The need for sustainable development is driving a major focus shift in the biowaste treatment sector. While traditional practices such as landfilling are progressively being banned/penalised due to their obvious environmental impacts and prevention policies are being implemented, the potential of food waste (FW) as a resource is being increasingly recognised. The immense amounts of food waste produced worldwide -and its overall characteristics -make it a promising candidate for resource recovery if collected separately, a practice that is gaining popularity. This chapter aims at giving a general overview of the different processes that are being developed/implemented for resource recovery from FW, including energy, carbon, and 2 nutrients (i.e. N and P). The main options are critically assessed and compared. In addition, a special focus is given to potential state-of-the-art research/technological developments that could be applied in the future. Key challenges to be faced are also discussed, including legislative, social and technological aspects. KeywordsSolid waste; valorisation; biogas; biohydrogen; biomolecules; single-cell 14.1. Food waste production and characteristics How much food waste is produced worldwide?FW can be precisely defined as the "mass of food lost or wasted in the part of food supply chains leading to edible products for human consumption" (Gustavsson et al., 2011). It is important to note that the FW definition shown above does not include the source-separated residues from industrial activities related to food production (e.g. dairy effluents, sugar-refining residues, brewery wastes or agricultural residues). As each of these industrial effluents has different characteristics and treatment/valorisation options, discussing them separately falls out of the scope of this chapter, which focuses on general, non-specific FW.

The effect of supplementing granular activated carbon and trace elements on the anaerobic digestion performance of consecutive batch reactors treating food waste was investigated. The results from the first batch suggest that addition of activated carbon favored biomass acclimation, improving acetic acid consumption and enhancing methane production. Adding trace elements allowed a faster consumption of propionic acid. A second batch proved that a synergy existed when activated carbon and trace elements were supplemented simultaneously. The degradation kinetics of propionate oxidation were particularly improved, reducing significantly the batch duration and improving the average methane productivities. Addition of activated carbon favored the growth of archaea and syntrophic bacteria, suggesting that interactions between these microorganisms were enhanced. Interestingly, microbial analyses showed that hydrogenotrophic methanogens were predominant. This study shows for the first time that addition of granular activated carbon and trace elements may be a feasible solution to stabilize food waste anaerobic digestion.

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