A comparative performance analysis on energy efficiency and emissions of fuel briquettes made from fecal sludge blended with other biomass materials
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This study explored the potential of utilization of fecal sludge mixed with a variety of agricultural residues, for production of solid biofuels for use in household and institutional combustion systems. A mixing ratio of 2:1 (fecal sludge: biomass) was used when making all the five batches of briquettes with red soil as a binder. These included; fecal sludge (FS) + red soil (RS), fecal sludge + peanut shells (PS) + red soil, fecal + charcoal dust (CD) + red soil, fecal sludge + empty bean pods (BP) + red soil, fecal (FS) + red soil (RS) + rice husks (RH). The five batches of briquettes (FS+RS, FS+PS+RS, FS+CD+ RS, FS+BP+RS, FS+RH+RS) were tested for different fuel properties including; physical, thermo-chemical, and combustion characteristics. These included moisture content (%), density (g/cm3), compressive strength (N/mm2), maximum force (N), ash content (%), volatile matter (%), calorific value (kcal/g), ignition time (min), burning rate (min) and thermal efficiency (%). This study also evaluated gaseous emission from the combustion of the developed biofuels to quantify their indoor pollution hazard. Emissions (nitrogen oxides (NOX), Methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2) were evaluated using a portable infrared syngas analyzer (Gasbord- 3100P), (HubeibCubic-Ruiyi Instrument Co Ltd). All data on biofuel properties were analyzed using Microsoft Excel software. The results were compared using one-way analysis of variance (ANOVA-single factor) to determine if there was a significant difference among the different briquette parameters. Briquettes made of FS+CD+RS had the highest calorific value (12479.63Kcal/Kg). Briquettes made of FS +RS had the lowest calorific value (9505.586Kcal/Kg). Density was highest in briquettes made of FS+CD+RS (2.788g/cm3) and lowest in briquettes made of FS+RH+RS (2.689g/cm3). Compressive strength was highest in briquettes made of FS+PS+RS (2.2743N/mm2) and was lowest in briquettes made of FS+CD+RS (1.403N/mm2). Briquettes made of FS+RH+RS had the highest moisture content with average of 4.879%. Volatile matter was highest in briquettes made of FS+PS+RS (50%) and was lowest in briquettes of FS+RS+CD (35.89%). Ash content was highest in briquettes made of FS+PS+RS (42.35%) and lowest in briquettes made of FS+RS+CD (40.54%). Highest burning rate was recorded in briquettes of FS+PS+RS (12.005g/min) and was recorded lowest in briquettes of FS+BP+RS (5.665g/min). It was noted that FS+PS+RS briquettes had better chemical properties (volatile matter, ash content, calorific value) compared to other types of briquette while FS+CD+RS briquettes had better physical properties (compressive strength, moisture content, density) compared to the other briquettes’ types. For gaseous emissions the briquettes made from FS+RH+RS had the highest levels of CO (27.87%) and while the lowest was recorded for FS+CD+RS (3.96%). High levels of NO2 was recorded for FS+PS+RS (44.69%) and lowest in FS+RH+RS (16.83%). FS+RH+RS had highest levels of CH4 (12.53%) and no CH4 emissions was recorded for FS+BP+RS. Highest levels of CO2 were recorded for FS+CD+RS (24.25%) and lowest for FS+PS+RS (3.1%). Briquettes made of biomass emitted more gaseous emissions compared to briquettes made of fecal sludge alone. Further studies should be done on people’s perception towards the use of briquettes made from fecal sludge blended with other biomass.