Improving food waste anaerobic digestion : effects of digestate recirculation, post-treatment and methane-methane serial digestion

Anaerobic digestion of food waste generates two valuable products: digestate and biogas. Today, most food waste in Norway is incinerated because it is collected as mixed waste. Hence, a shift from incineration to anaerobic digestion of food waste will produce more value and be a contribution to the emerging circular economy. As more food waste becomes available for anaerobic digestion, optimization of the process to allow higher substrate loading rates to existing biogas plants is needed. \nIn this thesis, several strategies for improved food waste anaerobic digestion was investigated. This included recirculation of digestate, post-treatment with thermal hydrolysis, and methane-methane serial digestion. Moreover, different approaches for organic matter determination was compared, and the relevance of small-scale experiments as a model system for large scale biogas plants was investigated.