Green synthesis of biomethanol—managing food waste for carbon footprint and bioeconomy

Various microbial treatments and value-added transformations to treat and manage wastes including food wastes (FW) from numerous sources have emerged as leading concepts. The ever-increasing FW from households, retail establishments and food service industry totals 931 MMT annually globally. Landfill, incineration and bioprocess of FW have their own advantages and drawback as a waste recycling and energy recovery solution. Bioconversion of FW to produce value chemicals and bioenergy forms through anaerobically operated semicontinuous bioprocessing after a systematic solid–liquid separation followed by pretreatment seems a viable solution. Thus, the FW properties and pretreatment strategies to enhance the recovery of biofuels as well as other value products need to be standardised. Various strategies investigated to valorise FW as value-added products to biofuel, bioactive compounds, bioplastics, etc., and generate revenue have their merits and demerits. FW generates higher volatile fatty acids that may lead to bioconversion process breakdown under acidic conditions, especially during a biological strategy. The Gram (-) Methanotrophs which are proteobacteria use methane as carbon source and energy to thrive. Methane, biologically repossessed by methanotrophs, is catalytically oxidised to methanol by methane monooxygenase (MMO), an endogenous irreversible enzyme. The food waste biorefineries would ensure circular bioeconomy, the recovery of nutrient and energy. The review also discusses the circular economy strategies closing the energy loop through the food supply chain, in light of strong and weak sustainabilities. Innovative technologies through integrated biotechniques to realise valuable materials and bioenergy from FW with minimal waste generation are detailed.