A1 Journal article (refereed), original research

Evaluation of thermochemical routes for the valorization of solid coffee residues to produce biofuels: A Brazilian case

Publication Details

Authors: Mendoza Martinez Clara Lisseth, Saari Jussi, Melo Yara, Cardoso Marcelo, de Almeida Gustavo Matheus, Vakkilainen Esa

Publisher: Elsevier

Publication year: 2021

Language: English

Related journal or series: Renewable and Sustainable Energy Reviews

Volume number: 137

ISSN: 1364-0321

eISSN: 1879-0690

JUFO level of this publication: 1

Digital Object Identifier (DOI): http://dx.doi.org/10.1016/j.rser.2020.110585

Permanent website address: https://www.sciencedirect.com/science/article/pii/S1364032120308698

Social media address: https://www.researchgate.net/publication/346785091_Evaluation_of_thermochemical_routes_for_the_valorization_of_solid_coffee_residues_to_produce_biofuels_A_Brazilian_case

Open Access: Not an Open Access publication


Coffee production in Brazil creates significant amounts of residues. The goals of this study are to evaluate the characteristics of these residues (parchment, husk, pulp, spent grounds, silverskin and defective beans); to discuss their potential for conversion to improved biofuels via thermochemical methods; and to develop mass and energy balances of the processes to help determine the value of residues for direct combustion, fast and slow pyrolysis, gasification, hydrothermal carbonization and torrefaction.

Particularly the pulp, but also husk and parchment, are characterized by high moisture, as well as high contents of cellulose (41–64%) and hemicellulose (27–35%). These residues are suitable for several conversion routes, albeit with the drawback of drying need for the dry methods. The ash of these also creates a risk of fouling, corrosion and agglomeration with high-temperature and fluidized bed technologies. The silverskin and some of the defective beans are available at lower moisture. The spent coffee grounds appear a particularly advantageous residue for energy use: while moisture varies, the roasted product dries easily and has the highest heating value of the residues. For defective beans, little thermochemical treatment data is available.

Among the technologies, for wet feedstocks hydrothermal carbonization has the advantage of post-conversion drying. Gasification appears advantageous for parchment with a high syngas yield and heating value. Fast pyrolysis of biomass suffers from the oxygen content of the liquid, requiring additional treatment; slow pyrolysis may be more appropriate. In conclusion, coffee residues have potential as feedstocks for a number of thermochemical conversion processes.

Last updated on 2021-15-04 at 07:24