<p>This work aims to develop green composite sorbents from discarded polymeric coffee capsules with holocellulose extracted from pulp industry residues of <i>Eucalyptus urograndis</i>. Part 1, discussed in this article, investigates the lignocellulosic components of these three discarded parts (bark, chip splinters, and leaves) from the pulp industry of Eucalyptus wood. The physical–chemical properties, chemical structure, morphology, and thermoanalytical behavior of these lignocellulosic components and the green composites obtained were also evaluated using characterization techniques (thermogravimetry/derivative thermogravimetry, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy). It was found that the treatment submitted on the fibers directly influenced their composite properties. Chips had higher holocellulose content (75%), and leaves were richer in extractives and lignin (26 and 34%). DRX results showed that holocellulose extracted from chips exhibited the highest crystallinity index. The green composite formed by discarded coffee capsules reinforced with composites with holocellulose from bark showed superior thermal stability using the thermal analysis technique compared to polypropylene alone, which is promising. The Part 2 paper will examine the specimens manufactured from these green composites with nanocellulose and their performance in static adsorption tests for simulating a marine environment contaminated with crude oil spills.</p>