Nicholas Darkwa - Academia.edu (original) (raw)
Papers by Nicholas Darkwa
Traditional charcoal production, firewood sourcing and over-dependence on the national grid for e... more Traditional charcoal production, firewood sourcing and over-dependence on the national grid for electricity are associated with high greenhouse gas emissions relative to other common energy options. However, there have been few attempts to analyze the potential of cogeneration and briquetting as favourable energy options for climate change mitigation. The possibility of utilizing abundant wood residues to produce energy for domestic and industrial application through co-generation and sawdust briquetting was assessed. Annual residues generated in the three mills studied ranged from 19,230 m 3 to 32,610 m 3. Annual output of semi-carbonized and carbonized sawdust briquette from the briquette factory studied was 1400 tonnes. Heating values of the wood species ranged from 8.2 to 20.3 MJ/kg. Power requirements for the mills, necessary for sizing co-generation units were derived from their monthly electricity bills. Power ratings for co-generation units were specified between 400 kWe to 2000 kWe with heat to power ratios of 19 to 21. The energy generated could be used to produce electrical power and reduce dependency on the national grid. Conversion of sawdust in the briquette factory potentially contributes a saving of 5,600 tonnes of trees/year that would have been cut from the forest. Thus, adoption of co-generation and sawdust briquetting nationwide could be of immense benefit to the country in terms of climate change mitigation.
UDS International Journal of Development, 2019
Wood absorbs moisture from the surrounding environment and releases moisture according to the tem... more Wood absorbs moisture from the surrounding environment and releases moisture according to the temperature and the relative humidity of the surrounding environment leading to dimensional changes. Changes in dimensions can be reduced by chemical modification. The reduced dimensional changes of chemically modified wood depends on either the degree of blocking the hydroxyl groups of the wood polymers in the cell walls and/or bulking the cell wall to reduce the amount of water that can be absorbed into the wood cell wall. However,there is a conflicting result in literature concerning the dependence of absorption of water molecules into the cell wall. In this study, Celtis mildbraedii (esa fufuo), a tropical hardwood species was chemically modified and the dependence of dimensional stabilisation of the chemically modified esa fufuo has been evaluated. The dimensional stability of the modified samples was found to be dependent on bulking at a weight percentage gain below 20%.
FPRI Technical Newsletter; 8( 1&2):11-16, 1974
The aim of this work was to substitute cassava flour, a local material for imported wheat flour a... more The aim of this work was to substitute cassava flour, a local material for imported wheat flour as extender in adhesive mix for plywood manufacture. The previous laboratory trial of the adhesive mixture indicated that cassava could be used as a substitute for wheat flour. It became necessary to give it an industrial trial. Consequently five mills were selected for such a trial. The results showed that four out of the mills management were eager to use cassava flour as a substitute for the wheat flour.
Scientific Research and Essays, 2011
Article published in Scientific Research and Essays Vol. 6(34), pp. 6835-6839, 30 December, 2011.... more Article published in Scientific Research and Essays Vol. 6(34), pp. 6835-6839, 30 December, 2011. Also available online at http://www.academicjournals.org/SRE DOI: 10.5897/SRE11.797
Journal of Bamboo and Rattan, 2008
Journal of Pharmacognosy and Phytochemistry, 2014
Although herbivores feed on various plant parts (e.g. leaves), inherent phytochemicals present va... more Although herbivores feed on various plant parts (e.g. leaves), inherent phytochemicals present varying degrees of antagonism. Bamboo leaves have therapeutic and nutritional properties, making them a good source of fodder for livestock. To be sure of their safety or otherwise, phytochemical analysis was undertaken on three bamboo species [Bambusa vulgaris Schrad. ex J. C. Wendl., Bambusa ventricosa McClure, and Oxytenanthera abyssinica (A. Rich.)]. The leaves were tested in their wet and dry states. Leaves of all the species contained saponins, general glycosides, coumarins and cyanogenic glycosides. Those of B. ventricosa and O. abyssinica contained polyphenols and flavonoids as well. However, there were no alkaloids, carotenoids, triterpenoids and steroids, anthraquinones and anthracene glycosides in any of the species/varieties. Generally, air-drying of bamboo leaves does not affect presence of inherent phytochemicals and equally makes them suitable as hay just like fodder in the ...
The Chemistry and Processing of Wood and Plant Fibrous Material, 1996
ABSTRACT The chemical composition of some Ghanaian hardwoods are described as well as investigati... more ABSTRACT The chemical composition of some Ghanaian hardwoods are described as well as investigations into their pulping characteristics. The results show that the chemical composition of these hardwoods are as varied as their densities. Klason lignin values cut across the whole range of values for both temperate softwoods and hardwoods. The cellulose contents range from as low as 33.0% to 53.1%. The extractive contents are also high compared to temperate woods. The results of the pulping studies reveal that these tropical hardwoods could be pulped individually and in mixtures with soda process at 20% alkali on wood to produce pulps with total yields ranging from 45.93 to 53.2% and kappa numbers of 20 to 55.
Ghana Journal of Forestry, 2007
Pterygota macrocarpa has emerged as a very popular timber species for the manufacture of plywood ... more Pterygota macrocarpa has emerged as a very popular timber species for the manufacture of plywood in Ghana. However, the blue stain fungus, Lasiodiplodia theobromae moulds and insect borers cause serious damage to the timber between the time of felling and extraction. This study assessed the potential of some chemical preservatives to reduce the impact of blue stain and insect borers on P. macrocarpa logs and determined the best treatment period for short-term preservation of the timber. Logs were treated with (i) fungicides (Antiblue and Bumper) (ii) an insecticide (Pyrinex) (iii) a combination of a fungicide and an insecticide and (iv) Kerosene. Experiments were conducted during both dry and wet seasons and included controls (no treatment). Treatments with combinations of Antiblue and Pyrinex soon after felling prevented sapstain and mould growth during the first fourteen days in the dry season but traces of sapstain appeared after seven days in the wet season. All preservatives showed at least 95% effectiveness in controlling stain in both dry and wet seasons when treatments were carried out immediately after felling but dropped to below 80% after seven days exposure in the wet season. The best chemical treatment for the suppression of insect borers was combinations of Pyrinex and Bumper and Pyrinex and Antiblue for dry and wet seasons, respectively. Keywords : Pterygota macrocarpa , chemical preservatives, sapstain, logs Ghana Journal of Forestry Vol. 17 & 18 2005: pp. 56-70
Pakistan Journal of Chemistry, 2013
In an effort to find new preservatives which are less hazardous, the efficacy of branch bark, lea... more In an effort to find new preservatives which are less hazardous, the efficacy of branch bark, leaf, and heartwood water extractives of Erythropleum suaveolens (Potrodom), a highly durable timber species, was tested on Antiaris toxicaria (Chenchen) and Canarium schweinfurthii (Bediwonua) of low natural durability by presssure impregnation. Impregnated Chenchen and Bediwonua were exposed in the field for 6 months in accordance with a modified EN 252. Durability ratings, hardness and mass losses were measured in assessing their field performance. Though Bediwonua and Chenchen retained branch bark water extractives minimally, it conferred the highest resistance to deterioration. Branch bark water extractives represent a potential source of wood preservative.
![Research paper thumbnail of Corrigendum to “Biodeteriorating agents associated with three tropical timber species” [For. Ecol. Manage. 195 (2004) 311–323]](https://attachments.academia-assets.com/102414780/thumbnails/1.jpg)
](Forest Ecology and Management, 2004
Forest Ecology and Management, 2004
Biodeteriorating agents are major problems of wood particularly in tropical Africa. Biodeteriorat... more Biodeteriorating agents are major problems of wood particularly in tropical Africa. Biodeterioration is widely observed in light coloured hardwood species especially Celtis mildbraedii, Ceiba pentandra and Pterygota macrocarpa. To determine biodeteriorating agents associated with these degradable woods, logs of C. mildbraedii, C. pentandra and P. macrocarpa were left for 6 weeks at the loading bay during the dry and wet seasons of the year 2001. The surfaces of logs were assessed for stain and mould after 7, 14, 28, and 42 days of storage. Pterygota macrocarpa harboured the highest fungal population count of 60:3 Â 103 colony-forming units (CFU) with C. mildbraedii harbouring the least at 4:2 Â 10 2 CFU after a week exposure in the dry season. Fusarium solani and Penicillium citrinum were the dominant surface moulds on log ends of wood samples, while Lasiodiplodia theobromae and Ceratocystis fagacearum were the dominant sapstain fungi. Pterygota macrocarpa and C. pentandra were more susceptible to woodborers than C. mildbraedii because of the lack of true heartwood and richer store of nutrients in its wood cells.
This study examined the relationship between selected physico-mechanical properties, compact-ing ... more This study examined the relationship between selected physico-mechanical properties, compact-ing pressure and mixing proportion of briquettes produced from combination of maize cob par-ticles and sawdust of low, medium and high density timber species. Particle sizes of maize cobs and sawdust used for the study were ≤1 mm. The two materials were combined at mixing percen-tages of 90:10, 70:30 and 50:50 (Sawdust:maize cobs). Briquettes were produced at room temper-ature (28˚C) using compacting pressures 20, 30, 40 and 50 MPa. The results suggested that com-bining maize cob particles with sawdust of low, medium and high density wood species could sig-nificantly enhance the relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from agricultural biomass residue like maize cobs. The results further in-dicated that the physical and mechanical characteristics of briquettes produced from combina-tions of sawdust of low density species and maize cob...
International Journal of Science and Research (IJSR)
This study aimed at determining the relationship of anthropometric dimensions of workers from sev... more This study aimed at determining the relationship of anthropometric dimensions of workers from several offices in public institutions with the dimensions of institution chairs. Three dimensions of the chairs in daily use were evaluated to ascertain whether the fit is sufficient and the effect on workers’ sitting posture. The study comprised of a sample of 261 workers from six public institutions in Ashanti Region, Ghana and one type of furniture. Dimensions of institution chairs were compared with three anthropometric variables of the workers. Descriptive statistics were analyzed for all variables. The study results show that furniture of appropriate dimensions is not available to a large number of workers in Ghana. Currently supplied office furniture is provided in several sizes and do not fit the users. It is recommended that work chairs may be acceptable if they are issued in four heights or individually adjustable chairs be introduced in Ghanaian institutions. Furthermore it is s...
Traditional charcoal production, firewood sourcing and over-dependence on the national grid for e... more Traditional charcoal production, firewood sourcing and over-dependence on the national grid for electricity are associated with high greenhouse gas emissions relative to other common energy options. However, there have been few attempts to analyze the potential of cogeneration and briquetting as favourable energy options for climate change mitigation. The possibility of utilizing abundant wood residues to produce energy for domestic and industrial application through co-generation and sawdust briquetting was assessed. Annual residues generated in the three mills studied ranged from 19,230 m 3 to 32,610 m 3. Annual output of semi-carbonized and carbonized sawdust briquette from the briquette factory studied was 1400 tonnes. Heating values of the wood species ranged from 8.2 to 20.3 MJ/kg. Power requirements for the mills, necessary for sizing co-generation units were derived from their monthly electricity bills. Power ratings for co-generation units were specified between 400 kWe to 2000 kWe with heat to power ratios of 19 to 21. The energy generated could be used to produce electrical power and reduce dependency on the national grid. Conversion of sawdust in the briquette factory potentially contributes a saving of 5,600 tonnes of trees/year that would have been cut from the forest. Thus, adoption of co-generation and sawdust briquetting nationwide could be of immense benefit to the country in terms of climate change mitigation.
UDS International Journal of Development, 2019
Wood absorbs moisture from the surrounding environment and releases moisture according to the tem... more Wood absorbs moisture from the surrounding environment and releases moisture according to the temperature and the relative humidity of the surrounding environment leading to dimensional changes. Changes in dimensions can be reduced by chemical modification. The reduced dimensional changes of chemically modified wood depends on either the degree of blocking the hydroxyl groups of the wood polymers in the cell walls and/or bulking the cell wall to reduce the amount of water that can be absorbed into the wood cell wall. However,there is a conflicting result in literature concerning the dependence of absorption of water molecules into the cell wall. In this study, Celtis mildbraedii (esa fufuo), a tropical hardwood species was chemically modified and the dependence of dimensional stabilisation of the chemically modified esa fufuo has been evaluated. The dimensional stability of the modified samples was found to be dependent on bulking at a weight percentage gain below 20%.
FPRI Technical Newsletter; 8( 1&2):11-16, 1974
The aim of this work was to substitute cassava flour, a local material for imported wheat flour a... more The aim of this work was to substitute cassava flour, a local material for imported wheat flour as extender in adhesive mix for plywood manufacture. The previous laboratory trial of the adhesive mixture indicated that cassava could be used as a substitute for wheat flour. It became necessary to give it an industrial trial. Consequently five mills were selected for such a trial. The results showed that four out of the mills management were eager to use cassava flour as a substitute for the wheat flour.
Scientific Research and Essays, 2011
Article published in Scientific Research and Essays Vol. 6(34), pp. 6835-6839, 30 December, 2011.... more Article published in Scientific Research and Essays Vol. 6(34), pp. 6835-6839, 30 December, 2011. Also available online at http://www.academicjournals.org/SRE DOI: 10.5897/SRE11.797
Journal of Bamboo and Rattan, 2008
Journal of Pharmacognosy and Phytochemistry, 2014
Although herbivores feed on various plant parts (e.g. leaves), inherent phytochemicals present va... more Although herbivores feed on various plant parts (e.g. leaves), inherent phytochemicals present varying degrees of antagonism. Bamboo leaves have therapeutic and nutritional properties, making them a good source of fodder for livestock. To be sure of their safety or otherwise, phytochemical analysis was undertaken on three bamboo species [Bambusa vulgaris Schrad. ex J. C. Wendl., Bambusa ventricosa McClure, and Oxytenanthera abyssinica (A. Rich.)]. The leaves were tested in their wet and dry states. Leaves of all the species contained saponins, general glycosides, coumarins and cyanogenic glycosides. Those of B. ventricosa and O. abyssinica contained polyphenols and flavonoids as well. However, there were no alkaloids, carotenoids, triterpenoids and steroids, anthraquinones and anthracene glycosides in any of the species/varieties. Generally, air-drying of bamboo leaves does not affect presence of inherent phytochemicals and equally makes them suitable as hay just like fodder in the ...
The Chemistry and Processing of Wood and Plant Fibrous Material, 1996
ABSTRACT The chemical composition of some Ghanaian hardwoods are described as well as investigati... more ABSTRACT The chemical composition of some Ghanaian hardwoods are described as well as investigations into their pulping characteristics. The results show that the chemical composition of these hardwoods are as varied as their densities. Klason lignin values cut across the whole range of values for both temperate softwoods and hardwoods. The cellulose contents range from as low as 33.0% to 53.1%. The extractive contents are also high compared to temperate woods. The results of the pulping studies reveal that these tropical hardwoods could be pulped individually and in mixtures with soda process at 20% alkali on wood to produce pulps with total yields ranging from 45.93 to 53.2% and kappa numbers of 20 to 55.
Ghana Journal of Forestry, 2007
Pterygota macrocarpa has emerged as a very popular timber species for the manufacture of plywood ... more Pterygota macrocarpa has emerged as a very popular timber species for the manufacture of plywood in Ghana. However, the blue stain fungus, Lasiodiplodia theobromae moulds and insect borers cause serious damage to the timber between the time of felling and extraction. This study assessed the potential of some chemical preservatives to reduce the impact of blue stain and insect borers on P. macrocarpa logs and determined the best treatment period for short-term preservation of the timber. Logs were treated with (i) fungicides (Antiblue and Bumper) (ii) an insecticide (Pyrinex) (iii) a combination of a fungicide and an insecticide and (iv) Kerosene. Experiments were conducted during both dry and wet seasons and included controls (no treatment). Treatments with combinations of Antiblue and Pyrinex soon after felling prevented sapstain and mould growth during the first fourteen days in the dry season but traces of sapstain appeared after seven days in the wet season. All preservatives showed at least 95% effectiveness in controlling stain in both dry and wet seasons when treatments were carried out immediately after felling but dropped to below 80% after seven days exposure in the wet season. The best chemical treatment for the suppression of insect borers was combinations of Pyrinex and Bumper and Pyrinex and Antiblue for dry and wet seasons, respectively. Keywords : Pterygota macrocarpa , chemical preservatives, sapstain, logs Ghana Journal of Forestry Vol. 17 & 18 2005: pp. 56-70
Pakistan Journal of Chemistry, 2013
In an effort to find new preservatives which are less hazardous, the efficacy of branch bark, lea... more In an effort to find new preservatives which are less hazardous, the efficacy of branch bark, leaf, and heartwood water extractives of Erythropleum suaveolens (Potrodom), a highly durable timber species, was tested on Antiaris toxicaria (Chenchen) and Canarium schweinfurthii (Bediwonua) of low natural durability by presssure impregnation. Impregnated Chenchen and Bediwonua were exposed in the field for 6 months in accordance with a modified EN 252. Durability ratings, hardness and mass losses were measured in assessing their field performance. Though Bediwonua and Chenchen retained branch bark water extractives minimally, it conferred the highest resistance to deterioration. Branch bark water extractives represent a potential source of wood preservative.
Forest Ecology and Management, 2004
Forest Ecology and Management, 2004
Biodeteriorating agents are major problems of wood particularly in tropical Africa. Biodeteriorat... more Biodeteriorating agents are major problems of wood particularly in tropical Africa. Biodeterioration is widely observed in light coloured hardwood species especially Celtis mildbraedii, Ceiba pentandra and Pterygota macrocarpa. To determine biodeteriorating agents associated with these degradable woods, logs of C. mildbraedii, C. pentandra and P. macrocarpa were left for 6 weeks at the loading bay during the dry and wet seasons of the year 2001. The surfaces of logs were assessed for stain and mould after 7, 14, 28, and 42 days of storage. Pterygota macrocarpa harboured the highest fungal population count of 60:3 Â 103 colony-forming units (CFU) with C. mildbraedii harbouring the least at 4:2 Â 10 2 CFU after a week exposure in the dry season. Fusarium solani and Penicillium citrinum were the dominant surface moulds on log ends of wood samples, while Lasiodiplodia theobromae and Ceratocystis fagacearum were the dominant sapstain fungi. Pterygota macrocarpa and C. pentandra were more susceptible to woodborers than C. mildbraedii because of the lack of true heartwood and richer store of nutrients in its wood cells.
This study examined the relationship between selected physico-mechanical properties, compact-ing ... more This study examined the relationship between selected physico-mechanical properties, compact-ing pressure and mixing proportion of briquettes produced from combination of maize cob par-ticles and sawdust of low, medium and high density timber species. Particle sizes of maize cobs and sawdust used for the study were ≤1 mm. The two materials were combined at mixing percen-tages of 90:10, 70:30 and 50:50 (Sawdust:maize cobs). Briquettes were produced at room temper-ature (28˚C) using compacting pressures 20, 30, 40 and 50 MPa. The results suggested that com-bining maize cob particles with sawdust of low, medium and high density wood species could sig-nificantly enhance the relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from agricultural biomass residue like maize cobs. The results further in-dicated that the physical and mechanical characteristics of briquettes produced from combina-tions of sawdust of low density species and maize cob...
International Journal of Science and Research (IJSR)
This study aimed at determining the relationship of anthropometric dimensions of workers from sev... more This study aimed at determining the relationship of anthropometric dimensions of workers from several offices in public institutions with the dimensions of institution chairs. Three dimensions of the chairs in daily use were evaluated to ascertain whether the fit is sufficient and the effect on workers’ sitting posture. The study comprised of a sample of 261 workers from six public institutions in Ashanti Region, Ghana and one type of furniture. Dimensions of institution chairs were compared with three anthropometric variables of the workers. Descriptive statistics were analyzed for all variables. The study results show that furniture of appropriate dimensions is not available to a large number of workers in Ghana. Currently supplied office furniture is provided in several sizes and do not fit the users. It is recommended that work chairs may be acceptable if they are issued in four heights or individually adjustable chairs be introduced in Ghanaian institutions. Furthermore it is s...