Biorefinery integration of a green protein platform for maximum resource utilization

Abstract

Biorefineries are often proposed to reduce environmental impact, enhance energy independence, and minimize waste generation while generating multiple valuable products. In this work, an integrated biorefinery approach is proposed to improve the overall process performance of a system combining a green biorefinery (GB), hydrothermal liquefaction (HTL), and anaerobic digestion (AD) to produce a leaf protein concentrate, bio-crude, and biogas. Festulolium and ryegrass, two varieties of forage grasses, were employed as feedstock. Two different maceration technologies were evaluated for protein recovery, more severe maceration led to a 75 % increase in protein content in the leaf protein concentrate (LPC) when compared to a standard maceration. The fiber residues produced by the grass processing were converted to biocrude using HTL. This step was not affected by the maceration step and the use of brown juice as HTL media proved to be beneficial. The bio-crude yield of the grass fiber residues was similar for both biomasses and maceration steps, ranging from 25.7 to 32.1 %. Finally, the HTL process water and the brown juice were subjected to anaerobic digestion to produce biogas. The brown juice from ryegrass resulted in higher methane production compared to HTL water but adding brown juice to HTL water did not reduce the lag times observed for pure HTL water. The integration of GB, HTL, and AD is shown to be effective in increasing the overall carbon and nitrogen recovery of the starting biomass.