Wood residue generation and utilization: the technical, economic and environmental mix for some selected sawmills in Brong Ahafo and Ashanti Regions, Ghana.

The recovery rates of sawmills in Ghana are low (about 28-64%), leading to pressure on the limited available resources. Consequently, there is the need for studies into wood residue generation and utilization to address the situation. This study was carried out in four prominent sawmills in the Ashanti and Brong Ahafo regions of Ghana with four frequently processed timber species at the sites. These included Cylicodiscus gabunensis (denya), Entandrophragma angolense (edinam), Pterygota macrocarpa (koto) and Triplochiton scleroxylon (wawa). The first study involved a survey to determine the availability, types, quantity, production rates, composition and utilisation of wood residues. Wood residues identified in the production processes were sawdust (14.65%); slabs (27.15%); edgings (40.84%); and trimmings (17.36%). The average percentage lumber recovery at the four sawmills was 38.08% with residue forming 61.92% of the total input volume. The edger produced volume of coarse residues that was significantly greater (P>0.05) than that of the other machine levels, however, the volume of sawdust residue was statistically significantly lower for machine level, edger and trimmer, compared to the bandmill. The second study determined the uses of wood residues and the economics of wood residue utilization at the study sawmills. The study revealed that residues generated had no economic benefits at the study sawmills. The lesser the quantities of residues generated, the better the sawmill profitability, hence a better sustainable forest management. The cost of production in the timber industries were in the order raw material > electricity > transportation > labour > maintenance > general overhead > sawdust carting; so efficient utilization of raw material is very important. The third study was conducted using fieldwork, laboratory work and personal vi observations to determine the decomposition trends of wood residues. Generally sawdust residues decomposed at a very low rate (only about 35% decomposition of test samples during three months). There was no significant differences (P>0.05) between the rate of decomposition of the buried sawdust and the surface applied sawdust. The forth study determined the constraints in handling sawdust for power generation and its effect on the environment and human health. It was revealed that 9.07% of input volume generates sawdust, however; about 60% of the sawdust was not utilized but dumped and burnt openly, making the environment aesthetically unclean and causing health hazards to surrounding communities. It was recommended that wood residue producers should form partnership to facilitate its transportation, storage and marketing. They could also consider its value-added manufacturing processes into finger joints, crafts and toys, floorings and garden fencing. Fines such as sawdust could be used to manufacture briquette for household use or biochar for soil amendment to enhance nurseries, plantations and other agricultural interests for sustainable forest management purposes. This study consistently identified minimizing wood waste as a major point of departure for reducing the environmental impact of timber sector of Ghana. There is the need to train workers to upgrade their skills to meet the new technological challenges that might arise in the area of production. The findings could be used in the future planning towards a more cost effective management of wood flow of the selected species and their utilization

Source: KNUST