Comparative Analysis of Briquetting Most Viable Biomass Waste to Substitute Charcoal in Ethiopia
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Date
2014-04
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Addis Ababa University
Abstract
Agricultural residues seem to be the most promising energy resources for developing countries.
However, the majority of them have low energy density. One of the favorable technologies for
enhancing that property is charcoal Briquetting. A large amount of agricultural and solid wastes
are left in the field after harvest. The primary objective of the study was to investigate the
comparative analysis of resource availability, physico-chemical properties and performance of
biomass charcoal produce from the most promising wastes. Specific objective were to develop
and characterizing composite charcoal briquettes, investigate factors affecting densification of
composite charcoal briquettes and compare resources availability, physic-chemical property and
performance of charcoal briquettes with wood charcoal.
The composite charcoal briquettes were produced using ASTM standard by a combination of
process factors. The three process factors were dwell time, clay binder ratio and pressure.
Design expert software, Box-Henken model were employed to investigate the effect of process
factors. The Density was found in the range of 783.00-1,187.00 kg/m^3. The coefficient of
multiple determinations for prediction of the proposed density model was about 95.7%. The
effect of the three variables against density was investigated. When every two combinations of
the above variables were increased, density of briquettes was also found to increase. Optimum
point of dwell time, pressure and clay binder concentration was found at 3.6 minute, 45 bars and
18.27% respectively. The optimal point was validated.
The Production of 1300 tones/yr briquettes plant was evaluated. The total investment cost was
found to be 1.9137milloion birr. The net present value and the internal rate of return of the
project were 2,753,976 Birr and 19% respectively it implies the project was feasible.
Base on the resource estimation using production to residue ratio, the quantity of available
agricultural residue, cotton stalk, coffee husk, bamboo residue and jatropha press cake in
Ethiopia was approximately 4,655.887, 219.933, 109.757, 109.757,1,000 and 0.228Ktones/yr
respectively. When the fixed carbon of charcoal made from bamboo, cotton stalk, coffee residue
and composite with that of Acacia charcoal, 60.85, 58.4, 63.9, 68.25 and 69.74w/w % were
found respectively. The above value all had relatively similar which makes it possible to
substitute wood charcoal. Regarding heating values of briquettes produced from bamboo, cotton
Comparative Analysis of Briquetting Most Viable Biomass Waste to Substitute Charcoal in Ethiopia
AAU, AAiT, M.Sc. Thesis by Anteneh B. xiv
stalk, coffee residue, composite and Acacia spp. charcoal were 29135.94KJ/Kg, 19209.03KJ/Kg,
11710.48KJ/Kg , 23446.08KJ/Kg and 32573.304 KJ/Kg respectively. But all the heat values of
briquettes were lower than that of charcoal. If the country substitutes wood charcoal by charcoal
briquettes, it will reduce 47.06 CH4 / year and 1530.383 Co2/year for every production of 1300
tons per year. The study showed that charcoal from bamboo; cotton stalk, coffee residue and
agricultural residue could be used as substitutes for Acacia charcoal as they had comparable
potential energy. But jatropha press cake currently had a low possibility to be use in our scenario.
Generally, this research concludes that the biomass charcoal had positive value of production
method, fixed carbon and performance, but one negative value was obtained from calorific value.
With ¾ positive values, these biomass wastes can substitute wood charcoal in Ethiopia.
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Keywords
Comparative Analysis of Briquetting