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Composting is the most efficient technique for managing household organic waste; it is the most widely used technique in the world. To improve and accelerate the composting process and produce rich and stable compost, it is necessary to grind and shred organic waste into small pieces to facilitate the degradation of the material by microorganisms. This paper presents the design, sizing, and modeling of a new self-contained, solar-powered, rotating composter with a shredding shaft. This shredding shaft rotates at 350 rpm and must run for 5 minutes before starting the composting process. This innovative machine shreds and composts organic household waste in situ to produce stable, mature compost suitable for agricultural use, providing an effective solution for managing and recovering organic household waste.

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For the process of treating organic waste, rotary composters are frequently employed. The amount of energy used to move the organic waste is a crucial factor to consider when designing a composting machine and selecting an appropriate motor. Using a simplified model created by regression approximation from mechanical equations, the power for the movement of organic material can be expressed as a clear and specific function of the composter size, operational parameters (direction of the sun, humidity, etc.), and organic waste qualities. The effectiveness of this model is confirmed with experimental measurements on an industrial rotating composter, yielding satisfactory results and accuracy.

Anaerobic digestion is considered a beneficial treatment for biogas production (BP). To improve the performance of this bioprocess, the addition of well-selected inocula could be an interesting approach that affects the overall efficiency of the BP. In this study, the reactor performance and energy analysis of liquid-state anaerobic digestion of cattle manure (CM) at high solids concentration (TS%) (94.87%) with six different inocula—two cellulosic (C.I1, C.I2), one lipidic (Li.I), two lactic (La.I1, La.I2), and one saccharidic (Sacc.I)—were investigated. The results showed that inocula improved the biogas production and yield during anaerobic digestion of CM by 109%, 86%, and 52.4%, respectively, when the cellulosic (C.I1), lipidic (Li.I), and lactic (La.I1) inocula were added, compared with the substrate production alone at a substrate/inoculum (S/I) ratio of 5:3 (v/v). The addition of inocula in an appropriate range is useful for the performance of the anaerobic digestion process. In our study, the 16S rRNA sequencing approach was followed to investigate microbial community structure and diversity in the substrate CM and the three inocula that showed a significant improvement in biogas production (C.I1, Li.I, and La.I). The most abundant bacterial populations were found to be Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria, with different abundance percentages. Interestingly, C.I1, which resulted in the highest biogas production, showed the dominance of Cyanobacteria (53.44%) belonging mainly to the class Nostocophycidae. This study highlighted the role of inocula in improving biogas production from cattle manure (CM) thanks to their microbial diversity.