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.

Sustainable valorization of apple waste in a biorefinery: a bibliometric analysis

“…132,139,140 For this, the wastewater (effluents) generated by the apple processing industry can be used in the biorefinery for the generation of biomethane, using anaerobic digestion technology. 141 Hence, the anaerobic digestion of wastewater can be a technological route for bioenergy recovery in a biorefinery, 142,143 contributing to reducing the apple industry's carbon footprint while promoting the environmental, social and economic benefits of the productivity chain, being a powerful strategy to promote the circular economy transition of the apple industry.…”

Modeling of Pretreatment and Combined Alkaline and Enzymatic Hydrolyses of Blue Agave Bagasse in Corotating Twin‐Screw Extruders

“…[ 6–8 ] Biomasses have become effective alternative raw materials in the production of added‐value materials and biofuels, especially bioethanol. [ 9–14 ]…”

“…Although enzymes are expensive, their advantages in energy requirements, milder conditions, and minimal formation of by‐products seem to compensate for their high costs. [ 10–14,50,51 ] A correlation between lignin removal and an efficient enzymatic digestibility process is reported in the literature. [ 51–53 ] Enzymes also help in the fermentation step since they do not generate yeast inhibitory by‐products.…”

“…[6][7][8] Biomasses DOI: 10.1002/mren.202100059 have become effective alternative raw materials in the production of addedvalue materials and biofuels, especially bioethanol. [9][10][11][12][13][14] Biomasses are mainly composed of cellulose (C), hemicellulose (H), and lignin (L). L offers a natural protection to H and C. [15][16][17][18] However, when L is removed, C and H are available for hydrolysis and, consequently, to be converted into monomeric sugars.…”

Characterization of lignocellulosic crop residues for potential biogas production in Zimbabwe

“…Zimbabwe contributes about 7.8 Mt per year to the total global LCRs production. 10 Lignocellulosic crop residues are mostly produced by cereal crops (e.g. rice, wheat, maize, millet) and sugar cane.…”