Evaluation of sludge quality from cow feces and vegetable waste from biodigester

This study aims to evaluate the quality of biodigester fermentation sludge produced by continuously filling the biodigester with cow feces and vegetable waste. The study used a 200-liter capacity horizontal portable biogas digester, equipped with an agitator filled with cow feces and vegetable waste of kale, cabbage and Chinese cabbage. The research method is experimental research (true experimental research). This study was designed with a nested pattern, consisting of two factors, the first factor is a digester filled with cow feces (experiment I), cow feces and “Kol” vegetable waste (experiment II), cow feces and “Kangkung” vegetable waste (experiment III) and cow feces and “Sawi” vegetable waste (experiment IV). The results showed that the addition of vegetable waste consistently reduced (P<0.05) the Biological Chemical Demand (BOD) value of the sludge. Statistically, the Chemical Oxygen Demand (COD) values from the four experiments were not significantly different (P>0.05). The mixture of "Sawi putih" is very efficient in decomposing solids, or "Sawi putih" itself has a lower solid content and is more easily decomposed. The addition of vegetables succeeded in creating a more balanced C/N ratio, thereby preventing excessive ammonia release. The addition of vegetable waste can suppress the pathogen population, on the contrary, the CO2 content produced is higher, especially with the addition of "Kol" vegetable waste. The addition of vegetable waste to the cow dung-based biodigester can suppress the number of pathogenic bacteria. It was concluded that the addition of vegetable waste to the cow dung-based biodigester, consistently reduced the BOD value of the sludge and lower solid content, on the contrary, it can prevent excessive ammonia release and suppress the number of pathogenic bacteria.