Caracterização e conversão termoquímica e mecânica da biomassa residual do café (coffea arábica L.) para energia

Abstract

Coffee is one of the most important agricultural crops in the world. During its processing, a significant amount of residues are generated, which without treatment can represent serious environmental problems. This study was carried out with the objective of evaluating the quality and energy potential of residues obtained in the coffee production chain, proposing an alternative that can be applied in the energy matrix of countries that involve the coffee industry in its agricultural activities. In Article I the properties of the (I) parchment of the coffee cherry, (II) leaves and (III) wood, highlighting the woody parts of the coffee shrub, were evaluated. Physical-chemical properties of the different biomasses were determined. Among the biomasses, the stem, primary branch and secondary branch of the coffee shrub stood out due to the greater net heating value (16.10 MJ.kg-1-15.92 MJ.kg-1) and lower ash content (1.67%-3.45%), favorable properties for the production of energy by thermochemical methods such as slow pyrolysis, gasification and combustion, and physical methods such as pelletizing and briquetting. Article II aimed to study the feasibility of use residues generated in coffee cultivation and pine wood fines in the manufacture of briquettes for energy generation. The pine wood was mixed in proportions of 0%, 25%, 50%, 75% and 100% with residues from the coffee crop. Physical, mechanical and chemical properties of the briquettes produced were determined. The higher presence of pine in the treatments contributed to the improvement of the properties of resistance to diametrical compression, apparent density and energetic density. However, the compaction rate of the briquettes was affected, an important parameter to evaluate the stability of the briquettes when submitted to transport and storage conditions. Article III had the objective of analyzing the fast oxidative pyrolysis process in a fluidized bed reactor, fed with eucalyptus wood from the pulp industry and wood of the coffee shrub. The physical and chemical characteristics of the biomass, the bio-oil and the bio-char obtained in the process were determined. Bio-oils had a higher energy density than in natural biomasses (6.31 times higher for eucalyptus wood and 4.26 higher for wood of the coffee shrub). The biochar presented the highest heating value (21.19 MJ kg-1 for wood of the coffee shrub and 22.08 MJ kg-1 for eucalyptus wood), allowing its use as fuel. In general, the results indicate that the residues used are potential candidates in the production of bioenergy by fast pyrolysis. It was concluded that the use of residual biomasses obtained from the coffee production chain are viable raw materials to be used in the production of energy by implementing processes such as briquetting and fast pyrolysis