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.

Rearing broiler chickens generates large quantities of waste material in the form of bedding. Anaerobic digestion (AD) is a technology that can be applied to this waste. This study aimed to evaluate the AD of broiler litter, either screened (S) or unscreened (US), from different flocks, collected from each production batch, totaling nine, from a commercial farm. Anaerobic digestion was conducted in batch biodigesters, and fraction separation was performed through screening prior to loading. The S substrate from the second and fifth flocks did not produce biogas. Reductions in total (TS) and volatile solids were highest for S substrates from the third flock (50.5% and 58.3%, respectively). Only the third flock’s S substrates showed greater reductions in solids than the US substrates. Potential biogas and methane production were also highest in the third flock’s bedding for both the S substrate (336.8 and 218.2 L/kg of TS, respectively) and the US substrate (296.8 and 213.4 L/kg of TS, respectively). The methane concentration in the S substrate was highest in the third flock (64.8%), while in the US substrate, it was highest in the third and fourth flocks (70.3%). Screening the litter reduced the process efficiency. We conclude that fraction separation is inadvisable for broiler litter.

Aquaculture intensification increases waste generation, whose composition may influence methane emissions. This study evaluated the effects of dietary protein and energy sources on nutrient digestibility and the methane production potential of Nile tilapia feces. Nine experimental diets were tested in digestibility assays: one reference diet (RD) and eight test diets containing 80% RD and 20% of an animal or plant ingredient. Feces were collected and subjected to batch anaerobic digestion. Soybean meal and meat and bone meal diets showed the highest apparent digestibility coefficients (ADC) for dry matter (84.1 and 82.6%) and energy (87.3 and 87.9%), whereas poultry by-product meal presented the lowest values. Crude protein digestibility ranged from 78.74% for blood meal diet to 94.3% for soybean meal diet. Feces from poultry by-product meal generated the highest methane potential (260.9 L kg⁻¹ VS), whereas blood meal exhibited the highest methane production per unit of COD removed (310.5 mL g⁻¹ reduced COD). After 10 days, poultry by-product meal accumulated the highest biogas volume, while soybean meal and blood meal showed the lowest. Principal component analysis suggested inverse relationships between nutrient digestibility and fecal biodegradability. Overall, dietary composition influenced nutrient digestibility, physicochemical characteristics of fish feces, and their methane generation potential. This integrated assessment suggests that feed formulation could contribute to strategies aimed at reducing the methane generation potential of aquaculture wastes.

Monensin supplementation in ruminant diets to improve energy efficiency also results in the excretion of this compound through manure. However, in sheep, monensin excretion rates remain unknown and are of concern due to the potential risks of environmental contamination, as well as possible impacts on waste treatment and recycling processes. Therefore, the objective of this study was to evaluate monensin excretion in sheep manure and its influence on the anaerobic digestion of these residues when increasing dietary doses of monensin were administered. Sheep were fed 0, 8, 14, and 20 mg of monensin kg⁻¹ of dry matter intake, and the collected manure was used to prepare substrates for feeding biodigesters. The substrates were digested either as whole material or after sieving for separation and removal of the solid fraction and were maintained under anaerobic digestion for hydraulic retention times (HRT) of 20 and 30 days. Increasing monensin doses resulted in higher excretion rates, reaching 13.32%, 32.01%, and 34.57% for the 8, 14, and 20 mg doses, respectively. When fraction separation was performed prior to digestion, higher monensin concentrations were detected in the sieved substrates; however, the loading rates applied to the biodigesters were similar. During anaerobic digestion, fraction separation promoted greater reductions in volatile solids, with mean reductions of 47.88% and 53.30% for HRTs of 20 and 30 days, respectively. Consequently, biogas production potential increased, reaching 220.6 and 306.4 L kg⁻¹ VS, with methane concentrations of 72% and 69.87% for HRTs of 20 and 30 days, respectively. Both HRTs were effective in reducing monensin levels, achieving a minimum removal efficiency of 80.14% by the end of the digestion process. Under the conditions of this study, a 30-day HRT combined with prior solid–liquid separation improved biogas and methane production. However, further studies are needed to evaluate economic feasibility, scalability, operational costs, and management of the separated solid fraction.