Upcycling of agro residue with C/N > 50: case study of accelerated composting and fortified animal feed

Around 0.7–1.5 MT of agro-residue is produced per ton of production of crops. Typically with C/N ratio more than 50, these residues exhibit recalcitrant properties. Given the environmental challenges associated with traditional disposal methods, sustainable valorization of these residues is imperative. A novel enzyme cocktail, derived from rice straw using solid-state fermentation of a patented culture, was developed for the degradation of high C/N agro-waste. This study examines the effects of this enzyme pretreatment on the composition of high C/N materials. Pretreatment effects on rice straw are examined vis-a-vis consecutive treatments with enzyme and Trichoderma to analyze the efficiency in disintegration of the lignocellulosic matrix. Consecutive enzyme pretreatment significantly increased readily hydrolysable cellulose and hemicellulose fractions in rice straw by 103.65% and 63.42%, respectively. However, combined enzyme-fungal pretreatment yielded increases of 81.63% and 58.86%. The green upcycling of rice straw into compost and cotton stalk into enriched animal (ruminant) feed are considered as model cases in the present study using enzyme pretreatment. A 47% reduction in the C/N ratio of rice straw was achieved within 4 days through enzymatic pretreatment while the overall dry matter digestibility for cotton stalk increased by 4–5% in vivo.