Development of a Solar Aided Crib for Drying and Storage of Maize Cobs

The aim of this study was to design, construct and evaluate the performance of solar aided crib for storage of freshly harvested maize (Zea mays) in a humid tropical climate. A crib with two drying chambers of size 600 mm x 685 mm x 1500 mm with moisture emission chamber of 600 mm x 115 mm x 1500 mm was designed, constructed and evaluated using appropriate design procedures at the department of Agricultural and Environmental Engineering, Federal University of Technology, Akure, Ondo State, Nigeria. The roof of the crib is made of perspex which transmits the sun's energy into stored maize in the crib for effective drying purpose. The crib was raised at 50 mm above the ground surface and wire netted against rodents. It has two doors for easy loading and off-loading. Freshly harvested Maize weighing 500 kg of 30.5% moisture content (wet basis) was stored for three months. Moisture content of the maize was taken on weekly basis while relative humidity and temperature were measured on daily basis. Readings were taken at three positions (top, middle and bottom) in apertures that were made in those positions but were immediately covered up at the end of every reading.  The ambient temperatures varied from 20.90C to 380C and also relative humidity varied from 41% to 91% throughout the period of the experiment. The moisture content at the point of storage was 30.5 % but was reduced to 4 % after three months. The final weight of maize in cobs was 362 kg which implied that the Perspex roof significantly aided in the drying process. The structure is structurally balanced and there was no grain deterioration either by fungal invasion or insects attack during the storage period. Keywords: Crib, Drying, Moisture content, Storage, Temperatur

ECOSYSTEM OF BAGGED GRAIN STORED UNDER NATURALLY VENTILATED WAREHOUSE: ANALYSIS AND MODELLING

Grain in Africa and indeed most developing parts of the world are stored in polypropylene or jute bags arranged in stacks of varied dimensions in naturally ventilated warehouses. This practice is, however, associated with high postharvest losses due to poor temperature and moisture management during storage. This constitutes a major economic and food security challenge in these countries. Therefore, this study characterizes changes in moisture content and temperature occurring in a stack of bagged corn by determining the permeability of bag materials that influence moisture transfer and developing a mathematical model of heat and mass transfer which incorporates the unique physical and thermal properties of bagged corn in storage. Water vapor transmission rate and permeability of woven polypropylene bags and jute bags increase with an increase in vapor pressure deficient of the storage environment. Water vapor transmission rate was linearly correlated with vapor pressure deficit. The development of a monitoring device capable of acquiring temperature and relative humidity data from specific locations within the stack and its deployment for field use is also discussed in terms of providing data for analyzing the bagged grain ecosystem and also for validating the mathematical model. A comprehensive analysis of the effect of changing environmental conditions on temperature and moisture distribution as well as insect population in bagged corn is discussed. Small stacks of bagged corn (54 bags of 40 kg capacity arranged in two stacks) and a large stack (192 bags of 40 kg capacity) stored under naturally ventilated warehouses in Nigeria and US respectively were used. Generally, bagged corn temperatures followed the trends of the air temperature surrounding the bags with no differences between individual bags in the small stack. Moisture content increased uniformly in the small stacks and the warm conditions within the bags encouraged the proliferation of insects, of which maize weevil Sytophilus zeamais was the most predominant. These contributions are unique as it marks the first time that temperature and moisture distribution in a stack of bagged grain is critically studied for the purpose of improving management. Validation of the mathematical model was performed with experimental data from the two storage studies. There was a close agreement between the predicted and experimental data in terms of describing the temperature distribution within the stack of bagged corn, although predicted temperatures in the small stack showed higher standard errors. The average standard error between the experimental and predicted temperatures was 1.2 °C (0.8 to 2.1 °C). The average standard error between the measured moisture content and predicted equilibrium moisture content (EMC) was 1.0 percent point (0.8 to 1.1 %). The prediction accuracy of the model was improved with the use of experimental values for the physical and thermal properties of bagged corn. The monitoring systems and mathematical model will contribute to improved management of bagged grain in naturally ventilated warehouses

ACIAR Grain Storage Research Program: Research Report 1983-84

Crop Production/Industries,

Effects of Farmers’ Demographic Factors on the Adoption of Grain Storage Technologies Developed by Nigerian Stored Products Research Institute (NSPRI): A case study of selected villages in Ilorin West LGA of Kwara State.

This study was carried out to identify the factors that determine farmers’ adoption of NSPRI grain storage technologies in selected villages of Ilorin West Local Government Area of Kwara State. Data used were collected from a total of 120 respondents who were randomly selected from 6 villages of the Local Government Area. 10% of all the farmers in each of the villages were interviewed. The variables examined in the study are sex, age, marital status, primary occupation, secondary occupation, level of education, number of dependents, years of farming, farm size, years of grain production, means of farm land acquisition and types of grain produced. Descriptive statistics and logistic regression model were used to analyze data. The inferential statistical tool used indicated significant relationship between sex and NSPRI grain storage technologies’ adoption.  Level of education and occupation were also significantly related to adoption of NSPRI grains storage technologies. This study recommends a wholesome dissemination model that will benefit both educated and uneducated farmer and also the involvement of farmers’ group or representatives in participatory approach of technology development, introduction and use. Keywords: Education, farming, occupation, participatory development, logit regression model

Tropical Stored Products Information

This issue of Tropical Stored Products Information, presents the Proceedings of a Seminar on Post-Harvest Grain Losses, 'Introducing Food Loss Assessment Studies into Loss Reduction Programmes', convened by the Tropical Products Institute in London, 13-17 March 1978. The Seminar was attended by delegates from 31 developing countries and 31 donor and technical agencies. An abstract is given of each of the technical contributions and country papers presented at the Seminar, followed by the rapporteurs' summaries, donor statements and, finally, the Seminar conclusions. The latter are presented in English, French and Spanish. The paper on 'Coordination of Loss Assessment and Reduction Work, by A A C Huysmang is reproduced in full

Secado de maíz con aire natural en lecho fijo: comparación de simulaciones computacionales realizadas con modelos matemáticos de noequilibrio

En este trabajo se comparan dos modelos de no equilibrio para representar el proceso de secado natural de maíz en lecho fijo. Los dos modelos propuestos, que difieren básicamente en las ecuaciones de balance de materia y de energía para el aire, son (a) modelo pseudoestacionario (PsEst) en el que se desprecian los términos de acumulación y (b) modelo no estacionario (NEst), en el que se consideran los términos de acumulación. Ambos modelos se resuelven en forma numérica por el método de las líneas, usando los algoritmos más apropiados para resolver el sistema de ecuaciones diferenciales ordinarias (EDOs) que resulta de la discretización de las derivadas espaciales por diferencias finitas. Se analizaron, tanto en condiciones del aire constante como bajo condiciones realistas usando datos meteorológicos, los resultados predichos tales como tiempo de secado, humedad final, perfiles de humedad y temperatura y consumo específico de energía, así como también parámetros representativos del “costo computacional relativo”, a través del tiempo de cálculo. Los resultados predichos por los dos modelos son muy similares y seleccionando el algoritmo de resolución de las EDOS más apropiado para cada caso, los tiempos de cálculo son aceptables para ambos modelos. Aunque el paso de tiempos resulta mayor para el modelo NEst, lo que implica un mayor error de truncación local. Se concluye que el modelo simplificado (PsEst) es adecuado para modelar el secado de maíz en lecho fijo en las condiciones operativas típicas del secado natural.Centro de Investigación y Desarrollo en Criotecnología de Alimento

DESIGN AND TESTING OF A WIND ENERGY HARNESSING SYSTEM FOR FORCED CONVECTIVE DRYING OF GRAIN IN LOW WIND SPEED, WARM AND HUMID CLIMATES

Forced convective drying using a wind turbine mechanically connected to a ventilation fan was hypothesized for low cost and rapid grain drying in developing countries. The idea was tested using an expandable wind turbine blade system with variable pitch, at low wind speeds in a wind tunnel. The design was based on empirical and theoretical models embedded in a graphical user interface (GUI) created to estimate airflow-power requirements for drying ear corn. Output airflow (0.0016 - 0.0052 m3kg-1s-1) increased within the study wind speed range (2.0 - 5.5 m/s). System efficiency peak (8.6%) was observed at 3.5 m/s wind speed. Flow resistance was overcome up to 1m fill depth in 0.5 m x 0.5 m wide drying bin. Drying study at different airflow rates (no forced convection, 0.002 m3kg-1s-1 and 0.008 m3kg-1s-1) were conducted in a controlled environment at 35oC and 45% relative humidity with mean drying time; 40.3, 37.9 and 22.9 h respectively, that reduced with increasing airflow while drying the ear corn from 22% to 15% moisture content. The overall result supports the hypothesis that the wind convection system increased grain drying rates and should be further developed

The evaluation of losses in maize stored on a selection of small farms in Zambia with particular reference to the development of methodology (G109)

The terms of reference for this project were: (1) to develop a satisfactory methodology to evaluate the extent of losses; (2) to establish reasonably reliable cost- benefit relationships for a simple improved farm storage technique; and (3) to recommend whether a longer term project should be undertaken over a wider area to evaluate cost-benefit relationships of improved storage techniques for the purpose of planning development programmes. Following these criteria the report makes a detailed study of various methods of assessing losses. These methods are then applied to maize stored by small farmers in selected areas of Zambia and an evaluation made of the costs and benefits to these farmers of adopting an improved storage technique