Experimental study and analysis of the effect of detergent on the production of biogas from toilet drainage system linked to biogas digester in Ethiopia

Abstract

A biogas reactor that is coupled to a Toilet drainage system collects, stores, and treats excreta through the anaerobic digestion process. According to the data collected, cleaning agents directly get into the drainage system in most households. In this experimental study, the effect of detergent on the production of biogas from a toilet-connected reactor was analyzed. Three predominantly used household cleaning agents with anionic and ionic surfactants were considered and sample mixtures were prepared for 1:1:1 ratio. The experiment has been carried out in a 5-liter plastic bottle as a biogas reactor. The relationships between generated gas and its chemical compositions at various detergent concentrations (blank test, 80 ppm, 160 ppm, 320 ppm 400 ppm 800 ppm, and 1200 ppm) have been investigated using a Gas Chromatography Mass Spectrometry (GCMS) system and analyzed. The risk of Hydrogen sulfide production on human health has also been assessed at different Concentrations of Detergent (CoDe). The results demonstrate that during the early phases (blank test to 80 ppm) of CoDe addition, methane production increases from 62.5% to 63.8% but subsequently decreases by 6% as CoDe increases from 160 ppm to 320 ppm followed by adrastic reduction subsequently. This results in a reduction of methane production by 23% and a higher formation of gases like N2, HCl, NaC12H25SO4, C20H37NaO7S, and others. Therefore, the addition of cleaning agents above 320 ppm into a biogas reactor not only causes substandard biogas production but also has a risk to human health and the environment as a result of the higher production of hydrogen sulfide.