Pretreatment of food waste for methane and hydrogen recovery: A review

•Freeze and thaw and drying pre-treatments preserve the carbon for future processing.•Grinding pre-treatment of FW improves the surface property and bio-accessibility.•Combined grinding and thermal pre-treatments improves the digestibility.•Energy-economics of integrated FW pre-treatment require to be established. Food waste (FW) management by biological process is more attractive and eco-friendly approach than thermo-chemical conversion or landfilling. However, FW composition and physico-chemical and biological characteristics affect the overall biological process in terms of product yield and degradation rate. To overcome this major bottle-neck, the pretreatment of FW is proposed. Therefore this review aims to provide a comprehensive summary of the importance of pretreatment of FW with respect to FW management by anaerobic digestion (AD) and dark fermentation (DF). It also reviews the existing knowledge gaps and future research perspectives for better integration of FW pretreatments for AD and DF, which should include (i) the preservation of carbon mass through freeze and thaw, or drying; and (ii) improve the carbon accessibility through particle size reduction and thermal pretreatments for high-rate bioenergy recovery.