, operational systems, curing efficiencies, advantages and disadvantages. The main conclusion was that there is urgent need for improving energy efficiency in tobacco curing. In the short term, high fuel consumption can be reduced by optimizing the thermal efficiency of curing structures, particularly for smallholder tobacco growers in Zimbabwe.

Keywords: tobacco, flue-curing, smallholder farmers, energy efficient barns, heat transfer