Estimation of lumber recovery for small-scale mobile sawmills in Tanzania

Abstract

Lumber recovery is an important parameter in determining the production efficiency and viability of mobile sawmilling operations. In this study, lumber recoveries for mobile sawmilling machines operating in four different locations in Tanzania were estimated. A total of 11 mobile sawmilling operations were studied. On each piece of mobile sawmilling machinery, data on log sizes, including bottom, mid and top diameter, and log lengths were recorded. Results showed that the number of logs per machine ranged from 5 to 40 with an average of 28 logs. The middle diameter of the logs ranged from 8 to 44.60 cm, with an average value of 20.58 cm. The number of lumbers produced for each log varied from 1 to 9 pieces, with an average of 3 pieces across all the sites. The lumber recovery (%), varied depending on the individual machine, machine type, source of logs and geographical site within Tanzania. For all the machines, the average lumber recovery (%) per machinery ranged from 16.15 to 62.79%. Among the three types of mobile sawmilling machinery, Wood-Mizer had relatively higher lumber recovery (56.2%) than Ameck and Ding-Dong. The overall average lumber recovery value for all the machines, irrespective of log sizes, site and source of lumber was 43.34%. Analysis of variance (ANOVA) indicated that site, source of lumber, machine type and size of logs had a statistically significant effect (p < 0.05) on lumber recovery (%). The study concluded that mobile sawmilling in Tanzania produces sawn timber with reasonable lumber recovery. However, further studies are recommended to examine technical aspects, such as productivity and taper, as well as cost of the mobile sawmilling operations.