Comparative analysis of recovery efficiencies of some milling techniques in Ghana

Inefficient primary processing of timber in the Ghanaian sawmills has resulted in lower lumber recoveries/yields hence generating too much residues. But in situ primary processing of timber with appropriate technologies has not been well established to remedy the situation. This study considered freehand with two different chainsaw bland (Stihl 070 and Husqvarna 395XP), chainsaws with frame attachments (Husqvarna 395XP with Alaskan frame & Stihl MS880 with logosol frame/rail) and WoodMizer milling technologies. Forty-four (44) trees from six timber species were extracted from two ecological zones in Ghana. The conversion efficiency ratios, which include lumber recovery/yield, production rate and fuel consumption rate, have been determined for four milling technologies that were used based on the number of timber species and trees felled. Comparison of the efficiency ratios of the freehand (Stihl 070 and Husqvarna 395XP), attachments (Alaskan and logosol frames) and Wood-Mizer milling technologies (using the same species for all of them) indicate that the percentage mean average lumber recovery/yield was highest with Wood-Mizer milling technology (70.6%) than the attachment technologies (49.6%) and that of the freehand (43.5%). In terms of lumber production rate, Wood-Mizer recorded a mean rate of 1.52 m/hr as against 0.519 m/hr and 0.435 m/hr for freehand and attachment technologies. The mean average fuel consumption rates were also estimated to be 6.31 lit/m, 8.4 lit/m and 10.8 lit/m for Wood-Mizer, freehand and frame attachment technologies respectively. The quality of lumber generated with the Wood-Mizer, Alaskan and logosol frame attachments were observed to be comparable to that of sawmill lumber while those from freehand milling were rough and thick & thin..