Food waste: analysis of the complex and variable composition of a promising feedstock for valorisation

There are global concerns about the environmental, social, and economic consequences associated with the generation of food waste. To effectively address this challenge, and particularly to develop food waste valorisation approaches, it is necessary to acquire understanding of the physicochemical and biochemical characteristics of food waste. This study comprises a systematic overview and quantitative assessment of the characteristics of food waste biomass, and this was achieved through a comprehensive literature review. The resulting database encompasses the physicochemical, biochemical, and elemental composition of food waste. The study evaluates food waste variability, analyses correlations between components, and highlights patterns in composition. Overall, food waste is a rather variable material. Typology, collection source and geographical origin of food waste streams are the main contributing factors to variation in physicochemical, biochemical and elemental compositions of food waste, while collection season and storage temperature appear not to be contributing substantially to variation. A clear distinction between plant-based and animal-based food waste biomass can be observed with animal-matter enriched food waste having high contents of protein, lipid and ash, but a low starch content. On the other hand, plant-based food waste can be either high in lignin and low in starch or high in carbohydrates, starch and higher heating value. Fibre content appears an indicative parameter, distinguishing plant from animal enriched food waste, and correlating strongly with lignin-rich, starch-poor plant biomass. The heterogeneity of food waste biomass composition will create challenges in developing and scaling up appropriate food waste management. The current study shows that the analysis of specific food waste parameters, such as fibre content, can be used, to inform the choice of the most appropriate valorisation route.