The anaerobic co-digestion of cheese whey and garden waste was examined in this study, with particular attention paid to two important parameters: the feed-stock ratio and the garden wastes particle size. Two set of studies were carried out in the study. Four ratios of garden waste to cheese whey (1:1, 1:2, 1:4, and 1:6) were evaluated in the first phase with the 1:2 ratio identified as optimal. Using this optimal 1:2 ratio, the second phase was conducted with particle sizes of 20 mm, 40 mm, 60 mm, and 80 mm. Due to an ideal carbon-to-nitrogen (C/N) balance, the 1:2 ratio generated the highest cumulative biogas yield of 111.5 ml per 100 g of substrate. Particle size of 40 mm was showed the maxi-mum cumulative biogas yield of 76 ml per 100 g of substrate. The results indicate that a 40 mm particle size combined with a feedstock ratio of 1:2 is ideal for maximum biogas production. This work provides valuable insights for improving anaerobic digestion efficiency, especially for small-and medium-sized dairy farmers seeking to convert cheese whey into a sustainable energy source.