During composting, facilities usually exert greater control over the bio-oxidative phase of the process, which uses a specific technology and generally has a fixed duration. After this phase, the material is deposited to mature, with less monitoring during the maturation phase. While there has been considerable study of biological parameters during the thermophilic phase, there is less research on the stabilization and maturation phase. This study evaluates the effects of the type of starting material on the evolution of microbial dynamics during the maturation phase of composting. Three waste types were used: sludge from the fish processing industry, municipal sewage sludge and pig manure, each independently mixed with shredded pine wood as bulking agent. The composting system for each waste type comprised a static reactor with capacity of 600L for the bio-oxidative phase followed by stabilization and maturation phase in triplicate 200L boxes for 112days. Phospholipid fatty acids, enzyme activities and physico-chemical parameters were measured throughout the maturation phase. The evolution of the total microbial biomass, Gram + bacteria, Gram - bacteria, fungi and enzymatic activities (β-glucosidase, cellulase, protease, acid and alkaline phosphatase) depended significantly on the waste type (p<0.001). The predominant microbial community for each waste type remained present throughout the maturation process, indicating that the waste type determines the microorganisms that are able to develop at this stage. While fungi predominated during fish sludge maturation, manure and municipal sludge were characterized by a greater proportion of bacteria. Both the structure of the microbial community and enzymatic activities provided important information for monitoring the composting process. More attention should be paid to the maturation phase in order to optimize composting.

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The inclusion of sustainability and circular economy principles, as well as the compliance of the European requirements in municipal waste management, involves improving the waste separation, recovery and valorization. The current municipal solid waste management system of Galicia (Northwestern Spain) that includes most of the municipalities involves the treatment of biowaste (mixed in the same container with the nonorganic rest fraction) in a single management facility. This biodegradable fraction, which accounts for 42% of the total amount of household waste, is treated by incineration for energy recovery. The local government of Allariz (Galicia) undertook a project to implement a management model decentralized for biowaste separation and treatment through composting. Municipality structure (type of housing, urban and rural areas, etc.) made it necessary to implement different composting systems: home composters, community composting islands and a dynamic composter. During the first year of start-up of the management model, the level of citizen acceptance was adequate, biowaste was correctly segregated and good quality compost for soil fertilizer was obtained. So, a reduction of around 8% of the mixed waste sent to the centralized treatment facility was observed. The biowaste recovery had also resulted in a recycling improvement of all remainder fractions.