Sustainable technologies have enabled the production of degradable single-use plastics (SUPs) for various applications. However, environmentally friendly, porous disposable absorbents still lack the competitive functionality of synthetic options. In this work, we report the continuous extrusion of fully biopolymer-based porous absorbents derived from integrated proteins and lignocellulosic residues, all sourced from biomass waste. The results show that the saline absorption capacity of the extruded materials increases 1.5 times compared to the reference solely by including oat husk, a lignocellulosic byproduct from the food industry. The absorption was further improved 2 times by including a delignification step on the oat husk and wheat bran, demonstrating the importance of the biomass’s chemistry in increasing the material’s absorption. Here, the addition of 20 wt % of Keratin fibers from food waste increases the material’s absorbency to 6.5 g/g, with the ability to retain 2 g/g of the saline solution in its structure, which is also the highest reported value for extruded protein-based formulations so far. This work advances the development of porous absorbent materials with competitive performance, utilizing industrial methods and upcycling undervalued biomass waste into sustainable consumer products. Introducing porous biopolymer-based materials as alternatives to synthetic counterparts used in the hygiene and sanitary industries ensures the return of safe molecules to nature, paving the way for microplastic-free, single-use, porous absorbents.