2.3.9. Anaerobic co-digestion
This is a process where various organic wastes are mixed for co-digestion. The advantage of co-composting and co-digestion is it achieves a better balance of nutrients and can improve the treatment efficiency [53], particularly for pig and poultry waste at land fill sites. The effect of using various ratios of pig and poultry waste on gas production was studied by Magbanua et al. [54]. The waste was incubated at 35 2 °C for up to 113 d. This process produced high levels of biogas [54]. In another trial best results for methane production were achieved when 3 wastes were used; cattle and poultry waste and cheese whey (w/w on dry weight basis). The digesters initially operated at 40 C with a 10 day retention time [55]. Clearly hatchery waste has the potential to be included as a material for co-digestion.