Influence of kitchen biowaste addition on the effectiveness of animal manure digestion in continuous condition

The aim of the research was to establish the influence of kitchen biowaste as a co-substrate on the effectiveness and stability of animal faeces (pig manure) anaerobic digestion for biogas production, conducted in mesophilic conditions. Digestion process was conducted for manure as well as mixtures containing 10% of kitchen biowaste and 90% of manure. The proportion of substrates in the co-digestion mixture was established as optimal, on the basis of tests conducted in static conditions. The digesters were maintained at a mesophilic temperature of 36 ̊C and the process was carried out at the hydraulic retention times (HRT) ranging from 25 to 50 days. Anaerobic digestion of manure for the HRT value of 30÷35 days ensured the highest amounts of biogas produced (0,77-0,85 dm/dm×d) as well as degree of organic matter reduction (52-54%). Whilst The highest biogas production rate (1,25 dm/dm×d) as well as degree of organic matter reduction (66%) were achieved for the HRT value of 35 days. Co-digestion of kitchen biowaste and munure allowed to achieve between 10 and 60% higher biogas production rates. The co-digestion process conducted for the shortest value of HRT (25-30 days) turned out to unstable and exhibited a relatively low effectiveness.