Title : Wastewater sludge as a resource: Methane production and digestate valorization through anaerobic digestion
Abstract:
Anaerobic digestion represents a promising waste-to-energy strategy for wastewater sludge management, enabling renewable energy recovery through methane production while generating a nutrient-rich digestate that can be valorized in agriculture. This dual valorization pathway offers an opportunity to maximize resource recovery from wastewater sludge within a circular bioeconomy framework. This study aimed to evaluate both the energy recovery and agricultural valorization potential of three activated sludges collected from Moroccan wastewater treatment plants located in Marrakech, Youssoufia, and Khouribga. The activated sludges were subjected to mesophilic anaerobic digestion using cattle manure as inoculum. Methane production was monitored to assess the energy recovery potential of each sludge. Following digestion, the resulting digestates were characterized and evaluated for agricultural reuse. An agronomic experiment was conducted using two soil types collected from Benguerir and Bouchane and two crop species, triticale and forage pea. Two digestate application rates were tested and compared with a fertilized control, while plant growth and production parameters were monitored throughout the experiment. The results showed clear differences in methane production according to sludge origin, with the highest yield observed for the Khouribga sludge. Agronomic responses also varied according to digestate origin, soil type, application rate, and crop species. Among the tested digestates, the Khouribga digestate generally exhibited particularly promising agronomic performance for both crops. Under several experimental conditions, digestate application resulted in plant growth and production comparable to, or higher than, those obtained with the fertilized control. Differences between the two soil types further highlighted the influence of soil characteristics on digestate performance. Overall, the results demonstrate the potential of anaerobic digestion as an integrated valorization pathway for wastewater sludge, combining renewable energy recovery through methane production with the agricultural reuse of digestate.
Keywords: Waste-to-energy; Anaerobic digestion; Wastewater sludge; Methane; Digestate; Resource recovery
