Selected Drying Characteristics of Plantation Grown Gmelina Arborea under an Experimental Solar Drying Kiln

Abstract

High cost of operating the conventional kiln and the inherent limitations of air drying method in wood drying are undesirable to wood industries. Solar wood drying has gained considerable interests because it is efficient and economical. Study on selected drying characteristics (drying rate, moisture gradient and drying defects) of plantation grown Gmelina arborea was carried out. Five Logs of Gmelina arborea were felled and wood samples were prepared from three sampling heights (25%, 50% and 75%). Thereafter, wood samples were selected from three radial positions (inner, middle and outer wood) for each of the sampling heights and labeled for proper identification. Samples were separated into two groups for air and solar kiln drying. Result revealed that for solar kiln dried samples, highest mean values for drying rates (1.1266±0.09, 0.7946±0.07246, 0.4511±0.34269, 0.5327±0.20307 and 0.4253±0.05157) %/day were recorded for 4, 6, 8, 10, and 12 weeks respectively,. Whereas, for air drying, 0.2147 ±0.05788, 0.4007±0.15662, 0.2806±0.04109, 0.5296±0.05322 and 0.3613±0.12435 %/day were recorded for 2, 4, 6, 8, 10 and 12 weeks respectively. The drying factors (temperature and relative humidity) in both solar kiln and air drying shed influenced the drying rate of wood. Results from analysis of variance revealed that solar kiln performs better than air drying in terms of drying rate through out the drying period. Duncan multiple range test (DMRT) was used to separate mean values of drying rate for samples at the selected longitudinal and radial positions. Also, solar kiln dried samples had a better quality in terms of absence of drying defects and desirable moisture gradient between the core and surface of the wood samples.