This study examines the anaerobic digestion (AD) of fruit and vegetable waste (FVW) and digestates to assess the effect of particle size on anaerobic biodegradability (AB) and process rate at different stages of digestion progress. Batch assays were conducted with FVW mixtures and digestates from 5, 10, and 15 days of digestion, using four particle size ranges: Ø1 < 1.8 µm, 1.8 < Ø2 < 500 µm, 500 < Ø3 < 1000 µm, and Ø4 > 1000 µm. While AB and specific methanogenic activity (SMA) showed no significant differences among FVW mixtures, particle size significantly influenced these variables. Methane yields were 298.2 and 309.8 $\mathrm{m}\mathrm{L} \mathrm{C}{\mathrm{H}}_4·{\mathrm{g}}^{-1}\mathrm{V}\mathrm{S}$ for Ø4 and Ø3 particles, exceeding the 186.7 and 161.8 $\mathrm{m}\mathrm{L} \mathrm{C}{\mathrm{H}}_4·{\mathrm{g}}^{-1}\mathrm{V}\mathrm{S}$ obtained for Ø2 and Ø1, respectively. These results indicate that particle size reduction enhanced methane production; however, reducing the particle size below 500 µm inhibits methanogenesis due to intermediate accumulation. Compared to FVW, digestates exhibited a 23% reduction in AB, a 73.9% decrease in SMA, and methane yields of 55.8–294 $\mathrm{m}\mathrm{L} \mathrm{C}{\mathrm{H}}_4·{\mathrm{g}}^{-1}\mathrm{V}\mathrm{S}$. Additionally, the surface-based kinetic constant ($K_{SBK}$) decreased from 0.4523 $\mathrm{g}·\mathrm{d}{\mathrm{m}}^{-2}·{\mathrm{d}}^{-1}$for FVW to 0.0437 $\mathrm{g}·\mathrm{d}{\mathrm{m}}^{-2}·{\mathrm{d}}^{-1}$for digestates. These differences are attributed to the rapid consumption of easily biodegradable fractions within the first 5 days of digestion.

Glycerol can effectively replace corn as an energy source in lamb diets without negatively impacting productive performance. This study evaluated the effects of substituting ground corn with different glycerol levels on the productive performance, ruminal fermentation, carcass characteristics, and meat quality at 24 h, 7, 14, and 21 d post-slaughter. A total of 40 male Suffolk × Hampshire crossbred lambs (25 ± 5 kg live weight) were used in a completely randomized design with four treatment groups (n = 10 each): 0% glycerol (GLY₀), 5% glycerol (GLY0₅), 10% glycerol (GLY₁₀), and 15% glycerol (GLY₁₅). Including glycerol in the diet did not affect growth performance (p > 0.05). However, it did lead to an increase (p < 0.05) in the concentrations of NH₃-N and the proportions of propionic and butyric acids, while the acetic acid levels decreased (p < 0.05). The backfat thickness, loin eye area (LEA), and carcass yield were not significantly affected (p > 0.05) by the addition of glycerol. Additionally, pH and color were also unaffected (p > 0.05), although the water-holding capacity showed a decrease (p < 0.05) over the shelf life of the meat. The chemical composition of the meat remained similar across all treatments, time points, and interactions (p > 0.05). In contrast, the protein content was significantly affected (p < 0.05) by the glycerol inclusion, time, and interactions between treatment and time. The results indicate that substituting up to 15% of ground corn with glycerol in lamb diets does not negatively impact productive performance, backfat thickness, LEA, carcass traits, or meat quality during shelf life. Throughout the shelf life, the crude protein concentrations and water-holding capacity decreased, while the propionic acid and NH₃-N concentrations increased.