Physical and combustion properties of agricultural residue bio-char bio-composite briquettes as sustainable domestic energy sources
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
Renewable energy
Abstract
Domestic energy sources in sub-Saharan Africa are still mainly comprised of firewood and
charcoal. One of the main challenges affecting the uptake of carbonized briquettes is their
inefficiency in transferring heat. In this study bio-composite briquettes were developed from rice
husks, coffee husks and groundnut shells, in varying proportions. The briquettes were developed
under low pressure (≤ 7 MPa) after carbonization and application of starch binder. Thermal
properties of the developed bio-composite briquettes were determined by using a bomb
calorimeter and thermogravimetric analysis to determine calorific values and physical properties,
respectively. Drop strength tests and particle density determinations were performed to study the
mechanical strength and integrity of the developed briquettes. The water-boiling test was used to
determine time taken to boil 1 liter of water. Fourier’s Law of heat conduction was used to
investigate heat transfer rates across the briquettes for conditions of binder/binder-less bonding
conditions. Calorific values for the developed briquettes ranged between 16.6 MJ/kg and 22
MJ/kg. Results for drop strength for the developed composite briquettes were all above 86 %,
indicating satisfactory characteristics. Bio-composite briquettes developed using coffee and rice
husks bio-chars took less time to boil water compared to all the other bio-composite briquette
combinations. Particle densities ranged between 430 kg/m3 and 580 kg/m3. Heat transfer was
enhanced when no binder was present and coffee and rice husks were sequentially placed in the
briquette composition. This study showed the advantages of producing bio-char bio-composite
briquettes over single constituent briquettes. Bio-composite carbonized briquettes produced from
rice husks, coffee husks and groundnut shells are a suitable and sustainable alternative to
firewood and charcoal use in sub-Saharan Africa.
Description
Keywords
Bio-composite briquettes, Burning rates, Carbonization, hermogravimetric analysis
Citation
Lubwama, M., Yiga, V. A., Muhairwe, F., & Kihedu, J. (2020). Physical and combustion properties of agricultural residue bio-char bio-composite briquettes as sustainable domestic energy sources. Renewable energy, 148, 1002-1016. https://doi.org/10.1016/j.renene.2019.10.085