Fungal Pretreatment Methods for Organic Wastes: Advances and Challenges in Biomass Valorization

Abstract

Food wastes, municipal solid wastes, sewage sludge, plant’s materials, animal biomasses, aquatic and terrestrial wastes, agricultural and forestry wastes, industrial and domestic wastes and many other lignocellulosic biomasses are considered under the category of organic wastes or bio-wastes. Various techniques, mainly mechanical pretreatment (high pressure homogenization and ultra-sonication), thermal (temperature based) pretreatment, microwave technology of pretreatment, chemical pretreatment, and biological pretreatment are found to be effective in the organic wastes valorization. Fungal pretreatment of organic wastes is a promising biological technology because of its excellent efficiency of the decomposition of various types of organic wastes like food wastes, ligno-cellulosic biomasses, hemicellulose, agricultural wastes, hardwoods, softwoods, switchgrass, spent coffee grounds, park wastes, cattle dung, and solid digestate which have been reviewed pointedly. Fungal pretreatment of the organic waste materials may give advantageous products like biogases, energy source, sugars’ monomeric or oligomeric products, different type of acids, and many more. Major challenge associated with the fungal pretreatment technology is the requirement of higher time for greater degree of biomass valorization which raises the cost as well as vulnerability of contamination but the use of fungal pretreatment with other pretreatment techniques may reduce the time and enhance the functionality of the method with higher rate of biomass valorization. Heat generation in fungal pretreatment process and need of feedstock sterilization before fungal pretreatment are some other challenges to be properly tackled for its efficient application at industrial scale. In this review, use of different fungal pretreatment methods for the valorization of different types of biomasses and production of valuable products have been evaluated and discussed. Authors have provided an inclusive assessment of the fungal pre-treatment of various types of organic wastes along with the concise but effective discussions on the organic solid wastes and different pretreatment techniques involved in the bio-waste digestion processes. Techno-economic analysis, challenges and future perspectives have also been discussed.