Combustion performance of charcoal: a comparative study on Miombo woodland native species and Eucalyptus grandis

Abstract

Charcoal is the most preferred energy source in Mozambique and contributes to income generation for most households and small-medium scale commercial entities. However, charcoal production contributes to the illegal exploitation and rapid decrease of natural forest cover. Attempts from the government to address this challenge by implementing energy plantation projects using Eucalyptus spp. have failed due to local communities’ preference for charcoal produced from native wood species. Therefore, this study aims at evaluating the combustibility of charcoal produced from Eucalyptus grandis and Miombo native species, in order to support new energy plantation projects, as well as adequate interventions toward the improvement of residential cooking and heating appliances in Mozambique. All charcoals were produced on a laboratory scale at a final temperature of 450 °C. Charcoal samples were collected, and their proximate chemical composition, heat value, combustion parameters, and indexes obtained by thermogravimetric analysis were evaluated. The charcoal from Eucalyptus grandis presented lower ash content (0.49%) and fuel ratio (2.81), higher content of volatile materials (26.14%), and heat value (31.15 MJ kg−1) as compared to charcoal from Miombo species. However, Miombo species presented a higher combustion performance, especially Uapaca kirkiana, which presented higher combustibility (1.37 × 104% min−1/°C2) and ignition (13.13 × 103% min−3) indexes. Eucalyptus grandis is a fast-growing species, and its charcoal presented suitable chemical properties and combustibility for domestic use; therefore, its use as an alternative to Miombo species is recommended.