Drying characteristics and energy requirement of drying cowpea leaves and jute mallow vegetables

Thin layer drying of cowpea leaves (Vigna unguiculata) and jute mallow (Corchurus olitorious L) (African leafy vegetables) was studied at different temperatures (40oC -100oC) in a convective laboratory dryer. The study determined the drying characteristics of the vegetables, the maximum drying temperature and the drying energy requirements. Moisture content of the African leafy vegetables was determined on dry basis and the data were used to calculate moisture ratios and drying curves were plotted. The drying occurred in the falling rate period. The experimental data were fitted to fourteen thin layer drying models and the most appropriate drying model determined using correlation coefficient, mean square error and standard error of estimate. The model developed by Page showed good agreement with the data obtained from the experiments of this study because it consistently returned the required attributes from statistical analysis and its simplicity. The energy requirement of drying vegetables at the different temperatures was calculated. Cowpea leaves had a longer drying time of 304 min and a higher specific energy requirement of between 168 J/g at 100oC and 11.2 J/g at 40oC while jute mallow had a drying time of 256 min and an energy requirement of 155.3 J/g at 100oC and 10.6 J/g at 40oC respectively. <w:LsdException Locked="false" P

Modeling drying of seed maize using super absorbent hydrogel under hermetic conditions

The objective of this study was to establish the feasibility of applying the Page, Two term exponential, Newton, Logarithmic and Henderson and Pabis mathematical drying models for predicting the drying kinetics of seed maize using super absorbent hydrogel under hermetic conditions. To achieve this, the study was conducted using hydrogel to seed maize ratios by weight of 0:1, 1:5, 1:10 and 1:15 at four different drying temperature levels of 25oC, 30oC, 35oC and 40oC at different initial seed maize moisture contents of 16%, 28% and 53% (dry basis). The moisture data obtained were fitted into the five drying models using non-linear regression analysis (MS Excel 2003TM) based on the minimization of sum of squares by adjusting the model constants. The coefficient of determination (R2), root mean square error (RMSE) and chi-square (X2) were criteria for selecting the best model. High values of coefficient of determination (R2 > 0.95) were obtained for all the five drying models while the corresponding values of X2 and RMSE were in the range of (0.0016-0.0141) and (0.0400-0.3045) respectively. As a result Logarithmic model was the best fitted model with R2 (0.9749-0.9876) and the weakest values of X2 (0.0016-0.0036) and RMSE (0.04-0.128)

Characterization of brewery waste water and evaluation of its potential for biogas production

The issue of global warming and climate change is strongly receiving public attention and has become a major environmental concern both nationally and internationally. Brewing industries are among the largest consumers of water and the largest source of organic effluent mostly from the brewing, cleaning, and cooling processes which must be treated to allowable levels to reduce environmental pollution. Close to 10 L water is used for every 1 L beer that is brewed, though the amount of water in the final beer is small. A study was undertaken to characterize and assess the variations in the quality of untreated brewery waste water. Samples from different process streams including brewing line, clean in place line and mixing line from two brewing industries in Kenya were analyzed for BOD5, COD, TDS, TSS, sodium, total nitrogen and phosphorous using standard method as per American Public Health Association (APHA). There was a significant variation (p<0.001) in the all the physicochemical parameters between the industries and a significant interaction (p<0.001) between sampling point and the company. Analysis of the BOD to COD ratio showed the biodegradability index to range from 0.039 to 0.567 for brewing line, 0.177 to 0.766 for cleaning in place and 0.776 to 0.911 for mixing point, thus the waste water was found to be easily biodegradable at the mixing point for all the industries. However pretreatment would be required to improve anaerobic digestion

Quality Assessment of Rain and Storm Water Runoff for Nairobi City Industrial and Sub-Urban Areas

ABSTRACT Nairobi like most cities in the world is faced with water shortages because all the surface water sources have been tapped and the ground water overexploited, yet the water demand continues to rise as the population grows. The city must therefore seek alternative means of water supply. One of the promising sources is rainwater harvesting, which has successfully been adopted to supply water in many other cities. However, there is a concern about the quality of the rainwater falling through a heavily industrialized city atmosphere and flowing over polluted grounds. There is need to determine the quality of rainwater and the resulting storm water so as to make a decision on the best application or treatment of the water. The purpose of the study was therefore to determine the physical and chemical properties of rain and storm water runoff in sub-urban and industrial settings in Nairobi. Two sites were indentified namely Upper Kabete Campus (heavily vegetated agricultural suburb), and Jomo Kenyatta International Airport (heavily industrialized area of the city) to assess the water quality of rainwater received and storm water runoff exiting to drains. Water samples were collected directly from falling rain and also from runoff water at the sites for laboratory analysis. The samples were analyzed for water quality parameters namely pH, alkalinity, hardness, total dissolved solids, chlorides, calcium, nitrates, iron. The results from the two sites were compared statistically. It was found that the quality of rain water does not differ significantly in physiochemical parameters at 0.05 significant levels between the sub-urban and industrial setting. The falling rainwater was only slightly above the WHO requirements and required only modest treatment whole the storm water was significantly above the WHO limits and either need treatment or may be used for non potable application. Results of the study are useful in addressing challenges of water quality partly by encouraging use of rain and storm water for non portable uses and preserving the limited treated water for essential household uses

Effect of Soil tooling, Tractive wheeling, and Mechanical pulverization of Arable Soils in Tillage - A Systematic Review and Analysis

Abstract Seasonal soil-tool interactions, tractive wheeling and trailed tandem traverse of agricultural fields present ambiguities in defining and qualifying soil processing in tillage where the physio mechanical state of soil health is repeatedly perturbed. Precise and distinctive knowledge on quality characterization and mechanistic response behavior of soil-tool and soil-wheel interactions under tillage is sparse. We reviewed 116 state of art tillage studies in the US, Europe, UK, Australia, Africa, and Asia among others, concerning localized and integrated effects of soil-tool and soil-wheel interactions and associated dynamic response trends of mechanically distressed soils; to untangle and overcome persistent ambiguities in qualifying tilled soil state, expressed by physio-mechanical, biomechanical and hydromechanical soil heterogeneity. Studies revealed that soil-tool and soil-wheel interaction phenomena, and constitutive tractive tribologies portend sophisticated interrelations with dynamic, multivariate, and heterogeneous soil properties. Hitherto to such variabilities, soil-tool-wheel interactions and their perturbation descriptors have not consensually achieved any distinctive characterization under tillage. Nonetheless, tillage depth, tine widths, rake angles of attack, draft forces and traction performance had gained some generalized description of characterizing soil working. However, researchers still found it difficult to qualify the precise mechanistic relations of dynamic physio-mechanical soil states, unanimously and accurately with engaged tools in situ. This is by dint of, and amid multifaceted soil-tool-wheel-stress-strain interrelations that we consider dynamic and apart from soil type, are soil- tool and soil- wheel methodical. Attempts to fill this knowledge gap through soil tooling and soil wheeling models provided conditional results, defined and only due under the specified simulated model assumptions. We recommend further studies to elucidate and furnish with in-depth knowledge on dynamic soil response variabilities under complex tool-wheel stress loads, that are dynamically transmitted due to encounter with point specific and instantaneously varying properties of soil matrix in situ. This will optimize and accurately characterize soil-tooling, tractive wheeling, and trailed traverse in tillage. Key words. Tractor wheeling, Physio-Mechanical state, Penetration resistance, Soil tooling, draft force, Tractor-implement optimization

Edaphic Response and Behavior of Agricultural Soils to Mechanical Perturbation in Tillage

Mechanical perturbation constrains edaphic functionality of arable soils in tillage. Seasonal soil tool interactions disrupt the pristine bio-physio-mechanical characteristics of agricultural soils and crop-oriented ecological functions. They interfere with the natural balancing of nutrient cycles, soil carbon, and diverse organic matter that supports soil ecosystem interactions with crop rooting. We review soil working in tillage, associated mechanistic perturbations, and the edaphic response of affected soil properties towards cropping characteristics and behavior as soil working tools evolve. This is to further credit or discredit the global transition to minimum and no-till systems with a more specific characterization to soil properties and edaphic crop-oriented goals of soil tooling. Research has shown that improvement in adoption of conservation tillage is trying to characterize tilled soils with edaphic states of native soil agroecosystems rendering promising strategies to revive overworked soils under the changing climate. Soil can proliferate without disturbance whilst generation of new ecologically rich soil structures develops under more natural conditions. Researchers have argued that crops adapted to the altered physio-mechanical properties of cultivated soils can be developed and domesticated, especially under already impedance induced, mechanically risked, degraded soils. Interestingly edaphic response of soils under no-till soil working appeared less favorable in humid climates and more significant under arid regions. We recommend further studies to elucidate the association between soil health state, soil disturbance, cropping performance, and yield under evolving soil working tools, a perspective that will be useful in guiding the establishment of future soils for future crops

Edaphic Response and Behavior of Agricultural Soils to Mechanical Perturbation in Tillage

Mechanical perturbation constrains edaphic functionality of arable soils in tillage. Seasonal soil tool interactions disrupt the pristine bio-physio-mechanical characteristics of agricultural soils and crop-oriented ecological functions. They interfere with the natural balancing of nutrient cycles, soil carbon, and diverse organic matter that supports soil ecosystem interactions with crop rooting. We review soil working in tillage, associated mechanistic perturbations, and the edaphic response of affected soil properties towards cropping characteristics and behavior as soil working tools evolve. This is to further credit or discredit the global transition to minimum and no-till systems with a more specific characterization to soil properties and edaphic crop-oriented goals of soil tooling. Research has shown that improvement in adoption of conservation tillage is trying to characterize tilled soils with edaphic states of native soil agroecosystems rendering promising strategies to revive overworked soils under the changing climate. Soil can proliferate without disturbance whilst generation of new ecologically rich soil structures develops under more natural conditions. Researchers have argued that crops adapted to the altered physio-mechanical properties of cultivated soils can be developed and domesticated, especially under already impedance induced, mechanically risked, degraded soils. Interestingly edaphic response of soils under no-till soil working appeared less favorable in humid climates and more significant under arid regions. We recommend further studies to elucidate the association between soil health state, soil disturbance, cropping performance, and yield under evolving soil working tools, a perspective that will be useful in guiding the establishment of future soils for future crops

Vis-NIR Hyperspectral Imaging for Online Quality Evaluation during Food Processing: A Case Study of Hot Air Drying of Purple-Speckled Cocoyam (Colocasia esculenta (L.) Schott)

In this study, hyperspectral imaging (HSI) and chemometrics were implemented to develop prediction models for moisture, colour, chemical and structural attributes of purple-speckled cocoyam slices subjected to hot-air drying. Since HSI systems are costly and computationally demanding, the selection of a narrow band of wavelengths can enable the utilisation of simpler multispectral systems. In this study, 19 optimal wavelengths in the spectral range 400–1700 nm were selected using PLS-BETA and PLS-VIP feature selection methods. Prediction models for the studied quality attributes were developed from the 19 wavelengths. Excellent prediction performance (RMSEP 0.90, RPDP > 3.5) was obtained for MC, RR, VS and aw. Good prediction performance (RMSEP 2.0) was obtained for PC, BI, CIELAB b*, chroma, TFC, TAA and hue angle. Additionally, PPA and WI were also predicted successfully. An assessment of the agreement between predictions from the non-invasive hyperspectral imaging technique and experimental results from the routine laboratory methods established the potential of the HSI technique to replace or be used interchangeably with laboratory measurements. Additionally, a comparison of full-spectrum model results and the reduced models demonstrated the potential replacement of HSI with simpler imaging systems.Peer Reviewe

Modelling Moisture Sorption Isotherms of Superabsorbent Polymer Fabric for Desiccant Drying of Crops

Desiccants are important in the drying of temperature-sensitive grains such as seeds for planting. Superabsorbent polymers (SAPs) have previously been identified for possible application in the drying of crops. Applying the gravimetric technique to measure the sorption isotherms and the effectiveness of the desiccant in crop drying was determined at temperatures 20, 25, 30, 35, 40, 45, 50, and 55°C. Using R statistical software, eleven sorption isotherm models were fitted to the experimental data using the nonlinear regression functions. The coefficients of each model were obtained. The modified Freundlich, modified Henderson, and modified Oswin models best predicted the experimental data for the study temperature range. Using symbolic regression and nonlinear regression in R software, four mathematical models were obtained. R software codes were assembled for the analysis of sorption isotherm models. Compared to the existing models, the developed models were found to give a more statistically accurate association between the temperature, moisture content of SAP fabric, and relative humidity

Isolation and characterization of methanogenic bacteria from brewery wastewater in Kenya

The production of biogas from renewable resources is becoming a prominent feature of most developed and developing countries of the world. A study was undertaken to characterize methanogenic microbial community found in brewery waste water. Their performance with regards to methane production was also studied. Thirty-two isolates were obtained using brewer thyglycollate agar medium. Characterization of the isolates was done by culture and biochemical methods. 65% of the isolates were found to be positive with Gram staining reaction, while 35% were negative. The isolates were identified by method of polymerase chain reaction (PCR). From the phylogenetic analysis, thirteen isolates were clustered into genus Bacillus sp., isolate 93b was closely related to Bacillus subtilis strain, while isolates 20a1, 171 and 7 closely related to Bacillus methylotrophicus isolate 10 was grouped together with Bacillus tequilensis, isolate 31 was clustered together with Bacillus licheniformis, while isolates 132, 252, 15, 262 and 182 were closely related to Lysinibacillus sp. and isolate 191 was clustered together with Lactobacillus casei. The study also shows that three isolates 32, 181 and 4 were closely related to Ralstonia pickettii, Providencia rettgeri and Myroides odoratimimus, respectively. The presence of isolates 201a, 171 and 7 with abilities to ferment different sugars, hydrolysis starch, liquefy gelatin, split amino acid tryptophan, produce catalase enzyme and hydrogen sulphide gas suggests their involvement in biogas production. The percentage methane content in the total gas produced at pH 8 varied significantly (p<0.001) for all the temperature ranges. The highest concentration of methane for most isolates was recorded at temperatures of 35 and 37°C for all the pH ranges.Key words: Biogas, characterization, methanogenic bacteria, pH, temperature, wastewater