Physical Characteristics of Selected Bamboo Species and Their Charcoal Properties

Nurhazwani, Jarawi (2023) Physical Characteristics of Selected Bamboo Species and Their Charcoal Properties. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

In Malaysia, industrial-grade charcoal is typically manufactured from mangrove woods (commonly Rhizophora apiculata and Rhizophora mucronata). With the increasing concerns about the availability of mangroves, there is renewed interest in using a renewable, plantation-grown, abundantly available biomass such as bamboo as the raw material for charcoal production. Bamboo is abundantly found in Sarawak, but Sarawak has not capitalized on its commercial significance. One of the high-end products to utilize bamboo in Sarawak is bamboo charcoal. There is, however, a lack of information on the suitability of bamboo in Sarawak to be made into charcoal. This study was conducted first to determine five bamboo species' morphological and physical properties: Bambusa vulgaris, Dendrocalamus asper, Gigantochloa hasskarliana, Gigantochloa levis and Schizostachyum brachycladum. Secondly, to produce bamboo charcoal using a modified Iwasaki steel drum kiln and determine the correlation between the physical properties of bamboo and their charcoal properties, and thirdly, to determine and compare the quality of bamboo charcoal produced based on proximate analysis and elemental content. Generally, all bamboo species' mean green moisture content decreased with culm height (ranged from 72 to 111%). Contrarily, the mean basic density increased with the culm height. The internode length increases with height and reaches the maximum length at the middle culm. However, the internode diameter and culm wall thickness gradually decreased with height for all five bamboo species. Carbonization at 750 °C of all bamboo species using a modified Iwasaki steel drum kiln was successful and Scanning Electron Microscopy (SEM) micrographs showed that the charcoal was highly porous. A more than 30% charcoal yield was recorded in G. hasskarliana, G. levis and S. brachycladum. Charcoals made from G. hasskarliana could serve as the alternative raw material for charcoal production in charcoal industries due to their low moisture (5.3%), low volatile matter (22.8%), low ash (5.6%) and high fixed carbon content (66.3%) which are in the range of FAO’s quality specifications. Among different culm sections, the bottom section produced the best quality of charcoal considering its low moisture (5.2-7.5%), low volatile (21.2-32.7%), low ash (2.9-14.9%) and high fixed carbon (53.3-70.6%) content. The charcoal yield was positively correlated with the charcoal’s moisture content and ash content, but it was negatively associated with bamboo culm basic density, culm wall thickness, charcoal’s volatile matter content, and fixed carbon content. This suggests that lower charcoal yield is obtained with denser and thicker culm walls of bamboo. Charcoal volatile matter content is positively correlated with charcoal ash content but negatively correlated with charcoal fixed carbon. The results showed that charcoal fixed carbon is negatively correlated to all variables except for bamboo culm wall thickness, suggesting that thicker bamboo walls have higher fixed carbon. Based on the proximate analysis, the charcoal quality from all species was of high quality for domestic use. There are 21 elements detected from the bamboo species' ash sample. The mean concentration of heavy metals (Cr: not detected; Cd: 3 to 27 mg/kg, Pb: 3 to 23 mg/kg) in bamboo charcoal from the five species in this present study was very low, suggesting safe for human use (Cd: less than 85 mg/kg; Pb: less than 100 mg/kg).

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