Production of Low Emission Briquettes from Faecal Sludge as an Alternative Source of Cooking Energy

Abstract

Background In Tanzania, firewood, charcoal, and agricultural waste plays a crucial role in daily life as the source of cooking energy, especially in rural areas. Inefficient emissions of harmful substances lead to health problems, environmental degradation, deforestation, soil erosion, and loss of biodiversity. Faecal sludge has shown the potential to be used as an environmentally friendly and more sustainable alternative to traditional sources to meet the increasing demand for cooking energy in Tanzania. The whole process involved sludge characterization, drying, sorting, carbonization, milling, and briquetting. Results Faecal sludge from households was assessed for zinc (Zn), Cadmium (Cd), and Lead (Pb) and the results were within the acceptable limits of the Tanzanian Standards of 5.00 mg/L, 5.00 mg/L, and 30.00 mg/L. Septic tanks and pit latrines sludge had a concentration of 0.5 mg/L and 0.5 mg/L, 0.55 mg/L and 0.6 mg/L, and 10.01 mg/L and 4.87 mg/L, respectively. The carbonization process at 450°C kills all the pathogens present. The addition of 25% sawdust or charcoal dust improves the calorific value of the briquettes (gross and net calorific value in Kcal/Kg) from 2500 and 2426 to 3388 and 3296, and 3915 and 3823, respectively. The emission of particulate matter (PM2.5 and PM10 in micrograms/m3) was reduced from 30.4 and 35 to 10.3 and 11.8 and 7 and 8, respectively. The emission of CO (ppm) was reduced from 51.2 to 19.7, respectively. Conclusion Faecal sludge briquettes demonstrated promising results with the addition of other biomass materials in terms of emission levels, burning time, and compressive strength. Therefore, from this study, faecal sludge briquettes have shown the potential to replace traditional cooking energy sources.

Sustainable Solid Biofuel Production: Transforming Sewage Sludge and Pinus sp. Sawdust into Resources for the Circular Economy

“…By adopting such innovative methods for sludge utilization, WTPs can not only manage their waste more sustainably but also contribute positively to environmental conservation efforts. This underscores the importance of exploring diverse avenues for sludge utilization within the context of wastewater treatment [8].…”