Coffee Processing By Products Valorization an Overview of Energy and Environmental Applications

Abstract

The use of coffee residues as an animal feed for ruminants, pigs, chickens, and rabbits was examined (Bressani et al., 1979). However, the analysis of the amino acids contained in the protein of the coffee residues shows that half of the essential amino acids are absent. Therefore, a complement would be necessary for the coffee residues to be used as animal feed. For this reason, the idea was abandoned. Coffee processing by-products can be converted through thermochemical or biochemical processes into biogas, biofuel, biodiesel, bioethanol, or directly subjected to combustion. A pretreatment technique such as drying and torrefaction could be applied in the case of high humidity content to remove water for the coffee processing by-products. Moisture harms the performance of the thermochemical process and influences the quality of gas produced. Removing moisture increases the energy value of the coffee by-product. The use of coffee processing by-products has also paid much attention to environmental applications. In particular, the use of raw and modified coffee residues to remove pollutants from aqueous and gaseous phases is addressed. The modification of coffee residues includes chars, activated carbon, and catalyst support production. Raw coffee processing residues and their corresponding chars can be used as biosorbents to remove heavy metals and organic dyes from aqueous solution. Different activation protocols can transform the chars into activated carbons.

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