Development of Kiln-Drying Schedules and Within Tree Variability in the Physical Properties of Two Lesser-Known Timber Species in Ghana

Decreasing supply of most commercial wood as raw material inspires the forest products industry to look for other wood species which have similar or greater commercial values but are not currently utilized by the forest products industry. Wood is versatile and the oldest building material used by man. But there is limited knowledge about the properties of a large proportion of timber-grade wood species. Proper utilization of a particular wood species must be based on both basic properties and processing properties. Drying is one of the most important processing properties, because a proper drying process will be the main key to utilize efficiently and ensure high quality wood products. Cola nitida (Bese) and Funtumia elastica (Funtum) are two lesser- known species in Ghana that are not used for commercial timber purposes. The overall objective of this study was to develop kiln-drying schedules for Cola nitida (Bese) and Funtumia elastica (Funtum), as well as assess the variability of the physical properties as the basis for determining the potential uses that may encourage the utilization and promotion of these lesser known species. The basic properties were determined based on British Standard 373 (1957), whiles the drying schedules were determined using the quick drying test method developed by Terazawa (1965). The main statistical tools used were Descriptive Statistics and Analysis of Variance (ANOVA). Variation in physical properties was analyzed within the trees of the two species. Three trees each per species were used in the study. Results of the study showed that initial moisture content were 66.6% and 79.4% for Cola nitida and Funtumia elastica respectively. The basic density of Cola nitida was 623.8 kg/m3 and 499.6 kg/m3 for Funtumia elastica. According to TEDB (1994), Cola nitida is a Medium-Heavy species and Funtumia elastica a Medium Weight species. Mean total tangential shrinkage from green to oven-dry was 7.25 and 6.78% for Cola nitida and Funtumia elastica, respectively. Mean partial tangential shrinkage from green to 12% MC is very small (under 2.5%) for Cola nitida and medium (4.0-5.5%) for Funtumia elastica. The corresponding mean partial radial shrinkage values also showed that shrinkage was very small (under 1.0%) for Cola nitida and medium (2.0–3.0%) for Funtumia elastica. The shrinkage values for the two species compared favourably with those of some locally used species for timber production (like Scottellia coriacea and Lannea welwitschii), and therefore could be considered suitable for timber utilization. The drying schedules also comformed to those of Sterculia rhinopetala and Alstonia boonei as proposed by Ofori and Brentuo (2010b). Checks in the early stages of drying were less severe in both Cola nitida and Funtumia elastica samples (Class 3). There were no honeycombing (Class 1) in both Cola nitida and Funtumia elastica species. There was no deformation (Class 1) in both Cola nitida and Funtumia elastica species. Experimental dry kiln schedules for lumber of thickness up to 38 mm corresponding to two Madison schedules were proposed: Cola nitida (T10-C4) and Funtumia elastica (T10 – D4). The results of the analysis of variance (ANOVA) revealed that the three axial sections of the trees showed significant differences at 5% probability level (p < 0.05). The technical values of the study results compared favourably with technical values of some locally used species for timber production (like Scottellia coriacea and Lannea welwitschii), and therefore could be considered suitable for timber utilization.

Source: KNUST