Wood residue generation and utilization: the technical, economic and environmental mix for some selected sawmills in Brong Ahafo and Ashanti Regions, Ghana.
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Date
MARCH, 2016
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Abstract
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
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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
Description
A thesis submitted to the Department of Wood Science and Technology, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Wood Science and Technology.