Rwanda Journal

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Productivity and Energy Expenditure by Sawyers When Using Pitsawing and Portable Steel Log Sawing Platforms in Agroforestry Farms

F Rurangwa, GA Migunga, AE Kweka, E Mauya


Although the future increase in timber supply in many countries is expected to come from agroforestry farms, the problem of on farm timber sawing, physical strain on sawyers caused by “Pitsawing” have to be addressed in order to increase the timber sawing productivity. This study was designed to analyze the productivity and energy expenditure by sawyers when using Pitsawing platforms (PSP) and Portable Steel Log Sawing Platforms (PLSP) in agroforestry farms.The study was conducted in South Kilimanjaro in Kiruweni and Nduweni villages. Data on energy expenditure were obtained through heart rate measurement by using heart rate monitor. Productivity data of both Pitsawing and Portable log sawing platforms were obtained through time studies by using stop watch. Microsoft Excel spread sheet was used for data analysis. Results indicated that when using PLSP site preparation production rates increased from 0.1 m3 per hour observed under PSP to 2.9 m3/h.The skidding production rate when using PSP technique was 3.5 m3/h while when using PLSP, the production rate was 11.9 m3/h. Loading productivity improved from 4.97 m,sup>3/h when using PSP to7.27 m3/h when using PLSP. Sawing productivity improved from 0.055 m3/h when using PSP to 0.057 m3/h and the Energy Expenditure (EE) for the same work element was 12.69 kJ/min and 12.4 kJ/min respectively. During pit/structure assembling, PLSP reduced the energy expenditure from 14.05 kJ/min to 2.61 kJ/min and the physical workload were classified as unduly heavy and light respectively. For the skidding work element PLSP minimized the energy expenditure from 5.88 kJ/min to 4.48 kJ/min, the same to loading work element, the EE decreased from 5.20 kJ/min to 3.55 kJ/min. Therefore, based on overall results it is concluded that, the PLSP is technically more appropriate technology or method for reducing energy expenditure and for increasing productivity during timber harvesting in agroforestry farms.

Keywords: Productivity, Energy expenditure, Pitsawing and Portable log sawing

Rwanda Journal, Volume 23 Series C, 2011

AJOL African Journals Online