Otieno Austine O, Home Patrick G, Raude James M, Murunga Sylvia I, Gachanja Anthony
Soil, Water and Environmental Engineering Department (SWEED), Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya.
Department of Geoscience and the Environment (DGSE), Technical University of Kenya, P.O. Box 52428-00200, Nairobi, Kenya.
Heliyon. 2022 Aug 18;8(8):e10272. doi: 10.1016/j.heliyon.2022.e10272. eCollection 2022 Aug.
Over reliance on charcoal has accelerated deforestation in sub-Saharan Africa. Seeking alternative sustainable and environmentally friendly sources of biomass energy to meet the escalating energy demand is therefore vital. However, limited evidence exists on the concentrations of toxic emissions of different biomass fuels. Herein, dried human faeces and sawdust were pyrolyzed at 350 °C to produce biochar and mixed in equal ratio to produce briquettes through densification, with molasses (10 wt.%) used as a binder. A comparative study on the heating properties and emission level of carbon monoxide (CO), nitric oxide (NO), and hydrogen sulphide (HS) during combustion of charcoal, and co-combustion (50:50 wt. %) of charcoal with briquettes was conducted. The thermal profile of the flue gases indicated rapid combustion of volatile gases followed by slow oxidation of the char. Co-combustion significantly (P < 0.05) enhanced the amount of heat energy released with flue gases temperatures reaching a peak of 475 °C. The briquettes had a gross calorific value of 19.8 MJ/kg which was lower than 25.7 MJ/kg for charcoal. Combustion of charcoal did not emit NO, however the concentration of CO was above the critical short term limits of 35 ppm. The concentration of CO and HS was above the short term exposure limits of 35 ppm, and 0.005 ppm, respectively, during co-combustion, whereas NO concentration was below dangerous exposure levels of 100 ppm. These results suggest that co-combustion of charcoal with the briquettes is a promising approach to generate safe and sufficient heat energy for cooking and reduce deforestation.
过度依赖木炭加速了撒哈拉以南非洲地区的森林砍伐。因此，寻找可持续且环保的生物质能替代能源以满足不断增长的能源需求至关重要。然而，关于不同生物质燃料有毒排放物浓度的证据有限。在此，将干燥的人类粪便和锯末在350℃下热解以生产生物炭，并以等比例混合，通过致密化制成煤球，使用糖蜜（10重量%）作为粘结剂。对木炭燃烧以及木炭与煤球共燃烧（50:50重量%）过程中一氧化碳（CO）、一氧化氮（NO）和硫化氢（HS）的加热特性和排放水平进行了比较研究。烟道气的热曲线表明挥发性气体快速燃烧，随后是焦炭的缓慢氧化。共燃烧显著（P<0.05）提高了释放的热能，烟道气温度达到475℃的峰值。煤球的总热值为19.8兆焦/千克，低于木炭的25.7兆焦/千克。木炭燃烧不排放NO，但CO浓度高于35 ppm的临界短期限值。共燃烧过程中，CO和HS的浓度分别高于35 ppm和0.005 ppm的短期暴露限值，而NO浓度低于100 ppm的危险暴露水平。这些结果表明，木炭与煤球共燃烧是一种有前景的方法，可为烹饪产生安全充足的热能并减少森林砍伐。
