Effect of Activated and Non-activated Carbons on Biogas Production from Municipal Organic Wastes

Abstract

Study’s Excerpt • The use of activated and non-activated carbon additives to enhance biogas production from municipal organic wastes is assessed. • The research highlighted the role of activated carbon in improving anaerobic digestion through mechanisms like direct interspecies electron transfer (DIET). • Optimization of biogas production in waste management systems could hence be achieved using activated carbon. Full Abstract Because carbon-based additives are very adaptable to large-scale deployment and have minimal running costs, they are a suitable strategy to increase biogas yield. These Carbonaceous additives have been shown to have a positive effect on biogas generation with beneficial effects in the anaerobic digestion (AD) process as explained by the mechanism of direct interspecies electron transfer (DIET), the utilization of which is linked to a variety of additional mechanisms. This study investigated the effect of activated and non-activated carbons on biogas production from municipal organic wastes. In this study, a set of three (3) bio-digesters was used to process organic municipal wastes (food wastes) supplemented with activated carbon (AC) and non-activated carbon. In comparison to the control set-up without the carbonaceous additive, the results demonstrated a direct link between the activated carbon and the non-activated carbon. The biogas yield and rate of anaerobic digestion (measured based on the biogas yield per gram of the substrate per day; results not shown) are significantly increased when 5 – 10 gL-1 of activated or non-activated carbon is used. During biogas production, the bio-digester with activated carbon displayed more encouraging outcomes. During the 14-day retention period, the total Biogas produced by the set-up with activated carbon was the highest (12 870 mL) and most flammable (+++), followed by the non-activated carbon set-up, which produced 11, 250 mL of moderately flammable (++) Biogas. The lowest (9, 755 mL) and least flammable (+) biogas yield were, however obtained from the control set-up having no carbon additive. The activated carbon was shown to significantly improve biogas yield and its quality (flammability) due to its high surface area and porosity, high chemical stability, electrical conductivity, effective biofilm formation as well as its ability to remove harmful substances (micro-pollutants), which collectively improved the performance of the methanogens, thereby accelerating microbial methanogenesis. This study, therefore, revealed that carbonaceous additives supplementation enhances biogas production and, ultimately the overall biogas quality.

Keywords

• Anaerobic digestion
• Biogas
• activated carbon
• electron transfer
• methanogenesis