Employing forced aeration (FA) in composting static windrows (SW) from fish waste (FW) has the potential to enhance the development of process and, organic fertiliser quality. However, due to the impact of season, the FA may lead to excessive drying of SW and, difficulty in thermophilic temperature maintenance. The aim of this study was to assess the effects of passive aeration (PA) and FA on the composting of FW in SW during the summer and winter seasons. The temperatures of the windrows remained within the thermophilic range for most of the composting period, with peak temperatures observed shortly after starting and turning the windrows (at 50 and 70 days). The aeration benefited the initial TS degradations, resulting in 86.66 and 45.99% of the TS total reduced to FA and PA piles, at 50 days during the winter. The C organic reduction was 77.77 and 76.33% in summer and winter to FA piles, respectively, but this reduction was 59.24% and 67.82% for winter and summer, respectively, in PA windrows. At 50 days, the N reduction in FA piles was already at 70.32% and 71.87% for winter and summer. The volatile solids reductions were significantly higher (p < 0.01) in FA piles during the summer. Although the FA has been shown to enhance the organic constituents' degradation during the composting of FW, its adoption was not enough to improve the compost composition. Thus, by conducting piles on a small scale, with the perforated wall, as described in this study, the FA could be dispensed.

The co-digestion of swine manure with vegetable waste is an alternative that can increase the production of biogas and methane generated by the isolated digestion of manure. However, recommendations that are based on the best ratio between manure and forage, as well as the age of harvest, are still scarce in the literature. This study was conducted to evaluate inclusions (0, 25, 50, 75 and 100%) of the total solids (TS) of Elephant grass (Pennisetum purpureum Schum) harvested at two ages medium age (MA) at 45 days of growth and advanced age (AA) at 90 days in co-digestion with swine manure, using an entirely randomized design in a 5x2 factorial scheme. Batch digesters were used and biogas production was monitored for 12 weeks. There was influence of forage age (P <0.05) on the degradation of solids and neutral detergent fiber, with higher values for the substrates containing MA forage. The highest CH4 yields were obtained by the substrates containing MA forage in the inclusion of 27.7 and 31.6%, being 253.7 and 222.2 L of CH4 per Kg of total or volatile solids. The age of the forages influenced the onset and persistence of biogas production, being advantageous only in the inclusion of 25% of MA forage. The AA forage inclusion is not recommended for co-digestion with swine manure.

The incorporation of monensin into cattle diets can significantly alter the physicochemical properties of excreted manure, potentially affecting waste management and treatment systems given the persistence of substantial concentrations of ionophores in the effluent. This study assessed the impact of monensin on the compositional characteristics of cattle manure and its implications for anaerobic digestion efficiency, with and without the separation of manure fractions across two hydraulic retention times (HRTs). Manure samples were collected from cattle fed with doses of monensin at 0, 1.8, 3.6, 5.4, and 7.2 mg per kg of dry matter intake. The HRTs investigated were 20 days (HRT20) and 30 days (HRT30). Increasing monensin inclusion in the diets resulted in a notable decrease in the quantities of total solids (TSs), volatile solids (VSs), and neutral detergent fiber (NDF) per animal per day, accompanied by an increase in lignin content and mass. Fraction separation during anaerobic digestion enhances the reduction of TSs, VSs, and NDF, thereby optimizing biogas and methane production potentials and elevating methane concentrations. The presence of monensin correlated with the reduced degradation of organic components during the anaerobic digestion process. To maximize the efficiency of the anaerobic digestion of manure from cattle diets supplemented with monensin, a 30-day HRT combined with fraction separation is recommended. This approach can enhance biogas yield and methane content, thereby improving the sustainability and efficacy of waste treatment processes.

This study is aimed to evaluate the efficiency of biochar and crude glycerin as additives in N retention throughout the composting of cattle slaughterhouse waste in static piles receiving forced aeration. There were five treatments (control, biochar accounting for 5 and 10%, and glycerin accounting for 5 and 10%, both at total solids) and four times (20, 50, 70 and 90 days of composting). The slaughterhouse waste was composted with a bulking agent at a ratio of 3:1, and the mixtures of waste and the tested additives were placed in nylon bags. The piles reached thermophilic temperatures soon after the process started and following turnings. The reductions of volatile solids, carbon, hemicellulose, cellulose and lignin were not influenced by the additives, resulting in averages of 69.1, 67.1, 62.1, 51.6 and 35.3%, respectively. The control showed greater N losses (58.38%), compared to the treatments with additives. The inclusions of biochar yielded an average loss of 48.47% N, while 10% of glycerin resulted in the lowest N losses (44.83%). The use of biochar and glycerin as additives in the composting of slaughterhouse waste is recommended in order to decrease N losses and improve the concentration of nutrients, without compromising the biodegradation of organic components.