Biomass valorization for energy applications: A preliminary study on millet husk

Abstract

This study used millet husk which is a waste and gum Arabic as binder to develop briquettes for domestic cooking in Northern Nigeria. The objective was to investigate the effect of particle sizes, compaction pressures and binder concentrations on the physical, mechanical and thermal characteristics of the briquettes. Furthermore, the study also accessed the economic viability of the usage of millet husk briquettes as fuel. Particle sizes of 0.3, 0.4, 0.6 and 1.7mm; compaction pressures of 10, 15, 20 and 25 MPa and binder concentrations (gum Arabic) of 25, 30, 35 and 40% were used to densify the millet husk mixed with gum Arabic at room temperature with the aid of hydraulic press. The caloric value (15.27 MJ/kg) was determined using ASTM D2015, other physical and chemical properties of the millet husk was determined by proximate and ultimate analysis which showed that volatile matter (76%), ash content (6.5%) and sulphur content (0.3%) are within the recommended range for domestic cooking fuels. It was found that the density (438 kg/m 3 and 669 kg/m 3 ), impact resistance index (70-93%) and compressive strength of the millet husk briquettes increased with compaction pressures and binder concentrations and decreases with increase in particle sizes, while for porosity of the briquettes, the above case was a reversal. The performance of the briquettes for domestic cooking were accessed by ignition time (109 and 140 s); burning rate (0.09 g/s and 0.18 g/s) and water boiling test which took 5 and 11 min to boil 1 L of water as compared to fuel wood that takes longer. Economic analysis showed that utilizing the millet husk generated in northern Nigeria will lead to huge savings in fuel wood consumption, monetary savings of about ₦ 9,257,869,268.62, and reduction in deforestation and its attendant problems. A structured questionnaire as used to ascertain the acceptability of the produced briquettes. Most of the respondents (90%) in a survey expressed willingness to use millet husk briquette as replacement for wood. The study concludes that millet husk is good for briquetting for energy applications with high potential to reduce energy poverty, minimal waste and reduce indoor pollution for domestic cooking therefore, making millet cultivation more profitable in Northern Nigeria.

Development and Evaluation of a Coffee Husk Biomass Briquette Machine

“…However, the values obtained from the various studies were within the range of 19-186 s for bio-coal briquettes formed by mixing the ingredients at varying percentages of 10-50% with coal. In the study [32], the ignition time was between 109 s and 140 s. In…”

Study of combustion characteristics of macadamia shells and coffee husks briquettes in a fixed bed reactor

“…If the residue lacks natural lignin that helps in bonding or the percentage lignin is low, the application of binder will improve the quality of briquettes. The amount and the selection of a binder should be well undertaken to avoid smoke and emission of volatile material that impact human and environment [4]. There are materials that have natural binder, for example, cotton stalks, saw dust, corn stalk, etc.…”

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