초록
<P><B>Abstract</B></P> <P>Anaerobic digestion (AD) of kitchen waste (KW) for biogas production is a major challenge to all over the world due to significant compositional variations in KW, such as different types and quantities of spices used for preparing food. Spices may affect the AD process owing to their antimicrobial activity. In this paper, the effect of spices (garlic, red chili, cinnamon, coriander, clove, turmeric, cardamom, black pepper) on AD of KW has been investigated. Batch experiments were carried out to determine the maximum biogas production potential, methane production rate and lag phase for biogas production. Analysis of the results revealed different magnitude of inhibition of the AD process of KW in the presence of different spices. Cinnamon, cardamom and clove resulted >85%, black pepper resulted 75%, while coriander, chili, turmeric and garlic resulted 55–70% reduction in cumulative biogas yield. Elemental analysis showed high concentration of heavy metals in the spices, which along with other bioactive components of the spices could be responsible for the inhibitory effect of the spices on biomethanation. Microbial examination of the digestate also showed a decrease in population of fermentative and methanogenic bacteria in the presence of spices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Presence of spices in kitchen waste was found inhibitory for biogas formation in a batch experiment. </LI> <LI> In the presence of clove, cardamom and cinnamon reduction of >85% of biogas yield was observed. </LI> <LI> The CFU count results confirmed the reduction in microbial population in the presence of these spices after the digestion. </LI> <LI> Metal toxicity and presence of antimicrobial agents are correlated to inhibitory action of spices on AD of kitchen waste. </LI> </UL> </P>