Strategies for valorization of crop residues into biofuels and other value-added products

Abstract

Agricultural systems produce vast amounts of crop residues (CR) as by-products. More than 200 billion tonnes per year of CR are produced worldwide. They are mostly used as animal feed or disposed of by incorporation into soil for fertility purposes and by burning. Traditional CR management practices have environmental and techno-economic implications. Crop residues are an excellent bioresource, with multiple untapped applications. There is a significant lack of knowledge about commercializing the conversion of CR into value-added products in a sustainable way. A biorefinery concept is an important option that can transform CR into useful products. This paper reviews the potential state-of-the-art options for valorization of CR into multiple product streams. The paper focuses on 13 products. These are biogas, bioethanol, biobutanol, biohydrogen, biomethanol, pyrolytic products, enzymes, bioactive compounds, animal feed, mushroom, single-cell protein, organic acids, and biocomposites. The product streams can be divided into three categories: biofuels, animal feed and food, and phytochemicals. Biofuel production is the most promising strategy for the valorization of CR at large-scale biorefineries. Anaerobic digestion and fermentation are preferred to thermochemical conversions because they are cost effective and have improved conversion efficiency. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd