Colorimetry of pellets produced with eucalyptus and coffee cultivation residues and their relationship to quality standards

Abstract

The world's energy matrix relies on the use of fossil fuels, main cause of the greenhouse effect. For such reason, there is a need to find renewable fuel alternatives with the potential to supply current energy demands while reducing the environmental impacts. Therefore, one alternative is the production of pellets using agroforestry residues. Hence, despite having favorable edaphoclimatic conditions, Brazil still has much to learn and improve. The main constraints are: high logistics and transportation costs, maritime ports do not have the necessary conditions and infrastructure, and absence of equipment to produce pellets efficiently. This project's objective is to correlate the pellets' colorimetric characteristics under the Commision Internationale de lEclairage (CIE-L∗a∗b∗) to ash and extractives content and heating values. Three eucalypt clones (A, B, and C) and three coffee depulping process' residues (parchment, silver screen, and external bark) were used, and six compositions were created. Residues that were 100% pure were pelletized and one sample of a domestic commercial pellet (made with eucalypt biomass) was analyzed. The pellets' color was evaluated under the CIE-L∗a∗b∗ system and it was concluded that high ash percentages result in darker pellets. The pellets produced with silver screen (PP) and external bark (CE) presented a total variation (ΔE) of 31.14 and 29.34, respectively, after pelletization, resulting darkest than the others, and close to 30 in the luminosity scale (L∗). These values undermine the pellets' quality and energetic properties, as values above 32 would exceed the recommended ash values and the pellets would not adjust to European standards, thus precluding the commercialization in the international market.