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One of the important bottle-necks in production of microalgae based biodiesel is the lack of an efficient method for harvesting of microalgae from the culture medium. In this study, the electroflocculation method was developed for harvesting of microalgae Dunaliella cells from culture medium. The effect of several parameters such as the current density, electrical conductivity of culture medium, time, electrode gap, and electrode type on harvesting efficiency and energy consumption were also determined. The maximum harvesting efficiency of this method was 97.44% at EC= 1.35 S m-1 and current density of 90 A m-2 during 3 minutes electroflocculation process in a 300 ml beaker. The maximum efficiency was achieved by aluminum electrodes with 1 cm distance between electrodes and the maximum energy consumption for this practice was 0.621 kW h m-3. It was concluded that electroflocculation is an efficient and cost effective method for microalgae harvesting.

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Most cassava farmers in Africa rely solely on manual means of harvesting root and tuber crops due to low level of mechanization. Evaluating the energy required in harvesting cassava and soil properties could guide farmers’ decision on stress-free harvesting options and practices. Experiments were conducted at the University of Ibadan (UI) and the International Institute of Tropical Agriculture (IITA) to establish the relationship between energy required in harvesting cassava and soil physical properties. The experiments were laid out in a randomized complete block design with four replications. Salter suspended scale model 235 was used to take energy measurements, while data collected were subjected to analysis of variance at α = 0.05. Mean yields from the two locations showed that variety TMS 97/0162 had the highest tuber mass (50,450 kg ha^-1) followed by varieties TMS 30572, TMS 98/0505 and TMS 98/0510 (32,200–26,500 kg ha^-1) and least by TMS 99/2123 (8,000 kg ha^-1). There was a positive relationship between cassava yield and work done (R²= 0.21) at both locations, suggesting that yield affects the energy requirement in cassava harvesting. Soil moisture content showed a negative relationship with work done (R²= 0.52 and 0.24 at UI and IITA, respectively), indicating that increase in soil water reduces the force of harvesting. Also, soil bulk density had a negative relationship with work done (R²= 0.19 and 0.06 at UI and IITA, respectively). Energy required for harvesting cassava planted on coarse-textured soils could be reduced under high soil moisture content and bulk density conditions.