Drying characteristics of cassava slices was investigated in a mixed mode natural convection solar dryer to obtain a suitable mathematical model describing the drying. The average drying chamber temperature was between 34 ±2 °C and 50 ±1.8 °C, while 10 commonly used thin layer drying models were used for drying curve modelling. Coefficient of determination (R2) and root mean square error (RMSE) were used to determine the models performances. The drying curve of cassava slices showed a reduction of moisture content with increased drying time in the solar dryer, and the variation of moisture ratio exponentially decreased with increased drying time. The Midilli and Logarithmic models showed better fit to the experimental drying data of cassava slices. As compared with other models tested, there were no significant differences (p >0.05) in the R2 values obtained for the Midilli and Logarithmic models; hence, the Logarithmic model was preferable because of the lower RMSE. The diffusion mechanism could be used to describe the drying of cassava slices that was found to be in the falling rate period. A diffusion coefficient (Deff) of 1.22 × 10-8 m2 s-1 was obtained, which was within the established standard for food products.

At a high frequency of vibration; the cam of a vibrator always encounters the issue of jamming or the follower rolling off or losing contact with the cam when the appropriate design is not carried out. This study, therefore, developed the shape of the cam profile of mechanical yam vibrator using cycloid motion in the South. Displacement equations from the base circle to the cam profile were developed to obtain the shape of the cam using cycloid motion. A vibrometer was used to evaluate the developed 5 mm, 10 mm, and 20 mm cam sizes installed in a mechanical yam vibrator. The maximum displacement recorded for 5 mm, 10 mm and 20 mm cam sizes were 4.47 mm, 8.71 mm, and 14.54 mm respectively for low (1 – 5 Hz) frequency; 4.58 mm, 8.84 mm and 16.34 mm respectively for medium (60 – 100 Hz) frequency; and 4.66 mm, 9.09 mm and 17.30 mm respectively for high (150 – 200 Hz) frequency. This study shows that a cycloid cam would operate smoothly at low, medium, and high frequencies of vibration and function properly for frequency and displacement of vibration up to 200 Hz and 20 mm respectively without jamming and failing. A cycloid cam is therefore recommended for low, medium, and high frequencies motion of vibration.

A study was carried out to investigate the effect of pretreatment with plantain peel ash on biogas production from cow dung. Two portable floating drum digesters of the same capacity were used for the experiment. One was filled with substrate prepared from cow dung and the second was also filled with substrate prepared from cow dung but pretreated with plantain peel ash. Results showed that 11,998 cm3 of biogas was produced from the digester that contained substrate of cow dung only while 20,493 cm3 was produced from the digester that contained substrate pretreated with plantain peel ash. This showed that the increase in the volume of biogas producedas a result of plantain peel ash addition is 8,495 cm3 which is equivalent to 70.8%.

Yam tubers lose weight during storage and prolonged storage can reduce tuber quality and quantity. This study investigated the application of vibration techniques for the control of the physical properties of yam tubers during storage. Measurements were conducted on the physical properties of the tubers: weight loss, shrinkage of the middle diameter, shrinkage of the length, top and bottom diameter, on 108 tubers treated and 32 tubers untreated (control). The factors of the experimental design were three levels of vibration frequencies, i.e. low (1 – 5 Hz), medium (60 – 100 Hz) and high (150 – 200 Hz), amplitudes of low (5 mm), medium (10 mm) and high (20 mm), and durations of low (5 minutes), medium (10 minutes) and high (15 minutes). Tuber weights were classified as small (0.1 – 2.9 kg) and large (3.0 – 5.0 kg). The tubers were stored for ten weeks after vibration, and their physical properties were measured every week during the storage period. Our study demonstrated that as the frequency, amplitude, and duration of vibration increase, the physical properties of yam tubers decrease significantly in both tuber classes. The study shows that mechanical vibration can slow down the changes in the physical properties of the yam tuber during storage.